The lifetime of an unstable nucleus

[wdlang]

protons and neutrons interact with each other with the strong force, which is very strong

however, there are many unstable nucleus which have a lifetime in the order of millions of years

this is quite strange

the time scale of strong interaction is many many orders smaller than that of the lifetime

how is this possible?

 

[andrien]

you are confusing weak decay with strong interactions.

 

[wdlang]

you are confusing weak decay with strong interactions.

what is the force responsible for the decay of Ur?

weak interaction or strong interaction?

 

[andrien]

By what reaction it decay.that is the answer.

 

[mfb]

Beta decays are always weak (quark numbers are not conserved).
Alpha decays have a different issue: Those alpha particles do not have enough energy to escape in a classical way - they have to tunnel through a potential barrier, and the tunneling probability can be very small.
Gamma decays can be long-living, if they do not have a (significant) dipole moment, and require the emission of multiple photons at the same time. And, of course, the electromagnetic interaction is weaker than the strong interaction.