Lifetimes of Neutrons and Extra-galactic Photons
Most recent answer: 06/16/2015
- ana (age 13)
Iran
Hi Ana,
Nice questions. That number for the lifetime of the neutron, 15 minutes or so, is only for free neutrons. Neutrons bound inside nuclei, like most of yours are, don't decay because conservation of energy won't allow them to. There are a few odd-ball nuclei that will decay via positron emission, i.e. C14 --> N14 + e- + anti-neutrino but they are very rare and your body doesn't contain many of them . See for some more information.
As for your second question, photons don't decay. They just keep on going forever unless they bump into something and scatter or get absorbed. This allows astronomers to see objects at the far ends of the universe and the beginning of time.
LeeH
(published on 06/16/2015)