In 2019 it’s a normal emotion to want four or five times a day to go to space, but at the end of the world as possible to get rid of the bad obsession or bad weather, delayed trains or tight trousers, these ordinary things on Earth. But what will be waiting for you on this cosmological frontier? What is the edge, the edge of the Universe — what we see there? This is the boundary or infinity at all?
Let’s ask the scientists.
On the edge of the world
Sean Carroll, Professor of physics at the California Institute of technology
“As far as we know, the Universe has no boundaries. From the observable Universe have an edge — the limit of what we can see. This is due to the fact that light moves with finite speed (one light-year per year), so when we look at distant things, we peer back in time. At the end we see what happened almost 14 billion years, the residual radiation of the Big Bang. This is the cosmic microwave background that surrounds us from all sides. But it’s not a physical “border”, if so sue.
Because we can only see so far, we don’t know what it’s like things outside of our observable Universe. The universethat we see, quite homogeneous on a large scale and perhaps this will continue literally always. Alternatively, the universe could curl up in a sphere or torus. If so, the universe will be limited in overall size, but still will not have a border, just as a circle has no beginning or end.
It is also possible that the universe is heterogeneous beyond what we can see, and that conditions differ greatly from place to place. This possibility is the cosmological multiverse. We don’t know whether there is a multiverse in principle, but because they do not see neither that, nor another, it would be reasonable to maintain fairness”.
Jo Dunkley, Professor of physics and astrophysical Sciences at Princeton University
“Yes, all the same!
Okay, actually we do not believe that the universe has a boundary or edge. We think she either continues infinitely in all directions, either wrapped around itself, so that it is not infinitely large, but still has edges. Imagine the surface of a donut: it has no boundaries. Maybe the whole universe is like this (but in three dimensions — the surface of a donut just two dimensions). This means that you can go on a space ship in any direction, and if you travel long enough, go back to where we started. There is no edge.
But there are also what we call the observable universe, which is part of the space that we can actually see. The edge of this space is where the light is not enough time to reach us since the beginning of the universe. We can see only this region, and behind him, likely all the same that we see around us: superclusters of galaxies, each with billions of stars and planets.”
The surface of last scattering
Jesse Shelton, associate Professor of physics and astronomy, University of Illinois at Urbana-Champaign
“It all depends on what you mean by the edge of the universe. Since the speed of light is limited, the farther and farther into space we look, the further and further back in time we look, even when you look at neighboring galaxy Andromeda we see is not what is happening now and what happened two and a half million years ago, when the stars of Andromeda radiated the light that enters our telescopes until now. The oldest light we can see has come from the farthest depths, so, in a sense, the edge of the universe is the oldest light that we have achieved. In our universe is the cosmic microwave background is barely noticeable, long-lasting afterglow of the Big Bang, which marks the moment when the universe cooled enough to allow atoms to form. This is called the surface of last scattering, since it marks the place where the photons ceased to jump between the electrons in the hot ionized plasma and began to emerge through the transparent space, billions of light years in our direction. Thus, we can say that the edge of the universe is the surface of last scattering.
Located on the edge of the universe right now? Well, we don’t know and can’t know, we’d have to wait until the light emitted there now and coming to us, will fly for many billions of years in the future, but since the universe is expanding faster and faster, we are unlikely to see the new edge of the universe. I can only guess. On large scales our universe looks mostly the same everywhere you look. Chances are, if you were on the edge of the observable universe today, you would see a universe that plus-minus is similar to our own: galaxy, larger and small, in all directions. I think that the edge of the universe now is simply more universe, more galaxies, more planets, more living beings, asks the same question.”
Michael Troxel, associate Professor of physics at Duke University
“Despite the fact that the universe is probably infinite in size, in fact there is not a single practical “edge”.
We think the universe is really infinite and has no boundaries. If the universe was “flat” (like paper), as shown by our tests with precision to the cent, or “open” (like a saddle), then it is indeed infinite. If it is “closed” like a basketball, it is not infinite. However, if you go far enough in one direction you will eventually end up back where we began: imagine that you are moving on the surface of the globe. As once said the hobbit named Bilbo: “the road Runs on and on…”. Over and over again.
The Universe has an “edge” for us there are two. This is part of the General theory of relativity, which States that all things (including light) in the Universe have a limit speed of 299 792 458 m/s and this speed limit is stored everywhere. Our measurements also tell us that the universe is expanding in all directions, and expanding faster and faster. This means that when we observe an object that is very far away from us, light from that object takes time to reach us (distance divided by speed of light). The trick is that since space is expanding until the light comes to us, the distance that must pass the light also increases with time on the way to us.
So the first thing you might ask: what is the farthest distance we could see the light from the object, if it was emitted at the beginning of the Universe (about 13.7 billion years). It turns out that this distance is 47 billion light years (a light year is about 63 241 times greater than the distance between the earth and the Sun), and is called the cosmological horizon. You can put the question somewhat differently. If we sent a message at light speed, at what distance we could get it? It is more fun because the speed of expansion of the Universe in the future increases.
It turns out that even if this message goes on forever, it can only get to those who are now at the distance of 16 billion light-years from us. It’s called “cosmic horizon of events”. However, the furthest planet that we can observe is 25 thousand light years, so we still could welcome all who live in this Universe at the moment. But the farthest distance at which our current telescopes could distinguish the galaxy is about 13.3 billion light years, so we can’t see what is on the edge of the universe. No one knows what lies on both edges”.
Abigail of Vieregg, associate Professor of the Institute of cosmological physics. Have cavila at the University of Chicago
“Using telescopes on Earth, we look at light coming from distant places in the Universe. The farther the light source, the more time is required, so that this light got here. So when you look at distant places, you are looking at something that was like these places when you were born you have seen the light and not on how these places look today. You can continue to watch further and further, in order to match advancing further and further back in time until you see something that existed a few millennia after the Big Bang. Before this the universe was so hot and dense (long before there were stars and galaxies!), any light in the universe never could catch on, it cannot be seen with modern telescopes. This is the edge of the “observable universe” — the horizon — because there is nothing to see. Time goes by, the horizon is changing. If you could look at the Universe from another planet, you probably would see the same thing that we see on Earth: your own horizon, limited by the time which has elapsed since the Big Bang, the speed of light and the expansion of the universe.
Looks like the place that corresponds to the earth’s horizon? We don’t know because I can see this place as it was just after the Big Bang, not what it has become today. But all measurements show that all the visible universe, including the edge of the observable universe looks about the same, as well as our local universe today: stars, galaxies, clusters of galaxies and huge empty space.
We also think that the universe is much more a part of the universe that we can see from Earth, and that the universe has no “edge” as such. It’s just expanding space-time.”
The universe has no boundaries
Arthur Kosowski, Professor of physics at the University of Pittsburgh
“One of the most fundamental properties of the universe is its age, which, according to the different dimensions that we today define as 13.7 billion years. Since we also know that light propagates with a constant velocity, this means that the beam of light which appeared in early time was to date a certain distance (let’s call it “distance to horizon” or the “Hubble distance”). Since nothing can travel faster than the speed of light, the Hubble distance would be the farthest distance that we will ever be able to observe in principle (if you don’t find any way to circumvent the theory of relativity).
We have a source of light coming to us almost with the distance of the Hubble: cosmic microwave background radiation. We know that the universe does not exist “edge” on the distance to the source of microwave radiation, which is nearly a distance of Hubble from us. So we usually assume that the universe is much larger than our own observable Hubble volume, and that the real edge that may exist is much further than we have ever seen. Perhaps it’s true: maybe the universe is just outside the Hubble distance from us, followed by the sea monster. But since all of the observable universe is relatively uniform throughout and a uniform, such a turn would be very weird.
I’m afraid we will never have a good answer to this question. The Universe may not be the territory, and if it is, it will be far enough away that we never saw. We can grasp only that part of the Universe which we can observe”.
And do you have any idea what is on the edge of the Universe? Tell us in our chat in Telegram.