Echo of the universe
The universe will also make sounds , and this "sound" can almost resound throughout the universe, shuttle from one end of the interstellar to the other.
When incredible giant celestial bodies collide violently in space, they will hiccup and ripple in the universe, and reverberate in the universe for billions of years.
The universe is not always so quiet
916, Albert Einstein explained the problem of general relativity in his scientific papers, and predicted the existence of gravitational waves against this problem. General Relativity is a theory of gravity measurement, and its core is the thinking pseudo-Rymann manifold of Einstein's equation.
It describes the geometry of the energy-blocked beams representing space-time, and the spatial relationship between it and the space contained in the space-time of .
For inertial motion in space-time curved geometry in general relativity, there is no gravity that causes the object to deviate from its natural, straight path.
On the contrary, gravity corresponds to changes in spatial and temporal properties. This in turn changes the straightest path the object naturally follows. The most classic simple description of
is that space and time tell matter how to move, while matter tells time and space how to bend.
Spatial-temporal distortion under general relativity
Everything research on general relativity has brought many physical consequences, some from axioms of this theory, while others have only gradually become clearer in the years after Einstein's initial publication.
. In the prediction of 1916 , Einstein believed that ripples in the spatial and temporal measurement would propagate at the speed of light.
This is one of several analogies between weak field gravity and electromagnetics . is similar to the effect of electromagnetic waves .
As for how this effect is, something special happens when two large objects, such as stars and planets orbit each other.
Einstein believes that this kind of movement will cause ripples in space, like throwing a stone into water.
Einstein's home in Princeton, New Jersey,
's strongest gravitational wave is caused by catastrophic events, such as a black hole collision, or a supernova explosion , or a neutron star collision.
other waves may be caused by the rotation of neutron stars of imperfect spheres, and may even be radiation residues left by Big Bang .
Since gravitational waves cannot see , it cannot directly observe it. In addition, their propagation speed is still used for at the speed of light, which makes their observations more difficult.
Early scientists did not believe that this kind of thing would happen, and there was no substantial progress in this.
The original gravitational wave hypothesis came from the Big Bang
It was not until 1974, 20 years after Einstein's death that the first evidence of gravitational waves appeared.
This indirect evidence comes from the orbital decay of the Herrs-Taylor binary pulsar, which scientists found coincided with the decay predicted by general relativity, because gravitational radiation loses energy.
Gravitational Wave Experiment
Before officially entering gravitational wave observation , let’s learn more about gravitational wave knowledge.
We have basically explained the physical manifestations of general relativity and the basic concepts of gravitational waves.
In Einstein's view, gravity is a force that can bend space-time and time .
This bending is caused by the existence of mass.
Generally speaking, the more mass the given space volume of contains, the greater the spatiotemporal curvature of at its volume boundary .
When objects with mass move in space and time, the curvature of will change to reflect the position changes of these objects .
When gravitational waves pass by the observer, the observer will find that space-time and space are distorted due to this strain.
When a wave passes, the distance between objects will increase and decrease rhythmically at the same frequency of the wave.
The impact of anodized gravitational waves on particle rings
The magnitude of the influence of this is inversely proportional to the distance to the gravitational source , such as large events such as neutron star intersection, because their masses will produce a huge acceleration when they are close to each other.
Therefore, the neutron star merge event will cause it to generate powerful gravitational waves.
gravitational waves can penetrate the space area that electromagnetic waves cannot penetrate , and they can observe the merger of black holes and other strange objects that may be in the distant universe.
Staff checks hanging quartz fibers
(A staff member checks quartz fibers in the mirror hanging in the Virgo gravitational wave observatory)
If an optical telescope or radio telescope is used, gravitational waves cannot be observed. In principle, gravitational waves can exist at any frequency .
However, extremely low frequency waves are not likely to be detected, and there is no reliable source for detectable waves of very high frequency.
So in the past, it was not only very difficult for scientists to observe gravitational waves, but even the corresponding technical conditions were difficult to achieve.
Just processing these optical instruments is a headache
In order to verify Einstein's prediction, in the 1960s, scientists from the United States and the Soviet Union conceived a laser interference measurement.
and in the late 60s , the prototype interferometric gravitational wave detector was built by Hughes Research Laboratory.
In addition, with the support of National Science Foundation and Caltech Tech , the relevant research projects have received talent guarantee and financial support.
LIGO During the Livingston Control Room
, the discovery of binary pulsar brought hope to scientists.
orbital period decay measurements demonstrate the existence of gravitational waves, and Taylor and his graduate assistant also won the 1993 Nobel Prize in Physics .
In 1981, the orbital periodic decay of was measured in the astronomical observation system. The amplitude of its performance was completely consistent with Einstein's theory and within the range of slight observation uncertainty.
From this period until the late 1990s, related experimental projects and observations experienced various ups and downs, and the project process was sometimes good and sometimes bad.
started until 2002, and this Laser Interferometric Gravitational Wave Observatory (LIGO) , founded by a group of scientists and foundation executives, was finally in real progress.
Advanced LIGO detector simplified diagram
laser interference experiment
LIGO will run two gravitational wave observatory , LIGO Livingston Observatory and LIGO Hanford Observatory at the same time.
The straight-line distance of these places on the earth is 3002 kilometers, and the surface distance is 3030 kilometers.
Since gravitational waves will propagate at the speed of light, the difference in distance between this part will be as many as 10 milliseconds due to the time difference in gravitational wave arrival.
By measuring with trilateral, the difference in arrival time can help determine the source of the wave.
Each observatory supports an L-shaped ultra-high vacuum system , with each side length of 4 kilometers. Each vacuum system can place 5 interferometers .
LIGO Hanford Observatory is the main configuration of the
LIGO Livingston Observatory. There is also a laser interferometer here, which was upgraded in 2004.
is equipped with an active vibration isolation system based on hydraulic actuators. can provide 10 times the vibration isolation coefficient in the frequency band of 0.1~5Hz. The configuration of the
LIGO Hanford Observatory is basically the same as that of Livingston. During the initial and enhanced stages, the semi-length interferometer operates in parallel with the main interferometer.
Even if the interferometer reaches 2 kilometers in length, the Fabry-Perot arm cavity has the same optical accuracy, so its storage time is half that of the 4 kilometers of the interferometer.
LIGO Hanfude Observatory Real scene
When gravitational waves pass through the interferometer, the space-time and space of the local area will change . is based on wave source and its polarization, which will cause effective changes in the length of one or two cavity of . The effective length change between the beams of
will cause the light currently in the cavity to become very slightly out of phase with the incident light.
intersection of the laboratory
Therefore, the cavity will periodically and slightly lose coherence , and the beam tuned to destructive interference at the detector will have very slight periodic variation detuning, so a signal that can be measured can be generated.
For those less low frequencies or interference caused by other noise sources, scientists use pendulum suspension to effectively protect the detector from vibration.
After more than 40 years of development and thinking, finally, when the summer of 2015 was about to end, LIGO detector reached the detection standard sensitivity standard.
On September 14, as soon as the detector was opened, scientists discovered a signal that was strong enough to determine the source. The team of the LIGO project took several months to finally determine the discovery of gravitational waves , the first time in the world, and also fulfilled Einstein's prediction.
This signal source comes from gravitational waves generated by the merger of two black holes. They are about 1.23427103×10^25 meters from the earth.
In addition, this event proves that gravitational waves can propagate at the same speed regardless of frequency, as described in general relativity.
space-based gravitational wave observations are crucial. In terms of astrophysical , the properties of supermassive black hole generated when galaxies merge can only be determined by these waves. This great discovery of
not only provides humans with a new horizon and opportunity to observe the universe, but also further understands what is happening in the universe.
