4.5 Billion

The half-life of Uranium-238 is 4.5 billion years but the half-life of Uranium-228 is one-fifth of a second.

So what?

This is a pleasant reminder that all the facts we produce have a life span – some very long and others very short. Uraniam-238, like some scientific facts, may have a very lengthy period of utility. Other, similar sounding facts may have value for seconds, much like Uranium-228.