The UK Mirror recently carried a weird story claiming that there are numbers so big that they would create a black hole in your brain if you could memorise them. The title of the article is:
"The enormous number which could 'create a black hole in your BRAIN if you attempt to memorise it'"
The article talks about big numbers, such as Graham's Number and TREE(3). I was at a pub quiz last year where they asked about the largest number with a name. I got the answer wrong by answering Graham, and I learned later that TREE(3) is even bigger. But the annoying thing was that the quiz answer was a googolplex - which is a lot smaller than either of the other two.
The article goes on to say that:
"if you tried to hold all the numbers in your head it would collapse".
Obviously this is nonsense - trying to memorise a very big number is not going to make your head collapse - and certainly not because of the creation of a black hole inside your head. I've had a good think, and reckon that maybe the genesis of this idea is that someone's considered the storage of large numbers. If we worked out the mass of neurons it would take to record one of these large numbers, and imagine all of that brain mass stuffed into the space of a skull, the mass would pass the Chandrasekhar limit and gravity would pull all the matter into a singularity, creating a black hole. Obviously simply trying to memorise a big number is not going to make those extra neurons materialise and cause your brain to collapse.