Imagine removing everything from the deepest regions of the cosmic void. Removes normal matter, neutrinos, dark matter, cosmic rays, and radiation. It looks like all that’s left is empty space. It may sound contradictory, but these gigantic cavities are filled with the vacuum of space-time. And importantly, that vacuum isn’t really empty.
Vacuum spacetime contains something fundamental. Although difficult to explain precisely in everyday language, physicists call these fundamental components quantum fields. In quantum field theory, the particles that make up our world, such as electrons, top quarks, neutrinos, and even dark matter, are not independent objects in the usual sense. What we call particles are actually visible representations of something deeper.
These deeper structures are the fields themselves. Every type of particle has a corresponding field. These fields permeate every cubic centimeter of space and time. They have existed since the Big Bang and are spread throughout the universe.
When we observe particles such as electrons moving through space, we are actually detecting ripples and oscillations in the underlying field. Particles are moving excitations in a field. Even if all the particles are removed, the field still remains.
Origin of vacuum energy and dark energy
These fields also contain energy. Due to Heisenberg’s uncertainty principle, a vacuum cannot be completely devoid of energy. When physicists try to calculate how much energy exists in empty space, the results range from very large values to theoretically infinite values…another episode.
Importantly, this vacuum energy produces measurable effects. The effect is known as “dark energy,” a name scientists use to describe the accelerating expansion of the universe.
Observations show that the actual amount of vacuum energy, although not zero, is relatively small. In most environments in space, the effect is negligible. A region filled with matter completely dominates the local behavior of space.
For example, here on Earth, matter is so dense that dark energy has no noticeable effect. Even if dark energy suddenly disappeared, everyday physics would not change. The trajectory of the thrown baseball will be the same. Burritos cook at exactly the same speed in the microwave. Nothing changes in daily life.
Where dark energy rules the universe
The same situation applies to most of the universe. Galaxies, galaxy clusters, filaments, and the walls of the cosmic web are all regions filled with matter. In such an environment, dark energy plays little role.
The void in space is different.
A void is a huge region with very little material present. In these regions, the vacuum of space-time itself is the dominant influence. If you could place yourself in the middle of the cosmic void, you would essentially be surrounded by dark energy.
In fact, the void is where dark energy does its most important work. The accelerated expansion of the universe does not occur inside dense regions such as galaxies or star clusters. Instead, it takes place in a vast void.
The void in the universe is expanding
Cosmic voids are not just empty gaps between the structures of the universe. They are actively growing. As dark energy pushes space outward, the void expands and compresses the web of space around it.
Over vast amounts of time, this process gradually pulls apart the large-scale structure of the universe. The complex network of galaxies, galaxy clusters, and filaments that astronomers observe today won’t last forever. Over the next 5, 10, 20 billion years, the exact number doesn’t matter, but the web of the universe will slowly disappear as the expanding cavity stretches everything further and further.
Why empty space is never true sky
In that sense, the void in the universe is never empty. They are filled with the subtle energy of the quantum field. That energy causes an accelerated expansion that affects the entire universe.
The void is the only region where this effect is dominant, as it contains almost nothing else.
Yes, there is no matter in the void of space. That’s how astronomers identify and measure them. However, the lack of matter means that they are filled with dark energy.
No matter where you travel in the universe, whether in a nearby galaxy or the deepest interior of the emptiest space, you are never truly alone.
