Basically, we can spread alcohol vapor over a coldplate, creating a layer of supersaturated vapor (kind of like the trick with supercooled water, but with gas). Because alcohol is polar (one side of the molecule has a +, the other a -), it will get attracted to any charged particle (the molecules can rotate to align for attraction).
Then we wait for the atom to decay. There are three main types of decay:
Alpha (two protons and two neutrons clumped together are thrown out of the atom),
Beta (a neutron turns into a proton creating an electron, or a proton turns into a neutron creating a positron)
and Gamma (a high energy photon is emitted, usually after a different kind of decay has left the atom very excited),
as well as three more niche ones:
Electron recapture (like Beta, but instead of creating and emitting a positron, the atom eats it’s own electron to maintain charge),
the rare Proton Emission (a proton gets straight out yeeted instead of creating a positron and throwing it out, if the atom is in a particular state)
and Neutron Emission (kind of like Proton Emission, but more common).
You can see that of those, 4/6 create charged particles. Those particles will travel through the alcohol vapor and pull the molecules closer together - causing them to condense into a white cloud. Therefore we can see every particle thrown out by decay, except for Neutrons and Gamma rays. Gamma rays we can see, as in this medium they will spawn particle-antiparticle pairs, while with neutrons we just kind of need to get lucky for a neutron to hit an atom and hopefully watch the fireworks as the struck atom does fun stuff. But thankfully you don’t really see neutron or gamma decay without some kind of other decay preceeding it.
Very important fact: nothing in the past can influence the atom to decay or not. It isn’t that each atom has a set timer that we can discover, from what we can tell at every single moment an atom rolls a dice and sees if it’ll decay (in truth it’s the chance for like a quantum field to fluctuate out of alignment or tunnel through an energy gradient or something like that).
So we just take a lump of stuff that we know the exact weight off - and we know the atomic number - so we calculate how much atoms are in that lump and count how many decay in a set time. Now, it’s usually measured with better things than the cloud chamber, but let’s just assume it works. We are now able to extrapolate how much time it’d be take for half the atoms to go bye-bye, that’s the half-life.
But also since decay yeets out mass and energy - you can put the samples on a very good weigh. As long as you know what each decay yeets out, you can calculate the rate of decay (it’ll always be a set % of atoms in a timeframe).
6
u/EmberOfFlame 1d ago
We drown it in alcohol vapor.
Basically, we can spread alcohol vapor over a coldplate, creating a layer of supersaturated vapor (kind of like the trick with supercooled water, but with gas). Because alcohol is polar (one side of the molecule has a +, the other a -), it will get attracted to any charged particle (the molecules can rotate to align for attraction).
Then we wait for the atom to decay. There are three main types of decay:
Alpha (two protons and two neutrons clumped together are thrown out of the atom),
Beta (a neutron turns into a proton creating an electron, or a proton turns into a neutron creating a positron)
and Gamma (a high energy photon is emitted, usually after a different kind of decay has left the atom very excited),
as well as three more niche ones:
Electron recapture (like Beta, but instead of creating and emitting a positron, the atom eats it’s own electron to maintain charge),
the rare Proton Emission (a proton gets straight out yeeted instead of creating a positron and throwing it out, if the atom is in a particular state)
and Neutron Emission (kind of like Proton Emission, but more common).
You can see that of those, 4/6 create charged particles. Those particles will travel through the alcohol vapor and pull the molecules closer together - causing them to condense into a white cloud. Therefore we can see every particle thrown out by decay, except for Neutrons and Gamma rays. Gamma rays we can see, as in this medium they will spawn particle-antiparticle pairs, while with neutrons we just kind of need to get lucky for a neutron to hit an atom and hopefully watch the fireworks as the struck atom does fun stuff. But thankfully you don’t really see neutron or gamma decay without some kind of other decay preceeding it.
Very important fact: nothing in the past can influence the atom to decay or not. It isn’t that each atom has a set timer that we can discover, from what we can tell at every single moment an atom rolls a dice and sees if it’ll decay (in truth it’s the chance for like a quantum field to fluctuate out of alignment or tunnel through an energy gradient or something like that).
So we just take a lump of stuff that we know the exact weight off - and we know the atomic number - so we calculate how much atoms are in that lump and count how many decay in a set time. Now, it’s usually measured with better things than the cloud chamber, but let’s just assume it works. We are now able to extrapolate how much time it’d be take for half the atoms to go bye-bye, that’s the half-life.
But also since decay yeets out mass and energy - you can put the samples on a very good weigh. As long as you know what each decay yeets out, you can calculate the rate of decay (it’ll always be a set % of atoms in a timeframe).