Astrophysicist Boris Stern: 3 most amazing knowledge about the Universe that we received in the 21st century
Miscellaneous / / April 27, 2023
Cosmologists have deciphered the messages sent to us by the Big Bang, and astrophysicists have been convinced of the veracity of Einstein's predictions.
On April 29-30, the conference "Scientists against myths». On it, experts will fight stereotypes about life on Earth and in space. Astrophysicist Boris Stern will take part in the discussion "What are attempts to understand the structure of the Universe leading to?".
Especially for Lifehacker, he spoke about successful cases of space exploration and how they changed the scientific landscape and ideas about the world.
Boris Stern
Astrophysicist. Doctor of Physical and Mathematical Sciences, Leading Researcher at the Institute for Nuclear Research of the Russian Academy of Sciences and the Astrospace Center of the FIAN.
In the 20th century, a breakthrough occurred in the study of space - technologies developed, observation methods improved. If earlier scientists were content only with telescopes, now they have other, more perfect tools: satellites, radio astronomy devices, interferometers.
Thanks to this, over the past 20 years, the most important discoveries in cosmology and astrophysics have been made: the existence of gravitational waves, exoplanets discovered, and finally, the history of the universe and its contents are determined with a high accuracy. All this is the most important knowledge that has expanded our understanding of the world around us.
1. There are many planets where life is possible
«exoplanet epic” began in 1995, when the radial velocity method was first applied. Thanks to him, it was periodically possible to observe a shift in the spectral lines of stars according to the Doppler effect. As a result, a seemingly impossible giant planet with an orbital period of 4.2 days was found - very close to the star 51 Pegasi.
Then it became a scientific sensation and scientists began to search exoplanets. The real breakthrough in this area came in 2009, when the Kepler telescope was launched.
He was already working on a different method - transit. The point was to "catch" the small darkening of the stars caused by the passage of planets in their background.
As a result, there has been an explosive growth in the number of discovered exoplanets. If before that there were hundreds of them, now the number was in the thousands.
To date, of these, the existence of 5,357 has been firmly confirmed. These are completely diverse planets: both cold and hot, comparable both with the mass of Mercury and with the mass of 10 Jupiters. Among them, most likely, there are those whose surface is a continuous ocean, and ice with extremely low temperatures.
However, among all this exoplanetary "zoo" there are practically no such specimens on which life could be. This does not mean that they do not exist at all. It's just that the selection effect works here: in order to heat up in the same way as the Earth with a star of the Sun class, such planets must have rather large orbits - a “long year”. To fix their transits, it takes a very long time for the stars observe. But Kepler did not have this time - he worked for only 3 years. At the same time, even if such planets would be discovered, it would be very difficult to prove that they have life.
In addition, alien life is likely to be different from Earth. With a high probability, we would see only bacterial mucus. Because on the way from the emergence of life to a highly developed, and even more so its intelligent form, there are different unlikely events, and, most likely, on other planets, the process is slowed down in the early stages development.
In this sense, the Earth is a rare phenomenon.
Right now, we lack the precision of instruments to pick up such planets using the radial velocity method, and there are no telescopes like Kepler to track their transits.
But I think that soon the means will be improved and scientists will begin to detect the first "Earths". For example, there are hints that in the Tau Ceti system - close to sun star - there are planets in habitable zone.
2. Gravitational waves exist
According to Einstein's theory of relativity, the force of gravity is the result of the curvature of space-time under the influence of matter, where gravitational waves are its ripples.
Gravitational waves are formed as a result of the merger black holes or neutron stars - that is, massive objects. Near them, the space shrinks and expands by 10% or more, and with it, any object in it. We are getting tiny ripples, which are very difficult to register.
When Einstein formulated the theory of relativity, scientists began a long and unsuccessful attempt to experimentally detect gravitational waves.
The first reasonable method proposed Soviet scientists: Vladislav Pustovoit and Mikhail Gertsenstein. In the 1960s, they wrote a paper proposing the creation of a gravitational wave detector in the form of a laser interferometer.
The principle of his work was as follows:
- Two mirrors are at a distance of several kilometers from each other.
- The interference laser beam accurately measures the distance between them.
- If it begins to change, then this may be due to the influence of gravitational waves.
The idea is simple, but its implementation turned out to be associated with many difficulties. The fact is that the accuracy with which it is necessary to measure the change in the distance between the mirrors is tens of thousands of times less than the size of a proton in an atomic nucleus. To do this, you need a powerful laser beam, a vacuum, a unique detector setup.
It took several decades to achieve all this. As a result, in 2015, scientists from the United States managed to do this. They had two detectors, which recorded the signal of gravitational waves, and their results coincided both with each other and with theoretical calculations.
There is no doubt left: gravitational waves exist.
The general theory of relativity, beautiful from the very beginning, was confirmed in practice. It was very important to show all the doubters: look how powerfully it works.
Since then, the number of registrations of gravitational waves has exceeded a hundred. Scientists accumulate statistics, and also develop a project for an ultra-sensitive interferometer that can be used in space.
3. Microwave background - a textbook on the history of the universe
The microwave background is the light that formed in the first hundreds of thousands of years after the Big Bang. He reached us in the form of short radio waves - a fraction of a centimeter in size.
Where did this light come from? In the first moments of its life, the Universe was dense, hot and extremely ionized - that is, the nuclei of atoms were separated from electrons. Only after 380 thousand years did they “make friends” with each other and form neutral atoms. Because of this, the interaction of light with new substances has changed dramatically. The photons flew out in all directions, became less energetic as their wavelength stretched along with the expansion of the universe. This is how the light from the Big Bang reached us.
In the 20th century, studies of the microwave background began. In the 1990s, the sensitivity of the instruments increased so much that its spotting and unevenness became noticeable.
In the 2000s, a powerful WMAP microwave radiation detector was launched into space, which took a map of this radiation from around sky in good resolution.
Thanks to her, the contrast distribution of spots was built depending on their size, it had peaks and dips. Such a phenomenon is called Sakharov oscillations - it was first described by the Soviet physicist Andrei Dmitrievich Sakharov.
The ratio of these peaks and troughs shows exactly what the early universe was like and also describes its properties.
Now we know exactly the chronology of events from the first tiny fractions of seconds after the Big Bang to the present day. I believe that this is the most important achievement in the 21st century.
Unfortunately, this research has stalled. After the WMAP experiment, the Planck satellite was launched with a more advanced microwave telescope. He obtained data that was missing, but did not bring any fundamentally new discoveries.
Cosmology has exhausted the possibilities of the method for measuring relic radiation. Therefore, it is very difficult to move forward. But this is natural: after the revolution, a plateau appears. New breakthroughs will have to wait.
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