Cloud Chamber: The Birth of Helium Atoms
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Cloud Chamber: The Birth of Helium Atoms

[MUSIC PLAYING] So here we are on the last day
of the recording for the Christmas Lectures, but
I thought I’d take an opportunity to point this out
because it’s so beautiful. This is a really stunning cloud
chamber, and the tracks that you can see here show just
the natural radiation in the atmosphere around us. So if we actually have a look in
here, you can see sometimes there are thicker tracks which
are big heavy alpha particles. Sometimes they’re little
wispy ones, which are beta particles. But all of these, they’re all
working in the same way. So the atmosphere in
here contains a lot vapour of alcohol. And it’s sort of more
than it should have. And when these charged particles
fire through the atmosphere in here, they cause
little droplets to form, and those are the clouds
that you’re seeing. So this is a similar sort of
thing to when you get a track behind an airplane. There’s a lot of moisture in the
atmosphere and it’s just the exhaust, just helping those
drops of moisture to form together and leave
that cloud. And this is a tiny little
sample of the element called Americium. And this is used in
smoke detectors. So you’ve probably got some of
this in your home, at least you should have. So this is an artificially
produced metal. And as soon as this is
introduced, look at that. What we’re seeing here are
tracks from the alpha particles emitted from this
radioactive source. And these alpha particles, with
their two protons, two neutrons, and they
grab electrons and form Helium atoms. So what you’re seeing here are
the birth of Helium atoms. [MUSIC PLAYING]


  • RBGVelvet

    Yes, yes it can. I believe this is one of the only ways we can produce helium on Earth. A great proportion of the helium in the universe has been made in the stars.

  • Gerrit Zimmermann

    No. Radioactivity is a statistcal process that cannot be influenced easily.

    What leads to your oberservation is simply that alpha particles don't get very far until they collide with alcohol molecules in the chamber.
    Moving the rod around simply makes the vapor produced more visible in a kind of "Doppler-Effect", which is by concentrating wisps of vapor in one point and thereby making them more visible than on their own.

  • Advanced Tenchology

    How fast do the α particles travel in that? Couple of thousands of km/s? That's magnitudes more than the speed of that rod moving. I think this takes the "Doppler effect" or "shock front" out of the game. At least as I interpret those terms.

  • Gerrit Zimmermann

    The speed is not that important to the effect. The key is the length of "free space" a particle can travel before it hits a alcohol molecure and looses it's kinetic energy. It's basically like a game of billiards where the play ball is much smaller than the other balls on the table (a helium core has a relative mass of 4, alcohol 6*1 + 2*12 + 16 = 46).

  • Gerrit Zimmermann

    In a vacuum alpha particles can travel quite far, and yes, speed does have an effect as well, but the driving factor here is kinectic energy in relation to effective diameter. That's why beta radiation gives longer tracks in a cloud chamber than alpha radiation (similar (~1:10) kinetic energy, but much smaller effective diameter ~1:1000 IIRC) and a cloud chamber will predominantly show those from natural radiation / cosmic rays. Look up Thomson or Compton Scattering if you're interested.

  • Ocie Mitchell

    My thought on this "shock front" is that this cloud chamber only produces so much vapor in each area each second. This sample is essentially condensing all the vapor in the area immediately around it, so when you move the sample to a fresh area that has had time to recover, you see more intense condensation.

  • allnet20

    theres alot of natural gas mining in texas so i would assume that there are pockets of helium under the surf that are being vacuumed out of the earth

  • cpovey1

    On Earth Helium is rare—0.00052% by volume in the atmosphere. Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements (thorium and uranium), as the alpha particles emitted by such decays consist of helium-4 nuclei. This radiogenic helium is trapped with natural gas in concentrations up to 7% by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation.

  • EdMcF1

    Great device, wouldn't adding a powerful magnet and seeing the deflection of alpha and beta particles have been greater still?

  • p38b29

    There is one of these cloud chambers at the KKL nuclear power plant in Switzerland as well. Would anyone by chance know who the producer of these cloud chambers are?

  • ItCameFromTheSkyBeLo

    I saw this in my 12th grade chemistry class. And it forever changed the way I see the world. So glad I was able to find something showing it again.

  • fdefever

    We saw the exact same cloud chamber at the Cern open days this w/e, you can the instructions on how to make one here:

  • Propane

    I couldn't get the CERN link to work, so here's an instructional video on how to build your own (simple) cloud chamber: v=400xfGmSlqQ (paste this as applicable onto a Youtube link).


    So when people say that helium will completely disappear from earth because its lighter than what our atmosphere is composed of, The Ri will be like "nah bisshh we make dat sheet"?

  • mkd1r

    It would be nice, if you don't annoy visitors with tons of annoying youtube video overlays (like subscribe here, thank you I know how to subscribe, or watch our newest xy here).

  • Galejro

    Interesting, we were always shown radiation as some sort of perfectly spherical glowy green light, but it turns out radiation seems to look more like magnetism following bent paths and straight trails. No wonder, we always looked at auroras and never saw that pattern because we thought it was made by earths magnetism.

  • Dante Alighieri

    Thanks for sharing this vid!
    When I was a kid (~12 – 13), I had a book from the early 1960s with all kinds of great projects, the cloud chamber being one of them. I wanted to build it so badly but let's just say that home life wasn't so conducive for a burgeoning scientist. Fast forward ~30 years and I hadn't thought about it much until seeing this video. I have a boy of my own now and at five can tell you life is carbon-based (though MUCH simplified! lol). I think it's time I make that cloud chamber…

  • Gort Oregano

    Ahh delicious Americium 241.Ive inhaled & consumed,under my tongue sublingual,many times. Death wish,yes,cancer,no.After consuming it my body odor smells very sour/acidic. Im assuming its from the alpha or beta particles & possibly low energy gamma rays attacking my thyroid gland,which regulates metabolism & promotes excessive sweating.The bacteria multiply & consume edibles in my sweat which cause them to excrete byproducts that cause the odor.My wife is disturbed by my radioactive appetetite

  • Pop Corn

    Track behind an airplane are not just clouds. Have you heard about geoengineering ? or are you just doing disinformation here ?

  • KarbineKyle

    Wow! That's a PHYWE diffusion cloud chamber! They're SO expensive! They're like $60,000 for the large models! Man, I wish I had one! I have a collection of radioactive sources! Some americium-241 sources I have are 60 μCi – 60X more than the source here! The production quality of this video is amazing! The birth of helium atoms . . . that's exactly what's happening!

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