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New Gravitational Wave | Space

Ah!In 10 billion trillion trillion of seconds at the start of creation in the Big Bang. The universe is believed to have grown rapidly in a short period of time. but absurdly absurd This event is called inflation. It was so catastrophic that the structure of space and time was judged by gravitational waves (GWs). By comparison, GWs first detected six years ago to much fanfare were small events caused by black hole collisions. Now, scientists at the European Space Agency (Esa) are aiming for a bigger goal. And it is hoped that they will soon be able to detect the faint echo of the cosmic bloating, nearly 1

4 billion years after the event, using the largest instrument. ever created Esa’s planned gravitational wave detector is hundreds of times larger than Earth. will float in space and look for the wobbles of spacetime caused by the convulsions of all sorts of gigantic astrophysics.

The first GW was identified in 2015 by the Laser Interferometer Gravitational-Wave Observatory (Ligo), an international program that successfully won the 2017 Nobel Prize in Physics. Two large machines in the American state of Washington and Louisiana. Each tunnel uses two tunnels, 2.5 miles (4 km) long, intersecting at right angles. The laser beam travels to the mirror at the end and is reflected back. The reversed light waves collide as the arms cross. As GW passes, it shrinks or extends spacetime slightly. Because the effect varies from arm to arm. It thus changes the synchronization of light waves. Thus changing the interference of both beams.

Ligo was not alone. The second GW detected on Christmas 2015 was later confirmed in collaboration with the European Virgo detector based in Italy. The detector in Japan, known as the Kagra, went into operation earlier this year, and others are planned in India and China.

Most noticeable GWs are caused by the collision of two black holes. These are caused by stars many times more massive than our sun burning and collapsing under their own gravity. According to Albert Einstein’s theory of general relativity, gravity is a mass-caused warping of space-time. Collapse can continue until there is nothing left, except for the nearly innumerable “singularity”. This creates a gravitational field so strong that even light cannot escape from it.

The collision of two black holes, an event first detected by the Laser Interferometer Gravitational-Wave Observatory, or Ligo, can still be seen in computer simulations.
The collision of two black holes, an event first detected by the Laser Interferometer Gravitational-Wave Observatory, or Ligo, can still be seen in computer simulations. Image: SXSproject

If two black holes are influenced by each other’s gravity Those black holes may orbit each other and gradually Swirl inwards until they come together. General relativity predicted more than a century ago that such an event would send GWs ripple across the universe. Although there is no direct evidence for such an event until the detection of Ligo, another extreme astronomical phenomenon. These phenomena can also be caused, for example, the merger of neutron stars: Burning stars are less massive than black holes that stopped their collapse, at the point where they consist of matter so dense that their sheath size. The thumb weighs as an elephant 50 m.

GW can be produced with much larger objects. at the center of our galaxy and supermassive black holes millions of times the mass of the Sun. Formed by collapsing stars and cosmic clouds of gas and dust. These supermassive black hole swirling objects produce GW that vibrates at lower frequencies and longer wavelengths of smaller black hole merger waves seen by Ligo and Virgo.

Ground detectors cannot detect these. It’s like trying to catch a whale in a lobster pot. To see them Interferometric detectors will require a much longer weapon. that is difficult Because each arm must be a long, straight, empty space without any vibration. So the researchers plan to create a low-frequency GW in space instead. The most advanced of these plans is the device now built for Esa: the Laser Interferometer Space Antenna (Lisa).

Lisa will freely send a laser beam from one spaceship to bounce off mirrors floating in another. With 3 spaceships, you can build an L-shaped dual-weapon structure like the Ligo, but the arms don’t have to be at right angles instead of Ligo. Fizz will place its three spacecraft millions of miles apart at the corners of the triangle. so that each corner becomes one of the three detectors. All arrays will follow the Earth’s orbit. by following our world for about 30 meters

To test the feasibility of laser interferometry in space, in 2015 Esa launched a pilot project called Lisa Pathfinder, a spacecraft that demonstrated this technology on a small scale. the project scientist who oversees the mission. That completed its 2017 mission “disappointed us,” which was completed in 2017. “It satisfies our requirements on day one with no tweaks. Nothing.” It shows that the mirrors floating in the spacecraft can be incredibly stationary. by oscillations up to one-thousandths of a single atom to keep steady The spacecraft then uses a small thruster to push the force generated by the light coming from the sun.

In other words, McNamara said, “our spacecraft is more stable than the size of the coronavirus,” which is also. Because Lisa would have to detect changes in arm length, since GW at about one tenth of the atomic width is more than a million miles.

Lisa’s debut won’t happen for at least a decade. “We have three satellites to build. Each has many parts,” McNamara said. “It takes time. That’s one of the unfortunate realities of a very complicated mission.” Official “Task Acquisition” which is expected to be obtained in 2024. “At that point We will know the details of this mission. Who among the Isa member countries and the United States? What are the contributions? and how much it costs,” says astrophysicist Emanuele Berti of Johns Hopkins University in Baltimore.

Japan and China are still in the early stages of planning the GW detector in space. McNamara sees these as not a competition. but is good because with more than one detector Triangles can be used to indicate where the waves come from.

“Lisa will change GW astronomy in the same way as transcending visible light.” [to radio waves, X-rays etc] It’s a game-changer for conventional astronomy,” Berti said. “It will look at different classes of GW sources.” From studying supermassive black hole mergers, he said, “we hope to gain a great deal of insight into the formation of structures. in the universe and about self-gravity.” And if Lisa sees the “traditional” GW from the early inflation of the Big Bang? That might be a theory test of how it all started.

DuThis could be another way to look at low-frequency GWs that don’t require a dedicated detector at all. A collaboration known as the North American Nanohertz Observatory for Gravitational Waves (NanoGrav) is using observations made to a global network of radio telescopes to determine the effect of GW on the timing of the Nanohertz Observatory for Gravitational Waves (NanoGrav). The so-called “cosmic clock” pulsars.

Pulsars are fast-rotating neutron stars that send intense radio waves off their poles. swept across the sky like a lighthouse beam The pulsar signal is highly consistent and predictable, but “if GW passes between the pulsar and Earth,” said Stephen Taylor, a member of the NanoGrav team at Vanderbilt University in Tennessee, “It deforms the intervening spacetime,” causing the pulse to arrive sooner than expected.

Green Bank Telescope (GBT)
Green Bank Telescope (GBT) at the National Radio Astronomy Observatory in Virginia. which is part of the NanoGrav project Photo: Jon Arnold Images Ltd/Alamy.

As a result, the pulsar itself becomes a detector. According to NanoGrav team member Julie Comerford from the University of Colorado at Boulder, this gives the arm The “detector” is as long as the distance between the Earth and the pulsar can be thousands of light years. Due to its enormous size, the signals detected by NanoGrav have very long wavelengths and very low frequencies. Beyond Lisa’s reach and created by a supermassive black hole with a mass equal to the mass of the Sun billions of times. which merges when all galaxies collide. No other detector was able to detect these things, Taylor said. But such mergers are very common, and NanoGrav will see a lot of noise from them. “Across the universe There are pairs of supermassive black holes orbiting each other and producing GWs,” Comerford said. “These ripples form the sea of ​​GW that we are leaping into.”

In January, a NanoGrav team led by Joseph Simon, a postdoctoral researcher at Comerford in Colorado reported that this GW background had been detected for the first time. Although much work remains to be done to confirm that the signal is indeed caused by the GWs, Comerford calls the results “a spur of the moment”. “The most exciting astrophysics results I have seen in recent years.”

If NanoGrav were to use a light-year GW detector, physicist Sougato Bose at University College London believes we could build a detector small enough to fit in a cabinet. His ideas relied on one of the most bizarre effects in quantum theory. which typically describes very small objects such as atoms. Quantum objects can be placed in a position called This means that their properties are not specifically defined until they are measured: there is more than one result.

Quantum scientists can routinely insert atoms into quantum superpositions. But such peculiar behavior is lost for larger objects such as footballs that are here or there. whether we look or not as far as we know Not that stacking is impossible for something that big. But it is impossible to survive long enough to detect it. Because overlays are too easily destroyed by any interaction. with the environment of the object

Sougato Bose, a physicist at University College London, leads a team of researchers who plan to experiment with quantum gravity.
Sougato Bose, a physicist at University College London, leads a team of researchers who plan to experiment with quantum gravity. Image: Courtesy of Sougato Bose.

Bose and colleagues suggest that if we can create a quantum superposition of a medium-sized object between an atom and a soccer ball. which is a small crystal with a width of about 100 nanometers around the size of a large virus particle Overlapping will be extremely dangerous. that it is susceptible to the passing GW. As a result, two possible states of quantum superposition can be perturbed like two light waves, and the spacetime distortions caused by the GW are shown. It’s a change of disturbance.

Bose thinks that vacuum-contained diamond nanocrystals are more empty than space and cooled to absolute zero can be stored in superpositions long enough to do the trick not easy But he said all the technical challenges were proven individually – it was a matter of putting it all together. “I don’t see any obstacles to doing this in the next 10 years if there is enough funding,” he said.

If these developments and others create a boom in GW astronomy, what will we see? “When you open a new window into the universe You always see things you don’t expect,” McNamara said. as well as seeing other types of events As we already know causing GW, we may get a signal that we can’t easily explain, McNamara said. “That’s when the fun begins.”

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