On February 11, 2016 (January 4, 2016 lunar calendar), American scientists announced the detection of attractive force waves for the first time. American scientists announced the detection of attractive force waves for the first time. Einstein was right again! One hundred years after the great scientist made the prediction of attractive force waves, at 10:30 am local time on February 11, 2016 (23:30 on February 11, Beijing time), the National Science Foundation (NSF) convened scientists from Caltech, MIT and LIGO Scientific Collaboration to announce at the National Media Center in Washington, DC: Humans have directly detected attractive force waves for the first time! This is the first time that humans have been able to "hear" the "sound" of the universe. Attractive force waves are the last missing piece of the puzzle in the experimental verification of Einstein's general theory of relativity, and its discovery is a major milestone in the field of physics. We can "hear" the universe. "Ladies and gentlemen, we have detected attractive force waves, and we have found them." David Reitz, executive director of the Laser Interferometer Attractive Force Wave Observatory (LIGO) in the United States, announced at a press conference in Washington that day. Amid the noisy background noise, a crisp "poof" sound, like water droplets falling into the water, lasts for less than a second, which is the sound of the universe converted from attractive force waves. At the press conference that day, LIGO scientists played the "sound" from the universe live. "We can'hear 'attractive force waves, we can'hear' the universe, which is one of the most beautiful events of attractive force waves. We will not only'see 'the universe, we will'listen' to it," Gabriela Gonzalez, a Louisiana State University physicist and spokesperson for the LIGO project, said at the press conference. Reitz, from Caltech, likened the search for attractive force waves to a scientific moon landing. "We did it, we went to this'moon '," he repeated excitedly. The press conference was also attended by researchers from the Massachusetts Institute of Technology and the National Science Foundation, which funded the research. Attractive force waves are ripples in space-time produced by the merger of black holes, like ripples created by rocks thrown into water. Black holes, neutron stars and other celestial bodies can generate attractive force waves during collisions. 100 years ago, Einstein's general theory of relativity predicted the existence of attractive force waves. Other predictions of general relativity, such as the bending of light, the perihelion precession of Mercury, and the attractive force redshift effect, have been confirmed, but the attractive force wave has been hovering out of scientists' "line of sight". In the 1970s, scientists in the United States discovered indirect evidence of attractive force waves in the process of observing binary star systems, which won the 1993 Nobel Prize in Physics. In new research to be published in the journal Physics Review Letters, scientists detected an extremely short-lived attractive force wave signal generated by a black hole merger, lasting less than a second. It arrived at Earth on September 14, 2015, after a long journey of 1.30 billion years, and was captured by two newly upgraded LIGO detectors with a time difference of 7 milliseconds. The researchers estimated that the masses of the two black holes before the merger were equivalent to 36 and 29 solar masses, respectively. After the merger, the total mass is 62 solar masses. The energy of the three solar masses is released in the form of attractive force waves in less than 1 second, and the peak energy released is about 50 times higher than the energy released by the entire visible universe. Open a new window to observe the universe. LIGO is two attractive force wave detectors built by the United States in Livingston, Louisiana, and Hanford, Washington. Its detection sensitivity has been greatly improved after the modification and upgrade. More than 1,000 scientists from more than 10 countries are involved in this project to search for attractive force waves. Rumours of LIGO's discovery of attractive force waves have been circulating in the physics community for months. The first to reveal the news was Lawrence Krause, a physicist at Arizona State University in the United States, but it has not been confirmed by the LIGO project team. Krause said on the 11th that the discovery of attractive force waves is a "major milestone", which opens a new window to observe the universe, just like the invention of the telescope or the discovery of radio waves in space. "This discovery is the beginning of a new era, and attractive force wave astronomy is now a reality," said Gabriela Gonzalez, a spokesperson for the LIGO project team. Einstein must have been taken aback. "We detected attractive force waves. We did it. "On the early morning of the 11th local time, when David Reitz, the executive director of LIGO and a professor at the California Institute of Technology, announced the news in Washington, hundreds of researchers crowded in the California Institute of Technology Center for Astronomy and Astrophysics to participate in the simultaneous press conference boiled. Long cheers, applause and tears... No wonder the researchers were so excited. According to scientists, humans detected attractive force waves, just like a deaf person suddenly gained hearing, and then gained a new ability to perceive the world. This day, it has been a hundred years since Einstein predicted the existence of attractive force waves. "I'm sure Einstein would have been taken aback when he saw today's results," said Chen Yanbei, a professor of physics at Caltech and a research member of the LIGO scientific collaboration. "Although he would have been gratified by his contributions to general relativity, quantum mechanics, lasers and many other fields, physics has made unprecedented progress in the past hundred years. For human achievements today, Einstein must have been unimaginable." Einstein predicted the existence of attractive force waves a century ago, but also believed that attractive force waves were too weak to be detected. "We proved Einstein right, and on the other hand he was wrong, we really detected it," Ling Sun, a researcher at the University of Melbourne in Australia who is involved in the LIGO project, told reporters. Why is it so hard to catch attractive force waves? Attractive force waves are such a weak signal that even Einstein himself doubted whether he could build a sensitive enough detector, and detecting attractive force waves was considered an "impossible task" for a long time. Since the 1990s, large-scale laser interferometer attractive force wave detectors have been built around the world, really kicking off the golden age of attractive force wave detection. The United States has built two laser interferometric attractive force wave detectors (LIGO) in Livingston, Louisiana, and the small city of Hanford, Washington. LIGO has huge L-shaped measuring arms, each 4 kilometers long, with reflective mirrors at each end. The emitted laser beam travels along the perpendicular sides of the L-shape and is reflected back and forth. Normally, the lasers cancel each other due to interference, and the detector cannot receive the light signal, but once the attractive force wave passes, it changes the distance of the laser to pass through and is observed. Detecting attractive force waves requires extremely high sensitivity of the detector, and it is also necessary to distinguish the attractive force wave signal from environmental or instrument noise. On September 14, 2015, at 17:50:45 Beijing time, two detectors in Livingston and Hanford simultaneously observed the attractive force wave signal, which was later named GW150914. The scientists also confirmed through further data analytics that this is the event of the merger of two black holes. At the press conference that day, some people also asked if the detected attractive force wave signal was too good? The LIGO project scientists replied that it took them several months to verify, which is why the detection of the attractive force wave signal in September last year was delayed until today. The scientists also believe that with the improvement of the detector's sensitivity, more attractive force wave signals should be detected this year. How important is it to detect the attractive force wave? Scientists from many countries, including Chinese scientists, believe that the new discovery not only fills in the last missing piece of the puzzle in the experimental verification of general relativity, making the foundation of modern physics more solid, but also means that scientists have grasped the "key" to unlocking the mysteries of the universe, helping to understand the origin and operation mechanism of the universe. Stephen Hawking, a famous British theoretical physicist, said: "Attractive force waves provide a new way for people to look at the universe. This ability to detect attractive force waves has the potential to revolutionize astronomy. Ma Yinzhe, an attractive force wave research expert at the University of KwaZulu-Natal in South Africa, said that the discovery of astronomy has been mainly based on the measurement of electromagnetic spectrum for hundreds of years. Radio, optical, infrared, X-ray and other astronomical observation methods are collecting light and observing the universe by "looking". The discovery of attractive force waves will make astronomical observations from a completely different perspective, and the door of attractive force wave astronomy will be completely opened. Attractive force waves will become a new window to test Einstein's relativity, detect the mass of black holes, and measure the distance of the universe. Chad Hanna, a scientist at Pennsylvania State University who worked on the project, said that we cannot predict how attractive force wave astronomy will change our fundamental understanding of the universe, just as Galileo couldn't predict the universe shown to us by the Hubble Space Telescope with his small telescope. "We can expect that in 100 years, what our descendants know will be very different from what we know."