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[P]
Physicist Thinks He'll Have a Time Machine by Next Fall

By BLU ICE in News
Mon Apr 08, 2002 at 07:37:44 AM EST
Tags: Science (all tags)
Science

We all have dreamed about traveling through time. Seeing the wonders of the future, or visiting Caesar in ancient Rome. Now one physicist, according to this Boston Globe article, and this Eureka Alert article, thinks he'll be able to transport neutrons through time by next fall.


Previous concepts of time machines were woefully out of our technological grasp: wormholes requiring a Jupiter-sized amount of negative matter, infinitely long cosmic strings, and several other out of the question concepts. But Ronald Mallet from the University of Connecticut thinks he has a better way.

Think of this: You probably know gravity slows down time. It bends it. Now if you got enough gravity, it warps space so much that it whips it into a ring. He is going to warp gravity to make a circular region of time inside of his device. That's right, instead of time linearly flowing from the past to the future, it will turn back on itself.

A few years ago, a new concept for time travel was put forth: If you had two circular beams of immense amounts of light, (light, like matter, can warp space) it would bend space, creating a loop of time. The problem with this, however, is that you would need ungodly amounts of energy. But Mallet has a better plan. He will slow down two laser beams to just 40 miles an hour using a supercold Bose-Einstein Condensate. Slowing the light increases the light's inertia. Since it has more inertia, it has more energy, and therefore it has a more potent gravitational effect. Using this method, you only need low-power lasers, making time travel a real possibility.

Ok then, we will be able to transport a neutron though time, but what about a human? According to Mallett, that's not too far off either. Transporting a neutron does not require much energy. Of course transporting a person would require much more. Mallett thinks transporting a person, however, is not unfeasable at all. According to Mallett, it wouldn't take engineers long before they will be able to transport a person. Quips Mallett, "What we're talking about is at the edge of current technology, not beyond current technology."

However, many physicists express doubt on whether Mallett's time travel experiment will be sucessfull. Alan Guth, a physics professor from MIT, has his doubts on whether time travel is even theoretically possible. Another, Stanley Deser, a professor from Brandeis University, thinks that while time travel is theoretically possible, the engineering problems of time travel are insurmountable.

At this point, you may be thinking, "But what about the grandfather paradox? If I travelled back in time, wouldn't I be able to kill my grandfather? Wouldn't that make my own birth impossible, which would at the same time, prevent me from killing my grandfather in the first place?" Well, there is a simple answer for that and all other time-travel causuality problems: Parallel universes. The very well-accepted many-worlds theory states that for each quantum event, a new universe branches off for each possible outcome. Thus, we have innumerable universes being created every second. You can go back and kill your grandfather. It will just be your grandfather in a seperate universe.

If this experiment is sucessful, it will have wide repercussions for humanity. If it is unsucessful, it will not. Time travel could open up a whole new world. As this time machine creates a loop, we would be unable to travel back before it is created. So we couldn't visit Caesar. But we could communicate with the future. Even if we just had an early version of the time machine that only transports neutrons, we could send binary messages back and forth from the future. We could learn about new technologies years ahead of our time. Now if we had the capability to transport humans, time will no longer exist as we know it today. Visiting a different time would be like visiting a different country. We would be able to travel as freely though time as we travel to different parts of the world on jets.

I certainly hope Mallett and his team are sucessful. It may be the greatest invention since fire.

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Physicist Thinks He'll Have a Time Machine by Next Fall | 143 comments (120 topical, 23 editorial, 0 hidden)
Thank you for not MLPing (4.00 / 6) (#3)
by Canthros on Mon Apr 08, 2002 at 01:01:36 AM EST

It's nice to see an interesting bit of news actually written up for K5, instead slapped into an MLP in five minutes and thrown into the queue, never to be seen again.

--
It's now obvious you are either A) Gay or B) Female, or possibly both.
RyoCokey
Well thank you (2.00 / 1) (#15)
by BLU ICE on Mon Apr 08, 2002 at 01:28:10 AM EST

I got the idea from /. The same story, albeit just a short paragraph long, appeared on /. this morning. It now has over a thousand comments.

And, (bitch-mode ON) I spent about an hour and a half gathering info from all over the web and writing it out.

Do you know what I really hate right about now: I'm a High School sophomore. This is my very, very last night of spring break. No, I didn't go to Cancun, though I wish I did. I stayed home and played UT.

Christ, tomorrow it's back to school again. At least this is really the last leg of the school year before summer. Next year I'm going to running start at our piss-poor community college, and getting my A+ and CISCO certs from their tech place. That should be interesting. Maybe I should go forward in time and get a memory implant for Spanish Class.

"Is the quality of this cocaine satisfactory, Mr. Delorean?"
"As good as gold."

-- I am become Troll, destroyer of threads.
It's like an encyclopedia...sorta: Everything2

[ Parent ]

I know what your problem is. (4.20 / 5) (#6)
by andrewm on Mon Apr 08, 2002 at 01:12:07 AM EST

You seem to think that everyone turns patricidal as soon as they get near a time machine. Why wouldn't you go back and do something nice for the poor guy instead?

There's other explanations for why he's safe, even if time travel is possible. here's a few I can think of just now:

  • Free will is an illusion. You didn't kill him, you won't kill him, and you couldn't kill him even if you thought you were free to decide you would. You don't even have enough free will to decide if you'll believe me or not.

  • A little quantum* weirdness: There's a single 'real' world (not many worlds), but after you kill the poor man, histroy will record a man being killed by a stranger who literally came out of nowhere, then vanished into thin air again. It would be the perfect crime, at least if you continued to exist afterwards.

  • The time machine is actually powered by a perpetual cold fusion generator created by an irishman in his back yard. (Translation: the time machine is also fiction. The movie trailer doesn't look bad, though.) That's the one I suspect will be true, but I also expect that it doesn't need to work for people to believe that it will. Who knows, maybe one day a time machine will be written.

quantum: Noun, word used to sound like I know what I'm talking about while discussing physics I've never actually studied.

There are all kinds of paradoxes (1.50 / 2) (#10)
by BLU ICE on Mon Apr 08, 2002 at 01:16:06 AM EST

Not just the grandfather one. Without a many-worlds type of thing, time travel is all but ruled out. Anyway, suppose I go back and give my grandfather a gift of very expensive 12 year old scotch. Then he gets drunk and forgets all about his date with my grandmother that night.

"Is the quality of this cocaine satisfactory, Mr. Delorean?"
"As good as gold."

-- I am become Troll, destroyer of threads.
It's like an encyclopedia...sorta: Everything2

[ Parent ]

and that's different because..? (5.00 / 2) (#16)
by andrewm on Mon Apr 08, 2002 at 01:32:50 AM EST

well, aside from being a much nicer way to go about killing yourself, your parents, and any other descendents of your grandfather and original grandmother :)

It's still the same paradox - if your grandfather and grandmother don't have a specific child who'll be your mother (or father) then you're never born, so can't go back to change things, so that wouldn't happen and you'ld still be born, and still be able to go back, and so on and so forth. The specific technique of stopping yourself being born is just a detail.

Maybe I should point out I wasn't being serious about time travel causing homicidal urges?

And I still don't believe this time machine is going to work, really. (Esp. if it's only useful for travelling into the future - while it's true that the whole time-dilation is accepted, that's not much more helpful than saying we're travelling into the future one second per second - it certainly won't let us find out what's going to happen in the future, anyway. If that actually worked, it would be a neat thing though, and I'm sure it'll excite physicists.)

[ Parent ]

Experiment - Frederic Brown (1958) (none / 0) (#46)
by bob6 on Mon Apr 08, 2002 at 04:48:21 AM EST

short short story.

Cheers.
[ Parent ]
Not a paradox (5.00 / 1) (#52)
by streetlawyer on Mon Apr 08, 2002 at 06:20:33 AM EST

The grandfather paradox isn't an interesting paradox. It only seems paradoxical if you assume a kind of causation which precludes time-travel.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]
Kinds of causation (none / 0) (#63)
by lucius on Mon Apr 08, 2002 at 09:15:35 AM EST

What other kinds of causation are there?

Is there a type of causation in which my grandfather need not have borne my father, and my father need not have had me?

Or can I simply substitute my previous (dead) grandfather for another (living) one after I return from killing him?

Or are there far more exotic kinds around?

[ Parent ]

My theory (none / 0) (#90)
by Cro Magnon on Mon Apr 08, 2002 at 02:57:33 PM EST

My theory, based on years of experience reading/watching Sci-Fi is that it would be impossible to do anything that would cause a personal paradox. If you tried to shoot your grandfather, the gun would jam, or you'd get arrested, or you'd shoot the wrong person. You might, however, be able to make changes that don't cause personal paradoxes, but you may not get what you expect. For example, you go back in time to shoot Hitler. You return to your own time to find that WW2 Germany was led by a radical tyrant named Egbert, who hated Jews and tried to conquer Europe. Maybe the war ended in 1947 instead of 45, but the important events still happened much like before.
Information wants to be beer.
[ Parent ]
If he had a time machine next fall.. (3.42 / 7) (#8)
by Talez on Mon Apr 08, 2002 at 01:13:08 AM EST

Why doesn't he just come back in time and give his present self a time machine and the method to make said time machine so that he can go do that and oh my head hurts from all this relativity stuff...

Si in Googlis non est, ergo non est
Didn't you read the article? (4.00 / 1) (#11)
by sinblox on Mon Apr 08, 2002 at 01:18:13 AM EST

You can only go to the future with this time machine.

[ Parent ]
Ummm.... (3.25 / 4) (#13)
by Talez on Mon Apr 08, 2002 at 01:23:51 AM EST

With even more energy, it's possible, he believes, a second neutron would appear. The second particle would be the first one visiting itself from the future.

Wouldn't that require the neutron to be sent back in time?

Si in Googlis non est, ergo non est
[ Parent ]
No (1.00 / 2) (#12)
by krogoth on Mon Apr 08, 2002 at 01:23:38 AM EST

You aren't very funny, at least in my opinion.
--
"If you've never removed your pants and climbed into a tree to swear drunkenly at stuck-up rich kids, I highly recommend it."
:wq
[ Parent ]
he could, but (4.50 / 4) (#17)
by dr k on Mon Apr 08, 2002 at 01:37:40 AM EST

first he needs to figure out a way to shrink himself down to the size of a neutron so he can send himself back in time. Not only that, he'll need to design a machine that can unshink him from neutron size back to normal, and he'll need to shrink that down and take it with him. So you see, it will take him a few months to figure all that out. And yet he has all the time in the world. Since he hasn't done it yet, that means he probably gets hit by a bus next week.


Destroy all trusted users!
[ Parent ]

worse... (none / 0) (#118)
by Spork on Tue Apr 09, 2002 at 02:07:17 AM EST

He'd have to cool himself to Bose-Einstein Condensate temperatures. :)

Still, if he could send elementary particles back, he could probably send back information. The frequency of neutron sendings could be done in accordance with Morse Code. He might send back stock tips, get rich, and use the money to build his time machine (which he later uses to send back stock tips). See?

[ Parent ]

Well duh. (none / 0) (#55)
by xriso on Mon Apr 08, 2002 at 06:45:50 AM EST

That's what I'm waiting for right now. I hope that I'll get around to sending this time machine to myself soon.

...

SEND IT, ALREADY!

grumble...
--
*** Quits: xriso:#kuro5hin (Forever)
[ Parent ]

Why you won't see humans time travelling (4.00 / 8) (#22)
by Mr. Piccolo on Mon Apr 08, 2002 at 01:53:17 AM EST

Let's see: To not require "ungodly" amounts of energy, this guy is throwing light through a Bose-Einstein condensate, presumably somewhere within which is this neutron that's supposed to go back in time.

Now, to send a human back in time, you're going to need a heck of a large Bose-Einstein condensate to put your human in. So, how is the human going to withstand the temperatures required to create the condensate???

Therefore, I claim it'll take more energy than this guy thinks to send humans back in time, barring some other breakthrough that doesn't require cryogenic freezing of the test subject first.


The BBC would like to apologise for the following comment.


woah woah woah... (4.60 / 5) (#37)
by tenpo on Mon Apr 08, 2002 at 03:11:50 AM EST

Noone said the human had to be ALIVE, right? 1950's newspaper headline: "Dead Guy Drops Out of Rip in Space Time Fabric - NYPD Baffled"

[ Parent ]
Don't be silly. (5.00 / 2) (#62)
by ghjm on Mon Apr 08, 2002 at 09:10:30 AM EST

It's well-known that the insulating properties of a 1985 DeLorean are more than sufficient to withstand the immersion of a flux capacitor into a Bose-Einstein condensate, at least if the condensate is correctly tuned such that light travels at exactly 88 miles per hour.

-Graham

[ Parent ]
Silliness (none / 0) (#142)
by superflex on Wed May 29, 2002 at 10:26:23 AM EST

88 miles per hour being the speed at which light obtains inertia equivalent to kinetic energy of 1.21 jigowatts

[ Parent ]
I'm confused (3.25 / 4) (#23)
by G hoti on Mon Apr 08, 2002 at 01:53:26 AM EST

In both the Boston Globe and the Eureka Alert articles they mention of somthing going back to visit itself wether it be a neutron or whatever. But how can this be?

Is this not creating energy?

And if not where is it comming from?

alex

It is not creating energy (none / 0) (#99)
by BLU ICE on Mon Apr 08, 2002 at 06:45:14 PM EST

You are thinking in Newtonian terms. Time is more like a dimension of space than as the typical static, ongoing process that we think of it as. Moving energy through time is like moving energy or matter from place to place. It doesn't violate thermodynamics.

"Is the quality of this cocaine satisfactory, Mr. Delorean?"
"As good as gold."

-- I am become Troll, destroyer of threads.
It's like an encyclopedia...sorta: Everything2

[ Parent ]

Do we understand the universe REALLY? (4.84 / 13) (#25)
by awgsilyari on Mon Apr 08, 2002 at 02:02:37 AM EST

By all means, post it. Maybe we'll see more measured, intelligent discussion that we saw on that other site... I'm posting the following to try and make people step back and wait a second before they vote -1, just because they "know" this is impossible:

As someone who knows a bit of physics, the idea of time travel is more than a little disturbing to me. The two issues that are quoted most often are the issue of causality (grandfather paradox) and the issue of conservation (if I go to the past, how can mass/energy possibly be conserved?)

But can we really be so confident that we can say, with absolute certainly, that time travel is impossible because of these issues? Do we really understand the universe enough to say "conservation IS law," and "causality IS law?" It certainly SEEMS logical -- but for millions of people on this planet it also SEEMS logical to murder each other. Human perception cannot be the final measure of truth.

A century ago, a man called Planck was having a hell of a time explaining the wavelength distribution of blackbody radiation. In order to explain it, he was forced to postulate that atomic oscillator energy came in small, discrete pieces. Planck's radiation law was born, and the path to quantum physics was opened up. But even Planck himself had a hard time accepting that oscillator energy was quantized. He viewed his triumph as a mathematical "trick," a nasty "fast one" he pulled in order to get the numbers to work out. In short, Planck was deeply DISTURBED by his own discovery.

Although I really believe this man will fail in his efforts, I think he shouldn't be discouraged to try. Quantum mechanics seemed infinitely weird when it first was discovered, but these days (at least, for physicists), quantum physics is not all that strange. It's become natural.

Imagine what would have happened (or rather, NOT happened) if Planck had failed... Or if he had been discouraged by others. Quantized energy? What raving nonsense...

--------
Please direct SPAM to john@neuralnw.com

a little help from another perspective (4.71 / 7) (#36)
by adiffer on Mon Apr 08, 2002 at 03:09:11 AM EST

While I'm inclined to join in the snickers and chuckles when someone claims they will have time travel real soon, I certainly don't mind people talking about it. I look at it as a learning experience for them all.

You did bring up a couple of things I can speak to, though. From your statement that physics is your bag, I expect you will be able to read up on the references.

First off, causality is not the rule. There are perfectly valid physics theories that explain much the same universe that do not rely upon causality to do it. Look at Feynman's dissertation and you will find a variation on electromagnetism that allowed a non-causal universe. The neat thing is that the universe you derive from it is no different (experimentally) from the old electromagnetism that does rely upon causality. For another example, look to QED. The way it is taught to us does have causality. The way Feynman originally pictured it did not. So, does causality really matter? Probably not. It is taught like it does though.

Secondly, coservation is not the rule either. Continuity is. In a three dimensional world with a time parameter, conservation is a measurable thing. In a four dimensional world, conservation only works if things can't be scattered forward and backward along the time axis. One way to think of antimatter is that it is matter going backward. There are a couple of other things to deal with to make the equations work, but the general idea holds. A positron-electron collision that produces a photon could be viewed as a photon collision with the electron that gets scattered backward along the time axis. The numbers work. Conservation works if you are careful to define things correctly to encompass the whole situation. Continuity works just fine since time is just another possible direction. Field theories can be derived from continuous currents just like they can for conserved currents, so there is no real problem at the equation level.
-Dream Big. --Grow Up.
[ Parent ]

I propose a subcategory to MLP (3.16 / 6) (#29)
by Demiurge on Mon Apr 08, 2002 at 02:19:10 AM EST

Mindless Link Plagarism.

Instead of just posting a MLP to the story, you cut-and-paste the contents and submit it as your own insight.

No (3.50 / 2) (#33)
by BLU ICE on Mon Apr 08, 2002 at 02:47:20 AM EST

I did not cut and paste any content. Some is similar. But that is because I am writing about the same thing. Look at this article on /.

"Is the quality of this cocaine satisfactory, Mr. Delorean?"
"As good as gold."

-- I am become Troll, destroyer of threads.
It's like an encyclopedia...sorta: Everything2

[ Parent ]

You should have taken the 5th (2.00 / 5) (#38)
by Demiurge on Mon Apr 08, 2002 at 03:15:14 AM EST

All you did was restate, with inferior grammar and a less sophisticated vocabulary, exactly what the article said. It's MLP. You want to stroke your bloated geek ego? Go start a blog

[ Parent ]
Scientific equivalent of "I'll be right back! (4.66 / 12) (#34)
by demi on Mon Apr 08, 2002 at 02:49:50 AM EST

Generally, it's not a good idea to start a widely publicized media blitz before embarking on a series of experiments whose results are highly uncertain and likely to be misinterpreted. That's a good way to bury whatever real insights that may arise from these experiments underneath a stubborn layer of tarnish. Whether or not this guy is successful, there are now some famous scientists that have risked their public credibility by doubting that his ideas are realistic. That might make publishing the results in a real journal difficult, because the reviewers may fear losing prestige if the data means that they turned out to be wrong.

He will slow down two laser beams to just 40 miles an hour using a supercold Bose-Einstein Condensate... According to Mallett, it wouldn't take engineers long before they will be able to transport a person.

I didn't see any mention of this in the press articles yet, but based on my limited knowledge of BECs, their scaling properties aren't well-understood for sizes beyond a few thousand atoms. Just in terms of the temperatures required to see any of the BEC effects (sub-nano Kelvin), and considering that the deadly cold of outer space is ~2.7 K, the logistical problems (how could you keep it uniformly cold?) and amounts of energy that it would take to reproduce a macro-scale version of the experiment should make any serious investigator a little more circumspect.

At this point, you may be thinking, "But what about the grandfather paradox? If I travelled back in time, wouldn't I be able to kill my grandfather?

The trouble with this pedagogical tool is that people believe that as long as human history isn't changed, the adverse effects of such paradoxes could be headed off (i.e., as long as time travelers observe from their orbiting spacecraft the Earth remains unharmed), when there are serious problems thermodynamics-wise why you should not even be able to transport neutrons backwards in time with any significant persistance. There are known to be temporary violations of energy-conservative relationships in situations like the production of virtual photons (during a reaction, a small energy surplus exists briefly but then vanishes). But if you actually transported a massive object backwards in time permanently, you would have increased the total energy (by matter-energy equivalence) of the universe by one small increment. Perhaps that's where all of the energy goes, I don't know, but that's something I wish sci-fi writers would consider more often.



And what about getting back? (none / 0) (#50)
by zocky on Mon Apr 08, 2002 at 06:10:35 AM EST

If we take the leap of faith and agree that universe splits on every quantum event and if the guy really builds a time machine (which I very seriously doubt) and transports you back in time, then what? How do you get back? The answer is you don't.

There's another thing. Let's say he transports you back in time. But where does that put you in spece? On Earth, where you started? At the point in universe, where Earth is now, but wasn't back at the time to which you are travelling? Point in universe relative to what?

A lot of fundamental questions that need answers before any of this is realistic to discuss.

-1, FUD

---
I mean, if coal can be converted to energy, then couldn't diamonds?
[ Parent ]

getting back should be easy... (none / 0) (#67)
by demi on Mon Apr 08, 2002 at 12:02:35 PM EST

...comparatively. I'm not sure I agree with the universe-splitting hypothesis, especially considering that quantum events often have outcomes that are distributed rather than discrete (taking the two-slit interference pattern for example). What might happen is that the possibilities in the future that result from time-traveling interference are all represented partially, in some weird way. None of this translates well to the macro world that humans experience, of course, but that's quantum mechanics for you.

Moving far into the future is a matter of taking a short trip at near-lightspeed velocities (with respect to your point of origin), and if that's a time machine, it's something that scientists have already demonstrated on the subatomic and macro-scale. If anything, conservative laws should dictate that you must return to the future, and very quickly at that (your trip may only last a few femtoseconds).



[ Parent ]

Discrete? (none / 0) (#75)
by Hatoyama on Mon Apr 08, 2002 at 01:52:21 PM EST

Do we really have to have discrete universe?
Couldn't they (also) be regarded as a continuous distribution, sort of in analogy to the wave/particle dualism of light?

[ Parent ]
the universe (none / 0) (#92)
by demi on Mon Apr 08, 2002 at 03:10:22 PM EST

to be more specific, what I'm not so comfortable with is the application of quantum mechanical formalisms to the entire universe, when generally those effects are only apparent at the subatomic to nanoscale size regime. It makes more sense to me for a time traveller's paradoxical actions to have multiple alternative consequences, each expressed in its own degree, than to split the whole universe into a distribution of separate states. Again, quantum reality doesn't hold up well when people try to apply it to real-world insights. That's why it's so hard to understand and so frequently mis-interpreted.

This is all speculation for entertainment anyway, though, so we shouldn't take it too seriously.



[ Parent ]

You can slow down light in other ways as well. (none / 0) (#101)
by BLU ICE on Mon Apr 08, 2002 at 07:00:26 PM EST

He will slow down two laser beams to just 40 miles an hour using a supercold Bose-Einstein Condensate... According to Mallett, it wouldn't take engineers long before they will be able to transport a person.

I didn't see any mention of this in the press articles yet, but based on my limited knowledge of BECs, their scaling properties aren't well-understood for sizes beyond a few thousand atoms. Just in terms of the temperatures required to see any of the BEC effects (sub-nano Kelvin), and considering that the deadly cold of outer space is ~2.7 K, the logistical problems (how could you keep it uniformly cold?) and amounts of energy that it would take to reproduce a macro-scale version of the experiment should make any serious investigator a little more circumspect.

Light can be slowed down to less than a hundred miles an hour in other non-cryogenic ways. Like in special crystals. It's been done before. BEC just slows it down the most. I do doubt that BEC could be scaled up to a human-size. Anyway, your own body heat would be a disaster for the fragile BEC. Also, you said that they have not made BEC's over a few thousand atoms. That is not true. They have made BEC's over a millimeter accross.

At this point, you may be thinking, "But what about the grandfather paradox? If I travelled back in time, wouldn't I be able to kill my grandfather?

The trouble with this pedagogical tool is that people believe that as long as human history isn't changed, the adverse effects of such paradoxes could be headed off (i.e. , as long as time travelers observe from their orbiting spacecraft the Earth remains unharmed), when there are serious problems thermodynamics-wise why you should not even be able to transport neutrons backwards in time with any significant persistance. There are known to be temporary violations of energy-conservative relationships in situations like the production of virtual photons (during a reaction, a small energy surplus exists briefly but then vanishes). But if you actually transported a massive object backwards in time permanently, you would have increased the total energy (by matter-energy equivalence) of the universe by one small increment. Perhaps that's where all of the energy goes, I don't know, but that's something I wish sci-fi writers would consider more often.

With causality, you absolutely cannot violate it. There are real reasons, not with your grandfather, but with paradoxes in quantum physics, that would prevent time travel without the many-worlds hypothesis. I don't care if your ship is so far away from the earth that you cant see the sun. Time travel doesn't really violate the law of conservation of energy and matter. If I, in 2200, go back to 2100, yes, 2100 is gaining more matter. But 2200 is being starved of my matter and energy. It all evens out.

If you think of time travel more as travel within space dimensions, you can kind of see how it doesn't violate thermodynamics.

"Is the quality of this cocaine satisfactory, Mr. Delorean?"
"As good as gold."

-- I am become Troll, destroyer of threads.
It's like an encyclopedia...sorta: Everything2

[ Parent ]

about BECs and conservation (none / 0) (#106)
by demi on Mon Apr 08, 2002 at 08:58:26 PM EST

Also, you said that they have not made BEC's over a few thousand atoms. That is not true. They have made BEC's over a millimeter accross.

While I don't profess to be an expert in Bose gas dynamics, what I said was that the scaling properties of BECs are not known beyond the few-thousand atom regime, which I think is still true. It's not known how or why the single-atomic properties of BECs will persist at larger length scales. Since CCDs are required to observe the condensates, it's not surprising that sample fields in the millimeter range are used, though, although they are not homogeneous.

If I, in 2200, go back to 2100, yes, 2100 is gaining more matter. But 2200 is being starved of my matter and energy. It all evens out.

What evidence do you have that would support such a far-reaching statement? The only such imbalances that I know of involve photons or leptons, for very short periods in ultracold, ultrahigh vacuum. The only reason a virtual particle can survive is due to allowances by the Heisenberg Uncertainty principle (dE = h-bar/2dt), so for large rest energies the lifetime is next to nothing.

I'm sorry, but I think you have greatly misunderstood this phenomenon. You can learn more about it here.



[ Parent ]

This is such a crock. (3.55 / 9) (#39)
by Stickerboy on Mon Apr 08, 2002 at 03:20:33 AM EST

But Mallet has a better plan. He will slow down two laser beams to just 40 miles an hour using a supercold Bose-Einstein Condensate. Slowing the light increases the light's inertia. Since it has more inertia, it has more energy, and therefore it has a more potent gravitational effect. Using this method, you only need low-power lasers, making time travel a real possibility.

Repeat after me: Photons have zero inertial mass at any velocity. Photons have zero inertial mass at any velocity. Photons have zero inertial mass at any velocity...

The entire reason photons are able to travel at the speed of light is because its inertial mass is zero. If it was nonzero, its mass would grow to infinity as it accelerated to the speed of light.

Christ, this is stuff you can find in any introductory physics textbook. I can't believe people are paying any attention to him.

You miss the fact (4.00 / 1) (#43)
by KWillets on Mon Apr 08, 2002 at 03:57:33 AM EST

That he's discovered a perpetual motion machine.

If the photons can gain mass/energy by travelling into a bose-einstein condensate, then apparently they're gaining energy from nowhere.

[ Parent ]

From the future! Or maybe the past... -nt- (4.00 / 1) (#69)
by mold on Mon Apr 08, 2002 at 12:15:05 PM EST



---
Beware of peanuts! There's a 0.00001% peanut fatality rate in the USA alone! You could be next!
[ Parent ]
Rest mass of a photon. (5.00 / 2) (#59)
by claudius on Mon Apr 08, 2002 at 08:51:22 AM EST

Actually, there is a completely consistent (though now considered somewhat baroque) way to interpret special relativity where one regards photons' nonzero momenta as corresponding to nonzero photon masses. The predictions of this interpretation of SR are identical to those of the more canonical picture of SR (zero photon mass, nonzero energy and momentum), and no experiment has "pinned down" what is ultimately a semantic interpretation of photon mass. When I studied quantum field theory, it seemed to me at the time that the "massive photons" interpretation might be more awkward to work with than the canonical interpretation of SR, but, like you, I may be biased in my thinking having "grown up" with massless photons. (I've heard, but I don't feel like looking up to verify, that Feynman himself preferred thinking of photons as having mass). I've been told by a colleague who does general relativity/cosmology that for him the opposite is true--he prefers thinking of photons as having mass since he can get the same answers for many of his calculations more simply.

This is not to say that the guy isn't a fruitcake and that his proposed experiment isn't wrongheaded in some significant way (such as possibly reading too much into the BEC-analogue-of-a-black-hole rhetoric), but rather that your objections to what he's proposing aren't necessarily as patently obvious as you seem to believe. For pedagogical reasons, physics textbooks tend to be written with only one interpretation of SR, and most introductory physics texts published in the last two decades adopt the massless photon picture.

If you are interested, I can dig up some references on this subject. (I used to keep them handy since this debate would come up pretty much every time a time travel or black hole article got posted to slashdot.org).

[ Parent ]

Introductory physics (4.75 / 4) (#74)
by awgsilyari on Mon Apr 08, 2002 at 01:41:47 PM EST

Christ, this is stuff you can find in any introductory physics textbook. I can't believe people are paying any attention to him.

If you go beyond the introductory books, you'll see that the issue is a little more complicated than that. It depends on how you define "inertial mass." One reasonable definition is "the apparent mass of an object, as judged by how it is influenced by gravitational fields."

If you define it this way, a photon indeed DOES have an inertial mass, which turns out to be in exact proportion to E = hf = mc^2. A photon "falling" in a gravitational field blueshifts precisely according to how its energy WOULD change, if it had a mass fitting the proportion E = hf = mc^2.

And general relativity states that the energy of the photon distorts spacetime EXACTLY AS IF it were a piece of matter, fitting the proportion E = hf = mc^2. Relativity deals with energy density in a uniform way, regardless of whether that energy is mass-energy or light-energy.

Also, I should point at that photons are not "able" to travel at the speed of light. They are FORCED to travel at this speed. I'll leave it as an exercise for the reader, but you can prove it by working from the special relativistic equation, and making note of the fact that photons have zero mass:

E = mc^2/sqrt(1-v^2/c^2).

--------
Please direct SPAM to john@neuralnw.com
[ Parent ]

Forced? (5.00 / 1) (#79)
by guidoreichstadter on Mon Apr 08, 2002 at 02:15:50 PM EST

It is an axiom of special relativity that the speed of light in vacuo is constant as measured in any inertial reference frame. Isn't it then circular to 'derive' this constant from the equations of special relativity?


you are human:
no masters,
no slaves.
[ Parent ]
Not a derivation (none / 0) (#81)
by awgsilyari on Mon Apr 08, 2002 at 02:20:26 PM EST

It isn't a derivation. It is a check of mathematical consistency. For the record, here is the proof:

E = mc^2/sqrt(1-v^2/c^2).

Square both sides and move the denominator on the right hand side to the left:

E^2 (1-v^2/c^2) = m^2c^4.

The photon has zero mass, so the right hand side is now zero:

E^2 (1-v^2/c^2) = 0.

The photon energy is clearly non-zero, so the parenthesized factor must be zero:

1-v^2/c^2 = 0 --> v^2/c^2=1 --> v/c = 1 --> v=c.

I didn't claim this was a derivation of the speed of light. Wouldn't it be shocking if, by following the above steps, a DIFFERENT result was obtained?



--------
Please direct SPAM to john@neuralnw.com
[ Parent ]

why photons are forced? (none / 0) (#139)
by johwsun on Thu Apr 18, 2002 at 08:29:23 AM EST

photons are forced to travel at the speed of light because other particles are stopping them.

is that right?

[ Parent ]
Why couldn't you have given us *this*... (2.57 / 7) (#40)
by elenchos on Mon Apr 08, 2002 at 03:28:29 AM EST

...instead of that navel-gazing you posted over at Adequacy.org? Something tells me this will be too controversial for K5; if so, send it our way. (But spell check it first, could you?)

I'm especially impressed because this comes from a physicist who tells everyone right from the get go "I am not a nut." That's a guy who knows about credibility, that's what that is.

Adequacy.org,

Always a good explanation for everything (3.33 / 3) (#42)
by snappy on Mon Apr 08, 2002 at 03:41:24 AM EST

It seems that no matter what- scientist will always be able to 'justify' their research, and explain the unexplainable with something you really can't argument against.

Like parallel universes. We don't know if they exist, we yet accept it as a valid answer to the paradox.

I would suggest looking at the fundamental questions before jumping into the making of a time machine. Questions like the paradox.

But it's more fun to do 'test and trial' research :).

That's the point of making the dang thing (none / 0) (#115)
by kerinsky on Tue Apr 09, 2002 at 01:29:44 AM EST

There are plenty of things that we don't "know" exist, and yet are willing to accept as valid. Heck most people couldn't even prove to themselves that gravity exists, as opposed to a theory that all objects are simply growing at a constant rate.

We don't even really know what time is, and yet people are willing to say that time travel is impossible because then you could kill your own grandfather. So what? Why should the universe be laid out in a way that prevents you from killing your grandfather before you're born? Why does the universe have to be your babysitter and keep you from, perhaps, annihilating yourself?

Common sense tell us what time is, and that you can't kill your own grandfather. Scientific progress is often the destruction of common sense, but invariably a new version of common sense then comes along and everything is hunkey dorey, and this version of common sense is of course absolutely correct. Unlike those old versions that we were just as sure were correct when they said that the speed of light will appear to slow down if you're moving away from a light source, that heavy objects fall faster, that the earth is the center of creation, and a million others.

In the end those fundamental questions that you mention cannot be accurately answered without an actual working time machine. Which may mean they'll never be accurately answered.

-=-
Aconclusionissimplytheplacewhereyougottiredofthinking.
[ Parent ]
-1 No convincing evidence (3.40 / 5) (#44)
by KWillets on Mon Apr 08, 2002 at 04:10:25 AM EST

I actually dug up the supposed theoretical revolution that this guy published last year. The entire 4-page paper is a calculation of the predicted frame-dragging from photons going around a square "ring". If he had proven that this process does not take place, then that would be news.

Beyond that I can find nothing on the current "breakthrough", or even the supporting claims, beyond some hand-waving articles of the type linked above.



Proof (2.00 / 5) (#48)
by MotorMachineMercenary on Mon Apr 08, 2002 at 06:04:30 AM EST

I have absolute proof that we will never ever ever at any point in our future have a time machine: we have not received any messages nor contact from the future.

Caveat 1: Of course the people from the future could be very adamant about non-interference with us barbarians. But hey, is that really possible; we've all seen the movies!

Caveat 2: The above "proof" could be "proof" for the parallel time-verse theory.

It sounded so much better without the caveats. Oh well..

My bodyweight is muscle and cock MMM
Tenured K5 uberdouchebag Herr mirleid
Meatgazer Frau gr3y


Hang on there... (none / 0) (#64)
by lucius on Mon Apr 08, 2002 at 09:25:14 AM EST

How about a time machine that required both a transmitter and receiver, so that you could only travel back to the point in time at which the original machine was made, but no earlier?

So history would be fine, dandy and linear until, say, 11:15am 9/5/2015, and then it was a homogenous mess forever after that?

[ Parent ]

unless (none / 0) (#66)
by Altus on Mon Apr 08, 2002 at 11:27:55 AM EST

you sent the machine back in time along with someone to get it up and running... but I dont even want to think about that!

"In America, first you get the sugar, then you get the money, then you get the women..." -H. Simpson
[ Parent ]
a fairly common answer to that... (none / 0) (#102)
by rebelcool on Mon Apr 08, 2002 at 07:03:36 PM EST

is one that suggests that time travel is only possible if you have a machine waiting on the other side, a receiver so to speak.

Therefore, you could travel back to as far back as the invention of the machine. Since we do not have such a machine, no future traveler (at least not with a human-made device...) has come by.

COG. Build your own community. Free, easy, powerful. Demo site
[ Parent ]

Just a minute... (3.50 / 2) (#49)
by tombuck on Mon Apr 08, 2002 at 06:10:00 AM EST

Hell, I can't even spell the word, but I do have an "A" for my Physic's GSCE, so anyway...

A few years ago, a new concept for time travel was put forth: If you had two circular beams of immense amounts of light, (light, like matter, can warp space) it would bend space, creating a loop of time. The problem with this, however, is that you would need ungodly amounts of energy. But Mallet has a better plan. He will slow down two laser beams to just 40 miles an hour using a supercold Bose-Einstein Condensate. Slowing the light increases the light's inertia. Since it has more inertia, it has more energy, and therefore it has a more potent gravitational effect. Using this method, you only need low-power lasers, making time travel a real possibility.

Eh? I remember this little thing called "convervation of enery" or suummit like that. OK, so somwhere in the equation you need ungodly amounts of energy. Using low-power lasers surely just transfers the enery source from them to somewhere else. Slowing down the beams screams out at me for this, but still. Am I being typically stupid with this?

--
Give me yer cash!

Hmmm... (none / 0) (#71)
by Ghost Shrew on Mon Apr 08, 2002 at 12:32:47 PM EST

Would the energy perhaps be provided from the coolant? You could argue that firing a gun takes a great amount of energy, and if you were using electromagnetic power, that would be true. But the energy comes from the potential energy in the gunpowder being released in a chemical reaction. Perhaps he plans to basically move the work onto the coolant.
Free tabletop RPG!! Grey Lotus
[ Parent ]

Venture Capital Time! (3.71 / 7) (#51)
by RobotSlave on Mon Apr 08, 2002 at 06:18:20 AM EST

If the "many-worlds" theory pans out, and the device works, then we will have effectively solved all of our resource problems.

Need oil? Just go back in time in a place where there was lots of easily-extracted oil, pump it out, and bring it to the future. Since you took it from a parallel universe, it wouldn't have any impact on the present. This would go a long way toward solving the problems in the middle east.

Moreover, once you were done, you could do it all over again, taking the oil (or gold or diamonds or dinosaur skins) from yet another parallel universe! You could even set up as many parallel extraction operations as you could fit on the site!

The profit potential here is staggering! I'll do the paperwork to set up the business, and start putting together a mission statement. Please reply below if you are interested in investing!

One minor problem.. (5.00 / 2) (#54)
by ajduk on Mon Apr 08, 2002 at 06:23:26 AM EST

You can never return to your 'original' universe. Net result: Every universe has all it's oil pumped out and transferred to the next..

[ Parent ]
Need oil? (5.00 / 2) (#58)
by synaesthesia on Mon Apr 08, 2002 at 07:19:01 AM EST

I don't think so, if you've got enough energy to transport it through time.

Sausages or cheese?
[ Parent ]
Unlimited oil! (4.00 / 1) (#76)
by fluffy grue on Mon Apr 08, 2002 at 02:10:20 PM EST

Let's extract it from snakes, too!
--
"...but who knows, perhaps [stories about] technology and hardware will come to be [unpopular]." -- rusty the p
[
Parent ]
Doesn't make sense (none / 0) (#141)
by awgsilyari on Sun Apr 21, 2002 at 04:43:17 PM EST

If you can go backward in time, surely you can go forward also. Just go forward to a time where they've figured out fusion technology (or something even better), learn all about it, then come back and implement it.

I realize you are joking, but if I was really an investor I wouldn't invest in such a scheme. It's too backward-looking.

Then again, if I really could go forward to a time when things are "better," I really doubt I'd want to come back.

--------
Please direct SPAM to john@neuralnw.com
[ Parent ]

But Wait: (4.00 / 2) (#56)
by theshunt on Mon Apr 08, 2002 at 06:48:52 AM EST

"Time travel could cause a rupture in the space-time continuum!"
-Dr. Emmett Brown

The problem with wormholes as time travel (3.50 / 2) (#57)
by xriso on Mon Apr 08, 2002 at 07:01:21 AM EST

Not only do they require massive amounts of energy (think black-hole), but one would require a wormhole at both ends (you would enter a wormhole and leave through a wormhole). The chance of two wormholes connecting is incredibly small, and the chance that they stay connected for a significant time is also incredibly small. To improve your chances, you would keep the wormholes close together in time and space, but then you could not travel very far. And even if you somehow managed to get them to connect and stay open longer than a microsecond, then you would have to make them large enough to pass a particle through. Oh yeah, and there's also the problem that any large object, such as a human, would be ripped apart due to the huge difference in gravitational pull between their head and feet.
--
*** Quits: xriso:#kuro5hin (Forever)
Another solution to parrallel-universe woes... (3.33 / 3) (#60)
by fortytwo on Mon Apr 08, 2002 at 08:55:46 AM EST

Simply eliminate any possibility of paradox. Say 'I don't care if the alretnetive has a probability of 0.001%, do it anyway'. Therefore, if you try to kill your grandfather, you'll be stopped by some very improbable events... Wait, can we build an Infinite Improbability Drive from this? ;)

Forward (none / 0) (#70)
by Ghost Shrew on Mon Apr 08, 2002 at 12:29:05 PM EST

You've been reading Timemaster, haven't you? Or one of Forward's other books... though he may not be the only author espousing this theory.

Personally, I think it sounds about right.


Free tabletop RPG!! Grey Lotus
[ Parent ]

No, actually... (none / 0) (#135)
by fortytwo on Thu Apr 11, 2002 at 01:01:15 PM EST

Never head of the series.

[ Parent ]
Now if only... (none / 0) (#136)
by fortytwo on Thu Apr 11, 2002 at 01:02:08 PM EST

...I could go back in time to when I posted this, only equipped with a spell checker. But, It'd probably crash.

[ Parent ]
Grandfather Paradox (2.50 / 2) (#61)
by hardburn on Mon Apr 08, 2002 at 09:09:58 AM EST

"But what about the grandfather paradox? If I travelled back in time, wouldn't I be able to kill my grandfather? Wouldn't that make my own birth impossible, which would at the same time, prevent me from killing my grandfather in the first place?" Well, there is a simple answer for that and all other time-travel causuality problems: Parallel universes.

I think this just changes the question from one of science to one of morality. What right do we have to screw with other people's realities?


----
while($story = K5::Story->new()) { $story->vote(-1) if($story->section() == $POLITICS); }


Another subject (1.00 / 1) (#73)
by bobpence on Mon Apr 08, 2002 at 01:31:54 PM EST

Could you clone yourself, then take the clone back in time so that it ages along with you, effectively giving you an undocumented twin for most of your life that maybe handles gym class on your behalf?
"Interesting. No wait, the other thing: tedious." - Bender
[ Parent ]
What right do I have to screw with this one? (none / 0) (#111)
by kerinsky on Tue Apr 09, 2002 at 01:01:21 AM EST

What right do I have to screw with the reality I'm in now?. If just being here gives me that right, then I'm gonna go exercise it in a cool reality once I get my Einstein Rosencrantz tunnel thingy working. Plus I could kill myself, and that'd be spiffy.

-=-
Aconclusionissimplytheplacewhereyougottiredofthinking.
[ Parent ]
Time travel (3.60 / 5) (#65)
by Hopfrog on Mon Apr 08, 2002 at 10:42:56 AM EST

When I was a bit younger, I used to think about time travel.

First of all, you cannot create or destroy matter. You need energy to do this, and energy is created by the destruction of matter. So if you move any object from the future into the past, there can only be one instance of that object. For that object to actually move into the past, and exist beside it's former self, you will need to generate enough energy to fill the void it leaves. Understand?

Again. The sum of matter and energy in the universe are constant. If energy goes up, matter goes down. If matter reduces, energy increases. Time is just the movement. If there was absolutely no movement, there would be no time.

Now imagine the entire universe consisted of an equal amount of energy and matter. 1 grain of matter, and so much energy, that it could codense (you know what I mean), into the same grain of matter.

This grain cannnot move, because there is nothing to measure its movement against. So there is no time for this grain. So let us introduce a second grain. The 2nd grain is our fixed position. The 1st grain can move relative to the second. Immediately you bring in the 2nd grain, you have time. You have change in position, and this is time.

So to build a time machine in our universe, you have got to undo every movement in the universe. This will make time go backwards, but your timemachine will also become "uninvented", and your time travel will stop.

The obvious solution is to keep your time machine from being affected by the movement. So you shield it. So in effect, you make all particles do the exact thing that they did, but in a reverse order, yet keep the particles that make up your time machine from doing the same thing.

You see what will happen. You will create a matter void, and matter will immediately collapse into the space you are forcing empty.

By moving back in time, you will change time, and you cannot stop this.

Parallel universes are nonsense. They aren't proven, and there is not even strong theoritical evidence supporting their existence. What will really happen is that you can kill your grandfather without problems. You can move back in time, but it is actually a move forward in time. The universe will perceive it as being a move back, but if you isolate your time machine, then your time machine becomes your point of reference. Everything is relative. So, time, according to your time machine looks this way - your grandfather is born, your father is born, you are born, you build timemachine, you change the universe so that it resembles a previous time, in the resemblance, you kill your grandfather, you modify it again, so that life continues as normal, and you arrive at normal time. What do you see? There is a new you, there is no time machine.

If we use your grandfather as reference, it looks this way: Grandpapa gets born, grandfather is killed by someone who comes in a timemachine. End.

Hop.

I didn't read your whole post, but ... (4.00 / 2) (#80)
by Kalani on Mon Apr 08, 2002 at 02:18:00 PM EST

... when I saw this statement at the start of it I was unwilling to continue reading your argument:

First of all, you cannot create or destroy matter. You need energy to do this, and energy is created by the destruction of matter.

I think that you need to work on how you phrase things (I read down through the rest of your comment and it seems that you don't actually believe this statement but it's important to point out anyway). Energy is not created by the destruction of matter, since you can't destroy matter (as you've said). Energy is equivalent to matter, and both can be transformed into each other. So the statement should read, "neither matter nor energy can be created or destroyed, but either can be converted into the other."

-----
"I [think] that ultimately physics will not require a mathematical statement; in the end the machinery will be revealed and the laws will turn out to be simple, like the checker board."
--Richard Feynman
[ Parent ]
Stop nitpicking. You know what I meant [n/p] (none / 0) (#120)
by Hopfrog on Tue Apr 09, 2002 at 02:44:49 AM EST



[ Parent ]
It's not nitpicking (none / 0) (#127)
by Kalani on Tue Apr 09, 2002 at 09:01:52 AM EST

It's an important point, and if your message comes across as confused it's less likely to be taken seriously (or really considered). I only meant my post to be taken as constructive criticism.

-----
"I [think] that ultimately physics will not require a mathematical statement; in the end the machinery will be revealed and the laws will turn out to be simple, like the checker board."
--Richard Feynman
[ Parent ]
Why would you think that? (none / 0) (#114)
by Spork on Tue Apr 09, 2002 at 01:25:30 AM EST

By moving back in time, you will change time, and you cannot stop this.

Why would you think that? I honestly don't understand the picture you're working with, though many people seem to have it. Do you think that if I send a buddy to kill the infant Hitler in 1900, as he vanishes with the time machine, the sentence in the history books on my shelves will suddenly change? I think that's crazy. Whenever we send someone to the past, whatever meddlings he is responsible for are done. There is nothing that is "up in the air" anymore. If you really succeed in travelling to the past, you cannot screw anything up, because everything you did after you arrived has already happened before you left. For all we know, our history may be full of time travelers. A time traveler may have killed JFK, or whatever. However, we know that no time traveler will ever go back and save JFK. How do we know that? We just look at history. If somebody succeeded in saving him by jumping in front of the bullet, we would have already known about it, because it would have been in 1963, and I'm sure someone would have taken a picture.

Philosophers debate whether a time traveler can kill his grandfather. I tend to think he can, though he won't. There is a lot of things we can do, but won't. However, even if you prefer the account that he can't do it, I don't see the big deal.

Think about this: suppose this guy Mallet gets done with the neutron time machine, sets it to "10 minutes into the past" and holds a press conference while the thing is still off, describing the experiment he's about to do. Then, during his press conference, a neutron appears from the future. Does he have any choice about turning on the machine 10 minutes later? (The appearance of the neutron, there and then, made it necessary for him to send it into the past, 10 minutes later.)

[ Parent ]

Old argument (none / 0) (#116)
by Hopfrog on Tue Apr 09, 2002 at 01:38:42 AM EST

This is one of the stock arguments. You don undrstand what I wrote

[ Parent ]
umm... (none / 0) (#117)
by Spork on Tue Apr 09, 2002 at 01:53:31 AM EST

I was trying to say that I suspect you don't. Nobody who works in this field has any temptation to take your view (common enough among laymen) seriously.

[ Parent ]
Explanation (none / 0) (#119)
by Hopfrog on Tue Apr 09, 2002 at 02:43:47 AM EST

I am saying that you CANNOT change the past. I say that a move back in time, is a move into the future, so if you change that, you are doing it in a "parallel universe" if you wish to call it that.

And what I meant by the quoted sentence is the energy void that you will cause immediately you start moving. This has nothing to do with your grandfather, and much to do with your surviving the trip. How do you explain the energy and matter youwill be carrying back with you? You can't destroy or create it.

It is your view that is common among laymen. You work from the theoretical premise that you can move back in time like you can move back in space, which is entirely impossible. Your theory only holds water in a case were you could do so, and since you cannot, it is not to be considered seriously apart from by writers of fiction.

Hop.

[ Parent ]

Fire is not an invention (4.50 / 4) (#68)
by inerte on Mon Apr 08, 2002 at 12:07:48 PM EST

Wheel was an invention. Fire was a discovery.

Really, think about the difference. There was fire before it was controlled/created. And that's the point, you can't invent something that was already there.

Just a quickie note ;-)

About parallel universes, that would make things really strange. I guess I can accept that there are parallel realities, otherwise we would know people from the future, but what also might be is that there is no future. What never happened doesn't exist.

I don't know. If time travel (to the past or to the future) is possible, but what travelled is sent to a parallel reality, then there isn't much usefulness on this.

Unless those who travel can communicate with us, or if you travel so many times that maybe you will hit a previous reality. But that would make the number of other realities almost infinite, if not really infinite.

But if we could communicate, imagine what a good thing it would be. Someone would travel, improve the past of this reality, leave a note about how to construct the time machine and how to communicate, and these notes would get back to us, along with more technological advances.

But what's a dream is a dream, at least for now ;-)

--
Bodily exercise, when compulsory, does no harm to the body; but knowledge which is acquired under compulsion obtains no hold on the mind.
Plato

Some things (3.50 / 4) (#72)
by trhurler on Mon Apr 08, 2002 at 01:16:05 PM EST

First of all, the many worlds hypothesis is a poor interpretation of a theory nobody really knows the meaning of. It is not a solution to the seeming paradoxes of time travel, unless it is shown that it is actually correct. An experiment which could "prove" this hypothesis is well beyond our present theory, much less our present technology.

Second, we have no idea what will happen if we manage to travel backwards in time and change something. The only way we'll find out is if we manage do to it. The QM models at our disposal don't have an answer to this problem, which ought to be a sign to someone that a grand unified theory has to include more than just QM and gravitation, but since pretty much every physicist after Einstein was just a mathematician with a hard on for lasers and big explosions, it is little surprise nobody noteworthy has noticed.

Third, there is no general consensus as to what "bending time" means. It is not at all clear that a "time loop" mathematically speaking is in fact a "time loop" in the sense that people are imagining. Even if it is, there is no currently known reason to believe that this would permit anything to travel in any direction but backwards, and one way trips are considerably less useful than you might at first think.

Fourth, visiting a different time would not be like visiting a different country for several reasons:
  • We don't know how "paradoxes" would resolve. Maybe this is just flat out a bad idea.
  • We don't know whether you could ever come home. It is doubtful.
  • We have no reason at present to believe that the forces needed to warp spacetime in this way would even allow life to go on within; human beings are fragile things.
  • Most periods in history are less educated and less tolerant than previous times. If this pattern holds, which seems reasonable, then odds are you'd have to do some pretty serious homework just to avoid being imprisoned or killed while on your little "vacation."
  • Due to the massive increase in the number of places this would give to hide both people and things and the other opportunities it creates for criminal activity, time travel would almost certainly be regulated to the point of uselessness by your average person.
There are certainly more problems, but these were what I thought of without having to slow down from my regular typing speed. I suspect that at best, even if it works, time travel will be a curiosity with such limitations and dangers that for your average person, it will be less "real" than space travel.

--
'God dammit, your posts make me hard.' --LilDebbie

Interesting comments (none / 0) (#77)
by Kalani on Mon Apr 08, 2002 at 02:11:16 PM EST

The QM models at our disposal don't have an answer to this problem, which ought to be a sign to someone that a grand unified theory has to include more than just QM and gravitation, but since pretty much every physicist after Einstein was just a mathematician with a hard on for lasers and big explosions, it is little surprise nobody noteworthy has noticed.

I think that, given the properties of gravity predicted by General Relativity, the unification of QM with GR would actually cover what you mention (specifically the types of transformations mass performs on spacetime). Even then, GR only permits time travel for certain shapes of space.

As for your comment about every physicist since Einstein being "just a mathematician," I assume that you're joking. If you aren't joking: What about Richard Feynman? His contribution to QED goes far beyond mathematics ... and in fact the method of describing quantum-scale transactions that he developed (Feynman diagrams) is a perfect example of his abilities beyond mere mathematics. Then of course there are the experimental physicists, who are really more engineer than mathematician these days.

I agree with the rest of your comment though.

-----
"I [think] that ultimately physics will not require a mathematical statement; in the end the machinery will be revealed and the laws will turn out to be simple, like the checker board."
--Richard Feynman
[ Parent ]
Ah (none / 0) (#85)
by trhurler on Mon Apr 08, 2002 at 02:33:31 PM EST

You didn't take the qualifier seriously. When I said "almost every" physicist, I did not mean "every physicist." And you're right, the experimental guys are basically engineers. I have no problem with specialization of labor, but the fact remains that there have been damn few real theorists of any quality at all, and a whole lot of math people with delusions of grandeur. Obviously modern physics requires a lot of math, but the idea that it is nothing BUT math has all but destroyed real progress in physics today. Mention anything that doesn't seem logical or would require a different model(even trivially different,) and everyone's up in arms about how "this violates that." I'm all for finding the legitimate flaws in bad ideas, but modern physics is a vehicle for preventing progress by denying funds, credibility, and careers to anyone who isn't a dogmatic apologist for the status quo.

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
Sorry I haven't had much sleep (none / 0) (#87)
by Kalani on Mon Apr 08, 2002 at 02:44:24 PM EST

I do agree that, especially in physics, it's silly to spend so much time bickering over whether or not your idea goes against the laws of physics. It's nature, not the "laws of physics," that determines the validity of a theory. Of course, if your new theory, which doesn't seem logical, actually predicts something that doesn't happen then of course it's your theory that's wrong. As for logic and intuition (the latter is what most people mean when they mention the former), I agree that any new theories are going to have to be pretty out there (since the behavior of tiny particles is pretty out there). Really though, Feynman's and Dirac's work are exactly what you describe. There has been great work in theoretical physics as recently as the 1960s, it's just incredibly slow.

It's good to see people with a real sense of what Scientific Method means.

-----
"I [think] that ultimately physics will not require a mathematical statement; in the end the machinery will be revealed and the laws will turn out to be simple, like the checker board."
--Richard Feynman
[ Parent ]
modern physics hurdles (5.00 / 1) (#121)
by adiffer on Tue Apr 09, 2002 at 02:52:06 AM EST

Funding clots? Not much has changed, really. The physics community has always been like that. The revolutionaries are rarely needed when the evolutionaries are sufficient to continue advancement of the knowledge frontier. The revolutionaries are usually labelled as quacks until they are needed. The problem is that even in a time of need (which is rare) most of them really are quacks. Good luck sorting us all out.

I've seen sociological models for how science really works. The models are definitely not flattering. We are strongly hypocritical much of the time and downright apathetic regarding each others research at other times.

Don't worry too much though. Our quacks don't know when to give up. They get replaced rapidly enough to account for aging too.
-Dream Big. --Grow Up.
[ Parent ]

"any direction but backwards" (none / 0) (#82)
by kubalaa on Mon Apr 08, 2002 at 02:24:28 PM EST

Well, backwards is the only direction we care about; most things seem to go forwards in time naturally. That is to say, it's not one-way. Funny thought though, if many-worlds is true then there must be some universe where the experiment fails. The mind boggles.

[ Parent ]
No (none / 0) (#83)
by trhurler on Mon Apr 08, 2002 at 02:27:29 PM EST

First of all, many worlds does not hypothesize that the rules are different - just that history is a bit different in each one.

Second, things move forward at a constant rate; if you go back ten years, you cannot come forward to the "present" you left again. That's my point.

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
Huh? (none / 0) (#86)
by Kalani on Mon Apr 08, 2002 at 02:37:43 PM EST

Second, things move forward at a constant rate; if you go back ten years, you cannot come forward to the "present" you left again.

Do you mean that time moves forward at a constant rate locally? GR (and the experiments that have confirmed this) shows that time is relative to the observer (and that it varies under gravitational/acceleration influence).

Also, there's the interpretation in QED that antiparticles are the same thing as particles that travel backward in time, but that's more of a philosophical issue than one that's relevant to practical applications of time travel (if we turn into antiparticles to go backward in time we'll obviously die).

-----
"I [think] that ultimately physics will not require a mathematical statement; in the end the machinery will be revealed and the laws will turn out to be simple, like the checker board."
--Richard Feynman
[ Parent ]
PS (none / 0) (#89)
by Kalani on Mon Apr 08, 2002 at 02:47:24 PM EST

GR (and the experiments that have confirmed this) shows that time is relative to the observer (and that it varies under gravitational/acceleration influence).

It also varies between observers in inertial reference frames with a constant velocity between them, of course.

-----
"I [think] that ultimately physics will not require a mathematical statement; in the end the machinery will be revealed and the laws will turn out to be simple, like the checker board."
--Richard Feynman
[ Parent ]
Yes, but... (4.00 / 1) (#91)
by trhurler on Mon Apr 08, 2002 at 03:06:25 PM EST

Unless you can propose a way to accelerate human beings to near the speed of light without harm, this will not allow a person who travels back in time to move forward again. I personally question whether it is even possible in principle to use time dilation as a means of time travel for living organisms, but even if you don't, doing so is a lot harder than what is being proposed as a means of travelling backwards.

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
Of course you can use time dilation (none / 0) (#98)
by BLU ICE on Mon Apr 08, 2002 at 06:39:56 PM EST

I personally question whether it is even possible in principle to use time dilation as a means of time travel for living organisms, but even if you don't, doing so is a lot harder than what is being proposed as a means of travelling backwards.

And why not? It is perfectly possible to use time dilation as travel for organisms. It is currently out of our technological grasp to build a proxiluminal spaceship, but we have concepts on how to do it. I bet we will have manned intersteller craft in which you do see time dilation within 200 years.

"Is the quality of this cocaine satisfactory, Mr. Delorean?"
"As good as gold."

-- I am become Troll, destroyer of threads.
It's like an encyclopedia...sorta: Everything2

[ Parent ]

Two things (none / 0) (#100)
by trhurler on Mon Apr 08, 2002 at 06:52:15 PM EST

First of all, look at the speeds involved, and look at the maximal G forces a person can withstand. How long will it take to accelerate and decelerate? A long, long time.

Second, if a spaceship travelling at .5c carrying what can only be described as fragile life support systems hits a pebble, just what do you think is liable to happen? The energy involved would be ludicrous; more of the ship would vaporize than be harmed by the actual impact - far more.

Just building a big beefy engine isn't enough.

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
It's still possible (none / 0) (#104)
by BLU ICE on Mon Apr 08, 2002 at 07:25:30 PM EST

The chances of hitting pebble in intersteller space are quite slim. If you were doing the regular slow accel-decell as in a fusion or laser sail rocket, it would take several years to accelerate. A long time. But not that bad.

"Is the quality of this cocaine satisfactory, Mr. Delorean?"
"As good as gold."

-- I am become Troll, destroyer of threads.
It's like an encyclopedia...sorta: Everything2

[ Parent ]

Yes, but... (none / 0) (#105)
by trhurler on Mon Apr 08, 2002 at 08:15:52 PM EST

At speeds low enough to be survivable in the solar system(where pebbles and so on are common enough that people would die if precautions were not taken,) it will take you several more years to exit and reenter the solar system, in addition to your several years of acceleration for time dilation. I for one would not spend 10 or 15 years of my life just to get a "vacation" in some previous time period, even if there were options available for this that I haven't lived through anyway. In addition, if it takes that long, then you have to have supplies for that long. We're now talking a very large spaceship, which will greatly increase the energy inputs required.

You need a better way.

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
tackle them one at a time (none / 0) (#122)
by adiffer on Tue Apr 09, 2002 at 03:06:03 AM EST

Each of your arguments against near-light speed travel can be attacked one at a time. Obviously, we aren't going to go build one capable of protecting a human any time soon. We have a hard enough time getting humans into space, let alone getting them out of the solar system.

First off, you can leave and enter the solar system along the ecliptic poles. You avoid most of the left over trash that way.
Second, the occupants of the vehicle can be protected from high energy radiation and particulates with shielding. Yes, it takes a lot of mass, but you will have to be able to handle that kind of mass anyway if you are keeping people alive out there.
Third, the mass and the technologies for making near-light speed ships are out there right now. The engineering would have to be tested and improved a lot before I'd risk my behind on anything, but it is conceivable with today's ideas.

I would bet if you actually calculate the energies involved, it will be much easier to send a human occupant to near-light speed safely than it would be to warp space-time enough to get a temporal loop. The gravitational coupling constant is just too damn weak.
-Dream Big. --Grow Up.
[ Parent ]

Not really (5.00 / 1) (#109)
by awgsilyari on Tue Apr 09, 2002 at 12:39:40 AM EST

First of all, look at the speeds involved, and look at the maximal G forces a person can withstand. How long will it take to accelerate and decelerate? A long, long time.

Not really. The speed of light is 300 million meters per second. Assume that a craft accelerates at the steady rate of 1 g (9.8 m/s^2). This craft will reach a speed of 0.5c in: 1.5e8/9.8 = 3e7 seconds = 177 days.

Also, I can arbitrarily choose a reference frame in which the craft is ALREADY moving at 0.5c.

It's all relative, friend.

--------
Please direct SPAM to john@neuralnw.com
[ Parent ]

arbitrary reference frame (none / 0) (#124)
by kubalaa on Tue Apr 09, 2002 at 04:01:59 AM EST

Yes, but the FOR you probably care about is that of the Earth. And in order for time dilation to take place you'll have to eventually return to the original reference frame. That is, if you send a spaceship away from the earth, and then accellerate the earth to catch up to the spaceship, then the people on earth will be the ones who aged less. Am I right?

[ Parent ]
Complicated (none / 0) (#128)
by awgsilyari on Tue Apr 09, 2002 at 10:14:48 AM EST

Leaving aside the problem of how to accelerate the earth...

You chose a complicated scenario :) There are five stages in your scenario:

1) Craft accelerating
2) Craft moving at constant (high) velocity
3) Earth accelerating
4) Earth decelerating and catching up to craft
5) Earth moving at constant (high) velocity (but at rest WRT the craft)

Step 4 is necessary, otherwise the Earth would never catch up to the spacecraft -- in order to catch up, it must move FASTER than the craft.

It gives me a headache thinking about working this problem. :) I suspect that the people on Earth and on the craft end up being pretty near the same age by the end of it, depending on how much the Earth "overaccelerates" to catch up to the craft.



--------
Please direct SPAM to john@neuralnw.com
[ Parent ]

No, you cannot (none / 0) (#129)
by trhurler on Tue Apr 09, 2002 at 12:28:16 PM EST

First of all, the craft is unlikely to accelerate steadily at 1g for 177 days using any technology known today, unless it is humongous beyond words and consists almost entirely of a fuel tank.

Second, you cannot arbitrarily choose a frame of reference if your purpose is time dilation, because the time in question is the Earth frame; you MUST choose the Earth frame, and you must start in the Earth frame, and that means a whole lot of acceleration from and then back to the velocity of that frame. I don't know whether you didn't understand what we were talking about or don't understand relativity, but for our purposes, this is mandatory.

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
Missed that.. (none / 0) (#131)
by awgsilyari on Tue Apr 09, 2002 at 09:43:35 PM EST

I misunderstood what you were saying. I thought you were talking about the improbability of getting a craft to move at 0.5c, when there already exist an infinite number of reference frames where the craft is already moving at this velocity.

Also, I was responding to your claim that it would take an enormously long amount of time, even at large accelerations, to reach 0.5c. You were saying that the necessary accelerations would kill humans, when in actuality a modest acceleration of 9.8 m/s^2 would reach 0.5c in 177 days. By "modest" I mean modest by human physiological standards, not technological standards.

On top of that, accelerating at 1g would have the nice side effect of providing gravity for the occupants of the craft. Sure, it isn't realistic, but we ARE talking about time travel here...

--------
Please direct SPAM to john@neuralnw.com
[ Parent ]

Agreed (5.00 / 1) (#133)
by trhurler on Wed Apr 10, 2002 at 12:02:21 PM EST

However, my whole point when arguing with the guy was to show that it is an almost unbelievable engineering feat that would both accelerate slow enough not to kill humans and accelerate long enough to get them to a useful velocity for time dilation. Add in the time to reach a place where you can safely travel at such velocities, and the whole thing is pretty damned silly without significant technological advances that we do not have sitting "just around the corner."

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
rules are different (none / 0) (#123)
by kubalaa on Tue Apr 09, 2002 at 03:57:13 AM EST

Forgive me, but I fail to see how history can be different without the rules being different. Unless the universe is non-deterministic, which is to say no rules at all...

As already pointed out, relativity allows you to move forward through time arbitrarily slowly or quickly. Even if impractically.

[ Parent ]

Several things (none / 0) (#130)
by trhurler on Tue Apr 09, 2002 at 12:33:35 PM EST

First, if the rules are the same, but the starting configuration is different, the results will be different, even in completely deterministic universes.

Second, there is as yet no proof that the universe is deterministic.

Third, "non-deterministic" does not imply that there are no rules at all. Your imagination is failing you. What if there are rules for some things, and not others? What if we have a completely rule based universe, but some things are probabilities and cannot be considered otherwise, and can thus happen differently in different universes? Determinism is not as rigid as determinists like to think, or as rigid as their opponents fear.

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
two things (5.00 / 2) (#93)
by demi on Mon Apr 08, 2002 at 03:31:42 PM EST

The QM models at our disposal don't have an answer to this problem, which ought to be a sign to someone that a grand unified theory has to include more than just QM and gravitation, but since pretty much every physicist after Einstein was just a mathematician with a hard on for lasers and big explosions, it is little surprise nobody noteworthy has noticed.

Actually, though quantum mechanics may be not the best model upon which to base predictions of a human experiencing time travel, relativistic effects in particles have been observed for decades. It requires thinking about events happening along a time axis, upon which particle scattering reactions may be co-incident, but there are many examples of forward time scattering (by particles moving near the speed of light) and possibly in the reverse direction too (manifested as antimatter). These temporal effects have not yet been investigated systematically, and the experiments wherein the effects were observed are not optimized to do so, which is why it's good to be skeptical at this point.

Due to the massive increase in the number of places this would give to hide both people and things and the other opportunities it creates for criminal activity, time travel would almost certainly be regulated to the point of uselessness by your average person.

It's always hilarious how the first things people think about, when confronted with a new or disruptive technology, are the various ways in which it can be used to kill, steal, or commit Orwellian crimes of domination. People will always be ragged and vicious animals, no matter what toys we have to play with.



[ Parent ]

We cannot prove the many worlds theory. but (3.50 / 2) (#96)
by BLU ICE on Mon Apr 08, 2002 at 06:14:14 PM EST

We cannot prove a lot of theories: Big Bang, formation of earth, end of the universe, many, many things.

In fact, no theories or laws are proven. That is one of the main principles of the scientific method. There are no facts. A theory or law can always be proven otherwise.

Most periods in history are less educated and less tolerant than previous times. If this pattern holds, which seems reasonable, then odds are you'd have to do some pretty serious homework just to avoid being imprisoned or killed while on your little "vacation."

Didn't you read the article? You cannot go farther back then when the machine was created.

The many worlds hypothesis has many followers. While we can never prove it's authenticity, it explains many things that other theories don't. For example, most physicists think that time travel is at least theoretically possible. If it is theoretically possible, than that means it is not ruled out by the laws of physics. So in order for time travel to be theoretically possible, you would need somthing to prevent you from violating causality. The many-worlds hypothesis is the only real accepted way to do that. The many worlds theory may not be true. But it is currently the best explanation.

String theororists 15 years ago went through a lot of ridicule. Many thought their ridiculous wrapped up 11 dimensional space and all that weird stuff was just too far out. Now, string theory is widely accepted. The general consensus now is that matter and energy are all strings ossilating in 11 dimensional space.

"Is the quality of this cocaine satisfactory, Mr. Delorean?"
"As good as gold."

-- I am become Troll, destroyer of threads.
It's like an encyclopedia...sorta: Everything2

[ Parent ]

Heh (5.00 / 1) (#103)
by trhurler on Mon Apr 08, 2002 at 07:04:01 PM EST

In fact, no theories or laws are proven. That is one of the main principles of the scientific method. There are no facts. A theory or law can always be proven otherwise.
I'm glad you paid attention in high school. However, you could not even design an experiment that could possibly falsify this "hypothesis," and that was my point. A nonfalsifiable hypothesis is epistemologically identical to a religious belief.
Didn't you read the article? You cannot go farther back then when the machine was created.
So you think our times are as "liberal and enlightened" as we're ever going to get? The taboos of today may well be the accepted norms of tomorrow, and things we don't think twice about today may be shunned and even illegal in the future.
The many worlds hypothesis has many followers. While we can never prove it's authenticity, it explains many things that other theories don't.
The same can be said of half a dozen different explanations, at least one or two of which require less fanciful imagination than this one. Occam's razor is unkind to the many worlds hypothesis.
So in order for time travel to be theoretically possible, you would need somthing to prevent you from violating causality.
This is not true. It is entirely possible that you might go back in time, kill your grandfather, and immediately cease to exist, with all of future events rewritten to accomodate your act. We simply DO NOT KNOW what will happen. You prefer to believe it will all be ok, because you are a time travel advocate, but that is not science - that's belief for the sake of emotion.
String theororists 15 years ago went through a lot of ridicule. Many thought their ridiculous wrapped up 11 dimensional space and all that weird stuff was just too far out. Now, string theory is widely accepted. The general consensus now is that matter and energy are all strings ossilating in 11 dimensional space.
This isn't even close to true. Have you been basing your whole worldview on the Discovery Channel or something like that? I doubt a majority of physicists "accept" string theory at all, and of those who think it is promising, not one can provide a complete enough theory to even begin to make it testable in any useful sense. To call string theory "tentative and highly questionable" would be an overstatement of enormous proportion.

By the way, rating people down simply because you disagree with them is pretty lame. If you're going to do that, why not just go and post on Slashdot, where that's normal and accepted behavior?

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
On the "laws of physics" (4.66 / 9) (#78)
by awgsilyari on Mon Apr 08, 2002 at 02:12:07 PM EST

People here keep quoting the "laws of physics" and using that as evidence that time travel is impossible. I have great faith in the laws of physics, but I think it pays to remember what exactly is meant by "law."

A law of physics is a principle, usually embodied in an equation, which is based on empirical observation, and which applies to all known physical phenomena. A law cannot be "proven," and this unprovability is actually a part of the definition of a "law."

Take, for example, Newton's force law: F = ma. Newton and many others before him noticed that the acceleration of a body ALWAYS seems to be proportional to the force applied, with the constant of proportionality being the mass of the object. There is no way to "prove" Newton's law.

Guess what? Newton was WRONG. F = ma is a damned good approximation of reality, but there is an even better approximation:

-h^2/2m d^2P/dx^2 + VP = ih dP/dt.

This is the nonrelativistic Schroedinger equation (in one dimension -- the three dimensional form is very similar), and this applies in ALL situations where particle velocities are much much less than the speed of light. Like any other law, Schroedinger's equation cannot be "proved." It is based on empirical observation (and some truly ingenious reasoning on the part of Schroedinger).

There is another law, which is the law of mass-energy conservation. It is based on empirical observation. We know of no instance in which mass-energy is not conserved. But you cannot PROVE this law.

We shouldn't be so arrogant as to think that the universe MUST obey our conception of it. Perfect conservation might turn out to be a damned good approximation of reality, not a perfect descriptor.

I see people being incredulous about this man's efforts. Try turning that incredulity around, and try doubting EVERYTHING instead of just what you are uncomfortable with. That's how science gets accomplished.

--------
Please direct SPAM to john@neuralnw.com

Exactly (5.00 / 2) (#84)
by Kalani on Mon Apr 08, 2002 at 02:29:07 PM EST

That's how science gets accomplished.

It's also OK to be skeptical and believe that the experiment will fail to achieve time travel, but if it turns out to be true then there's no use demanding that nature change.

Another point that I believe is important is that, while it's always important to test a theory as much as possible, it's of at least equal importance to test conditions where the theory is ambiguous (or where it's untested). It's not the act of performing a particular experiment that is pseudoscience anyway; it's a flawed method or unreasonable conclusion that is pseudoscience.

Still ... I don't think that the guy should announce anything until after the experiment has been performed. It's unfortunate when things like this get into the mainstream press because a lot of emotion and expectation gets attached to it.

(PS: Nice demonstration of the approximate nature of theories of physics.)

-----
"I [think] that ultimately physics will not require a mathematical statement; in the end the machinery will be revealed and the laws will turn out to be simple, like the checker board."
--Richard Feynman
[ Parent ]
Science by press release (none / 0) (#94)
by awgsilyari on Mon Apr 08, 2002 at 03:41:28 PM EST

Still ... I don't think that the guy should announce anything until after the experiment has been performed. It's unfortunate when things like this get into the mainstream press because a lot of emotion and expectation gets attached to it.

Yes, that irritates me too. I guess for some scientists in some universities, this tactic actually helps them get funding. Ultimately, I think this diverts funding away from more reasonable research and hurts science in general by sensationalizing it.

Someone at Caltech (cannot remember who) wrote an entire article on this phenomenon, calling it "Science by press release." If I can dig up the link I'll post it here.

--------
Please direct SPAM to john@neuralnw.com
[ Parent ]

Link (5.00 / 1) (#95)
by awgsilyari on Mon Apr 08, 2002 at 03:47:15 PM EST

Here's the link I was thinking of. It looks like I didn't remember correctly, because nowhere in the article does he say "science by press release," but it's still quite interesting nonetheless:

Cold Fusion

--------
Please direct SPAM to john@neuralnw.com
[ Parent ]

only God knows how right you are! (none / 0) (#140)
by johwsun on Thu Apr 18, 2002 at 08:37:25 AM EST

..I also think that you are tottaly right!

[ Parent ]
Time travel could open up a whole new world... (4.00 / 3) (#88)
by Kasreyn on Mon Apr 08, 2002 at 02:46:35 PM EST

...but it might not be one we'd want to live in.

I refer you to the short story "The Dead Past" by Isaac Asimov. It covers a unique angle on a very non-obvious drawback to a mere side application of time travel, "time viewing". This unlooked-for downside has the slight drawback of bringing human society as we know it to a complete and utter end. Read it.

Additionally, many believe that the lack of explorers from the future among us indicates that either time travel into the past is impossible, or travellers from the future are, one and all, very careful not to reveal themselves.

In any case, if I had seen this in queue, my editorial comment would have been along the lines of "lose the paragraph about parallel universes and the grandfather paradox, since it has little or nothing to do with the rest of the article". Another poster already got you on the "invention of fire" thing, at least.


-Kasreyn

P.S. Another interesting story about time travel is William Sleator's book, "Strange Attractors". Delves into chaos theory and such, but is kept very simple so the layman can enjoy the book (Sleator's not really "hard" sci-fi).

P.P.S. "If it is unsuccessful, it will not."?? Something makes me think your average K5er did not need that sentence to understand that concept.


"Extenuating circumstance to be mentioned on Judgement Day:
We never asked to be born in the first place."

R.I.P. Kurt. You will be missed.
Read the article, please :-P (4.50 / 2) (#97)
by BLU ICE on Mon Apr 08, 2002 at 06:34:38 PM EST

There is a good reason why we haven't seen anyone from the future.

The reason why we haven't seen anyone from the future is because there is no time machine that has been conceived that can transport users back before it was created!!!

Half the people here seem to think that no visitors from the future is conclusive proof of time travel. That exactly like someone from the 1930's saying that space rockets are impossible because he has never seen someone from the future with a rocket. OK, bad example. But you see what I am saying.

In any case, if I had seen this in queue, my editorial comment would have been along the lines of "lose the paragraph about parallel universes and the grandfather paradox, since it has little or nothing to do with the rest of the article". Another poster already got you on the "invention of fire" thing, at least.

That is one of the most important paragraphs in my article. It has everything to do with the rest of the article. The grandfather paradox would make time travel impossible. But that is prevented by the many worlds interpretation, which states for each quantum event there is a new universe for each outcome.

The many worlds theory is an interpretation of quantum mechanics. It has wide support.

Here is an excellent many-worlds interpretation FAQ.

From the site: "Political scientist" L David Raub reports a poll of 72 of the "leading cosmologists and other quantum field theorists" about the "Many-Worlds Interpretation" and gives the following response breakdown [T].

1) "Yes, I think MWI is true" 58%

2) "No, I don't accept MWI" 18%

3) "Maybe it's true but I'm not yet convinced" 13%

4) "I have no opinion one way or the other" 11%

58% of scientists believe the many worlds theory is true!! It is not a fringe theory. These include Steven Hawking and Richard Feynman.

The MWI sounds really weird. I can understand that. But the many worlds interpretation is not weird at all compared to some quantum mechanical stuff. 11 dimensional string theory, quantum teleportation, wormholes.

Now if you think the Many Worlds Interp. is weird, look at string theory. Now that states that all matter and energy is actualy strings vibrating in 11 dimensional space. A single proton is made of untold numbers of these tiny strings. The strings differentiate between matter and energy by the frequency of their occilations. That theory is accepted by 90+% of physicists.

"Is the quality of this cocaine satisfactory, Mr. Delorean?"
"As good as gold."

-- I am become Troll, destroyer of threads.
It's like an encyclopedia...sorta: Everything2

[ Parent ]

I did read it. (2.00 / 1) (#107)
by Kasreyn on Mon Apr 08, 2002 at 10:31:47 PM EST

"The reason why we haven't seen anyone from the future is because there is no time machine that has been conceived that can transport users back before it was created!!!"

...huh? Of course time machines haven't been conceived yet (I hope...). This is all still in theory, remember? But they might be conceived in the future, and then people can travel back. You have no basis to say visitors haven't come simply because time machines haven't been invented YET. That's like a 1950's computer programmer saying no chess program would ever beat a grandmaster just because a grandmaster-defeating program hadn't YET been written. Of course, we now know that they were written after that time, and have handily defeated grandmasters.

I was pointing out the lack of visitors from the future (or past :-P) merely as an aside, I did read in the article where the proposed device would only send neutrons forward in time.

"That exactly like someone from the 1930's saying that space rockets are impossible because he has never seen someone from the future with a rocket. OK, bad example."

Yes, a very bad example. My point is, I think, logical: Either there are no visitors from other times, or there are and we have failed to detect them, either because they remain hidden or because they're simply not so different from us that we'd notice them. But the idea of an infinite future of time travel capability, in which every time traveller sticks carefully to a non-interfering role in the past, seems a bit far-fetched to me. Wouldn't SOMEONE using the time machine be tempted to take some of the future science back here and set himself up as a god among primitives? Wouldn't someone show himself, against regulations against so doing, through greed or accident? Either that or our time period is too dull for anyone to visit, which I also doubt. Imagine humanity living on for millions more years; even in such a case, this time will still be historically significant (if it's not forgotten in the ashes of their prehistory), because it is the first time (approximately) that we have had the power to wipe ourselves out as a species. Thus, in my opinion, the time period from the Industrial Revolution through now and into our near future will draw researchers and/or tourists from the future, if time travel ever becomes available to more than a very small elite. Thus, my "either they're hiding very carefully or simply not visiting" theory.

"58% of scientists believe the many worlds theory is true!!"

No, 58% of "leading cosmologists and other quantum field theorists" believe the many worlds theory is true. Who cares what the biologists, entomologists, and geologists think? =P For the record, I'm in favor of it also, but I hold a much less strict set of conclusions about paradoxes. I, personally, think they're possible (paradoxes), and spacetime will simply be warped or scarred by their existence. I believe the timelines would fracture into multiples, but there might be alarming, chaotic discrepancies which would be visible to human observation.

By the way, I've done my share of reading in quantum physics and astronomy; wormholes, string theory, and MWI are not new to me, thank you very much ^_^

However, I do agree with you that a working time machine that could travel into the past would probably be among the most important inventions ever for the human race, probably coming in about 5th on my list of most important inventions I can imagine we might ever make (1: perpetual motion machine, 2: faster-than-light travel, 3: AI, 4: matter replicator/transporter, 5: time travel to the past). Time travel to the future would be far less useful, unless it were used to bring knowledge of one of the first four back.


-Kasreyn


"Extenuating circumstance to be mentioned on Judgement Day:
We never asked to be born in the first place."

R.I.P. Kurt. You will be missed.
[ Parent ]
Re: I did read it. (none / 0) (#113)
by Therac-25 on Tue Apr 09, 2002 at 01:06:20 AM EST

I was pointing out the lack of visitors from the future (or past :-P) merely as an aside, I did read in the article where the proposed device would only send neutrons forward in time.

You can only have visitors from the past if the device has already invented.

Or what past were you thinking they'd come from?

As for visitors from the future, I'd imagine we're not talking "dump the time traveller in a barn driving a stainless steel car 30 years previous". There would probably have to be some kind of conditions maintained at the destination -- which would only exist if they had already been invented. Same with a teleporter -- teleporters would probably only work with machinery at both endpoints.


--
"If there's one thing you can say about mankind / There's nothing kind about man."
[ Parent ]

Suppose this thing actually works... (none / 0) (#108)
by Skwirl on Tue Apr 09, 2002 at 12:34:34 AM EST

What's to prevent a feedback effect? Once Neutron A's future twin drops by, Neutron B's future twin also comes to visit and before you know it, the neutrons of infinite quantum realites all decide to visit this guy's lab. Methinks that might get a little messy.

On the other hand, maybe this universe is due for another big bang.

Hm. I found this comment in an old K5 discussion that says a similar dealie wouldn't suffer feedback.

--
"Nothing in the world is more distasteful to a man than to take the path that leads to himself." -- Herman Hesse

Maybbe... (5.00 / 1) (#110)
by kerinsky on Tue Apr 09, 2002 at 12:47:22 AM EST

How do we know this isn't already happening? We can't tell two Neutrons apart in the first place, so maybe every neutron in the universe is really one really busy time traveling neutron.

Of course I've ripped this idea off of someone much smarter than me, and part of the problem is I'm not smart enough to remember who...

-=-
Aconclusionissimplytheplacewhereyougottiredofthinking.
[ Parent ]
Parallel universes or time travel? (4.00 / 1) (#112)
by Spork on Tue Apr 09, 2002 at 01:02:52 AM EST

Repeat after me: parallel universes have nothing to do with time travel. It shouldn't be hard to understand; just think about it. This machine does not purport to get you to a parallel universe with clones of Elvis and JFK. If it works, it puts a physical object into the past. That's why it will look like there are two neutrons rather than one. They really are one particle whose world-line doubles up on itself. This doesn't happen in some parallel universe. Nobody thinks the neutron is going to beam out of our universe; it will go into the past, and that's why for a while, we'll be able to see it twice. Where did people get this parallel universe crap?

The author of the k5 post seems to think we need parallel universes to avoid grandfather paradoxes. If s/he ever looked at an intro book to philosophy of time, s/he would understand the grandfather paradox is a red herring. If you think straight about it, there is no paradox. You're not gonna kill your grandfather, because your grandfather didn't die before he conceived your parent. It's not like when we send someone back to the past, we have to wait eagerly to find out what he did. After all, everything he did has already happened, and if historians were accurate enough, we could read about everything he did before he ever left... even before the time machine was finished. Everybody thinks that time travel means that history is somehow "up in the air", but that's just stupid. Every time traveler who visited our past is done with his meddlings (get it, because they're in the past?), and we are the product of the world which has him in our history.

There is a fair question as to whether a time traveler has free will after traveling into the past, given the fact that an accurate historian could have told him exactly what he was going to do before he ever left. However, most philosophers agree that the answer is yes, he does indeed have free will in the past. The hand of logic doesn't hold him back, or anything like that. To understand the reasons why, you would have to read some philosophy. Here is an article by one of the many smart people who have given the matter some thought. The classic paper on the subject is:

  • Lewis, David. 1976. "The Paradoxes of Time Travel", American Philosophical Quarterly 13: 145-152.

    It's amazing how willing people are to defer to experts on matters of science, but act like they're hot-shit pros when it comes to shooting their mouth off about something philosophical. Even physicists sometimes get this attitude, and what it gets you is junk like "time travel takes you to parallel universes." That's just a sign they're not thinking. Of course, I don't deny there might be parallel universes, but if there are, and we can visit them, doing so will not be the same thing as time traveling.

  • The Gods Themselves (none / 0) (#125)
    by gnovos on Tue Apr 09, 2002 at 04:21:22 AM EST

    Asimov had a great book about something very similar to this. By finding a parallel universe that consists of nothing but energy (one where the gravitational constant was slightly different then here, leading to a tiny universe of pure super-hot energy), we could create a virtual free energy machine. And since there are, theoretically, a nearly infinite number of these tiny universes, we could suck all the energy out of one and begin on the next one and never run out. The possibilities are amazing!

    A Haiku: "fuck you fuck you fuck/you fuck you fuck you fuck you/fuck you fuck you snow" - JChen
    Oops, one more comment I forgot... (none / 0) (#126)
    by gnovos on Tue Apr 09, 2002 at 04:23:58 AM EST

    Don't know if it's been posted yet, but since time is just another dimension of space, time travel and faster then light travel are one in the same. If you can beam an atom one second into the past, then you can also beam it one light-second across the room. Transporters! Finally!

    A Haiku: "fuck you fuck you fuck/you fuck you fuck you fuck you/fuck you fuck you snow" - JChen
    Time travel? (none / 0) (#132)
    by Nuke Skyjumper on Tue Apr 09, 2002 at 10:20:06 PM EST

    So much arguing back and forth... Why not just ask the guy who bought this? :)

    Next Fall? Travel back! (5.00 / 1) (#134)
    by phliar on Wed Apr 10, 2002 at 07:40:24 PM EST

    Why wait for next fall? All the guy has to do is: invent the thing, then travel back in time to give it to himself much earlier! If time travel were possible, we'd have it already!!!


    Faster, faster, until the thrill of...

    Parallel universes (none / 0) (#137)
    by webwench on Wed Apr 17, 2002 at 01:10:35 PM EST

    What, you didn't read the whole 'parallel universes' theory? The guy did travel back in time to give himself the time machine... which caused a parallel universe to split off, in which time travel does already exist. Just not in our universe.

    Oh yeah, by the way, the cat in the box is dead.

    Webwench: Answering the unanswerable in this universe... and all the others.

    [ Parent ]

    ..since I was a kid... (none / 0) (#138)
    by johwsun on Thu Apr 18, 2002 at 08:16:02 AM EST

    ..I believed that parallel universes is a reality. Thats why I also believe that the time travel is possible.

    Here's some time travel for ya... (none / 0) (#143)
    by CrazyJub on Mon Jun 10, 2002 at 02:53:00 PM EST

    This story was posted in APRIL, and I'm replying to it in JUNE!! Ooooooohhhhh

    Physicist Thinks He'll Have a Time Machine by Next Fall | 143 comments (120 topical, 23 editorial, 0 hidden)
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