There is no limit to what can fit in your suitcase if you are ok with creating a singularity.
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
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 know we’ll probably never know, but I always wonder how the singularity came to be. Some will say it was a previous universe that reverted back and has been infinitely doing so, but how did it start??
That is the question, what banged and why did it bang. There’s some quantum theories that elude to a possible source of the big bang, but nothing widely accepted. As to why, that’s an even tougher question.
The term singularity as applied in cosmology comes from the mathematical definition where one variable approaches infinity as another goes to zero. This is bad in math since it means an equation is not defined across all values. This is what happens mathematically as you get closer to time zero for the big bang. Same with the gravity of a black hole as you move toward the center. In that sense the size of the big bang at time zero would be zero, but the math breaks down so it’s not actually defined. Physicists generally believe that’s not the case due to the quantum nature of the universe, but we don’t have the math to explore it.
There are ways for things to come from nothing in quantum mechanics. Positive/negative particle pairs can pop into existence because their average energy is 0. They’re typically very shortly lived though. It’s possible it didn’t come from anything and just was. Time is also part of space-time, so there wasn’t a “before” most likely either
Is it really so crazy to think that it might have always existed? I mean, it is very bold of us to assume that it is not possible to not have a starting point when there is so much we just don’t know. We barely understand the physics of our universe when things start to get wonky.
In the grand scheme of things I guess it is not. The problem is that statement is infalsifiable, like the Last Thursdayism theory. Therefore, it falls into more of philosophical space, where Occam’s Razor would eliminate this because the alternative requires less assumption. It isn’t wrong, it just requires much more assumptions to be correct in order to work.
