I did a bit of searching and the initial size you mention seems to be the initial size to which extrapolation is possible given information we have and that past that point it’s unknowable?
the time with a hot QGP filing every bit of space is what things would look like immediately after the Inflationary Epoch, around t=10^32. The region of space that would eventually become the visible universe was maybe the size of an orange then. Inflation is often described as the “bang” in the Big Bang. Physics can describe the universe back to inflation very well, but before that things get less clear. Most think the four fundamental forces (gravity, electromagnetism, and the strong and weak nuclear forces) were all one, at a temperature of 10^30 degrees, and things spread out and cooled until the gravity peeled off on its own. Things spread out and cooled a bit more and the strong force separated from the electroweak force. It may have been this transition that triggered cosmic inflation. Things spread out a lot more (by a factor of at least 10^26!), then stopped and returned to growing gently. That point in time is where the laws of physics are well-described, and testable in particle accelerators
I did a bit of searching and the initial size you mention seems to be the initial size to which extrapolation is possible given information we have and that past that point it’s unknowable?
the time with a hot QGP filing every bit of space is what things would look like immediately after the Inflationary Epoch, around t=10^32. The region of space that would eventually become the visible universe was maybe the size of an orange then. Inflation is often described as the “bang” in the Big Bang. Physics can describe the universe back to inflation very well, but before that things get less clear. Most think the four fundamental forces (gravity, electromagnetism, and the strong and weak nuclear forces) were all one, at a temperature of 10^30 degrees, and things spread out and cooled until the gravity peeled off on its own. Things spread out and cooled a bit more and the strong force separated from the electroweak force. It may have been this transition that triggered cosmic inflation. Things spread out a lot more (by a factor of at least 10^26!), then stopped and returned to growing gently. That point in time is where the laws of physics are well-described, and testable in particle accelerators