"Polaris, the closest Cepheid variable star to Earth, is also hundreds of light-years away, but the farther away the star is, the smaller it is, and in this way, after complex calculations, we have finally calculated the approximate distances of the various constellations containing the variable stars.

The process will be published in the journal Nature, where you have heard about the most cutting-edge developments in astronomy, and before I speak, the exact size of the Milky Way was not known in the astronomical community. And with the great trick of Cepheid variables, we can measure it with certainty.

We can even point our telescopes at globular clusters that are very different from our neighboring astronomical environments and find that they are so dense that if the Earth were to appear in globular clusters, the sparkle of stars alone would turn night into day.

And we can say with certainty that these clusters are far from us beyond all previous astronomical scales - less than 10,000 light-years. There are about 100 globular clusters observed in the Milky Way, and there are probably about the same number that have not been seen. It's about 20,000 to 200,000 light-years away.

We've finally expanded the scale to 200,000 light-years. And we were able to reduce the self-process distances of a large number of stars to a picture of revolving around the center of the Milky Way. We used a computer to track millions of stars on its own fully automatically, and this imaginary map was born. ”

For the first time, humans "viewed" the Milky Way from the vertical angle of the Milky Way's disk, and the big screen on the podium gradually flashed millions of stars one by one, shining to show the magnificent Milky Way as it was.

Even the people who watched the excitement felt very funny, and the astronomers were even more intoxicated, and it was the first time that they had seen that the knowledge of astronomy could be used in front of ordinary people.

For the first time, the Milky Way also has a beautiful spiral arm, and our solar system is on one of them, not at the center of the Milky Way, as previously wishfully believed, but at the edge of the Milky Way.

Downing complemented the galaxy with the addition of stars to perfection, and pointed out the exact location of the solar system, saying, "Don't think it's good to be in the center. If so, why don't we live on the sun? Why don't we live in the center of the earth? Sometimes, the edge is better.

Like the edge where the warm current meets the cold current in the ocean, the waves are rough and bring a lot of nutrients to the surface of the sea, where life is the most abundant, and the beauty of the edge is indescribable. Galaxy Center ...... Hehe, I guess the gravitational pull there is so great that even light can't be brought out, and some life will be torn into elementary particles under that terrifying gravitational pull. ”

This last sentence slashed at people's hearts like a knife, causing a commotion and whispering.

Listening to Downing talk about this number, everyone can understand what the gravitational force of terror is: "According to the rate of rotation of the Milky Way, we estimate that the mass of the galactic core, which occupies most of the mass of the Milky Way, is far more than 100 billion times the mass of the Sun (there is an exclamation here), and then it is estimated that the Milky Way galaxy has about 200 billion to 300 billion stars, which is the first w to estimate this number." Mr. Herschel's number is 3,000 times that of 100 million. (There is another exclamation here)

Our Milky Way, with its true diameter of about 100,000 light-years, resembles a disk, and the thickness of the plate is 20,000 light-years at the center, and we are located about two-thirds of the way from the center of the galaxy to the edge, if you understand it as the golden section line. The thickness here is about 3000 light years.

Our Milky Way has two small neighbors, and the same galaxy-level objects as the Milky Way, one is the Small Magellanic Cloud and the other is the Large Magellanic Cloud. The Big Magellanic Cloud is 150,000 light-years away from us, and the Small Magellanic Cloud is 170,000 light-years away from us.

The Magellanic cloud is also of great significance to astronomy, because it has 25 Cepheids, and they are so far away that the distance between them is no longer important, so it forms a very regular brightness, which allows us to draw the periodic curve of the variable stars, which becomes the basis for the comparison of interstellar coordinates.

The sages of astronomy once speculated that some faint star specks might be made up of stars that were too far away to be true, but until we made their moves, even the best telescopes could not see its internal structure, only that a star of very weak luminosity occasionally appeared there.

Personally, I speculate that it was the last explosion of energy in the evolution of stars, and the energy of the eruption could illuminate the entire galaxy, that is, if we had such an explosive star in the Milky Way, its energy would be equivalent to the sum of the energy of the entire galaxy stars.

However, this theory is not important, because we have built the largest aperture optical telescope, reaching 200 inches, and finally turned the conjecture of the sages into real observations, which is the interior of the famous Andromeda Nebula, which often produces superstar explosions. ”

The participants of the UN General Assembly were fortunate enough to see galaxies far from the Milky Way, which also possessed Cepheid variables, which were able to obtain accurate distances of 2.5 million light-years on the occasion of the unexpected political meeting turned into a scientific meeting.

"Is this the farthest away? Of course not, there are many distant galaxies similar to the Andromeda Nebula, more distant than Andromeda, so far we have mapped the scale of the universe to the geological evidence that the Earth is more than 2 billion years old. The farthest galaxies have been traveling through the vastness of space for billions of years by the time they are seen by our telescopes.

Just by thinking that the magnificent starry sky we witnessed was a picture of 2 billion years ago, a sense of grandeur for the universe and a sigh for the insignificance of humanity naturally rises in our hearts.

These two billion years are not the maximum age of our universe, and we will have more powerful tools in the future. As we all know, light has a short wavelength and is easy to hit obstacles, while electromagnetic waves have a long wavelength and can bypass obstacles. We're at the edge of the Milky Way, and it's logical to see a much richer array of stars when we look at the high density of the galactic center.

But the truth is that no matter which direction we look at, the density of the starry sky is about the same. So our previous astronomers would have thought that our solar system was at the center of the Milky Way. In fact, this is because the density of the silver core is high, and the density of gas and dust is also large, which blocks a large amount of starlight.

There are often many coincidental things in nature that cause us to misjudge. For example, the size of the moon looks about the same as the size of the sun, and it is a coincidence that the moon can just cover the sun in all the perfect solar eclipses. That's because the Sun is massive and can be closer to us and the Moon is less massive and can be very close to us.

The two parameters work together to create a coincidence like a solar eclipse. And the moon doesn't look like it's turning, the spots on it barely move. This made our ancestors think that the moon does not rotate. Actually, this is the phenomenon of tidal locking.

The rotation of the Moon coincides with that of the Earth, and one side of the Moon is always facing away from the Earth and the other is always facing away from the Earth.

To make our vision look through the annoying gas dust, we also built huge radio astronomical telescopes that receive electromagnetic waves, and this time, we saw farther and more. ”

The farthest that an optical telescope can directly see is a million-light-year, while the image synthesized by a radio telescope is a dark void that is completely invisible to an optical telescope, equivalent to a picture billions of light-years away.

At this scale, people have become numb, as if billions of light-years are not as shocking as Galileo first saw the Milky Way, nor as shocking as the Cepheid variable star determined that the Andromeda Nebula is 2.5 million light-years away.

"I've noticed that people don't seem to be interested in billions of light-years away. Yes, imagine that there is a prince and princess in such a distant place who are married and live happily together, and we want to visit this little couple, but by the time we arrive at the speed of light, billions of years have passed! Isn't that interesting? ”

The audience burst into laughter, and everyone felt that the story of the galaxy that was too far away was really ridiculous.

"The radio telescope tells us a deeper truth, in fact, the Andromeda Nebula, which the sages thought was inconceivably distant and called the 'cosmic island' by Kant, turned out to be only a close neighbor of our Milky Way, and it is one of the galaxies that make up the 'local cluster' in which our Milky Way is located.

Such a casual neighbor is bigger than our galaxy and has more stars than ours. Our home cluster is only part of a large number of galaxy clusters, and this cluster also forms a larger organization with other galaxy clusters - superclusters.

In the future, we may also discover superclusters. The universe is like an infinite space, whether it is infinite or not, hundreds of millions of distances make us sigh.

Unfortunately, to date, the upper limit of the speed of the universe is the speed of light, not to mention too far away, our nearest 4. 3 light-years of Alpha Centauri is enough to keep us going for a while. Approaching the speed of light is very difficult, and we can imagine that with great engineering, scientific efforts, we are able to travel at a tenth of the speed of light.

This is already very difficult, so it will take almost a hundred years to make a round trip to the nearest star. Based on the four-year government, it takes 25 governments to complete a scientific examination. What a difficult decision for one government and one generation of people.

We are here to remind everyone how small the distance is, and the inspiration for us is that perhaps it is more reliable to manage the one-third of an acre of land within our reach. A light year, if measured in meters, is close to 10 to the power of 13.

And the number of cells in our adult human individuals is about 10 to the 14th power. We ourselves are like a cosmic space. Bacterial cells are much smaller than human cells, and they exist in our small universe at 10 times the total number of human cells.

Since the universe is so vast that it can only be viewed from a distance and cannot be played with, why don't we pin the greatest hopes of mankind on our own small universe? Everyone has their own small universe, their own space. Moreover, the scale and grandeur of this small universe are no less than that of the large universe.

The * of mankind is endless, and the development of civilization has a bright future. Religion tells you to either go to heaven and find bliss, or to strangle yourself*. Our school of science reveals that bliss and abundance can be discovered in infinitesimal directions.

Today, we will also discuss the question of the unity of physics and philosophy that is so far away, and which Newton was puzzled by - why does the gravitational pull still seem to reach celestial bodies so far apart, so that the masses of celestial bodies can attract each other?

Our curiosity may be greater than Newton's, because our radio astronomy telescopes have revealed an even grander picture of how the gravitational pull between superclusters of galaxies can survive millions of light-years away. What is the secret of them being so good?

I'm now creating a miniature model of a small solar system, or a small galaxy, on the spot, so that you can see a possible explanation, and hopefully inspire science lovers. ”