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Gamma-ray space telescope study may have spotted dark matter
New study of gamma rays and gravitational lensing points to the possible presence of dark matter.
28 March, 2020
NASA
- Analyzing data from the Fermi Gamma-ray Space Telescope, researchers find hints of dark matter.
- The scientists looked to spot a correlation between gravitational lensing and gamma rays.
- Future release of data can pinpoint whether the dark matter is really responsible for observed effects.
<p>By comparing data derived from gravitational lensing and gamma ray observations by the <strong>Fermi Gamma-ray Space Telescope</strong>, a study showed that certain regions of the sky emit more gamma rays. While the main cause of this phenomenon may be supermassive black holes, the researchers think that some of the emissions may be because of <em>dark matter</em>. It's a so-far-undetected substance that supposedly takes up as much as <strong>27% </strong>of all matter in the Universe, with <em>dark energy</em> taking up another <strong>68%</strong> (<a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy" target="_blank">as per NASA</a>).</p><p>The study builds on nine years of gamma-ray data from the <strong>Large Area Telescope (LAT)</strong> that's part of the <a href="https://fermi.gsfc.nasa.gov/" target="_blank">Fermi space observatory,</a> and was carried out by <a href="https://rubrica.unito.it/rubricaRisultati.php?tipoRic=cog&lang=ita&txtNome=Simone&txtCognome=AMMAZZALORSO" target="_blank">Simone Ammazzalorso</a> at the University of Turin in Italy, <span style="background-color: initial;"><strong>Daniel Gruen</strong> at Stanford University in California, </span><span style="background-color: initial;">and colleagues.</span></p>
<p>The data from the telescope previously pinpointed many individual gamma-ray sources, like the remains of supernova explosions or jets of ionized matter called <a href="https://astronomy.com/news/2018/07/what-is-a-blazar" target="_blank"><em>blazars</em></a> created from accretion of material by supermassive black holes.</p><p>While many sources were located, some of the radiation that was detected by the LAT could not be traced. To investigate this, Ammazzalorso and the team of researchers compared gamma-ray background data with the first-year data from the <a href="https://www.darkenergysurvey.org/" target="_blank">Dark Energy Survey</a>, carried out by the Dark Energy Camera on the <a href="http://www.ctio.noao.edu/noao/node/9" target="_blank">Victor Blanco 4-m Telescope</a> in Chile, which took optical snapshots of 40 million galaxies.</p><p>The research team was trying to figure out if there's a correlation between the location of gravitational lenses and gamma ray photons. <strong>Gravitational lensing</strong> measures the distribution of the Universe's matter by utilizing an effect predicted by Einstein. The effect takes place when light traveling to Earth from a distant object is distorted by the gravitational pull of the matter on the way. </p>
The Difference Between Quasars, Blazars, Pulsars and Radio Galaxies
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="8c4a44762134cae06132534b51a15a65"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/Kc_d_sNBuN8?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>Comparing two sets of data, the scientists realized that regions of the sky with more matter were also responsible for emitting more gamma rays. On the flip side, the regions that were less dense produced fewer gamma rays. </p><p>Specifically, the researchers observed this relationship holding at at high energies and <em>small angular scales, </em><a href="https://physicsworld.com/a/gamma-rays-and-gravitational-lensing-provide-hints-of-dark-matter/" target="_blank">as reports Physics World.</a> Blazars were likely the cause of these kinds of gamma ray emissions, according to the physicists. </p><p>The scientists spotted a weaker version of this kind of emission at larger <a href="http://physicsformom.blogspot.com/2010/09/angular-scales-from-cmb.html" target="_blank">angular scales.</a> This other source of the gamma rays was likely dark matter, thinks <a href="http://lapth.cnrs.fr/pg-nomin/calore/" target="_blank">Francesca Calore</a>, an astroparticle physicist at Annecy-le-Vieux Theoretical Physics Lab in France, who wrote a commentary for the new paper.</p><p style="margin-left: 20px;">"This result is exciting as it marks one of the few hints at the existence of dark matter via indirect detection methods, and it opens up new possibilities for probing dark matter particle models," <a href="https://physicsworld.com/a/gamma-rays-and-gravitational-lensing-provide-hints-of-dark-matter/" target="_blank">said Calore. </a></p><p>She warned that there is still a chance the noticed correlation could be due to blazars, which are still not completely understood.</p>
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjkwMjYxMy9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYwMTg4MDUzMH0.BCWGRi26pCoVAw9L0s9fXo6_yJkVESZs2zAJs-GaA0s/img.png?width=980" id="674f8" class="rm-shortcode" data-rm-shortcode-id="71f15dfd638997d57a99cc249cf86e29" data-rm-shortcode-name="rebelmouse-image" />
An overlap of gravitational lenses and gamma-ray signals could indicate the presence of dark matter.
Credit: D. Gruen/SLAC/Stanford; C. Chang/University of Chicago; A. Drlica-Wagner/Fermilab
<p>New data that will be released from the Dark Energy Survey, including 100 million galaxies, as well as other upcoming sky research like the <a href="https://www.lsst.org/" target="_blank">Legacy Survey of Space and Time</a> at the Vera Rubin Observatory in Chile should shed more light on the matter.</p><p style="margin-left: 20px;">"With deeper redshift coverage and a better angular resolution, future instruments will enable scientists to better understand the sources behind the universe's gamma-ray glow and, potentially, uncover the nature of dark matter," Calore stated.</p><p>Check out the new study in <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.101102" target="_blank">Physical Review Letters.</a></p>
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There is no dark matter. Instead, information has mass, physicist says
Is information the fifth form of matter?
21 January, 2020
Photo: Shutterstock
- Researchers have been trying for over 60 years to detect dark matter.
- There are many theories about it, but none are supported by evidence.
- The mass-energy-information equivalence principle combines several theories to offer an alternative to dark matter.
<p><br></p>
</div>
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The “discovery” of dark matter
<p>We can tell how much matter is in the universe by the <a href="https://www.space.com/20930-dark-matter.html" target="_blank">motions of the stars</a>. In the1920s, physicists attempting to do so discovered a discrepancy and concluded that there must be more matter in the universe than is detectable. How can this be? </p><p>In 1933, Swiss astronomer Fritz Zwicky, while observing the motion of galaxies in the <a href="https://www.space.com/vera-rubin.html" target="_blank">Coma Cluster</a>, began wondering what kept them together. There wasn't enough mass to keep the galaxies from flying apart. Zwicky proposed that some kind of dark matter provided cohesion. But since he had no evidence, his theory was quickly dismissed. </p><p>Then, in 1968, astronomer Vera Rubin made a similar discovery. She was studying the Andromeda Galaxy at Kitt Peak Observatory in the mountains of southern Arizona when she came across something that puzzled her. Rubin was examining Andromeda's rotation curve, or the speed at which the stars around the center rotate, and realized that the stars on the outer edges moved at the exact same rate as those at the interior, violating <a href="http://www.astronomy.com/news/2016/10/vera-rubin" target="_blank">Newton's laws of motion</a>. This meant there was more matter in the galaxy than was detectable. Her punch card readouts are today considered the first evidence of the existence of dark matter. </p><p>Many other galaxies were studied throughout the '70s. In each case, the same phenomenon was observed. Today, dark matter is thought to comprise up to 27% of the universe. "Normal" or baryonic matter makes up just 5%. That's the stuff we can detect. Dark energy, which we can't detect either, makes up 68%. </p><p>Dark energy is what accounts for the Hubble Constant, or the rate at which the universe is expanding. Dark matter on the other hand, affects how "normal" matter clumps together. It stabilizes galaxy clusters. It also affects the shape of galaxies, their rotation curves, and how stars move within them. Dark matter even affects how galaxies influence one another.</p>Leading theories on dark matter
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjU5ODExNS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzOTY4MzM0Nn0.3AXqxP2fpr37ZFWTbMp1lYrLt2VYVAbT7BngypUYfoc/img.jpg?width=980" id="ccb58" class="rm-shortcode" data-rm-shortcode-id="984bda92c8dfd2a770d107e403c3b66c" data-rm-shortcode-name="rebelmouse-image" />NASA writes: 'This graphic represents a slice of the spider-web-like structure of the universe, called the "cosmic web." These great filaments are made largely of dark matter located in the space between galaxies.'
Credit: NASA, ESA, and E. Hallman (University of Colorado, Boulder)
<p>Since the '70s, astronomers and physicists have been unable to identify any evidence of dark matter. One theory is it's all tied up in space-bound objects called <a href="https://imagine.gsfc.nasa.gov/educators/galaxies/imagine/dark_matter.html" target="_blank">MACHOs</a> (Massive Compact Halo Objects). These include black holes, supermassive black holes, <a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy" target="_blank">brown dwarfs</a>, and neutron stars.</p><p>Another theory is that dark matter is made up of a type of non-baryonic matter, called WIMPS (Weakly Interacting Massive Particles). Baryonic matter is the kind made up of baryons, such as protons and neutrons and everything composed of them, which is anything with an <a href="http://astronomy.swin.edu.au/cosmos/B/Baryonic+Matter" target="_blank">atomic nucleus</a>. Electrons, neutrinos, muons, and tau particles aren't baryons, however, but a class of particles called <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/lepton.html" target="_blank">leptons</a>. Even though the (hypothetical) WIMPS would have ten to a hundred times the mass of a proton, their interactions with normal matter would be weak, making them hard to detect. </p><p>Then there are those aforementioned neutrinos. Did you know that giant streams of them pass from the Sun through the Earth each day, without us ever noticing? They're the focus of another theory that says that neutral neutrinos, that only interact with normal matter through gravity, are what dark matter is comprised of. Other candidates include two theoretical particles, the neutral axion and the uncharged photino.</p><p>Now, one theoretical physicist posits an even more radical notion. What if dark matter didn't exist at all? Dr. Melvin Vopson of the University of Portsmouth, in the UK, has a hypothesis he calls the mass-energy-information equivalence. It states that information is the fundamental building block of the universe, and it has mass. This accounts for the missing mass within galaxies, thus eliminating the hypothesis of dark matter entirely.</p>Information theory
<p>To be clear, the idea that information is an <a href="https://bigthink.com/philip-perry/the-basis-of-the-universe-may-not-be-energy-or-matter-but-information" target="_self">essential building block</a> of the universe isn't new. Classical Information Theory was first posited by Claude Elwood Shannon, the <a href="https://www.bell-labs.com/claude-shannon/" target="_blank">"father of the digital age"</a> in the mid-20th century. The mathematician and engineer, well-known in scientific circles—but not so much outside of them, had a stroke of genius back in 1940. He realized that Boolean algebra coincided perfectly with telephone switching circuits. Soon, he proved that mathematics could be employed to design electrical systems. </p><p>Shannon was hired at Bell Labs to figure out how to transfer information over a system of wires. He wrote the bible on using mathematics to set up communication systems, thereby laying the foundation for the digital age. Shannon was also the first to define one unit of information as a bit. </p><p>There was perhaps no greater proponent of information theory than another unsung paragon of science, <a href="https://futurism.com/john-wheelers-participatory-universe" target="_blank">John Archibald Wheeler</a>. Wheeler was part of the Manhattan Project, worked out the "S-Matrix" with Niels Bohr and helped Einstein develop a unified theory of physics. In his later years, he proclaimed, "Everything is information." Then he went about exploring connections between quantum mechanics and information theory. </p><p>He also coined the phrase "it from bit" or that every particle in the universe emanates from the information locked inside it. At the Santa Fe Institute in 1989, Wheeler announced that everything, from particles to forces to the fabric of spacetime itself "… derives its function, its meaning, its very existence entirely … from the apparatus-elicited answers to yes-or-no questions, binary choices, <a href="https://blogs.scientificamerican.com/cross-check/why-information-cant-be-the-basis-of-reality/" target="_blank">bits</a>."</p>Part Einstein, part Landauer
<p>Vopson takes this notion one step further. He says that not only is information the essential unit of the universe but also that it is energy and has mass. To support this claim, he unifies and coordinates special relativity with the <a href="https://physics.aps.org/articles/v11/49" target="_blank">Landauer Principle</a>. The latter is named after Rolf Landauer. In 1961, he predicted that erasing even one bit of information would release a tiny amount of heat, a figure which he calculated. Landauer said this proves information is more than just a mathematical quantity. This connects information to energy. Through experimental testing over the years, the Landauer Principle has held up.</p><p>Vopson says, "He [Landauer] first identified the link between thermodynamics and information by postulating that logical irreversibility of a computational process implies physical irreversibility." This indicates that <a href="https://aip.scitation.org/doi/10.1063/1.5123794" target="_blank">information is physical</a>, Vopson says, and demonstrates the link between information theory and <a href="https://www.nature.com/articles/nature10872" target="_blank">thermodynamics</a>. </p><p>In Vopson's theory, information, once created has "finite and quantifiable mass." It so far applies only to digital systems, but could very well apply to analogue and biological ones too, and even quantum or relativistic-moving systems. "Relativity and quantum mechanics are possible future directions of the mass-energy-information equivalence principle," he says. </p><p>In the paper published in the journal <a href="https://aip.scitation.org/doi/10.1063/1.5123794" target="_blank"><em>AIP Advances</em>,</a> Vopson outlines the mathematical basis for his hypothesis. "I am the first to propose the mechanism and the physics by which information acquires mass," he said, "as well as to formulate this powerful principle and to propose a possible experiment to test it."</p>The fifth state of matter
<p>To measure the mass of digital information, you start with an empty data storage device. Next, you measure its total mass with a highly sensitive measuring apparatus. Then, you fill it and determine its mass. Next, you erase one file and evaluate it again. The trouble is, the "ultra-accurate mass measurement" device the paper describes doesn't exist yet. This would be an <a href="https://aip.scitation.org/doi/10.1063/1.5126530" target="_blank">interferometer</a>, something similar to <a href="https://www.ligo.caltech.edu/page/what-is-ligo" target="_blank">LIGO</a>. Or perhaps an ultrasensitive weighing machine akin to a <a href="https://www.nist.gov/si-redefinition/kilogram/kilogram-kibble-balance" target="_blank">Kibble balance</a>.</p><p>"Currently, I am in the process of applying for a small grant, with the main objective of designing such an experiment, followed by calculations to check if detection of these small mass changes is even possible," Vopson says. "Assuming the grant is successful and the estimates are positive, then a larger international consortium could be formed to undertake the construction of the instrument." He added, "This is not a workbench laboratory experiment, and it would most likely be a large and costly facility." If eventually proved correct, Vopson will have discovered the fifth form of matter. </p><p>So, what's the connection to dark matter? Vopson says, "M.P. Gough published an article in <a href="https://www.mdpi.com/1099-4300/10/3/150" target="_blank">2008</a> in which he worked out … the number of bits of information that the visible universe would contain to make up all the missing dark matter. It appears that my estimates of information bit content of the universe are very close to his estimates." </p>
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Mystery effect speeds up the universe – not dark energy, says study
Russian astrophysicists propose the Casimir Effect causes the universe's expansion to accelerate.
29 December, 2019
Credits: NASA's Goddard Space Flight Center/Jeremy Schnittman
- Astrophysicists from Russia propose a theory that says dark energy doesn't exist.
- Instead, the scientists think the Casimir Effect creates repulsion.
- This effect causes the expansion of the universe to accelerate.
<p><br></p></div>
<p>Dark energy, one of the most controversial physics ideas, is getting another challenge. After all, if this force is supposed to <a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy" target="_blank">make up about </a><strong><a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy">68%</a> </strong>of the mass-energy of the universe, where exactly is it? A new paper by a pair of Russian astrophysicists says dark energy simply doesn't exist. Instead, they point to the mysterious<strong> Casimir effect</strong> as the explanation for the accelerating expansion of the universe.</p><p>The study, from Professor <strong>Artyom Astashenok</strong> and undergraduate student <strong>Alexander Teplyakov</strong> of the <em>Immanuel Kant Baltic Federal University</em>, takes issue with the fact that as far as dark energy's suggested role, "no one knows what is it and how it works," as remarks Astashenok in a <a href="http://eng.kantiana.ru/news/261163/" target="_blank">press release.</a></p>
<p>The astrophysicists say the discovery that the universe is not only expanding, but accelerating in that process, can be explained by an effect named after the Dutch physicist <a href="https://physicsworld.com/a/the-casimir-effect-a-force-from-nothing/" target="_blank">Hendrik Casimir</a>. Back in 1948, he proposed that if you'd put two metal plates in a vacuum, you could still observe attraction between them. Logic would dictate that there'd be nothing in the vacuum to cause such a force, but as Astashenok <a href="http://eng.kantiana.ru/news/261163/" target="_blank">explained</a>, "according to quantum theory, particles constantly appear and disappear there, and as a result of their interaction with plates, which indicate certain boundaries of space (which is extremely important), a very small attraction occurs." </p><p>This phenomenon, now dubbed the <strong>Casimir effect,</strong> has been extrapolated by the Russian scientists to space. They believe there is no enigmatic "Dark Energy" but a "manifestation of the boundaries of the universe" that is responsible for an additional repulsion that causes the universe to speed up its expansion.</p>
Gravity Should Slow the Expanding Universe, but Dark Energy Is Speeding It ...
<div class="rm-shortcode" data-media_id="TXFqpm0M" data-player_id="FvQKszTI" data-rm-shortcode-id="e242a06f4b4464e0cffae45d5142d2ea"> <div id="botr_TXFqpm0M_FvQKszTI_div" class="jwplayer-media" data-jwplayer-video-src="https://content.jwplatform.com/players/TXFqpm0M-FvQKszTI.js"> <img src="https://cdn.jwplayer.com/thumbs/TXFqpm0M-1920.jpg" class="jwplayer-media-preview" /> </div> <script src="https://content.jwplatform.com/players/TXFqpm0M-FvQKszTI.js"></script> </div><p>Ashashenok further expounds that their idea doesn't claim that the universe has an end. Rather a "complex topology" occurs. </p><p style="margin-left: 20px;">"You can draw an analogy with the Earth. After all, it also has no boundaries, but it is finite,"<a href="http://eng.kantiana.ru/news/261163/" target="_blank"> says Astashenok.</a> "The difference between the earth and the universe is that in the first case we are dealing with two-dimensional space, and in the second - with three-dimensional".</p><p>Check out the new study in the <a href="http://www.worldscientific.com/doi/10.1142/S0218271819501761" target="_blank">International Journal of Modern Physics</a>.</p>
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Astrophysicists discover why black holes and neutron stars shine bright
Researchers find what causes the glow coming from the densest objects in our universe.
29 November, 2019
Credit: NASA, ESA, J. Hester (Arizona State University)
- Columbia University astrophysicists discovered the cause of the unusual glow coming from regions of space with black holes and neutron stars.
- The researchers ran some of the largest computer simulations ever to reach their conclusions.
- They found that turbulence and reconnection of super-strong magnetic fields are responsible for the light.
<p><br></p></div>
<p>Demonstrating again that space is a limitless reservoir of scientific wonders, a new study discovered why areas hosting black holes and neutron stars emit strange bright glows. Astrophysicists found that <strong>turbulence</strong> and <strong>reconnection of super-strong magnetic fields</strong> are behind the cosmic mystery.</p><p>The cause of the phenomenon, which illuminates these super-dense parts of space, has been attributed previously to high-energy electromagnetic radiation. Scientists speculated that it's created by electrons moving at just about the speed of light. The new study from researchers at Columbia University explained why these particles accelerate.</p><p>Astrophysicists <a href="https://lucacomisso.com/about/" target="_blank">Luca Comisso</a> and <a href="http://user.astro.columbia.edu/~lsironi/Site/Home.html" target="_blank">Lorenzo Sironi</a> carried out the research by running some of the largest super-computer simulations ever conducted in this area. They managed to calculate the trajectories of hundreds of billions of charged particles.</p>
<p>Comiso, a postdoctoral research scientist at Columbia, explained their conclusion:</p><p style="margin-left: 20px;">"Turbulence and magnetic reconnection—a process in which magnetic field lines tear and rapidly reconnect—conspire together to accelerate particles, boosting them to velocities that approach the speed of light," said Comisso in a <a href="https://news.columbia.edu/news/black-holes-neutron-stars" target="_blank">press release</a>. </p><p>As Comiso further described, the space region that is home to black holes and neutron stars is also full of a super-hot gas of charged particles. Their chaotic motion affects magnetic field lines and results in "vigorous magnetic reconnection". This, in turn, creates an electric field which accelerates particles to energies that are "much higher than in the most powerful accelerators on Earth, like the Large Hadron Collider at CERN," added Comisso.</p>
Amazing astronomy: How neutron stars create ripples in space-time
<div class="rm-shortcode" data-media_id="skGLOb3j" data-player_id="FvQKszTI" data-rm-shortcode-id="4181b5782ae4c412ce8a339ea70571ff"> <div id="botr_skGLOb3j_FvQKszTI_div" class="jwplayer-media" data-jwplayer-video-src="https://content.jwplatform.com/players/skGLOb3j-FvQKszTI.js"> <img src="https://cdn.jwplayer.com/thumbs/skGLOb3j-1920.jpg" class="jwplayer-media-preview" /> </div> <script src="https://content.jwplatform.com/players/skGLOb3j-FvQKszTI.js"></script> </div><p>Interestingly, the simulations showed that the particles gathered most of their energy through the process of random bouncing at super-high speeds.</p><p style="margin-left: 20px;">"This is indeed the radiation emitted around black holes and neutron stars that make them shine, a phenomenon we can observe on Earth," said Sironi, the study's principal investigator and an assistant professor of astronomy at Columbia.</p><p>Next, the scientists plan to confirm their findings by comparing them to the electromagnetic spectrum from the Crab Nebula, a bright remnant of a supernova. </p><p>You can check out the study published in the December issue of <a href="https://iopscience.iop.org/article/10.3847/1538-4357/ab4c33" target="_blank"><em>The Astrophysical Journal</em></a><em>.</em></p>
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjExMzI3My9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyMDA3MTU2Mn0.ESRk0s8UeKMmTIIRY_iBz6LSM7pNLKbhg1egqx_o79A/img.jpg?width=980" id="ab685" class="rm-shortcode" data-rm-shortcode-id="b47a1d1e3159133ec95b8a6225669f77" data-rm-shortcode-name="rebelmouse-image" />
A massive super-computer simulation demonstrates the strong particle density fluctuations that happen in the extreme turbulent environments home to black holes and neutron stars. The dark blue regions are low particle density regions, and the yellow regions are over-dense regions. Particles are accelerated to extremely high speeds from interacting with turbulence fluctuations.
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New study says cosmic acceleration and dark energy don't exist
An Oxford scientist claims a Nobel-Prize-winning conclusion is wrong.
31 October, 2019
NASA
- Paper by Oxford University physicist Subir Sarkar and his colleagues challenges how conclusions about cosmic acceleration and dark energy were reached.
- Physicists who proved cosmic acceleration shared a Nobel Prize.
- Sarkar used statistical analysis to question key data, but his methodology also has detractors.
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<p>Is our Universe's expansion speeding up? The 2011 Nobel Prize went to three scientists for proving just that. But what if the evidence they used to come up with this conclusion was wrongly interpreted and the supposed cosmic acceleration is simply an <em>artifact</em> of our movement through a local part of the Universe? In the big picture, there's no speeding up. What's also not there is the mysterious <strong>dark energy, </strong>thought to be creating that acceleration, says a new paper from a group of physicists who take issue with the supernovae-related evidence that was used to come up with the original Nobel-worthy conclusion. </p><p>The <a href="https://www.nobelprize.org/prizes/physics/2011/press-release/" target="_blank">Nobel Prize</a> for the cosmic acceleration idea, if you're wondering, was won by <strong>Saul Perlmutter, Brian Schmidt,</strong> and <strong>Adam Riess </strong>for "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae". They used evidence from exploded stars called <strong>"la supernovae"</strong> or <strong>"standard candles"</strong> to show that the Universe's expansion was getting faster. These kinds of supernovas are so bright that we actually know their absolute brightness. This fact allows scientists to calculate the distance of these explosions from Earth, while studying the red shift in the light they emit points to the Universe's rate of expansion. In 1998, groups led by Perlmutter and Schmidt found light from 50 supernova to be dimmer than it was supposed to be, leading them to conclude that cosmic expansion was actually accelerating (thanks to dark energy – a yet-to-be-directly-observed enigmatic force that supposedly takes up <strong>68% </strong>of all mass-energy in the Universe while causing it to expand).</p>
<p>But while the expansion has become accepted as science fact, there have been some who see things differently. Following up on his 2015 paper on this subject, Oxford University physicist <strong>Subir Sarkar </strong>and his colleagues at the <a href="https://www.nbi.ku.dk/english/" target="_blank">Niels Bohr Institute</a> and the <a href="http://www.iap.fr/?langue=en" target="_blank">Paris Institute of Astrophysics</a> now published a second study taking issue with the idea of a Universe growing with acceleration. </p><p>As explained in <a href="https://physicsworld.com/a/dark-energy-debate-reignited-by-controversial-analysis-of-supernovae-data/" target="_blank">Physics World,</a> by statistically analyzing a sample of <strong>740 l</strong>a supernovae in their 2015 paper, Sarkar's team found "only marginal" support for cosmic acceleration with low statistical significance. The difference in their approach was in how they looked at the procedures used to calculate the absolute brightness of supernovae and how their light is absorbed by dust that gets in the way.</p>
2011 Nobel Laureates in Physics, Saul Perlmutter, Brian P. Schmidt and Adam G. Riess
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="28ce83ddb06a68f48f7723de30df35de"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/7RDs9qJ-kw0?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>2011 Nobel Laureates in Physics, Perlmutter, Schmidt and Riess, describe how an assumed error turned into the surprise discovery that the universe is expandi...<p>Critics of that paper abounded, taking issues with their methodology and pointing to other data that showed acceleration. Now, in the second paper, to be published in <em>Astronomy and Astrophysics</em>, the scientists continue to assail the supernovae evidence and the idea of cosmic acceleration by pointing to anomalies in the red-shift data and how calculations with respect to the Cosmic Microwave Background (CMB) are carried out. </p><p style="margin-left: 20px;">"If you look at supernovae in only a small part of the sky, it would look like you had cosmic acceleration," <a href="https://physicsworld.com/a/dark-energy-debate-reignited-by-controversial-analysis-of-supernovae-data/" target="_blank">Sarkar says.</a> "But we are saying that it is just a local effect, that we are non-Copernican observers. It has nothing to do with the overall dynamics of the universe and therefore nothing to do with dark energy."</p>
<p>Riess disagrees with Sarkar's conclusions and data, calling it outdated. His team used data from <strong>1,300</strong> supernovae in their latest study and came up with clear-cut support for the acceleration's existence. Furthermore, <a href="https://physicsworld.com/a/dark-energy-debate-reignited-by-controversial-analysis-of-supernovae-data/" target="_blank">he stated, </a>"The evidence for cosmic acceleration and dark energy are much broader than only the supernovae Ia sample."</p><p>Who would argue with a Nobel Prize-winner? Subir Sarkar, who believes that "The CMB does not directly measure dark energy," adding "That is a widely propagated myth." </p><p>You can check out his new paper for yourself at <a href="https://arxiv.org/abs/1808.04597" target="_blank">arXiv</a>.</p>
Lisa Randall: Dark Energy Will Take Over
<div class="rm-shortcode" data-media_id="oDcTSObk" data-player_id="FvQKszTI" data-rm-shortcode-id="01b8205e912851fbc31a81335b0b463b"> <div id="botr_oDcTSObk_FvQKszTI_div" class="jwplayer-media" data-jwplayer-video-src="https://content.jwplatform.com/players/oDcTSObk-FvQKszTI.js"> <img src="https://cdn.jwplayer.com/thumbs/oDcTSObk-1920.jpg" class="jwplayer-media-preview" /> </div> <script src="https://content.jwplatform.com/players/oDcTSObk-FvQKszTI.js"></script> </div> <p><em>Physicist Lisa Randall on why dark energy doesn't dilute as the universe expands.</em></p>
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