"The signal came at the frequency of human speech"

Astrophysicist Sergey Popov - about what gravity waves are

On February 11, it became known that scientists managed to fix gravitational waves-distortion of space-time, predicted by Albert Einstein. Their existence was proved due to observations with the help of high -precision equipment - scientists recorded the fusion of two massive black holes in a billion of light years from the Earth. Astrophysicist and popularizer of science Sergey Popov explained to Konstantin Benyumov, the Medusa journalist, what gravitational waves are and how they flee in space-time.

- What are gravitational waves?

-Starting with the general theory of relativity, we believe that gravity is associated with the geometry of space-time; Modern theories of gravity are geometric. In these theories, the geometry of space is described by metric: on a plane it is easy to draw - such a carpet, different in a cell. This is a flat space. We can bend it in every way, but it is better to do it not with our hands, but, for example, massive bodies-any heavy body distorts the space around us. Further - if this heavy body will fidget, or, for example, two heavy bodies will spin around the common center of the star, then they will periodically disturb the space, and ripples will run around the space. This is gravitational waves.

Imagine that someone is floating on the water, and waves go from him on the surface. That's about the same, gravitational waves run around space-time. And when they pass some kind of piece where we live, they outrage the space-time around us. They are indignant very weakly, because gravity compared to other forces is very weak. It is difficult to measure, but you can. And people have tried to do this over the past 50 years. And then, finally, it turned out.

- The fact that the waves managed to fix right now is associated with the advent of suitable equipment?

- Yes, first of all, these are equipment . LIGO detector, Virgo detector, which will soon begin to work in Europe, are absolutely amazing machines for measurement accuracy. Before that, people used cheaper, simpler approaches. Ligo is 25 years of labor, huge amounts of money spent, first of all, on research, on the creation of new technologies, to bring these technologies to mind and to manufacture these amazingly accurate devices.

- Black holes with this story are connected only because these are massive bodies that distort the space ?

- In order to get a strong signal, you need not just a massive body, but at the same time massive and compact. In fact, what is happening is one black hole falls on the other. At this moment, heavy bodies interact with each other and move almost at the speed of light, so a lot of energy emerges immediately, for a very short time interval. Therefore, Ligo and Virgo were specially created to fix signals from neutron stars and black holes. There are more neutron stars, and they merge more often, but black holes are more massive - they can be seen from a large distance.

- How much did you have to watch black holes to find a merging pair?

- In this case, Ligo was just lucky. Almost as soon as they turned on, they saw a signal - the merger of two very massive black holes. The signal is very dependent on the mass. Normally, on average, black holes are three times or even four times easier, but in this case it was possible to see the signal from a very large distance.

-As the signal passes through the space-time, does it weaken? If the phenomenon occurred in a billion of light years from the Earth, then should it get to us in a subtle form?

- Naturally, and therefore it is also important that it was possible to find two very heavy black holes. In a normal situation, detectors will see signals from the merger of two neutron stars, which are five or ten times closer to us.

- The last question: why is the signal recorded in the form of sound?

- There are two points. Firstly, people love pictures and sounds. Therefore, many signals-fluctuations in stars, some other-translate into a sound form. But here, by the will of fate, the signal actually comes at a frequency of approximately corresponding to the frequency of our speech. Physically, these phenomena are different, but the frequencies are the same - Killer. Therefore, scientists decided that this was such a beautiful move. The drawn schedule adopted during the experience indicates the form of a gravitational-wave signal about how the wave fluctuates the mirror in the measuring device. But usually people want not just to see the squiggle, but to get some kind of multimedia content.

Konstantin Benyumov