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Physicists invent a new way to search for dark matter using lasers
Japanese physicists devise technology to discover axion dark matter.
- Physicists from the University of Tokyo plan to use lasers to discover axions.
- Axions are theoretical particles that may be components of dark matter.
- Dark matter is a mysterious substance that may compose up to 27% of the universe.
Japanese physicists propose modifications to existing equipment that could allow them to pinpoint axions, hypothetical particles that may be components of dark matter. Dark matter, a mysterious theoretical substance that is thought to make up about 27% of all matter in the universe, is yet to be directly observed.
The scientists hope to track down the elusive axions using experiments with lasers.
The difficulty in finding dark matter is that it is made of, as many physicists think, weakly interacting massive particles or WIMPs, produced in the early Universe. While we haven't figured out how to spot these particles directly, interacting with regular matter, but we've been able to predict their existence by the gravitational effects they have throughout the universe.
The celebrated Large Hadron Collider in Switzerland has been used to search for WIMPs, and now a new approach from Japan hopes to use the KAGRA Observatory to discover dark matter by tracking down axions.
KAGRA stands for the Kamioka Gravitational Wave Detector. This first major gravitational wave observatory in Asia is located deep under a mountain of the Kamioka mine in Japan's Gifu Prefecture.
The Assistant Professor Yuta Michimura from the Department of Physics at the University of Tokyo, which runs the KAGRA project, explained that because axions are light and don't interact with normal matter, they are good candidates for dark matter.
Interestingly, he also quantified how much dark matter is there, saying the amount of it inside our planet would weigh as much as a squirrel —
"We don't know the mass of axions, but we usually think it has a mass less than that of electrons, " said Michimura. "Our universe is filled with dark matter and it's estimated there are 500 grams of dark matter within the Earth, about the mass of a squirrel."
The proposed instrument that would hunt for axion dark matter.
Credit: 2019 Nagano et al | University of Tokyo Institute for Cosmic Ray Research
As you can imagine, spotting such particles is no easy task. Physicists have to figure out ways that can make the particles reveal themselves through their signatures.
Koji Nagano, a graduate student at the Institute for Cosmic Ray Research at the University of Tokyo, says that their models show that axions affect light polarization, which describes the geometrical orientation of oscillating electromagnetic waves.
Their method of finding axions relies on this finding.
"This polarization modulation can be enhanced if the light is reflected back and forth many times in an optical cavity composed of two parallel mirrors apart from each other, " further expounds their approach Nagano.
The best examples of such cavities, says the researcher, are the long tunnels of gravitational-wave observatories.
"There is overwhelming astrophysical and cosmological evidence that dark matter exists, but the question "What is dark matter?" is one of the biggest outstanding problems in modern physics," said Nagano. "If we can detect axions and say for sure they are dark matter, it would be a truly exciting event indeed. It's what physicists like us dream for."
The team proposes plans to inexpensively modify existing observatories like KAGRA or the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the U.S. to search for the axions. The plan, according to Michimura, would be to add "polarization optics in front of photodiode sensors in gravitational-wave detectors."
The idea's additional benefit is that it doesn't require building entirely new facilities. Upgrading gravitational wave labs would not hamper their original missions — looking for gravitational waves. But the new functionality would open a new chapter in the search for dark matter.
The study involved Koji Nagano, Tomohiro Fujita, Yuta Michimura, and Ippei Obata.
Check out the their paper "Axion Dark Matter Search with Interferometric Gravitational Wave Detectors" in the journal Physical Review Letters.
What is human dignity? Here's a primer, told through 200 years of great essays, lectures, and novels.
- Human dignity means that each of our lives have an unimpeachable value simply because we are human, and therefore we are deserving of a baseline level of respect.
- That baseline requires more than the absence of violence, discrimination, and authoritarianism. It means giving individuals the freedom to pursue their own happiness and purpose.
- We look at incredible writings from the last 200 years that illustrate the push for human dignity in regards to slavery, equality, communism, free speech and education.
The inherent worth of all human beings<p>Human dignity is the inherent worth of each individual human being. Recognizing human dignity means respecting human beings' special value—value that sets us apart from other animals; value that is intrinsic and cannot be lost.</p> <p>Liberalism—the broad political philosophy that organizes society around liberty, justice, and equality—is rooted in the idea of human dignity. Liberalism assumes each of our lives, plans, and preferences have some unimpeachable value, not because of any objective evaluation or contribution to a greater good, but simply because they belong to a human being. We are human, and therefore deserving of a baseline level of respect. </p> <p>Because so many of us take human dignity for granted—just a fact of our humanness—it's usually only when someone's dignity is ignored or violated that we feel compelled to talk about it. </p> <p>But human dignity means more than the absence of violence, discrimination, and authoritarianism. It means giving individuals the freedom to pursue their own happiness and purpose—a freedom that can be hampered by restrictive social institutions or the tyranny of the majority. The liberal ideal of the good society is not just peaceful but also pluralistic: It is a society in which we respect others' right to think and live differently than we do.</p>
From the 19th century to today<p>With <a href="https://books.google.com/ngrams/graph?year_start=1800&year_end=2019&content=human+dignity&corpus=26&smoothing=3&direct_url=t1%3B%2Chuman%20dignity%3B%2Cc0" target="_blank" rel="noopener noreferrer">Google Books Ngram Viewer</a>, we can chart mentions of human dignity from 1800-2019.</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDg0ODU0My9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY1MTUwMzE4MX0.bu0D_0uQuyNLyJjfRESNhu7twkJ5nxu8pQtfa1w3hZs/img.png?width=980" id="7ef38" class="rm-shortcode" data-rm-shortcode-id="9974c7bef3812fcb36858f325889e3c6" data-rm-shortcode-name="rebelmouse-image" />
American novelist, writer, playwright, poet, essayist and civil rights activist James Baldwin at his home in Saint-Paul-de-Vence, southern France, on November 6, 1979.
Credit: Ralph Gatti/AFP via Getty Images
The future of dignity<p>Around the world, people are still working toward the full and equal recognition of human dignity. Every year, new speeches and writings help us understand what dignity is—not only what it looks like when dignity is violated but also what it looks like when dignity is honored. In his posthumous essay, Congressman Lewis wrote, "When historians pick up their pens to write the story of the 21st century, let them say that it was your generation who laid down the heavy burdens of hate at last and that peace finally triumphed over violence, aggression and war."</p> <p>The more we talk about human dignity, the better we understand it. And the sooner we can make progress toward a shared vision of peace, freedom, and mutual respect for all. </p>
Scientists find that bursts of gamma rays may exceed the speed of light and cause time-reversibility.
- Astrophysicists propose that gamma-ray bursts may exceed the speed of light.
- The superluminal jets may also be responsible for time-reversibility.
- The finding doesn't go against Einstein's theory because this effect happens in the jet medium not a vacuum.
Jet bursting out of a blazar. Black-hole-powered galaxies called blazars are the most common sources detected by NASA's Fermi Gamma-ray Space Telescope.
Cosmic death beams: Understanding gamma ray bursts<div class="rm-shortcode" data-media_id="cu2knVEk" data-player_id="FvQKszTI" data-rm-shortcode-id="c6cfd20fdf31c82cb206ade8ce21ba3f"> <div id="botr_cu2knVEk_FvQKszTI_div" class="jwplayer-media" data-jwplayer-video-src="https://content.jwplatform.com/players/cu2knVEk-FvQKszTI.js"> <img src="https://cdn.jwplayer.com/thumbs/cu2knVEk-1920.jpg" class="jwplayer-media-preview" /> </div> <script src="https://content.jwplatform.com/players/cu2knVEk-FvQKszTI.js"></script> </div>
Philosophers have been asking the question for hundreds of years. Now neuroscientists are joining the quest to find out.
- The debate over whether or not humans have free will is centuries old and ongoing. While studies have confirmed that our brains perform many tasks without conscious effort, there remains the question of how much we control and when it matters.
- According to Dr. Uri Maoz, it comes down to what your definition of free will is and to learning more about how we make decisions versus when it is ok for our brain to subconsciously control our actions and movements.
- "If we understand the interplay between conscious and unconscious," says Maoz, "it might help us realize what we can control and what we can't."
We’ve mapped a million previously undiscovered galaxies beyond the Milky Way. Take the virtual tour here.
See the most detailed survey of the southern sky ever carried out using radio waves.
Astronomers have mapped about a million previously undiscovered galaxies beyond the Milky Way, in the most detailed survey of the southern sky ever carried out using radio waves.
A new study shows our planet is much closer to the supermassive black hole at the galaxy's center than previously estimated.