Oh, quantum physics. Just when we think we've got you all figured out with your Schrödinger's cat experiment and your hologram Universe hypothesis, you go and throw us for a loop by coming up with a creepy thought experiment that could prove (or disprove) immortality once and for all.
All you have to do, as this video by Wendover Productions explains, is simply lock yourself in a room with a live nuke and play Russian roulette with a proton-shaped trigger. ¯\_(ツ)_/¯
(And, uh, do we need to tell you not to try this one at home? Because, you know, quantum physics doesn't necessarily have the best success rate.)
First of all, let's step back for a second, because this whole thing has escalated pretty quickly. To start with, let's make it clear that this is all a thought experiment - and that's because quantum mechanical systems, in all their weirdness, can't yet be measured without them being altered… which sort of defeats the point of measuring them in the first place.
Or as the Wendover Productions team explains so skilfully in the video above, it's like calculating how far away a medicine ball is by rolling a tennis ball up to it and seeing how quickly it bounces back. It works, but the tennis ball has just knocked the medicine ball out of its original position, oops!
That's why thought experiments are so great - just like Schrödinger's cat, scientists are able to test out their quantum hypotheses without having to mess up the precious systems they're considering.
In this case, it's the 'many world interpretation' - often called the MWI for short. And btw, this video calls it the many world "theory" - even though we're pretty sure they mean hypothesis (don't worry, guys, even smart people get that one wrong occasionally).
Theory/hypothesis mix up aside, the many world interpretation basically states that every single time a decision is made, our Universe splits into multiple universes in which each possible outcome happens.
So imagine you're standing on top of a cliff contemplating jumping into the water below. According to MWI, if in this Universe you jump (brave!), another universe exists where you didn't jump, and it's slightly altered forever as a result. Thinking Sliding Doors on a quantum scale.
But back to being locked in a room with that live nuke. You're hypothetically trapped in that sticky situation because it's a thought experiment we can use to test the MWI - and prove or disprove whether immortality is, in fact, scientifically possible. (In case you were wondering, the experiment has been given the name 'quantum suicide'. Nice.)
We'll let the video above run you through that, because it's seriously fascinating stuff. But long story short, if MWI is correct, then we're all immortal, and we have nothing to fear from playing Russian roulette with a live nuke - except spawning infinite other universes where we die a painful death over and over again.
Like we said, everyone's a winner when it comes to quantum physics. Everyone.