Scientists Explain: If the Universe Is Expanding, What Exactly Is It Expanding Into?

Scientists believe that the universe is expanding, but this statement has created confusion among the public. Because if the universe is really expanding, then what exactly is it expanding into? If the space encompasses all that exists, and the definition of the universe is everything, how does its expansion even work?

The simple answer is that the universe is not expanding into something external. Instead, it’s expanding within itself, and it could only be understood through the fabric of space and time rules. That really does not explain much, right? So hold on for the ride because this explanation is going to be fun.

Space Expands, Not Into Something External

Scientists at NASA, such as Edwin Hubble and others, said that we know the universe is expanding because we see galaxies receding from us, and from each other. In other words, the distance between each cosmic object is becoming greater at speeds proportional to distance.

However, this is not because of their motions through space, but rather, it is the expansion of the universe. The tricky part lies in comprehending how something expands if it encompasses everything. So, the best way to think about it is not to imagine an external or outside void that the universe will occupy.

The universe expands into itself as it has no boundaries or edges, and there is nothing that exists beyond it, including both space and time.

Read more: Discovery

The Fabric of Space-Time Itself Stretches

What Is The Universe Expanding Into?

When scientists say the universe is expanding, it is not only about the actual space, or the distance between galaxies or other celestial bodies. The very fabric of space-time continuum expands.

Under Einstein’s theory of general relativity, the dynamics of space and time are relative, which simply means it could expand, bend, contract, and even ripple, as it passes an object that has a massive gravitation force. Examples include black holes and supergiant stars.

In other words, the expansion of the universe is not simply the increase of distance between us and other stars or galaxies. It is the very structure of space and time stretching everywhere. The celestial bodies and systems do not move through this grid; they move with it.

This is why Dr. Albert Einstein’s theory still holds despite this expansion of the universe, because the objects are not traveling at the speed of light or faster; rather, the fabric of reality itself is getting bigger.

What Drives This Expansion—and Its Acceleration?

After the Big Bang, the expansion of the universe decelerated due to gravity. But scientists at NASA estimated that around 9 to 11 billion years ago, it began accelerating, because of a mysterious force now known as dark energy.

Dark energy is a hypothetical force, which means we can’t directly observe it, but it is thought to make up 68% of the universe and is the primary reason for the expansion’s acceleration.

It stretches the fabric of space and time by countereacting gravity on a very large scale, which makes it push galaxies away from each other. So, unlike gravity, which pulls objects together, forming planets, stars, and galaxies, dark energy repulses, pushing space itself apart.

Read more: NASA

Infinity or Not—No Outside Needed

Astronomers have several models of what the universe’s shape is, such as a sphere or a torus, donut-shaped, but we do not know if the cosmos is flat, open, finite, or infinite. However, regardless of its shape and whether it is infinite or not, the universe has no boundary, and so it doesn’t require an external space into which to expand.

The expansion is not the universe occupying a new space or location that has nothing. So, to answer the question once again, what is the universe expanding into? It is not expanding into anything at all.

The space itself is growing, and there is no outside of it because it encompasses everything that exists. It is not turning non-existent void into a new part of itself, but rather expanding what is currently is.

If the Universe Expands, What Is It Expanding Into?

Author's Final Thoughts

The universe expands not into an external void, but it stretches its own fabric of space and time with the help of hypothetical forces called dark energy. This is a process that has been going on for billions of years, and will likely continue for more, until it can no longer.

Which means that one day, the expansion of the universe could slow down, stop, or even reverse entirely, leading to various scenarios of how it could end, such as by ripping itself apart, collapsing internally, or by something we can’t yet predict or understand yet.

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