It is considered that the wave of 20 17 is a big problem: for the first time, astronomers have a tool to detect and record its past, which is called LIGO. They found that the first wave was the result of the collision of two black holes in distant space. Now, a team of astrophysicists has conducted another study on these records and found something that others thought would take decades to discover: the accurate confirmation of the hairless theorem. This important aspect of black hole theory can be traced back to at least the 1970s, and Stephen Hawking once famously questioned this theorem.
Physicists say that black holes have no hair. Massachusetts Institute of Technology physicist Maximiliano Isi and the lead author of the paper said that what they mean is that astrophysical objects are very simple. Black holes differ only in three aspects: rotational speed, mass and charge. In the real world, the charges of black holes may not differ much, so they actually differ only in mass and spin. Physicists call these naked objects kerr black holes.
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Isi told Life Science that hairlessness makes black holes very different from almost all other objects in the universe. For example, when a real bell rings, it will emit sound waves and some undetectable and incredibly weak gravitational waves. But it is a much more complicated object. The clock is made of a certain material, such as bronze or cast iron. According to the hairless model, the black hole is a unified singularity. Each clock also has a unique shape. A black hole is an infinitesimal and dimensionless point in the space surrounded by a spherical horizon. All these characteristics of bells can be detected from bells-at least if you know something about bells and sound waves. Isi said, "If you can feel the gravitational wave of the clock, you can also detect the difference in composition and shape of the clock.
"The secret of all this is that the waveform-this stretching and compressing mode-encodes the information of the source, that is, the thing that produces gravitational waves," Issy said. He told the scientific field,
Astronomers who study 20 17 waves know a lot about black hole collisions, but the records are weak and not very detailed. LIGO is the best gravitational wave detector in the world. In Washington state, it uses a laser to measure the distance between two L-shaped mirrors that are 2.5 miles (4 kilometers) apart. (Virgo, a similar detector, also found this wave in Italy. When this wave rolls over LIGO, it will distort the space-time itself and slightly change the distance. But the details of this gravity wave are not enough for the detector to record, Isi said.
"But we heard it from far away," said Isi.
This wave provided a lot of information at that time. Black holes behave as expected. Isi said: "There is no obvious evidence that it lacks the horizon (that is, there is no area where light can escape) and there is no obvious deviation from the hairless theorem.
But researchers are not sure about many of these problems, especially the hairless theorem. Isi said that the simplest part of waveform research is after two black holes merge into a larger black hole. It has been ringing for some time, much like a ringing clock, sending excess energy into space in the form of gravitational waves-a process called "* * *" by astrophysicists.
At that time, the researchers were looking at LIGO data and found only one waveform. Researchers believe that it will take decades to develop an instrument sensitive enough to capture any quieter tones in * * *. But Matt Giesler, a colleague of Isi and a physicist at California Institute of Technology, found that there was a short time after the collision, and the impact was strong enough for LIGO to record more details than usual. At these moments, the sound waves are loud enough that LIGO receives overtones-second waves with different frequencies, much like faint secondary notes in a bell.
In musical instruments, overtones carry most of the information that gives musical instruments a unique sound. He said that the meaning of gravitational waves is the same. Isi said that the overture of this new discovery clarified the data about ring black holes to a great extent.
This indicates that the black hole is at least very close to kerr black holes. Absence theorem can be used to predict the appearance of overtones; Isi and his team showed that the implication was very consistent with the prediction. However, the record of overtone is not very clear, so it is still possible that this sound is somewhat different from the theorem prediction, which is about 10%.
He said that in order to surpass this accuracy, you need to extract clearer overtones from the waveform of black hole collision, or build a more sensitive instrument than LIGO, Isi said.
"Physics is getting closer and closer." But you can never be sure.
It may even be that the overtone signal is untrue, and it just happens by chance due to the random fluctuation of data. They reported "3.6 horse confidence" in the implication. This means that about 1 of every 6,300 people think that this overtone is not the real signal from the black hole.
Isi said that with the improvement of instruments and the detection of more gravitational waves, all these figures should become more confident and accurate. LIGO has been upgraded, making it very routine to detect black hole collisions. According to Physical World, another upgrade planned for mid-2020 will increase its sensitivity by 10 times. In the mid-1930s, after the launch of space-based laser interference space antenna (LISA), astronomers should be able to determine the hairless degree of black holes, which is impossible today.
However, Isi says that black holes may not be completely bare-they may have some quantum peach fluff, which is too simple, too soft and too short for our instruments to accept.
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