Occasionally the claim comes up that the universe was somehow invented entirely for the benefit of the human race: a bunch of teeny-tiny humans squirreled away on a teeny-tiny planet in a corner of a single galaxy among hundreds of billions of galaxies. For point of reference, the current size of the universe is an estimated 93 billion light-years in diameter.
In comparison, I decided to compare what this would be like with creating an equivalent sized aquarium for a handful of small fish. I currently have said group of fish in a modest-sized 20 gallon tank that is 2 feet wide.
Scaling up the fish tank relative to the size of Earth in comparison to the entire universe, the equivalent size of aquarium for those fish would be about 7 light-years in diameter.
To put that size in comparison, our entire solar system is only 1.5 light-years in diameter. The nearest star is only ~4 light-years away. This would be a fish tank big enough to house multiple solar systems.
Would it make sense to build an aquarium 7 light years in diameter to house a handful of fish that are otherwise comfortably housed in a 20 gallon tank? Nope. That seems a highly impractical and rather wasteful use of space.
So why would anyone create a universe 93 billion light-years in diameter to house a bunch of tiny humans on a teeny-tiny planet?
(Note: I fully recognize this is kind of a dumb argument. But I thought it was worth making just to give a sense of scale to the size of the universe.)
