Here, read this:
We’ll pick up tomorrow where we left off—my eyes can’t even focus anymore.
I suspect part of the problem we are having is simply that there is no one theory of the growth of the universe. Things are changing so fast that there is no instant where everyone understands the theory. By the time one paper is published, others extending the ideas are already circulating.
One important point that Dr. Greene makes repeatedly. There is no theory of the origin of the universe. All the theories start with a the initial expansion of the singularity. No one has any idea what caused the singularity to form.
In fact, until Dr. Guth came up with his inflationary hypthosis based on repulsive gravity, there was no bang in the big bang. At least no theory as to why a mass of matter would just decide to fly apart against the force of gravity.
And lastly, as best I can tell it makes no sense to talk about how long the singularity existed-since spacetime itself didn’t exist there was no clock to time it with. Imagine the singularity existed for an instant or a billion years, both make no sense since time didn’t exist.
Our problem (and Prof Greene’s Fabric… book is helpful here) is that we can describe things that have mass/energy better than space.
We are utterly clueless about what “space” is and we don’t have any good description of it.
Without knowing what “space” is, its completely meaningless to talk about the “size” of the early universe as it were the size of a grapefruit sitting in…what?
Space? No; that initial entity contained all the “space” there ever was or will be. Space does not expand “into” anything, at least in current descriptions.
While Dr Guth added clarity to how to resolve some descriptive issues, in some ways the inflationary model (at least at my layman’s level) only worsened the layperson’s ability to conceptualize the size of space itself, because it puts emphasize back on the meaningless concept of space suddenly getting more volume, as if it were getting more volume inside of some other container…
Even if we were more clueful about space, most likely the physical laws we see today were not applicable during or right after the big bang. We’re looking at this from our own perceptions of gravity and what we’ve been able to figure out about space, so it all seems incredible, but I dont have a problem accepting that this event may be impossible for humans to comprehend properly because we dont have any reference to the science of universes coming into existance. We cant exactly duplicate this in a lab and we can only observe that one universe we happen to be in.
Obligatory wikipedia link:
The universe was the exact size it is now. It’s just the space between it all that was reaaaaly tiny.
But yeh, we don’t really know what space or time is. That’s one of the gigantic fundamental mysteries right now. Isn’t it cool to know that no one really knows yet?* We have some interesting ideas. They may even be likely. We can calculate how matter and energy work within it for the most part, but we’re not even sure we can ever truly figure it all out. I think we will, but who knows how far the rabbit hole goes, and what humanity’s limitations on experimentation are; not to mention the epistemic conundrum of what we can ever hope to understanding and comprehend.
*It’s kind of a bummer too, huh?
How do we know that the universe is expanding? Could it be that everything is getting smaller and only appearing to recede from everything else?
Asked only half in jest…
I don’t think it’s a dumb question really. But Redshift would be one of the biggest clues, if not the clue. Everywhere we point our telescopes, the light of each galaxy is smeared toward the red end of the visible spectrum. The lightwaves they emit is more elongated, like the sound waves trailing behind a truck as it rushes away (the Doppler effect), lowering its pitch. So, this is a tell tale sign they’re speeding away from us (and not only us, but mostly every galaxy is speeding away from every other galaxy).
ETA: I don’t think there’s any indication that matter is shrinking. Otherwise, if it were space that was shrinking, we’d see a blueshift.