The universe is 93 billion light years across

For a century now, astronomers have been exploring more and more of the universe. Less than a hundred years ago, the Milky Way was thought to be our entire universe, but today we know that the universe contains hundreds of billion galaxies like it.

The Hubble Space telescope has been in space for decades and has brought us many amazing pictures of space. In the image, a dark, deep space glows with points of light that are not stars but larger galaxies.

As our universe continues to expand faster than the speed of light, galaxies are being pulled further and further apart.

Scientists have calculated that our universe (the observable universe) is about 93 billion light-years across. Because the universe is expanding faster than light, light from outside the observable universe never reaches us, and what happens there is none of our business. But, predictably, there will still be a universe outside the observable universe.

So how big is the universe? What's out there in the universe? Scientists calculate the size of the observable universe. How big is the real universe?

First, what is the universe?

Einstein PUT FORWARD THE VIEW THAT THE UNIVERSE IS THE SUM OF ALL SPACE AND TIME, WHICH COINCIDES WITH OUR COUNTRY'S ANCIENT DESCRIPTION OF THE UNIVERSE: THE UNIVERSAL SAYS ABOVE AND BEYOND, TO ANCIENT TIMES AND NOW PHANTOMS. But time has no end, and the fact that time and space are indivisible as a whole means that we cannot find the boundaries of space-time structure.

Moreover, according to the current dominant theory, the Big Bang theory, our universe is not flat, it is full of all kinds of bends and distortions. Some people say that the Big Bang was like a balloon that was constantly being blown up, but that's not very precise. It's just a graphic expression.

This means that even if you could walk in one direction forever, it would be impossible to go out into the universe, just as walking on the ground can't get out of the Earth.

At the same time, to discuss the topic of "beyond the universe" must have a premise, that is: the universe has a boundary.

So does our universe have a boundary?

In fact, talking about the "boundary of the universe" doesn't make much sense, and is even a spurious proposition. Because as far as observations are concerned, our universe is "isotropic," meaning it's basically the same space no matter where you look.

For example, the diameter of what we call the "observable universe" is 93 billion light years, measured at the center of the Earth.

But in fact, the universe has no center, and the Earth cannot be the center of the universe. According to isotropy, even if you measured the diameter of the universe from Mars, or even the center of the Milky Way, you'd get 93 billion light years.

What does that mean?

It means the universe has no center and no boundary.

One might ask: Since the universe is expanding all the time, in which direction is it expanding? Where is it expanding?

In fact, the expansion of the universe from the singularity does not start from a single point, like when we light a firecracker, but expands everywhere. The expansion of the universe does not need space, because it is space. For an expanding universe, there is no "outside"; everything is "inside".

Of course, the Big Bang is not the truth, it is not perfect, and it may be replaced by a more advanced theory in the future.

For example, some scientists have proposed the multiverse theory that our universe is just one of an infinite number of universes. So beyond the universe there would be other universes, without end!

The search for the size of the universe will never stop, and we may never find the answer, but that doesn't stop us from going in that direction!