How to use big data to test the correctness of gravity and space-time theory

The universe, which excites all astronomers. Because there is a blue planet here, it is wrapped in the Milky Way. However, we have not been able to understand the complete universe, nor have we mastered all the laws of the universe. This is very regrettable for us. As Feynman said before, we can’t get involved, but we can stare as much as possible and find some rules. Now, all we can do is to use the powerful radio telescope to stare at the universe as much as possible, ask questions as much as possible, and find the answers as much as possible.

The problems we have raised are still being explored constantly, and many times they are about external forces such as gravity. Everyone knows gravity, and we have gravity for each time we fall. Gravity surrounds the earth, but in fact this gravitation exists in all celestial bodies, such as black holes. In this way, Einstein proposed general relativity. To this day, relativity is still the best description of gravity, although not necessarily correct. A few weeks ago, we humans were able to take a real black hole photo, but as you can see, this photo does not get an answer like the simulation. However, it is basically similar to our prediction of this gravitation: it contains the mass of six suns, so the discovery of black holes is basically similar to general relativity.

Gravitational waves can also be produced in life.
Gravity runs through all our physical concepts, including general relativity. In fact, it is slightly different, because gravity is a theory of relativity, which is a theory formed by time and space. Moving the mass, accelerating them, forming a center between space and time, and then forming a wave, this is the so-called gravitational wave, the faster the gravitational wave, the stronger the gravitational wave.

In the solar system we have the earth and the moon, and the moon revolves around the earth, and there is no direct revolution between the sun and the moon. More than 100 years ago, Einstein published his theory, but how do we verify it now? One final result is that if we improve the quality of a pair of interoperable operations, this happens in a systematic way. When energy is taken away from the system and the orbit is reduced, the two qualities will eventually collide and merge.

In fact, it is difficult to verify the theory of relativity as described above, because gravity is relatively weak, especially in contrast to electricity. That’s why you get hurt when you fall – the force in the ground molecule is much stronger than the gravity. As you can imagine, if an athlete stands on the stadium, he uses his mass to rotate to create gravitational waves. If the athlete is 100 kilograms, he will produce gravitational waves with a mass of 2 times each time. However, the energy of this gravitational wave is very small, so it is completely dangerous to watch athletes in the stadium. Obviously, gravitational waves of strong energy are unlikely to be produced in our daily lives, and only huge objects like stars and stars can do it.

Einstein gave the right answer. He said that scientists will be rewarded in the process of understanding the world, not just the possibility of discovering their application. As we all know, quantum mechanics was discovered by Einstein’s colleagues. It was just a vague theory when it was just discovered. There is no place to apply. Today we can do so much. We still hold such a place here. At the conference, everything is due to quantum mechanics. Some of the things that are encountered in society today are based on the theory of quantum mechanics. It can be said that quantum mechanics is the key to today’s digital world.

Time difference caused by position
We all know that clocks will go slower in the gravitational field. When there were two scientists, they did an experiment. They took two identical atomic clocks, one on the earth and one on the plane. They found that the clocks on the earth would go slower than the clocks on the plane. . The reason is that the timepiece placed on the plane is relatively high, and the influence of the gravity field is relatively small.

Another experiment is to put two identical clocks on the Eiffel Tower, one on the top of the tower and one on the bottom of the tower. As a result, the time spent on the two clocks is different. why? Because the position of the earth from the sun continues to change during the year, when it is closer to the sun in winter, then all the clocks will go slower; in the summer, it will be a little further away from the sun, our watches will go Go faster. Such a difference is about 1.7 milliseconds. People on the earth can’t feel it. Only when you have a clock outside the ground can you feel it.

In fact, many of us are making such adjustments every day. For example, you use GPS navigation, GPS navigation is based on satellites, and the satellite rotates around the ground, the clock on the satellite will go a little faster than the clock on the earth. GPS positioning is the use of different satellites to make accurate positioning based on time points. If you don’t know that the watch on the satellite goes faster than the watch on the earth and does not make adjustments, this difference may reach 46 seconds per day, which means that the difference in positioning on the ground will be as high as 12 kilometers, so the general theory of relativity and our daily life It is closely related.

Pulsar that will explode
Hawking believes that black holes generate radiation. Because radiation loses energy, very small black holes evaporate due to loss of energy. Another scientist has predicted that a relatively short infinite pulse will be observed under special circumstances.

In fact, pulsars can explode, such as supernovae. There was an explosion more than 1,000 years ago, with two stars, the upper left corner is the star, and the lower right is the pulsar. The pulsar does not stop flashing like a pulse, it is not really flashing, but it is spinning fast, so it is called a pulsar. At the same time, radiation is also emitted, and various beams emit light beams along the axis. Most pulsars can only be seen through radio telescopes, and the rotation speed is very high.

In 1974 we found the first pulsar connected to the stellar rotation, such a binary system shrinks at a rate of 1 millisecond per day. We have just talked about gravitational waves and binary systems. When the orbit is reduced, the entire system is disabled. These pulsars are very precise clocks and their density is very high. Here is an example for you to compare the pulsar with Guiyang, which is about the same size. But the mass can be as large as two solar systems, usually 40% higher than the sun, and the state is very stable.

Let me talk about the FAST radio telescope. A receiver can simultaneously view 19 adjacent pulsars. This means that the data you collect is 19 times that of ours. The amount of data is very large. It basically generates 144 terabytes of data per day. If it is stored, it requires a very large storage capacity. There are many things that can be done. For example, in South Africa we have a variety of telescopes, array telescopes, and my institute provides receivers for this 64-channel array. In addition, with such an array, we can use 1000 beams to scan the sky. This is a black hole photo, which is actually made by this group of telescopes. Approximately 20 petabytes of data can be generated each week. The more telescopes you add, the better the quality of the data. We hope to add more telescopes in the future.

So SKA faces huge data challenges every day and requires all data calculations to process. Here, the pulsar is very fast, and the amount of data generated is very large. We can do dynamic analysis. Now we calculate online, instead of doing offline calculations as in the past. In the past, many of our doctoral students helped me with calculations and treatments. It can’t be done now, because the amount of data is too large, we started developing algorithms and machine learning 10 years ago, and now we have some results. But these algorithms must be very reliable, so we need to continue to improve our level of artificial intelligence.

Basic research, it is actually a driving factor in technology. This is especially true for astronomy. Even if we can’t apply these basic research results very quickly, it will certainly be useful in the future. Nowadays, whether it is the generation of data, the transmission of data or the volume of data, it is a challenge for us.

At the same time, public participation is also important. The public likes astronomy, and astronomy can help them better understand the universe; public participation is also very helpful to our research. Just like the day after the black hole photo was released, the whole media industry was sensational. This shows that the public is very interested in astronomy. This is also an opportunity for astronomy. We should contact the public, reach the public, let the public help us, help. We solve the problem.

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