Far out cosmology: four types of nothing (Introduction)

by David Turell , Saturday, December 24, 2022, 18:55 (489 days ago) @ David Turell

Ethan Siegel offers definitions:

https://bigthink.com/starts-with-a-bang/4-meanings-nothing/?utm_source=mailchimp&ut...

"All of the things that we see and experience in the Universe today have only been around for a finite amount of time. The Universe didn’t always have galaxies, stars, or atoms, and so they must have arisen at some point. But what did they come from? While the obvious answer might seem to be “something,” that’s not necessarily true; they may have arisen from nothing. What does “nothing” mean to a scientist in that context? Depending on who you ask, you might get one of four different answers. Here’s what they all mean.

"1.) A condition where the raw ingredients to create your “something” didn’t exist...how did we wind up with a matter-filled Universe, instead of one with equal amounts of matter and antimatter? That’s the first scientific meaning of getting something from nothing.

"2.) Nothingness is the void of empty space. Perhaps you prefer a definition of nothing that contains literally “no things” in it at all. If you follow that line of thinking, then the first definition is inadequate: it clearly contains “something.” In order to achieve nothingness, you’ll have to get rid of every fundamental constituent of matter. Every quantum of radiation has to go. Every particle and antiparticle, from the ghostly neutrino to whatever dark matter is, must be removed.

***

"If you could somehow remove them all — each and every one — you could ensure that the only thing that was left behind was empty space itself. With no particles or antiparticles, no matter or radiation, no identifiable quanta of any type in your Universe, all you’d have left is the void of empty space itself. To some, that’s the true scientific definition of “nothingness.”

***

"But certain physical entities still remain, even under that highly restrictive and imaginative scenario. The laws of physics are still there, which means that quantum fields still permeate the Universe. That includes the electromagnetic field, the gravitational field, the Higgs field, and the fields arising from the nuclear forces. Spacetime is still there, governed by General Relativity. The fundamental constants are all still in place, all with the same values we observe them to have.

***

"3.) Nothingness as the ideal lowest-energy state possible for spacetime. Right now, our Universe has a zero-point energy, or an energy inherent to space itself, that’s at a positive, non-zero value. We do not know whether this is the true “ground state” of the Universe, i.e., the lowest energy state possible, or whether we can still go lower. It’s possible that we’re in a false vacuum state, and that the true vacuum, or the true lowest-energy state, will either be closer to zero or may actually go all the way to zero.

***

"4.) Nothingness only occurs when you remove the entire Universe and the laws that govern it. This is the most extreme case of all: a case that steps out of reality — out of space, time, and physics itself — to imagine a Platonic ideal of nothingness. We can conceive of removing everything we can imagine: space, time, and the governing rules of reality. Physicists have no definition for anything here; this is pure philosophical nothingness.

"In the context of physics, this creates a problem: we cannot make any sense of this sort of nothingness. We’d be compelled to assume that there is such a thing as a state that can exist outside of space and time, and that spacetime itself, as well as the rules that govern all of the physical entities we know of, can then emerge from this hypothesized, idealized state.

***

"This final definition of nothing, while it certainly feels the most philosophically satisfying, may not have a meaning at all. It could just be a logical construct borne out of our inadequate human intuition.

***

"Each of the four definitions is correct in its own way, but what’s most important is understanding what the speaker means when they’re talking about their particular form of nothingness. Each definition has its own scope and range of validity, with applications to a wide range of particular physical problems, from the origin of matter to dark energy to cosmic inflation to the zero-point energy of space itself. But these concepts have a drawback as well: they’re all constructs of our own minds. Everything we know of certainly came from nothing. The key is to understand how."

Comment: As a pure scientist he is not allowed to jump to the obvious: God made it all from No. 4, pure nothingness. Of course, it "steps out of reality".