Dark energy: The apocalyptic wild card of the universe
Dr. Katie Mack explains what dark energy is and two ways it could one day destroy the universe.
25 January, 2021
- The universe is expanding faster and faster. Whether this acceleration will end in a Big Rip or will reverse and contract into a Big Crunch is not yet understood, and neither is the invisible force causing that expansion: dark energy.
- Physicist Dr. Katie Mack explains the difference between dark matter, dark energy, and phantom dark energy, and shares what scientists think the mysterious force is, its effect on space, and how, billions of years from now, it could cause peak cosmic destruction.
- The Big Rip seems more probable than a Big Crunch at this point in time, but scientists still have much to learn before they can determine the ultimate fate of the universe. "If we figure out what [dark energy is] doing, if we figure out what it's made of, how it's going to change in the future, then we will have a much better idea for how the universe will end," says Mack.
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Columbia study finds new way to extract energy from black holes
A new study explains how a chaotic region just outside a black hole's event horizon might provide a virtually endless supply of energy.
19 January, 2021
Credit: NASA's Goddard Space Flight Center
- In 1969, the physicist Roger Penrose first proposed a way in which it might be possible to extract energy from a black hole.
- A new study builds upon similar ideas to describe how chaotic magnetic activity in the ergosphere of a black hole may produce vast amounts of energy, which could potentially be harvested.
- The findings suggest that, in the very distant future, it may be possible for a civilization to survive by harnessing the energy of a black hole rather than a star.
<p>Like the Sun, the stars scattered throughout our Milky Way and beyond produce unfathomable amounts of energy. But so, too, do the objects we can't see: black holes.</p>
<p>For decades, scientists have wondered whether it's possible to extract energy from black holes, which <a href="https://bigthink.com/surprising-science/black-hole-animation" target="_self">are the mysterious regions of spacetime</a> that form when stars collapse into themselves. Siphoning energy from these areas of ultra-condensed matter could provide a virtually endless power supply for deep-space civilizations, if physically and practically possible.</p>
<p>While undoubtedly the stuff of science fiction, the idea is far from new. </p>
<p>In 1969, the physicist and Nobel Laureate Roger Penrose proposed it might be possible to extract energy from a rotating black hole. He thought this could occur in a black hole's ergosphere. </p>
The ergosphere
<p>The ergosphere is a region just outside a black hole's event horizon, the boundary of a black hole beyond which nothing, not even light, can escape. But light and matter just outside the event horizon, in the ergosphere, would also be affected by the immense gravity of the black hole. Objects in this zone would spin in the same direction as the black hole at incredibly fast speeds, similar to objects floating around the center of a whirlpool.</p><p>The Penrose process states, in simple terms, that an object could enter the ergosphere and break into two pieces. One piece would head toward the event horizon, swallowed by the black hole. But if the other piece managed to escape the ergosphere, it could emerge with more energy than it entered with.</p><p>The movie "Interstellar" provides an example of the Penrose process. Facing a fuel shortage on a deep-space mission, the crew makes a last-ditch effort to return home by entering the ergosphere of a blackhole, ditching part of their spacecraft, and "slingshotting" away from the black hole with vast amounts of energy.</p><p>In a recent study published in the American Physical Society's <a href="https://journals.aps.org/prd/abstract/10.1103/PhysRevD.103.023014" target="_blank" style="">Physical Review D</a><em>, </em>physicists Luca Comisso and Felipe A. Asenjo used similar ideas to describe another way energy could be extracted from a black hole. The idea centers on the magnetic fields of black holes.</p><p style="margin-left: 20px;">"Black holes are commonly surrounded by a hot 'soup' of plasma particles that carry a magnetic field," Comisso, a research scientist at Columbia University and lead study author, told <a href="https://news.columbia.edu/energy-particles-magnetic-fields-black-holes" target="_blank" rel="noopener noreferrer">Columbia News</a>.</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTUwMzQyNi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2Nzg5NTgxM30.4aMhAHcj3YfXKEIvA7vH71EHIzxcJpTO3iulrpfnxSM/img.jpg?width=980" id="1cdf5" class="rm-shortcode" data-rm-shortcode-id="01d88a42afd0185a64424ecc5f420e4c" data-rm-shortcode-name="rebelmouse-image" data-width="494" data-height="494" />
Ergosphere representation
<p>In the ergosphere of a rotating black hole, magnetic field lines are constantly breaking and reconnecting at fast speeds. The researchers theorized that when these lines reconnect, plasma particles shoot out in two different directions. One flow of particles shoots off against the direction of the spinning black hole, eventually getting "swallowed" by the black hole. But the other flow shoots in the same direction as the spin, potentially gaining enough velocity to escape the black hole's gravitational pull.</p><p>The researchers proposed that this occurs because the breaking and reconnecting of magnetic field lines can generate negative-energy particles. If the negative-energy particles get "swallowed" by the black hole, the positive particles would theoretically be exponentially accelerated.</p><p style="margin-left: 20px;">"Our theory shows that when magnetic field lines disconnect and reconnect, in just the right way, they can accelerate plasma particles to negative energies and large amounts of black hole energy can be extracted," Comisso said. "It is like a person could lose weight by eating candy with negative calories."</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTUwMjMyOC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0MDA5NjA1MX0.nK1C4xO65fb1y4wdm9GmcDGZBvarQ2gyWdUXtZQcMOI/img.jpg?width=980" id="6482f" class="rm-shortcode" data-rm-shortcode-id="2bcedc4f32a64049524f4126311e3c28" data-rm-shortcode-name="rebelmouse-image" alt="Black hole" data-width="985" data-height="574" />
<p class=""><br></p>Black hole
Event Horizon Telescope Collaboration
<p>While there might not be immediate applications for the theory, it could help scientists better understand and observe black holes. On an abstract level, the findings may expand the limits of what scientists imagine is possible in deep space.</p><p style="margin-left: 20px;">"Thousands or millions of years from now, humanity might be able to survive around a black hole without harnessing energy from stars," Comisso said. "It is essentially a technological problem. If we look at the physics, there is nothing that prevents it."</p>
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Ten “keys to reality” from a Nobel-winning physicist
To understand ourselves and our place in the universe, "we should have humility but also self-respect," Frank Wilczek writes in a new book.
18 January, 2021
Photo by Andy HYD on Unsplash
In the spring of 1970, colleges across the country erupted with student protests in response to the Vietnam War and the National Guard's shooting of student demonstrators at Kent State University.
<p> At the University of Chicago, where Frank Wilczek was an undergraduate, regularly scheduled classes were "improvised and semivoluntary" amid the turmoil, as he recalls.</p><p>It was during this turbulent time that Wilczek found unexpected comfort, and a new understanding of the world, in mathematics. He had decided to sit in on a class by physics professor Peter Freund, who, with a zeal "bordering on rapture," led students through mathematical theories of symmetry and ways in which these theories can predict behaviors in the physical world.</p><p>In his new book, "Fundamentals: Ten Keys to Reality," published by Penguin Press, Wilczek writes that the lessons were a revelation: "To experience the deep harmony between two different universes — the universe of beautiful ideas and the universe of physical behavior — was for me a kind of spiritual awakening. It became my vocation. I haven't been disappointed."</p>
<p>Wilczek, who is the Herman Feshbach Professor of Physics at MIT, has since made groundbreaking contributions to our fundamental understanding of the physical world, for which he has been widely recognized, most notably in 2004 with the Nobel Prize in Physics, which he shared with physicists David Gross and David Politzer. He has also authored several popular science books on physics and the history of science.</p><p>In his new book, he distills scientists' collective understanding of the physical world into 10 broad philosophical themes, using the fundamental theories of physics, from cosmology to quantum mechanics, to reframe ideas of space, time, and our place in the universe.</p><p>"People wrestle with what the world is all about," Wilczek tells <em>MIT News</em>. "They're not concerned with knowing precisely what Coulomb's law is, but want to know more about questions like the ancient Greeks asked: What is space? What is time? So in the end, I came up with 10 assertions, at the levels of philosophy but backed up by very concrete facts, to organize what we know."</p>
<h3>A rollercoaster reborn</h3><p>Wilczek wrote the bulk of the book earlier this spring, in the midst of another tumultuous time, at the start of a global pandemic. His grandson had been born as Wilczek was laying out the structure for his book, and in the preface, the physicist writes that he watched as the baby began building up a model of the world, based on his observations and interactions with the environment, "with insatiable curiosity and few preconceptions."</p><p>Wilczek says that scientists may take a cue from the way babies learn — by building and pruning more detailed models of the world, with a similar unbiased, open outlook. He can recall times when he felt his own understanding of the world fundamentally shift. The college course on mathematical symmetry was an early instance. More recently, the rise of artificial intelligence and machine learning has prompted him to rethink "what knowledge is, and how it's acquired."</p><p>He writes: "The process of being born again can be disorienting. But, like a roller- coaster ride, it can also be exhilarating. And it brings this gift: To those who are born again, in the way of science, the world comes to seem fresh, lucid, and wonderfully abundant."</p>
<h3>"Patterns in matter"</h3><p>Wilczek's book contains ample opportunity for readers to reframe their view of the physical world. For instance, in a chapter entitled "There's Plenty of Space," he writes that, while the universe is vast, there is another scale of vastness in ourselves. To illustrate his point, he calculates that there are roughly 10 octillion atoms that make up the human body. That's about 1 million times the number of stars in the visible universe. The multitudes within and beyond us are not contradictory, he says, but can be explained by the same set of physical rules.</p><p>And in fact, the universe, in all its diversity, can be described by a surprisingly few set of rules, collectively known as the Standard Model of Physics, though Wilczek prefers to call it by another name.</p><p>"The so-called Standard Model is the culmination of millenia of investigation, allowing us to understand how matter works, very fully," Wilczek says. "So calling it a model, and standard, is kind of a lost opportunity to really convey to people the magnitude of what's been achieved by humanity. That's why I like to call it the 'Core.' It's a central body of understanding that we can build out from."</p><p>Wilczek takes the reader through many of the key experiments, theories, and revelations that physicists have made in building and validating the Standard Model, and its mathematical descriptions of the universe.</p><p>Included in this often joyful scientific tour are brief mentions of Wilczek's own contributions, such as his Nobel-winning work establishing the theory of quantum chromodynamics; his characterization of the axion, a theoretical particle that he named after a laundry detergent by the same name ("It was short, catchy, and would fit in nicely alongside proton, neutron, electron, and pion," he writes); and his introduction of the anyon — an entirely new kind of particle that is neither a fermion or a boson.</p><p>In April, and then separately in July, scientists made the first observations of anyons, nearly 40 years after Wilczek first proposed their existence.</p>
<p>"I was beginning to think it would never happen," says Wilczek, who was finishing up his book when the discoveries were made public. "When it finally did, it was a beautiful surprise."</p><p>The discovery of anyons opens possibilities for the particles to be used as building blocks for quantum computers, and marks another milestone in our understanding of the universe.</p><p>In closing his book, Wilczek writes about "complementarity" — a concept in physics that refers to two seemingly contrasting theories, such as the wave and particle theories of light, that can separately explain the same set of phenomena. He points to many complementary theories of physics throughout the book and extends the idea to philosophy and ways in which accepting contrasting views of the world can help us to expand our experience.</p><p>"With progress, we've come to consider people and creatures as having intrinsic value and being worthy of profound respect, just like ourselves," he writes. "When we see ourselves as patterns in matter, it is natural to draw our circle of kinship very wide indeed."</p><p>Reprinted with permission of <a target="_blank" href="http://news.mit.edu/">MIT News</a>. Read the <a target="_blank" href="https://news.mit.edu/2021/ten-keys-reality-wilczek-0112" rel="noopener noreferrer">original article</a>.</p>
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Dark matter axions possibly found near Magnificent 7 neutron stars
A new study proposes mysterious axions may be found in X-rays coming from a cluster of neutron stars.
16 January, 2021
Credit: D. Ducros; ESA/XMM-Newton, CC BY-SA 3.0 IGO
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<p>A study tantalizingly promises a possible location for new elementary particles called axions, which may also constitute the elusive dark matter. A team led by a theoretical physicist from <span style="background-color: initial;">the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab)</span> has pinpointed axions as the potential source of the high-energy X-rays coming out of a cluster of neutron stars called the Magnificent Seven.</p><p>Axions were first theorized as fundamental particles as far back as the 1970s but have yet to be directly observed. In a fun fact, the idea for the name "axion" came to the theoretical physicist Frank Wilczek from a laundry detergent brand. If they exist, they'd be produced in the core of stars, converting into photons (particles of light) upon encountering electromagnetic fields. Axions would likely have small masses and come into contact with other matter quite rarely and in a way that's hard to detect. </p><p>They may also be responsible for dark matter, which could comprise about 85% of the known universe but is also yet to be seen. We think we know about it from its gravitational effects. If axions are real, they could account for this "missing" mass of the universe. Astronomical observations tell us that visible matter, including all the galaxies with their stars, planets, and everything else we can conceive of in space is still <em>less than one sixth</em> of the total mass of all of the universe's matter. Dark matter is thought to be making up the rest. So finding it and finding axions could be transformative for our understanding of how the universe really works.</p>
<p>The new paper from Berkeley Lab proposes that the Magnificent Seven, a group of neutron stars that's hundreds of light-years away (but relatively not so far), may be a perfect candidate for locating the axions. These stars, coming into existence as the collapsed cores of massive supergiant stars, have very strong magnetic fields and feature an abundance of X-rays. They are also not pulsars, which give off radiation at varying wavelengths and would likely obscure the X-ray signature the researchers spotted.<br></p><p>The study utilized data from the European Space Agency's XMM-Newton and NASA's Chandra X-ray telescopes to discover high levels of X-ray emissions from the neutron stars.</p><p>Benjamin Safdi, from the Berkeley Lab Physics Division theory group which led the study, said they aren't saying yet they found the axions but are feeling confident the Magnificent Seven X-rays are a fruitful place to look.</p><p style="margin-left: 20px;">"We are pretty confident this excess exists, and very confident there's something new among this excess," Safdi said. "If we were 100% sure that what we are seeing is a new particle, that would be huge. That would be revolutionary in physics." </p>
Are Axions Dark Matter?
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="5e35ce24a5b17102bfce5ae6aecc7c14"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/e7yXqF32Yvw?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>Postdoctoral researcher Raymond Co from the University of Minnesota, who was also involved in the study, <a href="https://phys.org/news/2021-01-x-rays-magnificent-sought-after-particle.html" target="_blank">confirmed</a> that "It is an exciting discovery of the excess in the X-ray photons, and it's an exciting possibility that's already consistent with our interpretation of axions."</p><p>Building upon this research, the scientists also plan to use space telescopes like <a href="https://www.nasa.gov/mission_pages/nustar/main/index.html" target="_blank">NuStar</a> to focus on the X-ray excesses as well as to examine white dwarf stars, which also have strong magnetic fields, making them another possible location for the axions. "This starts to be pretty compelling that this is something beyond the Standard Model if we see an X-ray excess there, too," <a href="https://newscenter.lbl.gov/2021/01/15/study-x-rays-surrounding-magnificent-7-may-be-traces-of-sought-after-particle/" target="_blank">said</a> Safdi.</p>
<p><span style="background-color: initial;">Besides Berkeley Lab, the current study also involved support from </span><span style="background-color: initial;">the University of Michigan, the National Science Foundation, the Mainz Institute for Theoretical Physics, the Munich Institute for Astro- and Particle Physics (MIAPP), and the CERN Theory department.</span></p><p>Check out the study published in <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.126.021102" target="_blank">Physical Review Letters.</a></p>
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The incredible physics behind quantum computing
Can computers do calculations in multiple universes? Scientists are working on it. Step into the world of quantum computing.
15 January, 2021
- While today's computers—referred to as classical computers—continue to become more and more powerful, there is a ceiling to their advancement due to the physical limits of the materials used to make them. Quantum computing allows physicists and researchers to exponentially increase computation power, harnessing potential parallel realities to do so.
- Quantum computer chips are astoundingly small, about the size of a fingernail. Scientists have to not only build the computer itself but also the ultra-protected environment in which they operate. Total isolation is required to eliminate vibrations and other external influences on synchronized atoms; if the atoms become 'decoherent' the quantum computer cannot function.
- "You need to create a very quiet, clean, cold environment for these chips to work in," says quantum computing expert Vern Brownell. The coldest temperature possible in physics is -273.15 degrees C. The rooms required for quantum computing are -273.14 degrees C, which is 150 times colder than outer space. It is complex and mind-boggling work, but the potential for computation that harnesses the power of parallel universes is worth the chase.
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