kenotron

technically, no, the universe wasn't the size of a pinpoint, the visible universe may have been that size, but the capital-u Universe is very possibly infinite, so it was still infinite back then, just denser. /Much/ denser.

Two points on opposite ends of the visible universe right now (90-something billion light years apart) used to be a millimeter away from each other. Every thing and every where today was there then, just unimaginably compacted, and hot, hot enough to melt matter into an infinite quark gluon plasma. So there were no atoms, no protons even...so dense it would immediately collapse into a black hole today, but with just as much stuff in every direction, there was nowhere for the stuff to condense into.

So yeah, don't fill up your suitcase that much, or you'll make a black hole and your socks will be gone, like /really/ gone

y'all'dn't've forgotten an apostrophe if y'all'd de-contractify it: "you all would not have"

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