The internal attraction formed by all substances in the universe makes the space-time in the universe bend inward, forming a large-scale self-closure, so it is bounded. But it is precisely because of the self-enclosed nature of the universe that we (and all substances including light) can gallop freely in the universe, but no matter how diverse we are, we can't "find" the edge of the universe, so it is infinite.
Just like a giant apple, no matter how far the insects on the surface run, they can't reach the edge of the apple, so it is infinite. But bugs can never leave apples, so they are bounded.
According to the observation data, the farthest galaxy observed by people is 65.438+037 billion light years. That is to say, if a beam of light is emitted from a galaxy at a speed of 300,000 kilometers per second, it will take 65.438+037 billion years to reach the earth. This distance of 65.438+037 billion light years is the universe we know today.
More specifically, the universe as we know it today, or its size, is a spherical space with the earth as the center and the distance of 65.438+037 billion light years as the radius.
Of course, the earth is not really the center of the universe, and the universe is not necessarily a sphere. It's just limited to our current observation ability, and we can only know this extent. So the universe has no boundaries, and our observation ability determines how far we can see. Our observation ability is developing and the scope of observation is also expanding. However, according to BIGBANG's theory, the universe is still expanding.
The vast universe is boundless and the depth is unimaginable. 1in April, 999, an astronomical research team of new york State University in the United States used the great power of the Hubble Space Telescope.
After more than two years of careful observation and scientific processing by computer, more than 400 overlapping celestial images distributed in this direction were eliminated, and finally an oldest galaxy was "invited". Judging from its regression and expansion speed of 96.66% light speed, it should be at the edge of the universe of 65.438+037 billion light years!
The distance of 65.438+037 billion light years is really hard to compare. Even the fastest light will take 654.38+037 billion years to reach. It can be seen that this farthest galaxy is also the celestial body shortly after BIGBANG, and it is the most precious and oldest "cosmic fossil", because the early history of the universe will be of inestimable significance to exploring the origin and evolution of the universe.
The universe is not infinite, or the narrow universe we live in is not infinite. Where and in what form its boundary exists is still controversial, but the view that "our universe" is not infinite has been basically recognized.
Now there is a view that space-time is distorted at the edge of the universe, that is, you can approach it infinitely, but you can't reach it. As for the universe in a broad sense, that is, whether the universe outside "our universe" is infinite, it is not clear, just like we can't talk about summer insects, and now human science and technology don't know about it, and the current research has not broken through our universe.
The universe is infinite, but it is limited. Hawking's understanding of the universe is like a basketball. You can't find the starting point and the ending point on the sphere, but it is bounded. Just like many books on astronomy, if you look at stephen hawking's works, you will understand more.