The Center of Our Universe Does Not Exist. A Physicist Explains Why.

About a century in the past, scientists have been suffering to reconcile what appeared a contradiction in Albert Einstein’s principle of basic relativity.

Published in 1915, and already extensively permitted international by means of physicists and mathematicians, the speculation assumed the Universe was once static – unchanging, unmoving and immutable. In quick, Einstein believed the dimensions and form of the Universe at present was once, roughly, the similar measurement and form it had all the time been.

But when astronomers appeared into the evening sky at far flung galaxies with tough telescopes, they noticed hints the Universe was once anything else however that. These new observations advised the other – that it was once, as a substitute, increasing.

Scientists quickly learned Einstein’s principle did not if truth be told say the Universe needed to be static; the speculation may improve an increasing Universe as neatly. Indeed, by means of the use of the similar mathematical gear equipped by means of Einstein’s principle, scientists created new fashions that confirmed the Universe was once, in truth, dynamic and evolving.

I’ve spent a long time looking to perceive basic relativity, together with in my present process as a physics professor educating classes at the topic. I do know wrapping your head across the concept of an ever-expanding Universe can really feel daunting – and a part of the problem is overriding your herbal instinct about how issues paintings.

For example, it is exhausting to consider one thing as large because the Universe now not having a middle in any respect, however physics says that is the truth.

The space between galaxies

First, let’s define what’s meant by “growth.” On Earth, “increasing” means something is getting bigger. And in regard to the Universe, that’s true, sort of. Expansion might also mean “the whole lot is getting further from us,” which is also true with regard to the Universe. Point a telescope at distant galaxies and they all do appear to be moving away from us.

What’s more, the farther away they are, the faster they appear to be moving. Those galaxies also seem to be moving away from each other. So it’s more accurate to say that everything in the Universe is getting farther away from everything else, all at once.

This idea is subtle but critical. It’s easy to think about the creation of the Universe like exploding fireworks: Start with a big bang, and then all the galaxies in the Universe fly out in all directions from some central point.

But that analogy isn’t correct. Not only does it falsely imply that the expansion of the Universe started from a single spot, which it didn’t, but it also suggests that the galaxies are the things that are moving, which isn’t entirely accurate.

It’s not so much the galaxies that are moving away from each other – it’s the space between galaxies, the fabric of the Universe itself, that’s ever-expanding as time goes on. In other words, it’s not really the galaxies themselves that are moving through the Universe; it’s more that the Universe itself is carrying them farther away as it expands.

A common analogy is to imagine sticking some dots on the surface of a balloon. As you blow air into the balloon, it expands. Because the dots are stuck on the surface of the balloon, they get farther apart.

Though they may appear to move, the dots actually stay exactly where you put them, and the distance between them gets bigger simply by virtue of the balloon’s expansion.

Now think of the dots as galaxies and the balloon as the fabric of the Universe, and you begin to get the picture.

Unfortunately, while this analogy is a good start, it doesn’t get the details quite right either.

The 4th dimension

Important to any analogy is an understanding of its limitations. Some flaws are obvious: A balloon is small enough to fit in your hand – not so the Universe. Another flaw is more subtle. The balloon has two parts: its latex surface and its air-filled interior.

These two parts of the balloon are described differently in the language of mathematics. The balloon’s surface is two-dimensional. If you were walking around on it, you could move forward, backward, left, or right, but you couldn’t move up or down without leaving the surface.

Now it might sound like we’re naming four directions here – forward, backward, left and right – but those are just movements along two basic paths: side to side and front to back. That’s what makes the surface two-dimensional – length and width.

The inside of the balloon, on the other hand, is three-dimensional, so you’d be able to move freely in any direction, including up or down – length, width and height.

This is where the confusion lies. The thing we think of as the “middle” of the balloon is a point somewhere in its interior, in the air-filled space beneath the surface.

But in this analogy, the Universe is more like the latex surface of the balloon. The balloon’s air-filled interior has no counterpart in our Universe, so we can’t use that part of the analogy – only the surface matters.

So asking, “Where’s the middle of the Universe?” is somewhat like asking, “Where’s the middle of the balloon’s floor?” There simply isn’t one. You could travel along the surface of the balloon in any direction, for as long as you like, and you’d never once reach a place you could call its center because you’d never actually leave the surface.

In the same way, you could travel in any direction in the Universe and would never find its center because, much like the surface of the balloon, it simply doesn’t have one.

Part of the reason this can be so challenging to comprehend is because of the way the Universe is described in the language of mathematics. The surface of the balloon has two dimensions, and the balloon’s interior has three, but the Universe exists in four dimensions. Because it’s not just about how things move in space, but how they move in time.

Our brains are wired to think about space and time separately. But in the Universe, they’re interwoven into a single fabric, called “space-time.” That unification changes the way the Universe works relative to what our intuition expects.

And this explanation doesn’t even begin to answer the question of how something can be expanding indefinitely – scientists are still trying to puzzle out what powers this expansion.

So in asking about the center of the Universe, we’re confronting the limits of our intuition. The answer we find – everything, expanding everywhere, all at once – is a glimpse of just how strange and beautiful our Universe is.

Rob Coyne, Teaching Professor of Physics, University of Rhode Island

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