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<p>The accuracy of 20 Times of <strong>Gravity wave detection</strong>.</p>
<p>In 2016, gravity waves were observed for the first time in history in the US physics laboratory LIGO. This is a magnificent mechanism that sets up two observatory stations at 3000 km away and coordinates each other. Experimental facility... but now, a grand idea is progressing steadily towards realization.</p>
<p>Since the gravitational wave is very weak, in order to detect it, it is necessary to eliminate other noise to the limit. So Research Consortium of NASA and the European Space Agency (ESA), with less noise than the global launch of the gravitational wave detector in space. That is <strong>Lisa Pathfinder</strong>. Experiments on how much noise can be reduced after the launch showed that the results are far beyond expectations and 20 times better than the required level.</p>
<p>The gravitational wave is the time-space distortion in which Albert Einstein predicted existence. It occurs when a substance moves, and it propagates in space-time with the speed of light. Since observation for the first time in 2015, gravitational waves caused by tremendous events such as collisions between black holes have been observed. In 2017 gravity waves due to the collision of two neutron stars are captured together with explosive light.</p>
<p>However, the gravitational wave experimental facility on the earth including LIGO has a limited frequency of the gravitational wave that can be observed. With some detectors now, it can only detect "gravitational waves in the band generated when objects of the same star mass collide with each other". Even such as a giant black hole at the center of our galaxy, collide with each other, we are not aware of the gravitational waves generated by it. Specifically, we do not know if the <a href="https://arxiv.org/abs/1411.4547">frequency of the gravitational wave</a> is less than 10 Hz (waving 10 times per second) or less.</p>
<p>It is the mission LISA scheduled to be <a href="http://www.esa.int/Our_Activities/Space_Science/ESA_creates_quietest_place_in_space">launched</a> in 2034 that is trying to cover frequencies that can not be captured by such existing detectors while avoiding noise in outer space. The LISA Pathfinder experimented this time is positioned as a precedent test. LISA is planning to ride the solar orbit so that the three orbits are set missions while keeping a distance of 2.5 million kilometers away from each other while flying the laser to each other and following the orbit of the earth. If the gravitational wave passes through it, the space around the distortion is slightly distorted and the distance traveled by the laser changes accordingly, so we detect this and observe the gravity wave indirectly.</p>
<p>And, in order to accurately detect, it is necessary to prevent the mirror of the cube on the satellite from being affected as much as possible except for gravity, so in a <a href="https://en.wikipedia.org/wiki/Free_fall">free fall</a> state (<em>a state where the mirror and the satellite are not in substantial contact</em>). In order to realize this, LISA is supposed to fly with fine adjustment using a sensor so that the positional relationship between the mirror and the spacecraft is always constant. What is important here is to grasp all the forces on the mirror. LISA Pathfinder analyzed the power hanging on the mirror and was investigating the characteristics of the noise.</p>
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<p>The LISA Pathfinder launched in 2015 was like moving one of the three satellites used in this LISA by itself. In the <a href="https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.120.061101">report</a>, the characteristic of noise is written in much more detail than the purpose of the mission. Since it was possible to grasp extremely fine noise and the force that the cube received from outside was also very small, it is said that gravity wave observation became possible with 20 times higher precision than the original target. When saying that sensitivity, it seems that it is enough to <strong>detect its gravity just by mosquito flight</strong>.</p>
<p>However, elimination of noise is only a small part of LISA's assignment. In addition to that, need to complete the system for linking the three spacecraft and the laser system that connects between them. However, while doing this now the LISA team is steadily preparing for them.</p>
<p>By the way, what happens if LISA collides with asteroids , LISA is so small that its possibility is low . However, the research team considers even the impact of meteor dust on the micrometer level rather than asteroids, and if any of LISA 's satellites are pushed to some extent, that data can be deleted.</p>
<p>Regarding the method of gravitational wave detection, not only <strong>LIGO</strong> on ground and <strong>LISA</strong> in space, but also a method of analyzing the deviation of the timing at which radio waves arrive from a star emitting a pulsed radio wave called "pulsar timing array".</p>
<p>By the time LISA is launched in 2034, there will be more ways to know about the universe. If a gravitational wave detector comes with a <strong>commercially</strong> available <strong>astronomical telescope</strong> and anyone can experience the collision of star and black holes and others...</p>
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