Timeline for How close does a particle-antiparticle pair need to be for annihilation to happen?
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| Nov 12, 2019 at 3:39 | comment | added | Floris | The above was very approximate and quite possibly wrong (late night, no piece of paper). I encourage you to try this calculation properly for yourself, using conservation of momentum (assuming elastic collisions). If I’m even off by an order of magnitude, annihilating 2+2 grams of (matter + antimatter) material would release an astonishing amount of heat - about $4\cdot 10^16\ \rm{W}$. Hot. Very hot. Better keep the vacuum on. | |
| Nov 12, 2019 at 3:35 | comment | added | Floris | @SurpriseDog I see - you are referring to the “sizzling cannonball”. I suppose what they are saying is that the number of contact points may be relatively small and that the energy released may suspend the cannon ball in the way that a drop of water can “float” on a hot surface. I worry about the mass of air annihilating per second by hitting your object, and how hot that would make it. Spitballing: a pressure of 1 atm means about 10 N / $\rm{cm^2}$. If average air molecules travel at 500 m/s, that means the mass of air hitting one square cm is 20 gram. All of which would annihilate. NOT SAFE. | |
| Nov 12, 2019 at 3:11 | comment | added | SurpriseDog | @Floris Someone mentioned it in this chat: chat.stackexchange.com/rooms/100913/… | |
| Nov 12, 2019 at 3:07 | comment | added | Floris | @SurpriseDog Not at all. Where did you get the idea that the reaction rate would be slow? I only stated they need to be “close”. But while this means that magnetic confinement works just find for antimatter, it doesn’t mean you can touch it with a glove. While normal matter “can only get so close” until it feels a repulsive force, if an atom were made of antimatter it would keep going - and the moment a normal atom would feel repulsion, the antimatter would undergo annihilation. So - NOT SAFE TO HOLD IN A GLOVED HAND. | |
| Nov 12, 2019 at 3:00 | comment | added | SurpriseDog | Would this mean that antimatter would be safe to hold in a gloved hand, due to the slow reaction rate of the surface? | |
| S Feb 23, 2019 at 22:14 | history | suggested | Paul Young | CC BY-SA 4.0 |
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| Feb 23, 2019 at 20:56 | review | Suggested edits | |||
| S Feb 23, 2019 at 22:14 | |||||
| Feb 2, 2016 at 19:28 | comment | added | Floris | @jinawee - somewhat related. I think you have to do this numerically... | |
| Feb 2, 2016 at 19:06 | comment | added | jinawee | Would you know to get some numbers? I was thinking of modelling electron-positron as gaussian packets and then calculating the transition amplitude to a photon pair. But I think this is impossible to calculate. And I guess that plane waves are not a valid approximation in this case. | |
| Feb 2, 2016 at 18:57 | history | edited | Floris | CC BY-SA 3.0 |
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| Oct 28, 2015 at 14:45 | vote | accept | docscience | ||
| Oct 22, 2015 at 12:57 | comment | added | JiK | I've always thought that "isn't really a point [...] probability of finding it at any particular point" explanations are often more confusing than helpful. If they're not points, how come we still have probability of finding them at a point? And in this case: The wave functions overlapping means that it is possible that we find them at the exactly same point, right? But the probability of that would be infinitesimally small (if the particle positions are independent)? So it feels like there's still need for having positive probability of finding them close enough to each other. | |
| Oct 22, 2015 at 6:22 | comment | added | Iwillnotexist Idonotexist | Interesting! So any particle is in danger of being annihilated by its antiparticle, just with an absymally low probability. How does one compute the overlap? Integral of product of probability amplitude? | |
| Oct 22, 2015 at 0:27 | comment | added | Floris | @GennaroTedesco fair point - edited | |
| Oct 22, 2015 at 0:27 | history | edited | Floris | CC BY-SA 3.0 |
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| Oct 22, 2015 at 0:19 | comment | added | gented | Saying that a particle is a wavefunction is very dangerous, in my opinion (although it's quite clear what you mean anyway). | |
| Oct 22, 2015 at 0:06 | comment | added | dmckee --- ex-moderator kitten | Hadron annihilation reaction are automatically complicated. You are likely to get some light meson and lepton pairs. | |
| Oct 21, 2015 at 23:58 | comment | added | docscience | Regarding your last question ... not any particular pair in mind, but a neutron/antineutron might do for the purpose of discussion. | |
| Oct 21, 2015 at 23:31 | history | answered | Floris | CC BY-SA 3.0 |