dilletante said:
Scientists are hoping to create tiny black holes here on earth, which they are pretty sure will evaporate almost immediately due to Hawking radiation.
For starters, you can legitimately doubt that BH creation will occur. The scenarios in which BH will occur and be detectable are considered exotic. So it is extremely unlikely that BH creation will occur anyway. Second, it is extremely unlikely that Hawking evaporation can go wrong. I just can't make a list of all the things that could destroy the planet and that are more likely than "BH are created and they do not evaporate almost instantaneously". Believing BH will be produced and not evaporate is from this point of view schizophrenia : how could the theory be right on the unlikely, improbable prediction (BH created) and wrong on the robust prediction (evaporation) ? Again to be clear :
creation is not expected to occur, whereas evaporation not occurring would be a cataclysm in our understanding of physics. But let us admit this insane scenarion anyway... So, third, even considering this crazy scenario where BH
are created and they do
not evaporate, they would be so incredibly tiny that they can simply not interact with the environement. They would just fly away and that's it. Already at this point we are far away discussing impossible things, please realize this. But let us push on just for fun. Let us assume that besides being created, and not evaporating, they do not fly away. Let us assume that they just sit aroung here. How long will it take them to interact with the environment and start growing bigger, to the point that we could actually be scared ? Much,
much,
much[/size] more[/size] than the expected lifetime of our Sun.
While they consider the risk to be almost nonexistent
They do, and for good reasons. Physicists calculate and measure probabilities much smaller than a few parts in a billion. If that kind of things were an human attribute, it would be improbable to happen in the entire population of Earth. When we say "negligible", we mean it.
I can envision some scientist saying "cool -- wonder if we can make a little bigger one".
No way. That would require a bigger machine.
My question is how big would one have to be before it was a danger to the planet, and is it theoretically possible to make such a one in a lab?
Theoretically, anything is possible if you have enough time and money. But practically, I do not think we would have any clue hot to make a macroscopic BH. Franckly if we could, it would be worth to make one in orbit around the Sun and experiment with it. If we had the slightest clue how to do that, even in one hundred years from now, you would have quite a few people working on making this happen.
If so, I can imagine every advanced civilization eventually trying this experiment and ultimately destroying themselves.
No, definitely if we destruct ourselves, we have plenty of other ways which are zillion times more likely. Sorry for your theory. But sleep quietly about LHC destrying the world. Think about next time you take your car, which probabilities are the most relevant to spend one's time to evaluate.
