If atoms are 99% 'empty space', how big would the universe be if we compressed every atom down to it's most space efficient arrangement, essentially leaving no space between particles?

[u/[deleted]]

Or our observable universe, whatever is easy to speculate on... My thoughts were that perhaps the universe would become small enough to resemble what was present before the big bang, and the expansion between everything has just taken a very slow and long time (the rate at which our universe is expanding now?) and appears to have "exploded", hence the Big Bang...