# Half-Life Inquiry **URL:** \ **Category:** Factual Questions\ **Created:** [July 9, 2025, 4:25pm UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665 "2025-07-09T16:25:36Z")\ **Posts on this page:** 1\ **Showing post:** 20
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [July 11, 2025, 1:34am UTC](https://boards.straightdope.com/t/half-life-inquiry/1020665/20 "2025-07-11T01:34:26Z")
> [@Lumpy](#): > > What I have a problem with is that it seems to me that radioactive decay is an example of **spontaneous** decoherence: the unstable nucleus self-observes and then forces the rest of the universe to acknowledge that a decay took place. It’s still environmental at the heart of it. Consider a different scenario involving two laser-trapped atoms isolated from the rest of the universe and initialized in a superposed, entangled way such that Atom 1 is in state A and Atom 2 is in state B _or_ Atom 1 is in state B and Atom 2 is in state A. Upon measuring Atom 1’s state, there is a 50% chance (say) of measuring A and, immediately after that, Atom 2 would be measured as B with a 100% chance. But the environment interferes. In practice, Atom 1’s state might not be 50%/50% A/B, and Atom 2’s state won’t be 100% determinable from the measurement outcome for Atom 1. Coherence is lost with time, and it’s hard to fight even in extremely controlled settings. For the nucleus example: the state “The nucleus has decayed” is much _much_ less isolatable from the environment – so much so that one would never even think about the superposition of the pre- and post-decayed states in any practical situation. After all, stuff comes shooting out into the environment immediately, and there’s also no way to practically set up an experiment that could reveal a superposition without also measuring a specific state for the nucleus in the process. --- _[View the full topic](https://boards.straightdope.com/t/half-life-inquiry/1020665)._