Einstein's general theory of relativity predicts that the main properties of gravitational waves (also known as gravity waves) are: propagating at the speed of light in vacuum; Carrying energy and information related to the wave source; It is a shear wave, and it is a plane wave at the far source; The lowest order is quadrupole radiation; The radiation intensity is extremely weak; The absorption efficiency of matter to gravitational waves is extremely low, and the gravitational wave penetration is extremely strong, and the earth is almost transparent to gravitational waves; Its polarization characteristics are two independent polarization states, etc. The gravitational wave detector jointly built by France and Italy has just been completed and will be officially opened in 2004. Strong evidence shows that gravitational waves are not only Einstein's hypothesis, but also from the observation of neutron stars. Even Einstein thought that gravitational waves might never be detected, and it was technically difficult to observe them. If the cost of all detectors in the world is added up, the cost of capturing gravitational waves is undoubtedly astronomical.
Today, nearly 90 years after the publication of "General Relativity", it is finally possible for this mysterious wave to show us its true colors. Now the research on gravitational waves is in the ascendant, and the research on anti-gravity or anti-gravity has been put on the agenda. The possible results of this research may fully realize the dream of human beings to realize interstellar navigation, and scientists deserve to devote their life-long energy and talent to this research.
■ Noun explanation
gravity wave
Gravitational waves are also called gravity waves. As early as 19 16, Einstein predicted the existence of gravitational waves when he put forward the "general theory of relativity". However, only gravitational waves released by extremely large and dense celestial bodies in the universe, such as supernovae, collapsing black holes and neutron stars, can be detected: a supernova briefly bursts into light as bright as a galaxy composed of billions of stars, and then its fragments are shot deep into the universe. But its influence goes far beyond this. Supernovae will make the structure of space-time tremble and spread to millions of light years away. This phenomenon is called gravitational wave.
neutron star
Neutron stars are the product of the explosion of giant stars. They are composed of neutrons, and usually all substances are compressed in a space the size of a city. Some neutron stars rotate very fast and emit radio waves intermittently, which astronomers can identify with radio telescopes.
People can't directly detect gravitational waves because their destructive power is greatly diluted in the vast space. If you can get close to a supernova, gravitational waves will tear you and everything around you to pieces. But when gravitational waves reach the earth, they can only cause the slightest fluctuation in time and space.
General relativity predicts the existence of gravitational waves.
Today, nearly 90 years after the publication of general relativity, this mysterious wave may finally show us its true colors. In the past few years, astronomers have set up detectors in the United States, Japan and Germany, and recently set up one in Italy, which is 0/2 km away from Pisa/Kloc. This French-Italian probe, called Virgo, has just been completed and will be put into use in 2004. This is a big project and it costs a lot. Virgo has a 3-kilometer-long tunnel, which is located in the suburb of Pisa, Italy. The tunnel is only a part of Virgo. At the National Astronomical Observatory of Japan, there is also an isosceles right-angled triangular tunnel with a right angle of 300 meters. A laser interferometer gravitational wave detection device named "TAMA300" has recently started operation, which is one of the first efforts to search for gravitational waves in the world.
Gravitational waves are also called gravity waves. As early as 19 16, Einstein predicted the existence of gravitational waves when he put forward the "general theory of relativity". Relativity holds that time and space are inseparable. We can no longer treat three-dimensional space and ticking clock separately, they are actually part of the structure of time and space. However, a corollary of general relativity has yet to be confirmed: if an object moves suddenly, it should release energy in the form of gravitational waves, just like shaking a clock will ring. Theoretically, this applies to all objects, including human beings. However, only gravitational waves released by extremely large and dense celestial bodies in the universe, such as supernovae, collapsing black holes and neutron stars, can be detected: a supernova briefly bursts into light as bright as a galaxy composed of billions of stars, and then its fragments are shot deep into the universe. But its influence goes far beyond this. Supernovae will make the structure of space-time tremble and spread to millions of light years away. This phenomenon is called gravitational wave, and astronomers are trying to be the first to prove its existence. They may eventually take us back to the source of the big bang. All theories need evidence to support them, but it is very difficult to find evidence. People can't directly detect gravitational waves because their destructive power is greatly diluted in the vast space. If you can get close to a supernova, gravitational waves will tear you and everything around you to pieces. But when gravitational waves reach the earth, they can only cause the slightest fluctuation in time and space. It is technically difficult to observe gravitational waves, which is tantamount to measuring the width of the Milky Way and controlling the error of the results within 3 cm. So even Einstein thought that gravitational waves might never be detected.
Gravitational waves do exist.
The construction of Virgo took six years and cost about 55 million pounds. If the cost of all detectors in the world is added up, the cost of capturing gravitational waves is undoubtedly astronomical. Fortunately, no one thinks that this work will be in vain. There is strong evidence that gravitational waves are not just Einstein's hypothesis. This evidence comes from the observation of neutron stars. Neutron stars are the product of the explosion of giant stars. They are composed of neutrons, and usually all substances are compressed in a space the size of a city. Some neutron stars rotate very fast and emit radio waves intermittently, which astronomers can identify with radio telescopes. This neutron star is called a pulsar. 1974, American physicists joseph taylor and russell hulse first discovered a pair of pulse binary stars. They found that the intimate circle of these two celestial bodies was getting closer and closer. Although the change range is small (only about 1 cm per year), it is of great significance. This means that both celestial bodies are losing energy, and this orbital change is completely in line with the prediction of relativity. Taylor and Hall believe that energy is released in the form of gravitational waves, and this discovery won them the Nobel Prize of 1993.
Virgo, like other newly built gravitational wave detectors, is a large-scale laser interferometer, which captures gravitational waves by using their characteristics. This feature is that gravitational waves make space-time stretch along one direction axis and compress along another direction axis perpendicular to it. By continuously measuring the distance in these two directions, people can find the distance of stretching and compressing in these two directions at a certain moment. Like all big magic tricks, scientists use mirrors to do this. The light emitted by the laser passes through the optical splitter, and the optical splitter transmits the light beam to two L-shaped tubes respectively, forming a vertical angle. A mirror hangs at the end of each tube, reflecting two beams of light back and meeting at the intersection. People deliberately changed the wavelengths of these two kinds of light so that when they reflect back, they will cancel each other out. There is a photodiode that records light and usually does not show the appearance of light. However, if there is a gravitational wave passing by, the propagation distance of the two beams of light will be different. Then when two beams of light meet, the waveforms will not completely interfere, resulting in light emission.
The technical specifications of Virgo are amazing. The mirror surface is very smooth, and the convex and concave amplitude is less than one hundredth of a micron (1 micron equals one millionth of a meter). In addition, their reflectivity to light reaches 99.999%. Laser is also unusual because the beam it produces is by far the most stable. So, how likely is it that Virgo will observe gravitational waves? Professor Bangora Tasha prakash of Cardiff University said: "We expect that there will be one or two mergers of double black holes every year. These predictions are made on the basis of uncertainty theory, so the probability may be lower. Therefore, if we don't see anything in three or four years, it's not surprising. " After that, it is the test of the authenticity of Einstein's theory. People plan to upgrade Virgo and other gravitational wave detectors, so by 20 10, their sensitivity will be increased by 10 times. This can expand the observation range by 1000 times. In such a large area, there should be celestial activities that form gravitational waves every year, maybe every day. If people still get nothing, it will have a great impact on astrophysics. Tasha prakash said: "If we can't find gravitational waves, we will have to start to doubt whether some basic models of astrophysicists are correct, such as how binary star systems are formed."
Anti-gravity research returns to scientists' sight
Einstein's general theory of relativity predicts that the main properties of gravitational waves are: propagating at the speed of light in a vacuum; Carrying energy and information related to the wave source; It is a shear wave, and it is a plane wave at the far source; The lowest order is quadrupole radiation; The radiation intensity is extremely weak; The absorption efficiency of matter to gravitational waves is extremely low, and the gravitational wave penetration is extremely strong, and the earth is almost transparent to gravitational waves; Its polarization characteristics are two independent polarization states, etc. Gravitational wave is a gravitational field with waveform and finite speed propagation.
Although Einstein predicted that there might be gravitational waves in the accelerated mass in 19 16, his gravitational waves were related to the selection of coordinates. In one reference frame, gravitational waves may have energy, but in another reference frame, they may not. Therefore, at the beginning of gravitational waves, most people, including Einstein himself, were skeptical about gravitational waves. 1956, Pirani put forward a definition of gravitational wave that has nothing to do with the choice of coordinate system. 1957, the band-aid further proves theoretically the existence of plane gravitational waves that have nothing to do with the selection of coordinate system. 1959, Band-Aid, Pirani and Robinson further proved that stationary objects will move under the action of gravitational wave pulses, and indirectly proved that gravitational waves can carry energy and can be detected. Because the gravitational radiation is extremely weak, it is impossible to emit detectable gravitational waves in the laboratory at present, but the violent motion of massive celestial bodies, such as the revolution of binary star system, the rotation of neutron star, supernova explosion, the formation, collision and capture of theoretically predicted substances, can radiate strong gravitational waves.
For many years, scientists all over the world have been committed to detecting gravitational waves. Weber, a scientist at the University of Maryland in the United States, took the lead in using an aluminum rod as an antenna for detection, and claimed to have detected a signal that did not rule out gravitational waves. But other scientists did not get this result, and Weber's conclusion was not recognized. Now the research on gravitational waves is in the ascendant, and the research on anti-gravity or anti-gravity has been put on the agenda. The possible results of this research may fully realize the dream of human beings to realize interstellar navigation, and scientists deserve to devote their life-long energy and talent to this research. Scientists in China have conducted valuable experiments and research in this field.
Since the British science fiction writer Wells described "anti-gravity" (which can shield the influence of gravity and make the spacecraft fly to the moon), anti-gravity has become a dream of human beings for more than a century. If anti-gravity does exist, it will change the whole world. Cars, trains, ships, all the transportation systems you can think of can be driven by the energy obtained by the gravitational field. This anti-gravity research, which will change the taboos of the world scientific community and aerospace industry, has once again attracted people's attention, because it is reported that Boeing, the world's largest aircraft manufacturer, is exploring some new concepts, which may completely change the propulsion technology in the next century.
The anti-gravity research carried out by Boeing can be summarized as a project of the company called "Grasp (Advanced Space Propulsion Technology Gravity Research)". A related document obtained by Jane's Defense Weekly expounds the great significance of Boeing's belief in the success of this project. The document reads: "If anti-gravity does exist, it will definitely change the entire aerospace industry." This evaluation may not be enough. If anti-gravity does exist, it will change the whole world. Cars, trains, ships, all the transportation systems you can think of can be driven by "no propellant propulsion"-a mode of obtaining energy from gravity field.
Although anti-gravity is a beautiful dream, traditional science has always believed that anti-gravity is impossible. 1In April, 992, Brian Young, the late British Professor university of salford and then head of the strategic project of British space defense system, gave a speech at the London Institution of Mechanical Engineers. In his speech, he explained why anti-gravity research is related to the aerospace industry and even the world. The "Grasp" briefing explains why Boeing must hire Russian material expert yevgeny Podkretnov. Podcletnov claims to have invented a device that can shield the influence of gravity.
1992, Podkretnov, who works at Tampere University of Technology in Finland, submitted a paper to a British physics magazine. He described how an object placed on a high-speed rotating superconductor (which loses its resistance at extremely low temperatures) lost nearly 2% of its weight. This paper was leaked to a newspaper. First, because of the taboo concept of "anti-gravity", and second, because it caused an uproar in mainstream physics, Poldek Letnov was expelled from school. But the Russian research caught the attention of NASA. She has contacted a researcher at the University of Alabama in Huntsville, who claimed that she could create a gravitational field and repel or attract objects by using high-speed rotating superconductors.
In the mid-1990s, the Marshall Space Center of the National Aeronautics and Space Administration (NASA) in Alabama failed to repeat Bode Crete's experiment. However, the center admits that it doesn't know the unique method of Russian manufacturing superconducting disks, and it is largely blind research.
A few years ago, NASA paid $600,000 to Columbus Superconducting Components Company in Ohio, made the device that Podkletov used, and hired Russians as consultants. Although the experiment was postponed, Ron Kozol, the director of the experiment, was confident that the experiment could be completed. Podklenov, who now works in Moscow Chemical Research Center, further developed his ideas. Together with Italian scientist Giovanni Danis, he published a paper detailing the research work of a "pulse gravity generator", which can repel all objects. The device uses strong discharge power "emitter" and superconducting "emitter" to generate "gravity pulse". Pod Crete Novo said: "The time is very short. It travels along the discharge line at a very fast speed (actually instantaneous) and passes through many different objects without any obvious energy loss." He said that the experimental result is that any object hit by a light beam has a thrust effect, and the size is directly proportional to the mass of the object. When adjusting a laser aiming device, Pod Crete Novo said that his experimental device has shown the ability to knock down objects 1 km away. He claims that this device can knock down objects 200 kilometers away with the same energy. It is Poldek Letnov's research work on "Pulse Gravity Generator" that has attracted the attention of Boeing Company. In the "Grasp" briefing, Boeing described how the light beam emitted by the equipment can penetrate any object without any electromagnetic shielding.
The "gold rush" is heating up
At the Farnborough International Air Show, George Milner, the outgoing head of Boeing Phantom Research Project, admitted that his company was interested in Podkletov's research and other anti-gravity equipment. Milner also said that his company believes in the scientific principles contained in these devices. He said: "The principles of physics seem to be established, including basic scientific principles, and have not broken the laws of physics." The "Grasp" document pointed out that other large aerospace industry companies, such as British Aerospace Systems and Lockheed Martin, also made contact with Podek Letnov. Boeing may be ahead of the "gold rush" because it is one step ahead. Fifty years ago, many aviation industry companies, including Martin Company, Bell Aircraft Company and United Urti Aircraft Company, showed similar interest in anti-gravity research, and then fell silent. Some people speculate that silence is based on the fact that the whole anti-gravity research is classified as top secret because it may change the world.
In fact, the research on anti-gravity has no prospect for the time being can be traced back at least to the 1920s. Thomas Thomson Brown, an American inventor, invented a disk capacitor, the upward side of which is connected to the positive electrode and the downward side is connected to the negative electrode, and the capacitor tends to rise towards the positive electrode. A scientist from NASA applied for a patent for a "two-dimensional asymmetric capacitor plate"-a disk-shaped charged device that can generate thrust. I don't know if it's a coincidence, but the current research is very similar to Brown's idea. Boeing admits that it is studying the anti-gravity device in the DreamWorks in Seattle, and the devil who has been trapped for a long time will come out of the bottle.