Science Questions

How long do fundamental particles last?

Sun, 25th Nov 2012

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Salih asked:

Dear †Dr. Smith,


How long do protons and neutrons survive outside an atom?




Martin -   Protons and electrons, as far as weíre concerned in our lifetime last forever.  

Neutrons last for just under 15 minutes if they're on their own.  To do an experiment, actually the experiments we do with neutron scattering take place where you only need for them to last for less than a second.  So thatís not an issue.  But you can actually capture neutrons, put them in something like a little bottle.  They last for just under 15 minutes.  If you have a neutron thatís actually part of a nucleus then it effectively lasts forever.  But on its own,  just under 15 minutes.

Dave -   So being inside that nucleus is somehow stabilising it, making it last a lifetime.

Martin -   Yes, absolutely.


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Can Neutrons and Protons be considered Fundamental particles are they not just bundles of Quarks and Gluons that can only be separated at very high energy ?
It is an interesting point that the mass of a proton is much higher than its constituent parts in as much as they can be measured. syhprum, Tue, 27th Nov 2012

If the neutron lasts for only 15 minutes without the influence of the atomic nucleus, does the neutron exist as such in a neutron star because of the extreme pressures? And if this is so, what about the surface of the neutron star? Are the neutrons also stable at it's surface where pressures are much less than in the interior? Ethos_, Tue, 27th Nov 2012

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