Speed of light VS 1 Second

[swansont]

1 hour ago, John Cuthber said:

Strictly, that's also true of Rb- you just need to wait about 10^12 years for the unstable one to decay.

Rb-87 has a half life of about 49 billion years. In a 1g sample of Rb that’s of order 1000 decays a second.

 

But that’s not the issue. It’s interactions that give a frequency shift, such as collisions, and having a second isotope around is a source of such interactions. And Rb has two naturally-occurring isotopes.

[Ville502]

Wow. (thumbs up)