Where the universe begins and where it ends. The borders of the cosmos. Astronomy with the Deaf World #8

The border between countries – each of us knows what it is. There are signs put up, there may be a barrier on the road, Warning signs, etc. It’s easy to figure out where one country and begins another. And how about the boundary between Earth and the universe? At what point does the earth’s atmosphere and the cosmos begins? And does the universe have an end somewhere? And if so, where? The answers to these questions can be found in this video.

Where does the cosmos begin?

So let’s start with the first one: Where does the cosmos begin? You could say, That where the earth’s atmosphere ends Earth’s atmosphere, and the vacuum begins. However, such an answer has some problems. Observations conducted by the European Space Agency and NASA As part of the SOHO mission (Solar and Heliospheric Observatory), showed that the air surrounding the Earth extends as far as 630,000 kilometers, Which is twice as far as the Moon is! So we can say that the Moon is located in the Earth’s atmosphere!

Of course, it is not the same atmosphere as it is on Earth — we can’t breathe it. The air on Earth is dense and allows us to breathe. There is very little atmosphere on the moon – We are talking here about single atoms per cubic meter, but these atoms belong to the Earth’s atmosphere.

So there is no clear boundary between the Earth and the universe. In that case, at which place does the cosmos begin?

The contractual boundary between Earth and space

The most common assumption is the altitude approx. 100 km above sea level. Why. To explain this, we need to find out how … airplanes work. An airplane, in order to fly, needs air. The dense air causes the wings aircraft can “lean” on the air, and lift the aircraft. The higher you go, the less dense the air. Is when the air is less dense, can airplanes fly? Yes, they just need have a higher speed. For example, passenger planes often fly at an altitude of about 10 km, because at this altitude they can fly both safely and quickly, and at the same time consume the least amount of fuel. Military aircraft fly even higher, But to be able to fly even higher, Where the air is less dense, they have to fly much faster than ordinary passenger aircraft. So the higher the plane has to fly faster. Remember this about the altitude and the speed of the plane.

Kármán line

And what’s the deal with the 100 km above sea level? The altitude of about 100 km is a kind of boundary. The air at this altitude is already very thin. If a plane wanted to fly at that altitude, then the aircraft would have to reach a very high speed — greater than the orbital speed, That is, the speed required for an object to enter Earth’s orbit. If the aircraft exceeds altitude of about 100 km above sea level, then it will reach a speed allowing it to enter Earth’s orbit. Interesting fact: this altitude – the conventional the boundary between the Earth and space — is the most important. is called the Kármán Line. But not everyone recognizes it. US Army for the border between Earth and space assumes an altitude of about 80 km.

Does it matter whether the beginning of of space is 80 or 100 km? For science, no, it doesn’t matter. It’s more about distinguishing to what height you need to rise to, To be able to say, that someone has been in space. For example, some military pilots flew at an altitude of 80 kilometers. Does that mean they were in space or not? Right now from 2021, we are seeing the the beginning of so-called space tourism. From the episode on Space Tourism We learned that on July 11, 2021… Let’s see an excerpt from this video:

For example: (July 11, 2021) to an altitude of 86 km ascended by SpaceShipTwo rocket plane of the Virgin Galactic company owned by Richard Branson. On July 11, 2021, there was a successful flight to a height of 86 km. At an altitude of 86 km, is there already space?

That’s right! Were the passengers of this vehicle in space or not? What do you think?

Where does the universe end?

Another question: does the universe have a limit? And if so, where? To put it bluntly: we DON’T KNOW that. Scientists, talking about the universe, use the term “observable universe”. What is it about?

The observable universe

The observable universe is the one that we are able to see. Scientists have calculated, That the universe that we can see, is about 13.8 billion light years long. Why? The farthest objects that we can see are these, whose light has already managed to reach us, and are distant from us by about 13 billion light years. And what is a light year? How many kilometers is that? This video explains it. The observable universe can therefore imagine it as a circle, with a radius of more than 13 billion light years. And this is the only part of the universe we can see. And then? The light of objects that are even farther away, has not yet reached us.

The cosmos keeps getting bigger!

Since the farthest objects in the Universe that we can see, are more than 13 billion light years, does this mean that BOTH are located at a distance of more than 13 billion light years from Earth? No! The universe is constantly is expanding, getting bigger. It can be compared to an inflated balloon. See: You can see the points that are within 2-3 cm of each other. We can compare these 2-3 cm to objects 13 billion years distant from us. The cosmos is expanding all the time, much like an inflated balloon. The distances between points have expanded, as have the distances in the universe. And bigger again. And again the distances got bigger. And it’s the same with the universe. It’s constantly getting bigger, expanding.

When we see the light of an object from 13 billion light years ago, then in reality this object is no longer there, because the cosmos is expanding all the time. Scientists have calculated that what we see is 13 billion light years away, may in fact now be located as far away as 46 billion light years. A lot!!!

The universe in numbers

The observable universe is therefore a sphere, a sphere, with a radius of more than 13 billion light years, because that’s what we can see, and in fact, currently this expanding sphere has a radius of about 46 billion light years. And we remember that one light year is about 9 and a half trillion kilometers! Just one year! That’s 46 billion light years, that’s how many kilometers! The universe really is huge! Scientists estimate, that in the observable universe there are 180,000,000,000,000 galaxies! Wow!!!

The cosmos we can’t see

And what’s next? What is there where we can’t see anything anymore? Probably the same thing, As in “our” universe. So also galaxies, also nebulae, also stars, also planets. It’s just that we can’t see them. And interestingly enough, we can’t see them not because we have too poor technology or we are short of money, but because the light from these objects has not yet reached Earth. So it is a matter of the laws of physics.

So: where does the universe end?

THAT WE DON’T KNOW! We don’t know how far the universe that we can’t see. And we may never know. In addition, scientists believe, that when everything began, in the big bang, huge amounts of matter gave away, “fled” so fast and so far away, That the light from the galaxies they formed, will NEVER reach Earth. There are also scientists who believe, That, like our galaxy is one of many galaxies, that our universe is also just one of many universes. Of course, there is no any evidence at this time to support such ideas.

So we can see that there are still many, many, many more issues to discover, understand and prove. And perhaps that’s what makes the Cosmos is so fascinating? 🙂 Thank you for watching this episode. If you liked it, please write us about it in a comment below the video And show the video to your friends. Maybe this is what will make more people will love the universe? 🙂