General relativity reveals the strange universe

Einstein refreshed the concept of time and space. The extremely strange and magnificent universe predicted by his theory challenged the limits of human imagination. The general theory of relativity, which was born in a Swiss patent office and matured in Berlin, Germany, is a groundbreaking theory about the universe based on a new understanding of the deeper level of gravity.

New theory causes riots
Before general relativity, Newtonian theory of gravity had been popular for nearly 200 years. Newton believed that gravity looks like a pull between different masses. Einstein proposed that space and time are a unified structure distorted by mass and energy. Celestial bodies distort the space-time structure, like a heavy object on a trampoline. The curvature of the space-time framework guides the movement of celestial bodies. As a result, gravity was completely explained by Einstein.

In a series of lectures in Berlin at the end of 1915, Einstein described his general theory of relativity. But it wasn’t until a total solar eclipse in 1919 that the theory attracted widespread attention from scholars at that time. The theory predicts that massive celestial bodies such as the sun may distort nearby space-time to such an extent that the direct sunlight is bent. In this way, distant stars do not appear to be located exactly where they were predicted. The photos taken during this eclipse confirmed that the position of the sun moved in line with Einstein’s prediction. At that time, the headline given by a major newspaper was “The sky is skewed and the people of science are ecstatic.”

Ten years later, the sensation and even the riots caused by the general theory of relativity continue. At that time, 4,500 people flocked to the American Museum of Natural History in New York City, United States, to listen to scientists’ explanations of general relativity. As the number of people coming was much larger than the number of people allowed in the lecture hall, riots broke out in the crowd, people fisted together, and others broke through the iron gate. The police had to send additional manpower to control the situation.

In 1931, physicist Michaelson (the first American Nobel Prize winner in science) said that general relativity was unprecedented in the history of science and was a revolution in scientific thought. We already know today that general relativity has brought us far more than Einstein was willing or able to predict. This theory is a new way of observing the universe, and even Einstein himself did not want to accept some of its multiple meanings. However, the most bizarre predictions of general relativity have all been proven correct.

Einstein in Berlin (photo in 1920).

The solar eclipse attracted the initial attention of the scientific community to general relativity.

The universe is wild and far beyond imagination
The seemingly quiet, static, and finite universe is actually a vibrant and continuously expanding arena, in which the turmoil of time-distorting “great beasts” is constantly staged. The galaxies are clustered into very large galaxy clusters. The size of the galaxy clusters is so huge that scientists could not imagine before the 20th century. There are not only stars and planets in these galaxies, but also many strange celestial bodies. Their strangeness shows that the extremes predicted by general relativity are not extreme. For example, a neutron star is a kind of strange celestial body, which compresses the mass of a massive star to the size of a city. A black hole is also a kind of strange celestial body. It distorts time and space so strongly that no light can escape from the black hole. In this way, it is impossible for us to see the black hole directly. When these “behemoths” collided with each other, they shook space and time and emitted huge amounts of energy. In fact, our universe is very violent and continues to evolve, full of monsters predicted by general relativity that seem to belong to science fiction theory but actually exist.

Scientists commented that general relativity has built an extremely huge stage for us. There are an infinite number of characters on this stage for us to observe, explore and test. The universe itself is an extremely amazing character: it has its own life; it is constantly expanding; it may also collapse or even die; there may be other universes outside our universe. General relativity makes us realize that the universe is far more interesting than our wildest imagination.

General relativity has become the cornerstone of today’s theory of the universe, but today’s theory of the universe is far from complete. Whether it is for mysterious matter and power, for the beginning and end of the universe, or for how macroscopic science fits into microscopic sciences such as quantum mechanics, there are still a lot of unanswered questions. Some scientists believe that in order to answer some of the puzzles, one path of hope is the initially underestimated meaning of general relativity-that curved light can magnify the characteristics of the universe.

Scientists today continue to delve into general relativity to find clues that may be ignored by themselves. General relativity is being tested with unprecedented precision. Science is a two-way wonder: general relativity expands our horizons of the universe; in turn, we test the theory more rigorously. This kind of test may allow us to discover problems with general relativity, but so far no problems have been found with general relativity. Scientists believe that general relativity will lead us to discover more singularities of the universe and describe the universe more completely. In other words, more than 100 years after the appearance of general relativity, there are still many aspects of the universe to be predicted. We will find that the universe is even crazier than we now realize.

A huge cluster of galaxies.

Expanded scene
Einstein’s series of equations of general relativity is a big source from which the existing view of the universe flows. Part of the reason why general relativity is incredible is that it keeps asking us a lot of questions. In the past hundred years, scientists have detected some cosmic behemoths beyond imagination, and learned some important facts about our universe: the universe is accelerating; the universe began with a big bang 13.8 billion years ago; many mysterious forms The matter and energy of the universe are shaping the universe in unexpected and almost unknown ways.

In 2019, the Horizon Telescope team released the first ever black hole image. This image shows the “giant”-black hole surrounded by a bright disk of gas.

The origin of the black hole theory
A little more than 100 years after Einstein unveiled the general theory of relativity, scientists have visually confirmed one of the most amazing “behemoths” predicted by the theory. In 2019, a global telescope network-Horizon Telescope showed that a huge mass object is crazily distorting time and space, so that even light cannot escape its trap. This massive object is the black hole at the center of galaxy M87, and the Horizon Telescope synthesized its image for the first time. The chief scientist of the project said that he had already realized that the Horizon Telescope had discovered some kind of strange celestial body, but after seeing the photo of the M87 black hole, he was very surprised to find that this black hole completely accorded with the prediction of general relativity.

For a long time, black holes were just mathematical spectacles. Before the second 50 years of the 20th century, there was no evidence of the actual existence of black holes. But this is not uncommon in physics. A certain physicist’s equation points to a previously unknown phenomenon, prompting people to look for evidence for this. Once the data is obtained, plus a little luck, physicists can discover this phenomenon by searching.

The brightness of quasars can exceed that of the galaxy in which they are located. Scientists were confused about this at first, but later discovered that the quasar burst was driven by a massive black hole that was “eating”.

Speaking of black holes, in 1916, shortly after Einstein proposed the general theory of relativity, German physicist Schwarzschild gave an answer to Einstein’s equation for the situation near a spherical object (such as a star or planet). Kind of solution. Schwarzschild’s mathematical derivation shows how the curvature of space-time will be different around celestial bodies of the same mass but smaller and smaller (that is, the celestial bodies are getting denser). According to Schwarzschild’s solution, no matter how small the celestial body is, there must be a limit. This limit was later called the “Schwarzschild radius”.

By the 1930s, American scientists Oppenheimer and Schneider described the consequences of a massive star collapsing below the Schwarzschild radius under its own gravity—the light of the star (called a black hole today) may be forever Will not reach the earth. Nevertheless, Einstein himself and most other scientists do not believe that such stars (ie black holes) are real.

It wasn’t until 1964 that the American female journalist Ewing coined the term “black hole” while reporting on a meeting of the American Association for the Advancement of Science. It was about this time that there was indirect evidence that black holes might exist. A few months later, Ewing reported the discovery of quasars-“the most distant, brightest, most violent, heaviest and most confusing source of light and radio waves.” Although there was no connection between quasars and black holes at the time, the existence of quasars indicated that a cosmic “power plant” was needed to provide such huge energy for quasars. In the 1960s, advances in X-ray astronomy revealed some new features of the universe, including bright beams that might indicate that a black hole is eating a companion star. In addition, the motion of stars and gas near the center of the galaxy indicates that extremely dense objects may be lurking in the center of the galaxy.

In the 1970s, the astronomer’s measurements indicated that dark matter might exist.

Black holes are more extreme than many other “behemoths” in the universe. The largest black holes have an unknown number of billions (uncountable) times the mass of the sun, and when they tear apart a star, they emit particles with an energy of 200 trillion electron volts. This energy level is about 30 times that of the protons flying around the Large Hadron Collider, the world’s largest and strongest particle accelerator.

With the accumulation of relevant evidence from the 1990s to the present, scientists realized that black holes not only exist, but also participate in the shaping of the universe. Scientists point out that it is very important that those strange days predicted by general relativity and once belonged only to mathematical concepts have become real. It is now known that supermassive black holes exist in the centers of most (if not all) galaxies, and the energy flow emitted by black holes affects how and where stars are formed. It can be said that in the center of the galaxy, black holes dominate everything.

Although visually confirming the existence of black holes is a recent thing, scientists feel that black holes are like something they are already familiar with. Whenever they encounter an unknown space, an unknown abyss, or do their best but there is little return, the first thing they think of is to comfort themselves with the metaphor of “black hole”. Black holes in the true sense are rewarded richly: they provide some answers to the mysteries of the universe, present many new mysteries, and also provide topics for our entertainment (such as science fiction blockbusters). In fact, just thinking about how huge the black holes and other universe “behemoths” are, and how heavy and dense they are, is enough to amaze us.

The black hole emits jets (imagine picture).

So, how did scientists discover the MB7 black hole? Next, we will tell this interesting story.

Time and space waves reveal black holes
When the “behemoths” predicted by general relativity collide with each other, they will destroy the structure of the universe. Ripples called gravitational waves spread outward in time and space, and are the business card of the most turbulent and violent universe tango. The general theory of relativity predicts that gravitational waves will be generated regardless of whether it is a huge collision, a huge explosion, or other huge celestial bodies that are accelerating. But for a long time, discovering any type of time and space ripples is an unattainable dream. Only the most violent cosmic events can produce wave signals large enough to be directly observed. Einstein called this wave gravitational convexity, but he didn’t know that such a huge event actually existed in the universe.

Since the 1950s, when the scientific community is still debating whether gravitational waves really exist, American physicist Weber has devoted himself to detecting gravitational waves. After years of hard work, he announced in 1969 that he had detected an obvious gravitational wave signal, which may have originated from a supernova, or from a newly discovered class of rapidly rotating stars-pulsars. However, a number of studies in the following years have not been able to confirm Weber’s statement, nor can he find the so-called source of gravitational waves.

Black hole collision (imagine picture).

Until his death in 2000, Weber insisted on this statement, but the statement has not been confirmed. However, scientists increasingly believe that gravitational waves will be discovered. In 1974, two radio astronomers in the United States discovered a neutron star orbiting a dense companion star. Over the next few years, the neutron star and its companion star appeared to be gradually approaching each other, which is consistent with the hypothetical scenario that they lose energy to gravitational waves. In 1984, some scientists pointed out that this meant that gravitational waves might be detected.

A different strategy, which has been brewing for decades, finally provides the sensitivity required for gravitational wave detection. In 2016, the “Advanced Laser Interferometric Gravitational Wave Observatory” (LIGO) team, which relied on two detectors located in different locations in the United States, announced the first confirmation of the existence of gravitational waves. Each detector divides a powerful laser beam into two, with each branch propagating along one of the two arms of the detector. In the absence of gravitational waves, the two branches recombine and cancel each other (match). But if a gravitational wave stretches one arm of the detector while compressing the other arm, the laser will not match.

These two detectors are incredible engineering miracles-even if the space-time ripples caused by the collision of two black holes stretch an arm of the detector only one ten thousandth of the diameter of a proton, the detector can Perceive how much your arm is stretched. The announcement of the first detection of gravitational waves (from the collision of two black holes) is believed to have opened a new era of astronomy. This news is of course one of the biggest science news in 2016. The chief scientist of the MGO team won the Nobel Prize the following year.

The LIGO team and the Italian Virgo gravitational wave detector team have recorded dozens of gravitational waves so far, most of which originate from black hole mergers, and some originate from neutron stars. Gravitational waves have revealed the birthplace of some previously unknown heavy elements, as well as a bright jet of subatomic particles, which may provide clues to the mystery of gamma rays (a mysterious sparkle of high-energy light). Gravitational waves also show that medium-mass black holes (with a mass of 100 to 100,000 times that of the sun) do exist, and once again prove that Einstein’s theory has not yet been found flawed.

Only five years after the discovery of gravitational waves, some scientists are already expecting more bizarre “giants” in the universe to show their faces. For example, some scientists have proposed to detect black holes orbiting wormholes through gravitational waves. In fact, gravitational wave astronomy has really just started. By increasing the sensitivity of existing ground-based detectors, it will be possible to detect gravitational waves from more distant places with less energy intensity. Future detectors, including the gravitational wave space detectors scheduled to be launched around 2030, will avoid interference caused by the shaking of the earth’s ground. Scientists believe that the most exciting possibility in the future will be the observation of a small black hole falling into a large black hole. In such a magnificent event, the small black hole will fly back and forth in a few years, rotating in different directions, as if its orbit height deviated from a perfect circle. If this is the case, then Einstein’s equation will pass the ultimate test, and we will find out whether we really understand how time and space are distorted in an extreme sense.