The Physics of Nothing; The Philosophy of Everything

“Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing had happened.” –Winston Churchill

It’s often said that you can’t get something from nothing. And while this may be true for most practical applications of your life, it isn’t true for our physical Universe.

And I don’t just mean some tiny part of it; I mean all of it. When you take a look at the Universe out there, whether you’re looking at the wonders of this world or all that we can see for billions of light years, it’s hard not to wonder — at some point — where it all came from.

Image credit: FORS Deep Field, ESO Very Large Telescope, retrieved from imprs-astro.mpg.de.

And so we try to answer it scientifically. In order to do that, we want to start with a scientific definition of nothing. In our nearby Universe, nothing is hard to come by. We are surrounded by matter, radiation, and energy everywhere we look. Even if we blocked it all out — creating a perfect, cold, isolated vacuum — we still wouldn’t have nothing.

We would still exist in curved spacetime. The very presence of nearby objects with mass or energy distorts the very fabric of the Universe, meaning that if we want to truly achieve a state of physical nothingness, we cannot have anything in our Universe at all.

Physically, that ideal case would be true nothingness. No matter, no radiation, no energy, no spatial curvature. We can imagine existing in completely empty, void space, infinitely far away from the nearest star, galaxy, atom or photon. The spacetime around us, rather than having curvature to it, would appear as completely flat.

The only physical freedom that such nothingness could have is the freedom to expand or contract, depending on the nature of this nothingness. Recently, Edward Feser picked on me — among others such as Hawking, but me in particular — for using this scientific definition of nothing. (Which yes, I’m fully aware is not the same as philosophical nothingness, which I explicitly stated in the fourth sentence of the post Feser criticizes.)

Yet it is a form of this very nothingness that I have just imagined with you that — to the best of our scientific knowledge — the entire Universe is born from, and that it will return to in the distant future.

Here’s how.

You removed all the matter, energy, and sources of curvature from your Universe. You are left with empty spacetime. On large scales — where “large” means larger than the size of a subatomic particle like a proton — spacetime indeed looks like that flat grid we referred to earlier. But if you start looking at ever smaller scales, this picture breaks down.

On the tiniest physical scales — the Planck scale — spacetime isn’t flat at all. Empty space itself vibrates and curves, and there is a fundamental uncertainty in the energy content — at any given time — of nothingness.

This quantum vacuum — on these very small scales — manifests this fundamental uncertainty by spontaneously creating pairs of particles-and-antiparticles for very brief amounts of time.

Everywhere. All the time. Even in empty space.

This is not merely some theoretical quantum prediction.

Image credit: NASA/Michelle Murphy (WYLE).

This is experimental fact. We can artificially create a vacuum chamber (like the world’s largest one, above) that is — while imperfect — good enough to detect the physical effects of these spontaneously created particle-antiparticle pairs.

Take a vacuum, and inside of it, place two parallel, uncharged metal plates.

In the absence of these vacuum fluctuations, you would expect the force between the plates to be dominated by gravitation. But if you bring these plates close enough together, you find that these vacuum fluctuations cause the plates to attract one another! This attractive force is purely quantum in nature, and is the surefire experimental evidence — that’s been around since 1948 — that this is the physical nature of nothingness.

Now, combine this with the one thing this empty spacetime is allowed to do: expand.

Image credit: Flickr user Absolute Chaos; apologies that the animation is so large!

These fluctuations — if the Universe is expanding quickly enough — can get caught up in the expansion of spacetime so thoroughly that they do not re-annihilate, but instead get stretched across the empty spacetime of your Universe!

If the Early Universe existed in a metastable, or false vacuum, state, it would continue to stretch these quantum fluctuations across the Universe — on all scales — for as long as you remained in that state.

Image credit: Ned Wright, and see his cosmology tutorial for more details on this.

But this state does not last forever; there is a more stable state that the Universe will eventually find, just as a ball placed atop the hill above will eventually roll down into the valley below. When this happens, matter and energy spontaneously generate during the transition from the metastable state to the more stable state, through a process known as reheating.

These quantum fluctuations — that were stretched across the Universe — now become regions where matter/energy is initially slightly more or less dense than it is on average.

And as the Universe ages, the more dense regions grow and grow — under the influence of gravity and over many millions and then billions of years — into the stars, galaxies and clusters that fill our Universe today.

Image credit: CLEF-SSH.

By the time we arrive at today, we’ve obtained the Universe we currently exist in. We started from literally nothing; from empty spacetime containing solely the energy of the quantum vacuum, and have arrived at our Universe today, with its billions of galaxies, stars, and all that ever was or will be here on Earth.

Image credit: Bob Haslett.

And one of the most amazing things about all of this is that the Universe as we see it now is still expanding. Not only expanding, but it still contains a small amount of this energy of nothingness.

We have not fallen into the lowest possible valley of nothingness (region II); contrariwise, we still have some non-zero fundamental energy to spacetime. This fundamental fabric of spacetime — the Universe devoid of matter, energy, radiation, and anything else you can imagine — will eventually, as the stars burn and die and the galaxies separate and every unstable thing decays away, return to a cold, flat, empty, expanding state of nothingness once again.

For the more philosophically inclined among you, I give you Alan Watts, who has this to say about nothingness:

Nothingness is really like the nothingness of space, which contains the whole Universe. All the Sun and the stars and the mountains and rivers and the good men and the bad men and the animals and the insects, the whole bit: all are contained in the void. So out of this void comes everything, and you’re it.

Video credit: YouTube user dFalcStudios.

This entire Universe came from one form of nothing, this entire Universe will eventually return to a slightly different form of nothing, and despite the paradoxical nature of this, here it all is.

Out of this void comes everything, and you’re it.