97% of the observable universe is forever unreachable

The other day, I was reading a post by Ethan Siegel on his excellent blog, Starts With a Bang, about whether it makes sense to consider the universe to be a giant brain.  (The short answer is no, but read his post for the details.)  Something he mentioned in the post caught my attention. But … Continue reading 97% of the observable universe is forever unreachable

The size of the observable universe is complicated.

The radius of the observable universe is often stated to be 46 billion light years.  From a certain point of view, this is true, but I think it's a bit of a misleading statement.  Occasionally you also see people say that the observable universe is 13.8 billion light years in radius, which is also true, from … Continue reading The size of the observable universe is complicated.