Is Empty Space Really Empty?

Look up into the night sky, and you’d be forgiven for thinking that there isn’t much there.

With light-years between stars and even more distance between galaxies, space seems to be, for the most part, nothing but empty space.

It’s true that in those big gaps between galaxies, there isn’t always a lot going on.

At a glance, space appears to be a perfect vacuum: an area devoid of all matter. But even the furthest regions of space aren’t actually completely empty.

Space is only a partial vacuum, meaning that there’s always something there, no matter how small.

To learn exactly why the emptiness of space isn’t quite so empty, take a look at this guide to all the things you might find in a vacuum. 

Is Empty Space Really Empty?

Much of space looks empty from our perspective. We might be able to see some stars and galaxies with the naked eye, but for the most part, space is dark. 

With a telescope, we get a different perspective. Now, we can get a better idea of just what’s found within our universe.

What looked like voids and dark skies is revealed to be populated with celestial bodies.

Take a look through an even more powerful telescope, and empty space suddenly seems a lot less empty.

Even within those gaps, there appears to be movement, color, and interest.

But the universe is vast, and many of these celestial bodies have light-years between them.

This means the initial assumption that there’s a lot of empty space in space might be more accurate than first assumed.

According to the Big Bang Theory, space didn’t use to be quite so empty. Instead, dense and hot particles made up the universe.

A sudden period of rapid expansion (that Big Bang) created our larger universe. Eventually, matter cooled and was able to come together.

This gravitational collapse formed the stars, galaxies, and astronomical objects that make up our universe.

Between these objects is the vacuum that we consider outer space.

Outer space is close to a perfect vacuum, one which allows for astronomical objects to move without friction. But it isn’t completely empty.

Instead, gas, dust, light, and radiation from the Big Bang fill the space.

Even in the emptiest regions of outer space, small amounts of hydrogen atoms are found in every cubic meter.

Although it might look empty, there really is no such thing as empty space.

Vacuums

Outer space is a vacuum. That means it’s an area with close to no matter. There are two different vacuums: a perfect vacuum and a partial vacuum.

A perfect vacuum would be the total removal of everything and is purely theoretical.

A partial vacuum is a vacuum that still contains some elements of matter.

Outer space is as close to a perfect vacuum as we can get, but it’s still a partial vacuum.

So, what can be found in space that makes it a partial vacuum?

For a start, there’s often gas and dust, as well as charged particles coming from stars.

There’s also light traveling from nearby stars and radiation still hanging around from the Big Bang. 

There’s also Cosmic Microwave Background radiation (CMB), which are photons that were created during the Big Bang.

These are photons that help us learn about the early universe and fill space.

Alongside these are potentially an equally large number of neutrinos, forming the cosmic neutrino background.

The cosmic neutrino background is very difficult to detect but likely to fill the observable universe.

Magnetic fields have also been detected in outer space around celestial objects. Electrical fields can also be found in outer space. 

And if that wasn’t enough, space is also filled by cosmic rays – energetic subatomic particles – that are passing through.

Alongside these things which we can detect, outer space is filled with things we can’t detect.

Dark matter and dark energy are both theorized to be found in outer space, even if we can’t exactly find them. 

Even if we were able to remove all of the above, we still wouldn’t have a perfect vacuum.

That’s because what’s left behind includes vacuum energy, the Higgs field, and the spacetime curvature.

To remove these would be to remove the nature of space itself.

Vacuum Energy

Vacuum energy is an energy that exists across the entirety of the universe.

It’s zero-point energy, which is the lowest possible energy that can be found in a quantum mechanical system. 

Vacuum energy is formed of particles and antiparticles that briefly flash in and out of existence.

These vacuum fluctuations, as they’re sometimes known, exist even when there’s nothing else in outer space and have observable effects on everyday life.

Without vacuum energy, we wouldn’t have lasers. 

We know vacuum energy is there, and we can measure it using the Casimir effect.

The Casimir effect is observed when two uncharged conductive plates are placed nanometers apart in a vacuum.

We can see the vacuum energy in the plates’ attraction. 

Higgs Field

The Higgs Field was long theorized but only recently discovered. The Higgs Field can be found across space and is the reason that particles have mass.

It works by removing energy from the vacuum and transferring it as mass to a particle.

The Higgs Field is a scalar field and has a non-zero average scalar value in a vacuum.

Spacetime Curvature

Spacetime curvature is an important property of the General Theory of Relativity and an innate part of outer space.

This places gravity as a geometric property of space, defined by mass giving space curvature and space having mass travel in a curved shape.

Even in empty space, where there is no mass, there will still be a curve.

It would be impossible to remove space curvature because doing so would remove the shape of space.

It’s not possible to remove vacuum energy, the Higgs field, and spacetime curvature from any region in space.

Because of this, there’s no way to create a perfect vacuum, and even the emptiest areas of space will always have something going on.

Think of space as being like the ocean. To a fish, the ocean is mostly empty.

All that’s in there is water, and as water is the space in which everything exists, the fish doesn’t notice the existence, shape, and weight of water.

Space is to Earth as water is to a fish — just there and hard to notice.

And just as we notice the water from our distanced perspective, we’d notice space and reality if we were looking at it from the outside. 

Voids

Space has both vacuums and voids. Voids are the areas found between large galaxy filaments that are free of galaxies or contain very few.

Voids are typically between 30 and 300 million light-years in size, with large voids sometimes known as supervoids.

Although a void might seem like the emptiest regions of outer space, they still aren’t a perfect vacuum.

Instead, voids might be the best place to find dark energy.

Final Thoughts

The vast region of space appears to be empty. Take a look at the night sky, and you might think there’s hardly anything there at all.

But even in the vacuums between stars and galaxies, there’s still radiation and particles moving around.

And even if we were to remove these things, the very nature of space means that it can never be truly empty.