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The idiot's guide to how to view cosmic ray tracks from the comfort of your own home

By the in Science
Fri Dec 27, 2002 at 08:28:50 PM EST
Tags: Science (all tags)

Most of us are familiar with pictures from bubble chambers displaying the tracks of subatomic particles interacting. But what many people don't realize is that you can get similar results at home by spending about $40 on materials that are easy to obtain. What's more, I am one of those incompetent people who has no talent for anything practical and little attention span for anything without an instant reward and yet I managed to get succesful results. This means that if you have any interest whatsoever in seeing the tracks of subatomic particles in your own home then I can pretty well guarantee positive results in a few hours (including shopping time) whoever you are.

Prerequisites. Before discussing anything there is one potential showstopper. You need to obtain dry ice. If you think you can, read on. If you think can't then check the Dry Ice Directory to see if somewhere near you sells it. If you still think not then I'm sorry, maybe you should try this project instead.

Some Science. Now that's out the way we can get to the science. Fast moving charged subatomic particles leave a wake of destruction behind them as they travel. They knock electrons off from atoms leaving them electrically charged. These charged atoms then attract other nearby atoms. If this wake passes through a vapor that is just on the verge of condensation these little groups of atoms can provide a convenient location for other atoms to land on eventually resulting in the formation of droplets of liquid. So if we can

  1. Create such a vapor and
  2. Encourage subatomic particles to travel at high speed through it
we might expect to see trails of liquid droplets form just like the trails left by airplanes as they travel through the sky.

Let me deal with the second point first. For that we need do nothing. You see the universe contains many particles traveling at high speed as a result of various types of event such as supernovae. These are known as primary rays but the several miles of atmosphere above our heads shields us from these. Nonetheless when these particles collide with the atmosphere they send a rain of secondary particles down to ground level. The most common type of secondary particle that reaches ground level is the muon. Interestingly muons have a short half-life, around 2.2 microseconds, so you might not expect many to reach ground level. However, they travel at close to light speed so that because of time dilation they actually last quite a bit longer. The upshot of all this is that in any volume of space that isn't shielded by many miles of Earth we can expect an abundant supply of suitable particles for experimentation. So we're half way to success now without actually doing a thing.

For the first part you'll need the following:

  1. A jar with an airtight metal lid. (I don't think mine was 100% airtight but try your hardest anyway. Mine was from a jar of Williams-Sonoma chestnuts left over from making turkey stuffing).
  2. Isopropyl alcohol. (As pure as you can, I found a bottle of 99% pure stuff for $4 at Long's Drugs. This is what they wipe you with before an injection.)
  3. Some black card (around $5 from Long's. Black velvet might be better. What's important is getting something that doesn't reflect light too much.)
  4. Some glue. (This is going to get covered in alcohol so something not alcohol soluble is probably better. Mine was alcohol soluble and still worked well enough. This is a guide for idiots. You can do things wrong and it'll still work.)
  5. Various tools like a sharp knife, scissors and heavy duty gloves. (My Leatherman was useful here.)
  6. A bright localized light source. (I used a desk lamp.)
  7. Some cloth. (The darker the better. By the way, mine was bright pink.)
  8. And of course some dry ice (mine came from the local AM/PM gas station. Don't ask me why they sell it. It came as a 30cmx20cmx5cm slab.)

What we're going to do is create a temperature gradient in the jar while it has a little alcohol in it. Somewhere between the hot and cold ends will be a region where the vapor is supersaturated. That's where we'll see the tracks.

Beware. First some warnings: knives and scissors are dangerous so be careful in what follows. More importantly dry ice can be dangerous. Transport it back from your dry ice store in a cooler. (I didn't, I threw it in a plastic crate, but that's not recommended). Don't handle it directly. I actually used some heavy duty gloves left over from stripping paint to deal with it. Even things touching the dry ice need to be treated with care. I managed a slight 'burn' from handling the jar lid after it had been in contact with the dry ice. Also, if you have this thing in an enclosed space (such as your car) it's giving off carbon dioxide all the time, and in theory this could asphyxiate you. Fortunately, humans have mechanisms built into them to detect this gas - if there's too much in the air you'll start feeling out of breath and may find yourself breathing harder. So work in a well ventialted area. Be very careful. I really don't want to be held responsible for any accidents and this is all at your own risk.

The Apparatus. Scrub the label off the jar. Cut a circle of cloth that will be placed in the bottom of the jar. It should be of the same diameter as the base of the jar and glued inside. This will form a small reservoir for alcohol. The procedure is simply to wet the cloth with the alcohol (I put a few cc of alcohol in the jar and merely tossed the excess out of the window leaving the sides and base still wet - there's no need for measurements), close up the jar tightly and place it lid down on the dry ice. Note, it's important that the lid be metal in order to conduct heat easily, otherwise the jar will stay warm inside. If this setup is left for around 15 minutes tracks will probably start forming. Easy as can be!

But, you won't see anything. Now comes the hard bit. The challenge is in the lighting. In order to see the tracks you need to light the droplets from the side in such a way that they have a high contrast relative to the background. So what you do is wrap the jar in the black card. Then cut a window on the left (say), about 2cm from the bottom (ie. the lid, because the jar will be upside down at this point), maybe 3cm wide and 1.5cm high. You then cut a window at the front that is of the same dimensions but whose base is at the same height as the top of the left window (I'm now still thinking of the lid as being down). Work in a darkened room and arrange the light source to shine in from the left and view from the front. At this point I still had problems. Total internal reflection in the glass of the jar can carry light right round the jar and the rim of the jar itself glows. So what I did was make a small collar of black card which went on the inside to hide the rim and place a small 'screen' of black card against the back side of the jar (again on the inside). Any arrangement that provides a black background with as little light as possible reflected will work. (I still had reflections because everything was wet with alcohol but c'est la vie.)

If you do all of this and place the jar upside down on the dry ice you should see a region near the bottom of the jar with constant precipitation. When I first did this it took me almost an hour to see this as I had no idea what to look for. You expect to see a constant 'rainfall' of tiny tiny droplets starting a few cm from the bottom of the far and rapidly falling down. You can now play with adjusting the light to get the drops as bright as you can against the background.

Particle Tracks After around 15 minutes you should start seeing tracks. (I don't know why you have to wait - something happens to the vapor and tracks don't seem to form before then.) In my jar I was seeing several events a minute. The trick is to be able to focus your eyes on the droplets but with a good event the track should be visible to even casual observers looking through the viewing port. Sometimes you'll see long tracks extending all the way across the jar and sometimes short tracks traveling down through the supersaturated zone. Note that they are merely reflecting light from your lamp so lighting is important. Note also that they are just droplets that are larger than the surrounding ones. They won't hover in the air, they merely fall down to the bottom of the jar within a fraction of a second of forming. If your lighting is good you'll see the entire track illuminated as it falls.

If you're really lucky you'll see more than just straight tracks. Occasionally a low energy particle will come wandering through. If the energy is low enough then each time it wanders by a nucleus in the air it won't be able to barge straight through but will be deflected. What you'll see is a short randomly shaped track. If you're really lucky a high energy particle will whack straight into a nucleus in the middle of the jar and be deflected. What you'll see then is a sharp angular turn in the track.

Photography. I'm no photographer. I used my Sony DSC F505V digital camera to take pictures. I have posted a pair both with and without a track for comparison. (Check the 'Particle Tracks' album.) The camera was more or less in its default state (with no flash) except that I had to manually focus on the center of the air in the jar. Note it is more visible to the naked eye which is much more sensitive than the CCD in my camera. On seeing her first one my wife exclaimed "what was that thing like a bolt of lightning that just flew across?"

Advanced Options. If you have a really powerful magnet hold it by the jar. If any of the particles you are observing are charged (eg. muons or beta rays) then their paths will be curved. In you know the strength of the magnetic field you can even compute the charge to mass ratio of the particle. I didn't have a magnet unfortunately so I'd like to hear your results.

We did just so happen to have some of a radioactive thorium compound obtained from ebay. It was kept inside a small vial for safety which meant that the glass blocked much of the radiation. In particular it blocked the alpha rays which actually produce the best tracks (apparently). Nonetheless, it still produced beta rays. We placed the vial on the side of the jar (taping it in place) and after our eyes adjusted we could see frequent short wispy tracks. Many were formed every second though they weren't easy to see. However, radioactive material is dangerous, really dangerous. You need to know exactly what you are doing here. I trusted a friend of mine who brought the sample round and we used a geiger counter to check radiation levels.

Conclusion. So there you have it. With a minimum of effort you can view the tracks and interactions of subatomic particles. And remember: this is an experiment, so experiment. Try more alcohol, less alcohol, different lighting, adjusting the temperature gradient in various ways or putting your old radium based fluorescent watch display that you no longer need in the jar. Have fun!

References. There are numerous descriptions of similar apparatuses on the web. This was one of my main sources. I originally wanted to build the Berkeley Lab detector but I soon realised it was beyond my ability and budget! There is also a recent Scientific American article and not so recent ones from April and December 1956 (available on CDROM, thanks DesiredUsername).


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Related Links
o Dry Ice Directory
o this
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The idiot's guide to how to view cosmic ray tracks from the comfort of your own home | 76 comments (71 topical, 5 editorial, 0 hidden)
haw! (3.66 / 3) (#4)
by Work on Fri Dec 27, 2002 at 04:30:24 PM EST

Great. I love it. Now this is a quality article.

Nice! (4.00 / 1) (#6)
by RainyRat on Fri Dec 27, 2002 at 06:35:25 PM EST

Anyone know of a dry-ice vendor in or around Edinburgh?

Oh, and +1 FP.

Eagles may soar, but rats seldom get sucked into jet engines.
I'm in Glasgow... (none / 0) (#12)
by gordonjcp on Fri Dec 27, 2002 at 07:38:07 PM EST

I'll let you know if I get my hands on some.  It should be OK in a coolbox for the trip across...

Give a man a fish, and he'll eat for a day. Teach a man to fish, and he'll bore you rigid with fishing stories for the rest of your life.

[ Parent ]
look for places (none / 0) (#20)
by Hillman on Fri Dec 27, 2002 at 11:23:25 PM EST

That sell gasses like helium, nitrogen, etc...

And I know that meat processing plants use them to cool meat.

[ Parent ]

Edinburgh Dry Ice (none / 0) (#46)
by AndyM3 on Sun Dec 29, 2002 at 08:45:59 AM EST

Try Mac's Cube Ice of Musselburgh - they deliver sacks of CO2 cubes for 10 or 20 quid.

See the previous emails for handling instructions.

[ Parent ]

Science, parties, mucking about (none / 0) (#52)
by imperium on Mon Dec 30, 2002 at 08:43:24 AM EST

As a local I'm sure I'll find that useful one day: thanks!

[ Parent ]

Time spent (3.00 / 1) (#7)
by DesiredUsername on Fri Dec 27, 2002 at 06:51:14 PM EST

I tried basically the above. I wimped out on a few details, not having any black cloth and not wanting to take the time to cut the card stock window. It took me roughly 15 minutes to get everything set up, which has to be some kind of a record in the area of particle physics experiments.

My results were negative (i.e. I didn't see anything). I believe the main reason was the size of the jar I was using--a massive pickle jar. Using a smaller jar and using the windows as indicated would probably work better and not take significantly more time.

Play 囲碁

I don't know if jar size is an issue (4.00 / 1) (#9)
by the on Fri Dec 27, 2002 at 07:07:45 PM EST

But lighting is crucial. You need that black card or cloth for contrast. And I put card inside the jar - something I didn't see mentioned in other sources. Reflections from the glass itself could easil mask the tracks.

Did you see the constant precipitation of small droplets?

The Definite Article
[ Parent ]

No precip (3.00 / 1) (#15)
by DesiredUsername on Fri Dec 27, 2002 at 08:58:13 PM EST

I deviated from the instructions in another way as well. I put alcohol on a paper towel taped to the end opposite the lid, but not on the end where the lid was. Considering the distance due to the jar size, this was probably an error.

Play 囲碁
[ Parent ]
You need enough alcohol to form a vapor (3.00 / 1) (#23)
by the on Sat Dec 28, 2002 at 12:48:27 AM EST

But really. Getting the precipitation going is the easy bit! It starts immediately with almost no work :-)

The Definite Article
[ Parent ]
Walmart (4.00 / 2) (#8)
by influx on Fri Dec 27, 2002 at 07:05:33 PM EST

The Super-Walmart in our sleepy little town carries dry ice, so it shouldn't be too hard for most Americans to obtain it.

The more you know, the less you understand.
Great fun (3.00 / 1) (#10)
by thebabelfish on Fri Dec 27, 2002 at 07:18:33 PM EST

Cloud chambers are great fun and make excellant entertainment pieces.  I built a slightly more complex chamber than described in the article for a school project and had a blast.  If you're doing this, be sure to save a few bits of dry ice to put in a (plastic) cup of boiling water.  Crazy fun!  ; )

"I don't trust goats," --To Catch a Spy
'im no photographer' (2.00 / 2) (#13)
by turmeric on Fri Dec 27, 2002 at 08:38:58 PM EST

thats no excuse for giving us a crap picture. excellent article tho.

good article (1.00 / 1) (#14)
by Nesian on Fri Dec 27, 2002 at 08:54:53 PM EST

Well worth the read
~After all, if you stockpile a massive nuclear arsenal, it's only natural that people are going to want to go in and have a look around, maybe see what all those buttons marked 'detonate' and 'code red' mean.~
careful with those alpha radiation sources... (1.50 / 2) (#16)
by Phillip Asheo on Fri Dec 27, 2002 at 09:29:40 PM EST

Seriously, it is not to be messed around with. It can and will kill you. There may be laws governing posession too, check with your local fire department.

"Never say what you can grunt. Never grunt what you can wink. Never wink what you can nod, never nod what you can shrug, and don't shrug when it ain't necessary"
-Earl Long

Alpha Radiation... (none / 0) (#18)
by jasno2 on Fri Dec 27, 2002 at 10:46:57 PM EST

I thought alpha radiation was mostly harmless unless ingested...


[ Parent ]

Not just injested. (none / 0) (#19)
by Profane Motherfucker on Fri Dec 27, 2002 at 11:18:41 PM EST

Inhaled too.

[ Parent ]
Smoke Detector (5.00 / 1) (#24)
by Bad Harmony on Sat Dec 28, 2002 at 02:32:37 AM EST

You can get a relatively safe radiation source from an ionization chamber smoke detector, available at just about any hardware store. See here for a description of the technology.

54º40' or Fight!
[ Parent ]

relatively safe ? (5.00 / 1) (#26)
by Phillip Asheo on Sat Dec 28, 2002 at 05:35:24 AM EST

That's relativly safe as in still lethally dangerous, right ?

Didn't the EPA have to go in and clean up after some guy tried to make a reactor out of the innards of a few thousand smoke detectors ?

"Never say what you can grunt. Never grunt what you can wink. Never wink what you can nod, never nod what you can shrug, and don't shrug when it ain't necessary"
-Earl Long
[ Parent ]

Relatively Safe (none / 0) (#27)
by Bad Harmony on Sat Dec 28, 2002 at 06:50:09 AM EST

No radiation source is 100% safe, not even that banana (really) in the kitchen. The radiation source in a smoke detector is a sealed alpha emitter. Unless you place it inside your body, or grind it into dust and swallow or inhale it, it is not a hazard. The alpha particles have limited range and will not penetrate the skin of a human.

54º40' or Fight!
[ Parent ]

alpha particles have limited range. (none / 0) (#28)
by Phillip Asheo on Sat Dec 28, 2002 at 07:49:16 AM EST

That is not in question. What is in question is using alpha radiation sources in an uncontrolled environment. The laser in your compact disc player is perfectly safe, so long as it stays there. When you start using it for your amatuer science project, thats when the blindness can become an issue. Its the same with radioactive material. Safe, if you know what you are doing, which the average angst-ridden teenaged k5 reader probably doesn't

"Never say what you can grunt. Never grunt what you can wink. Never wink what you can nod, never nod what you can shrug, and don't shrug when it ain't necessary"
-Earl Long
[ Parent ]

Power (none / 0) (#32)
by ucblockhead on Sat Dec 28, 2002 at 02:17:52 PM EST

The laser in your CD player is so low power that it is safe outside of it as well.
This is k5. We're all tools - duxup
[ Parent ]
Perhaps. (none / 0) (#36)
by Phillip Asheo on Sat Dec 28, 2002 at 06:47:45 PM EST

I wouldn't point one in my eye though.

"Never say what you can grunt. Never grunt what you can wink. Never wink what you can nod, never nod what you can shrug, and don't shrug when it ain't necessary"
-Earl Long
[ Parent ]

eyes (5.00 / 1) (#37)
by ucblockhead on Sat Dec 28, 2002 at 07:12:43 PM EST

The laser in your CD doesn't have enough power to damage your retina. Just so you know.

The light from a laser isn't magic. It's just a bunch of photons. True, they tend to all stay together, which is why lasers are more dangerous than the equivalent light bulb. All the photons go to one place. But if there aren't many to begin with (and they aren't in the sort of laser used in consumer electronics) then there is no risk of damage.

But, alas, you give it a fancy scientific name, and people get all afraid of it.
This is k5. We're all tools - duxup
[ Parent ]

right over you.. (none / 0) (#41)
by nitroburn on Sat Dec 28, 2002 at 09:17:20 PM EST

i think you missed the point.

[ Parent ]
The point is... (none / 0) (#60)
by betaray on Mon Dec 30, 2002 at 04:40:05 PM EST

that there's no reason to get so worried about "potentially lethal radiation sources". Like some one up there said, not even a banana is 100% safe. What is the harm of using an "using alpha radiation sources in an uncontrolled environment." unless, say you eat it? So yes, it's potentially dangerous, but that potential is extremely low. This whole thread is alarmist, and comes from quite a bit of ignorance of the substances involved. I would encourage people to be aware of the danagers anytime you take something apart, but none of the ideas in this thread could hardly be considered "lethal".

[ Parent ]
Another possibility (5.00 / 1) (#29)
by chemista on Sat Dec 28, 2002 at 07:51:47 AM EST

You might try a plain cigarette too. Tobacco plants are amazingly efficient concentrators of polonium-210 which is a fairly active (half-life about 200 days) alpha emitter. (It's a bit of a crapshoot though, depending on whether there is much uranium in the soil where the tobacco was grown.) It's funny to point a Geiger counter at a cig, especially if you know there's a smoker in the room. ;)
Stop reminding people about the overvalued stock market! I'm depending on that overvalued stock market to retire some day! - porkchop_d_clown
[ Parent ]
MUCH SAFER SOURCE HERE!!! (none / 0) (#31)
by the on Sat Dec 28, 2002 at 01:15:39 PM EST

Try a Needle Source. I'm getting worried about all the talk of dismantling smoke detectors which may not be safe.

The Definite Article
[ Parent ]
Another source? (none / 0) (#38)
by squinky on Sat Dec 28, 2002 at 08:12:04 PM EST

Another source for alpha particles may be the mantles used in Coleman propane lanterns. There's a warning on them about them containing Thorium. You can get them at any camping store and pretty much any department store.

I recently threw away an very old smoke detector, in retrospect maybe it should have had haz-mat handling. There was a component in it that looked sorta like a capacitor (short shiny metal tube with two wires coming out) and over that component, the plastic was noticable degraded on the inside of the unit. It almost looked burned.

[ Parent ]

Thorium (none / 0) (#42)
by Bad Harmony on Sat Dec 28, 2002 at 10:47:26 PM EST

I've read that some welding rods contain thorium. One of these days I will have to check out a local welding supply store to see what is available.

54º40' or Fight!
[ Parent ]

Yes (none / 0) (#71)
by Polverone on Tue Dec 31, 2002 at 04:06:50 PM EST

This article inspired me to check. These aren't welding rods per se, but tungsten electrodes used for TIG and plasma welding. The closest welding supply outlet had a large selection of electrodes containing 1% or 2% thorium (in California; availability may vary geographically). I imagine that these will make very nice cloud chamber sources: radioactive enough to show activity, but not a health hazard unless you grind the hard metal and inhale/ingest the dust.
It's not a just, good idea; it's the law.
[ Parent ]
Pictures? (3.00 / 1) (#17)
by jasno2 on Fri Dec 27, 2002 at 10:45:17 PM EST

How about taking some pictures of the entire setup and not just the inside of the chamber?

Hang on a day or two... (3.00 / 1) (#22)
by the on Sat Dec 28, 2002 at 12:37:59 AM EST

And I will put them on the same web page.

The Definite Article
[ Parent ]
SCIAM Amateur Scientist (2.00 / 1) (#21)
by Enocasiones on Fri Dec 27, 2002 at 11:35:44 PM EST

It's funny, when I first skimmed the story I thought about the SciAm column, and there was the link at the end of the story. I think it was one of Shawn Carlson´s last articles for SciAm before they reorganized the magazine.

It's late here, but I have to find some dry ice next week ... (yeah, just like with the beer freezer!)



This brings back some memories (4.60 / 5) (#25)
by ArtFart on Sat Dec 28, 2002 at 02:53:42 AM EST

I remember doing a cloud chamber experiment like this when I was about 13 (40 years ago!!!). My inspiration was one of the old Bell Labs Science Series movies. (Anyone else old enough to remember Dr. Frank Baxter?)

One additional part they described was to put a hot iron on top of the chamber. This "hot-on-top/cold-on-the-bottom" configuration helps keep the vapor suspended and reduces the rate at which the particle tracks fall to the bottom. I used a 300 watt 35mm slide projector (which I still own!) as a light source.

I think I only saw three or four cosmic ray tracks. It may well have been on the low side of a sunspot cycle. Being as impatient as 13-year-olds generally are, I repeated the experiment with a radium-dial wristwatch sitting in the bottom of the chamber. The result was actually quite spectacular--lots and lots of tracks radiating out in all directions from the watch, all slowly falling to the bottom.

No (none / 0) (#44)
by Wah on Sun Dec 29, 2002 at 02:50:09 AM EST

No one else is able to remember Frank Baxter.  You should take this as a badge of honor.

How did you find the Internet anyway, you old^H^H^HArtFart?

always :-).
Fail to Obey?
[ Parent ]

Pppphut! (none / 0) (#63)
by A Trickster Imp on Mon Dec 30, 2002 at 09:05:40 PM EST

> How did you find the Internet anyway, you
> old^H^H^HArtFart?

What the hell are these caret-H things?

[ Parent ]

Caret-H things (none / 0) (#64)
by seraph93 on Mon Dec 30, 2002 at 10:32:49 PM EST

> What the hell are these caret-H things?

It's CTRL-H. It's what you press to delete the character to the left of the cursor when your terminal doesn't have a backspace key. Often mis^H^H^Hused by hackers attempting humor. :)

From the Jargon File:

The digraph ^H is often used as a print representation for a backspace, and was actually very visible on old-style printing terminals. As the text was being composed the characters would be echoed and printed immediately, and when a correction was made the backspace keystrokes would be echoed with the string '^H'. Of course, the final composed text would have no trace of the backspace characters (or the original erroneous text).

Ph-nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn.
[ Parent ]
interesting.... (none / 0) (#69)
by Luyseyal on Tue Dec 31, 2002 at 11:46:34 AM EST

And here I was thinking it was a visual representation of the English verbal idiom of sorta coughing over your breath when you make a Freudian slip...

George loves his new boyfriend Tim, but Tim has this habit of scratching his forehead that reminds George of his ex, Kiki. It doesn't help that Tim and Kiki are brothers and look quite a bit alike.

<George enters the room>
Tim: Hi George! <runs over to him>
George: <thinking of Kiki> Oh Kik*cough*cough*Tim! <shakes his head> I love you so much.

So, yeah, that's what it makes me think of!

[ Parent ]

Oh yeah. (none / 0) (#70)
by seraph93 on Tue Dec 31, 2002 at 02:26:03 PM EST

Hmmm...that's a much simpler way of describing it, now that I think about it.

"Bloody hell, now that is what I call thinking. Here, Vroomfondel, why do we never think of things like that?"
"Dunno. I think our brains must be too highly trained, Majikthise."
(from the Hitchhiker's Guide)

[ Parent ]
I have no interest (3.25 / 4) (#30)
by coillte on Sat Dec 28, 2002 at 12:08:23 PM EST

at all in practical demonstrations of physics.

I have no interest, at the moment, in extraneous projects which will take any time from my life at the moment.

No mechanical, or fabricatory aptitude of this nature at all, and my record with poisonous substances such that I have little wish to experience the ill effects of my lack of caution.

I so want to build this thing.

No higher praise can I give.

"XVI The Blasted Tower. Here is purification through fire,lightning, flames, war...the eye is the eye of Shiva... the serpent on the right is the symbol of the active will to live,the dove on the left is passive resignation to death"

Then stop wasting your time (and ours) on K5... NT (none / 0) (#54)
by Chakotay on Mon Dec 30, 2002 at 10:31:30 AM EST


Linux like wigwam. No windows, no gates, Apache inside.

[ Parent ]
Hmm? (none / 0) (#65)
by PurpleBob on Mon Dec 30, 2002 at 11:10:45 PM EST

I'd say you didn't finish reading that post and missed the point. But then there's the smiley face. Maybe you're not serious and I'm missing the point. Or maybe you're just happy about missing the point.

[ Parent ]
Missing points. (4.00 / 1) (#68)
by Chakotay on Tue Dec 31, 2002 at 05:31:22 AM EST

Lets just say some points were missed. We will not go into which points were missed by whom, and if they were eventually found back or not. I'd just like to make the unmissable point that points were missed.

Hmmm, did anybody se my point? It seems to have gone missing.....

Linux like wigwam. No windows, no gates, Apache inside.

[ Parent ]
Excellent! (2.00 / 1) (#33)
by graal on Sat Dec 28, 2002 at 02:49:30 PM EST

I originally saw this in your diary, I think. Glad to see it fleshed out. Given my penchant for el cheapo short-attention-style projects, I do believe I'll have to give this a shot.

For Thou hast commanded, and so it is, that every
inordinate affection should be its own punishment.
-- St. Augustine (Confessions, i)

This (2.50 / 2) (#34)
by inertia on Sat Dec 28, 2002 at 03:04:48 PM EST

looks like some good material to perform an extra credit physics lab on...

Queston? (4.00 / 1) (#35)
by dJCL on Sat Dec 28, 2002 at 05:52:42 PM EST

Will this detect radiation from the fusion device posted on slashdot earlier today? The one that you can make for about $500 - $2000 in parts? If so, that would be a good mix of two experiments, if not, oh well, I'll build them anyways...

my sig was too long, and getting annoying, so this is all you get. deal with it.

No (none / 0) (#39)
by DesiredUsername on Sat Dec 28, 2002 at 08:28:49 PM EST

The only radiation you'll get from fusion is neutrinos and gamma rays, neither of which (AFAIK) will show up in a cloud chamber.

Play 囲碁
[ Parent ]
right you are. (4.50 / 2) (#43)
by Work on Sun Dec 29, 2002 at 01:30:42 AM EST

neutrinos easily plow through a light year of solid lead without slowing down. This is why detecting them is very, very difficult and theres only really been 3 or 4 setups in the world that have done it.

One is a giant vat built into a mountain full of the same fluid used in dry cleaning. Neutrinos every once in awhile will hit a chlorine atom and turn it into argon. Now how in their several million gallon tank of fluid they detected the handful of argon atoms is beyond my knowledge.

The other uses heavy water and thousands of photodetectors to capture the occasional photon released by a neutrino impacting with it. This is like the one in japan which a year or two ago suffered the catastropic cascade and destroyed it.

Interestingly, only about a third of neutrinos predicted by theory have been detected. At first it was passed off as some kind of problem with the apparatus, but the different kinds have all returned the same data. Its still unknown where the 2/3rds of neutrinos emitted by the sun went. Though in the past year a little bit of evidence has been shown that inbetween the sun and earth, neutrinos can change forms into ones which have so far gone undetected.

I've really gone on about neutrinos havent i?

Gamma rays are merely high energy photons, and thus dont really behave like particles do which interact with the vapor.

[ Parent ]

Catastrophic cascade? (3.00 / 1) (#45)
by pwhysall on Sun Dec 29, 2002 at 08:22:40 AM EST

Please tell us more - but do remember that I'm a bit of a thicky when it comes to mathematics.

While I rather doubt that this particular cascade would have had the same effects as the resonance cascade at Black Mesa, a little more info would be most interesting.
K5 Editors
I'm going to wager that the story keeps getting dumped because it is a steaming pile of badly formatted fool-meme.
[ Parent ]

it was very odd (none / 0) (#47)
by Work on Sun Dec 29, 2002 at 12:04:54 PM EST

i'm not exactly sure what caused it - the final report with a conclusion might be available.

Anyway, the detector was about 2/3rds filled with the heavy water, when it began to detect massive amounts of neutrinos - millions of times normal. But then the photodetectors (they look like large glass domes, kind of like a tv screen only rounder) began to implode, one right after the other.

Thousands of them in a strange cascading pattern all quickly imploded and were destroyed. Almost every one of them below the water line was trashed.

Naturally an investigation began to look into what happened, things like perhaps a worker had dropped a tool or others were investigated, but AFAIK, no true cause was found.

[ Parent ]

found more (5.00 / 1) (#48)
by Work on Sun Dec 29, 2002 at 12:17:28 PM EST

did a little digging. Here is the homepage of the detector. Not much info, has some photos of damage.

I found a copy of the 2nd of 4 official reports on the incident, and its become clear that one of the PMT's at the bottom of the housing had been damaged during a routine upgrade some years before. When this imploded, it created a shockwave which cause adjacent PMT's to implode, which then created a shockwave etc.

[ Parent ]

Many thanks. (4.00 / 1) (#49)
by pwhysall on Sun Dec 29, 2002 at 01:45:37 PM EST

I was rather hoping for a serious trans-dimensional rift, causing the forces of chaos to invade and be repelled by a small but heroic force - but still, very interesting nonetheless.
K5 Editors
I'm going to wager that the story keeps getting dumped because it is a steaming pile of badly formatted fool-meme.
[ Parent ]
well (5.00 / 1) (#50)
by Work on Sun Dec 29, 2002 at 02:15:54 PM EST

the whole 'shockwave causes others to implode' thing sounds mighty convienent to me.

Being japan, im sure Godzilla was formed from this event.

[ Parent ]

You can detect secondary reactions (none / 0) (#40)
by QuantumG on Sat Dec 28, 2002 at 08:38:33 PM EST

There are a number of different ways to get neutrons to react to produce alpha particles, which is what this setup will detect. As with the fusor, this is extremely dangerous.

Gun fire is the sound of freedom.
[ Parent ]
Quick question (1.00 / 1) (#51)
by medham on Mon Dec 30, 2002 at 12:43:32 AM EST

If the "atom" in only a bit of theoretical shorthand, which I understand from the television, then does the concept of "subatomic" make any sense?

The real 'medham' has userid 6831.

Not really (none / 0) (#61)
by code shady on Mon Dec 30, 2002 at 05:45:22 PM EST

Atom isn't a bit of theoretical shorthand. An atom is the smallest unit of a given substance that still maintains the properties of said substance (if i remember correctly). Atoms are made up of protons, electrons, and neutrons, which would qualify as sub-atomic. Additionally, protons, neutrons and electrons are made up of even smaller particles, such as quarks, leptons, bosons, mesons, et cetera et certera. Those are also sub-atomic, being smaller than atoms.
--- Shut your noise tube, taco human!
[ Parent ]
Medham may be trolling (none / 0) (#62)
by the on Mon Dec 30, 2002 at 06:46:01 PM EST

But I take issue with this
An atom is the smallest unit of a given substance that still maintains the properties of said substance
But this is just one of those lies you tell kids in chemistry lessons. I don't know why they tell kids this. Probably because 200 years ago it seemed to make sense and school courses haven't been updated since then.

Think about it. Electrons, stripped from atoms, still share properties with gold, say. For example they have mass and momentum. On the other hand an atom of carbon fails to have many properties that diamonds do, for example diamonds are crystals.

But the correct definition says "chemical property" you object. How do you define chemical property without recourse to the notion of an atom?

The Definite Article
[ Parent ]

Definition still makes sense (5.00 / 1) (#72)
by Polverone on Tue Dec 31, 2002 at 04:35:10 PM EST

Mostly, anyhow. The commonly accepted definition of an atom - the one you object to - is newer than you might think. It's certainly not 200 years old. If you read old chemistry texts - from the 1850s, for example - you'll find "atom" used more loosely than it is today. "Two atoms of caustic soda combine with one of carbonic acid gas to form one atom of water and one atom of carbonate of soda," for example. Carbonic acid gas (carbon dioxide) isn't an atom in the modern sense, but a covalently bonded compound. Sodium carbonate and hydroxide are compounds that have covalent bonds (OH and CO3) but also ionic bonds (between the sodium cations and their paired anions). The author from 1850 uses "atom" where a modern writer might use "mol" or "molecule."

Chemical activity is mostly determined by the interactions of electrons in the outer electron shells of atoms. The mass from the nucleus still plays a role, though. Deuterium (with approximately twice the mass of hydrogen, because of the extra neutron, but the same electron configuration) may react significantly slower than hydrogen under the same circumstances because of its greater mass. Heavier elements generally don't show this strong isotope effect because the addition or subtraction of a few neutrons amounts to only a few percent difference in mass and not much difference in reactivity.

In reality, none of the elements (except the noble gases) are found as free atoms at STP; they all form bonds among themselves in the elemental state. Free atoms, excepting the noble gases, are extremely reactive and not encountered in everyday circumstances. If you keep this in mind, the atom definition still makes sense. Diamond is a particular compound of carbon bonded to carbon. It is different from a free-floating carbon atom because its carbon atoms are bonded to one another in particular ways. Water isn't just hydrogen atoms and oxygen atoms, and neither is diamond just carbon atoms and carbon atoms. Structure matters.

The elementary school definition of atoms isn't an untruth, but it doesn't give much useful information without more explanation and context.
It's not a just, good idea; it's the law.
[ Parent ]

Atoms (none / 0) (#74)
by the on Thu Jan 02, 2003 at 12:33:39 PM EST

it doesn't give much useful information without more explanation and context.
But by time you have that context it becomes redundant so I really do think it's valueless. I think it's just a string of characters kids are told to memorize on order to give examiners something to ask.

Compare with a statement lime E=mc2. It's also valueless without additional context. But when you get that context it doesn't become useless, it still remains useful.

The Definite Article
[ Parent ]

Really quick and cheap version (5.00 / 2) (#53)
by jmanning on Mon Dec 30, 2002 at 09:57:12 AM EST

Did you know you actually make one of these every time you open one of those glass soda/beer bottles?

Just grab the bottle, open the top, and peer into the top. By opening the bottle, you released pressure, cooling the vapor space down. You now have cooled, condensed CO2 vapor sitting there. It's the same thing you'll get with a cloud chamber, just on a smaller scale.

Don't breathe as you're opening it, or you'll blow it all away. Just look carefully for a trail before it fades.

If it doesn't work, drink that one and try again. I hope you bought a case...

So, it's not as clear and spectacular as the big project - maybe it's not even practical for actually seeing vapor trails - but it's something to do next time you're opening a few bottles. Now you know what that puff of cloud is on the top of the bottle.

On my second case.... (5.00 / 1) (#66)
by obyteme on Tue Dec 31, 2002 at 03:09:37 AM EST

No trails yet but I think the vapor is smiling at me?!!!

To err is human, or I could be wrong.
If you can't poke fun at it, get a sharper wit.

[ Parent ]
rofl (n/t) (none / 0) (#75)
by vile on Sat Jan 04, 2003 at 06:52:20 AM EST

The money is in the treatment, not the cure.
[ Parent ]
Can a black-light help this? (5.00 / 2) (#55)
by oroshana on Mon Dec 30, 2002 at 10:44:34 AM EST

I am thinking about doing this experiment. But I want to use a black-light to highlight the wisps. *If* this is possible, it might create more visible results. Does anyone know if the black-light will interfere with the experiment at all?

It would be cool to see the wisps from all around, instead of using black material to create contrast through a cut-out.

And yes, I know that I could try an experiment to answer my own question, but I'm too lazy. If the question seems stupid, it's because of my ingorance of physics. Just because I passes 4 semesters of undergraduate physics doesn't mean I understand any of it.  <;o)

this is unlikely to work (none / 0) (#73)
by I am the atom on Wed Jan 01, 2003 at 07:03:41 PM EST

For this to work, the vapour trails would need to be flourescent.  I just shined a blacklight at a bottle of whiskey and it did produce a green glow, but it was very faint and quite possibly caused by some other substance than alcohol in the whiskey.  

More to the point, the alcohol is not any more concentrated in the trails than in the rest of the jar, it's just in bigger drops, so I think you'd probably just see a uniform glow.  

[ Parent ]

Easier way to do this? (3.00 / 1) (#56)
by sakusha on Mon Dec 30, 2002 at 02:05:40 PM EST

Isn't there a way to do this without dry ice? There's a bubble chamber at the Griffith Park Observatory in Los Angeles, I think it just uses regular refrigeration coils. I would think that if you're just trying to create a temp gradient for the vapors, you could do this with standard refrigeration stuff. Hey, there must be some HVAC geeks out there, with all that overclocking/cooler hacking going on.

That's easier? (5.00 / 1) (#58)
by drivers on Mon Dec 30, 2002 at 02:40:27 PM EST

Rigging up some refridgeration contraption is easier than setting it on a block of dry ice?

[ Parent ]
Easier (none / 0) (#59)
by sakusha on Mon Dec 30, 2002 at 03:44:49 PM EST

Well, easier in the sense that you could just flip a switch to operate it, rather than run to the store for dry ice.

[ Parent ]
Nitpick (none / 0) (#57)
by awgsilyari on Mon Dec 30, 2002 at 02:34:47 PM EST

You claim you can use just a magnet to measure the charge/mass ratio. This is only true if you know the velocity of the particles. In this case you definitely do not. It would be neat to see the deflected tracks, though.

J. J. Thomson measured e/me by balancing the magnetic force against the electric force (so that the net force on the "cathode rays" was zero), thereby determining the particle velocities. In order to perform a similar experiment you would need a special vacuum tube apparatus. Quite involved, but probably not impossible given some determination.

Please direct SPAM to john@neuralnw.com

Or if you are completely lazy and have 8 bucks... (none / 0) (#67)
by sawilson on Tue Dec 31, 2002 at 05:01:02 AM EST


This kit also includes an alpha particle source.
Dry ice and alcohol not included. ;)

Sig:(This is your diatribe full of your titles
and lame beliefs and causes so men are impressed
with you and women want to bear your childr

argh (none / 0) (#76)
by glor on Wed Jan 08, 2003 at 02:42:50 PM EST

I have this set up in my kitchen and everything works except for seeing the tracks. I can see the droplets falling (looks like it's snowing) but they seem pretty uniformly distributed. I took the alpha source out of a smoke detector and put it in the jar, and that doesn't seem to make any difference. What am I missing?

My setup is a 12-oz pickling jar, a folded paper towel glued to the bottom of the jar and soaked with alcohol, a black construction paper tube with windows as described completely inside the jar, the smoke detector source sitting on the lid inside the jar, and the whole thing on the block of dry ice. Light is coming from a 150W halogen desk lamp. Droplets of alcohol are clearly visible; shaking the jar to move the source produces a definite fog which settles out after a minute or two.

Any suggestions?

Disclaimer: I am not the most intelligent kuron.

The idiot's guide to how to view cosmic ray tracks from the comfort of your own home | 76 comments (71 topical, 5 editorial, 0 hidden)
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