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Re: radioactivity

At 11:28 PM 10/25/00 -0700, Leigh Palmer wrote:
The strong force is sufficiently strong to stabilize the uranium
nucleus against decay.

It would be slightly better terminology to say the strong force is strong
enough to make U238 _metastable_ against decay.

This is in contrast to, say, Fe56 which is _stable_ against alpha decay
because the reaction products would have a higher energy than the reactant.

In nuclear reactions, just as in chemical reactions:
1) The binding strength (i.e. energy) says whether a given reaction is
possible.
2) In principle you should also worry about entropy; thermal effects can
drive things in a direction that is energetically unfavorable. In
practice, though, it is unusual to find T and S high enough to affect
nuclear reactions.
3) You then need to worry about the _rate_ at which a reaction will
proceed. That depends on the details of _intermediate_ states, not just
the energy of the initial and final states.

after many tries and billions of years, on average, the helium
nucleus escapes

There's also a 50ppm chance that it will undergo fission rather than alpha
decay.
http://klbproductions.com/yogi/periodic/U-pg2.html