In space, they found gravitational waves that change space and time. What does it mean?

What are gravitational waves?

Gravitational waves - changes in the gravitational field propagating

like waves.They are emitted by moving masses, but after radiation they break away from them and exist independently of these masses. Mathematically related to the perturbation of the space-time metrics and can be described as "ripples of space-time".

Polarized gravitational wave

In general relativity, as well as inMost other modern ones indicate that gravitational waves appear from the motion of massive bodies with variable acceleration. Gravitational waves propagate freely in space at the speed of light. They are very small and difficult to register.

Gravitational waves were first discoveredin September 2015 by two LIGO twin detectors, which recorded gravitational waves, likely from the merger of two black holes and the formation of one more massive rotating black hole.

Any binary star when rotating its componentsaround the common center of mass it loses energy (as it is assumed - due to the radiation of gravitational waves) and ultimately merges together. But for ordinary, non-compact, binary stars, this process takes a very long time, much more than the present age of the universe.

If the double compact system consists ofpairs of neutron stars, black holes, or a combination of both, the merger can occur in a few million years. At first, the objects approach each other, and their orbital period decreases. Then, at the final stage, a collision and asymmetric gravitational collapse occurs. This process lasts a fraction of a second, and during this time energy is released into gravitational radiation, which, according to some estimates, is more than 50% of the system's mass.

How are gravitational waves found?

It is rather difficult to register gravitational waves due to their weakness. Devices for their registration are gravitational wave detectors. Detection attempts have been made since the late 1960s.

Detectable amplitude gravitational wavesare born during the collapse of a double pulsar. Similar events occur in the vicinity of our galaxy approximately once a decade. The strongest and most frequent sources of gravitational waves for gravitational telescopes and antennas are catastrophes associated with collapses of binary systems in nearby galaxies. It is expected that in the near future, improved gravitational detectors will record several similar events per year, distorting the metric in the vicinity of the Earth by 10-21-10-23.

Two bodies moving in circular orbits around a common center of mass

New ways to detect gravitational waves

In 2017, scientists who conducted an experiment underThe Laser Interferometric Gravitational Wave Observatory (LIGO), won the Nobel Prize in Physics for the first-ever direct detection of gravitational waves produced by the merger of two black holes about 1.3 billion light-years from Earth. The waves generated by this collision violated the gravitational-wave background of the Universe and reached the Earth.

In addition to such one-time strong disturbances,which astrophysicists have already learned to fix, there is a so-called background of gravitational waves - a constant flow of gravitational radiation, which, according to the theory, is constantly washing the Earth.

Another opportunity to detect the backgroundof gravitational waves filling the Universe is a high-precision timing of distant pulsars - an analysis of the time of arrival of their pulses, which change in a characteristic way under the action of gravitational waves passing through the space between the Earth and the pulsar.

Estimated for 2013, timing accuracyit is necessary to raise it by about one order of magnitude so that background waves from many sources in our Universe can be detected, and this problem can be solved by the end of the decade. But the passage of a gravitational wave should slightly, by several nanoseconds, change the recording time of these flares. Thus, by accurately tracking the timing of distant pulsars, it is theoretically possible to detect the gravitational-wave background of the galaxy. This is confirmed by the preliminary results of the NANOGrav project.

What new gravitational waves have scientists found?

Scientists said they were able to detect signs of constant gravitational radiation that travels through the universe and distorts the fabric of space-time.

We found a strong signal in our dataset. We cannot yet say that these are background gravitational waves, but our goal is getting closer.

Joseph Simon, astrophysicist and lead author of the article

According to the authors, no other observatoryable to detect background gravitational waves, because they are focused on searching for one-time events lasting several seconds. As part of the experiment, scientists have been tracking 45 pulsars over several years - and have already found signs of slight changes in their frequency. Pulsars can be compared to galactic lighthouses that are constantly in the same place.

We are looking for waves that last for years or decades.According to the theory, mergers of galaxies and other cosmological events cause a constant burst of huge gravitational waves. It takes years or even longer for one such wave to pass by the Earth. For this reason, no other existing experiments can detect them directly.

Joseph Simon, astrophysicist and lead author of the article

The passing gravity waves changea stable pattern of light emanating from pulsars, increasing or contracting the relative distances that these rays travel through space. In other words, scientists can theoretically detect the background of gravitational waves by tracking correlated changes in the time of arrival of pulsar radiation on Earth.

What are these gravitational waves doing?

The passing gravity waves changea stable pattern of light emanating from pulsars, increasing or contracting the relative distances that these rays travel through space. In other words, scientists can theoretically detect the background of gravitational waves by tracking correlated changes in the time of arrival of pulsar radiation on Earth. However, this is not enough for final conclusions. Therefore, astronomers have announced plans to create IPTA - a network of instruments that will record such deviations for a large number of pulsars.

The detection of the gravitational wave background willa big step forward, but only the first step. The next step will be to discover their sources, and then - everything new that they can tell us about the Universe.

Joseph Simon, astrophysicist and lead author of the article

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