/sci/ - Science & Math

Sup /sci/? My physics teacher was telling me about this experiment on the whole space-time continuum and the future and whatnot. I'm posting because I want to read more about it and was hoping you guys can point me in the right direction: articles, websites, the actual name of the experiment, etc. I searched but never find.

Anyways, a scientist has this radioactive substance, and he knows that half of it will decay in a week. Okay, but in this substance, you know half of the particles will break up, but how do you know which particles will decay and which ones wont? So, the scientist decides at the end of the week he's going to test a set of specific particles and see which ones have decayed. So at the end of the week, he finds most of the ones he had decided he would check in the past are still there. He does this again and the same thing happens. So as long as he decides he'll check a particle at the end of the week, it doesn't decay!

This blew my mind, and I really want the article or whatever. If someone can point it out to me.