I know this is a total noob question, but once a number is so
big power towers are useless, how do you tell how big a number is
compared to other numbers? I know if they're in the same notation
it's pretty easy, but if I've got 2^^^^4 and I want to compare it
to something in, say, Hyper-E notation (just an example), how do I
do that?

I'm also having trouble with the Fast-Growing Hierarchy. Say
you've got and I just have no idea where to go from there.

I guess I'm not used to thinking beyond exponents. Can anyone
help me improve?