Correct me if I'm wrong but in quantum mechanics particles appear and disappear in space all the time without a cause.
I'm pretty sure that they don't so much dissapear as they do 'annihilate.' There are things called 'antiparticals' that, to my knowledge, can do anything a particle can. If a partical and antiparticle come in contact with eachother they're apparently canceled out of existence. So, they don't dissapear for no reason.
Now, and this part's from my hazy recollection of 'A brief history of Time' also by Stephen Hawking, they don't really 'appear' as so much come from the past or future via wormholes. There's also a way they can travel through time that has something to do with the Event Horizon of Black Holes(I think), but I can't remember it.
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