Archive for the ‘cosmology’ category

Apr 14, 2021

Fast-spinning black holes narrow the search for dark matter particles

Posted by in categories: cosmology, particle physics, quantum physics

Ultralight bosons are hypothetical particles whose mass is predicted to be less than a billionth the mass of an electron. They interact relatively little with their surroundings and have thus far eluded searches to confirm their existence. If they exist, ultralight bosons such as axions would likely be a form of dark matter, the mysterious, invisible stuff that makes up 85 percent of the matter in the universe.

Now, physicists at MIT’s LIGO Laboratory have searched for ultralight bosons using black holes—objects that are mind-bending orders of magnitude more massive than the particles themselves. According to the predictions of quantum theory, a black hole of a certain mass should pull in clouds of ultralight bosons, which in turn should collectively slow down a black hole’s spin. If the particles exist, then all black holes of a particular mass should have relatively low spins.

But the physicists have found that two previously detected black holes are spinning too fast to have been affected by any ultralight bosons. Because of their large spins, the black holes’ existence rules out the existence of ultralight bosons with masses between 1.3×10-13 electronvolts and 2.7×10-13 electronvolts—around a quintillionth the mass of an electron.

Apr 10, 2021

Long-Missing Midsize Black Hole Flashes Into View

Posted by in category: cosmology

Black holes seemed to come only in sizes small and XXL. A new search strategy has uncovered a black hole of “intermediate” mass, raising hopes of more to come.

Apr 6, 2021

‘Impossible’ EmDrive Actually Is Impossible, Comprehensive Test Shows

Posted by in categories: chemistry, cosmology, quantum physics, space travel

Humanity has come a long way in understanding the universe. We’ve got a physical framework that mostly matches our observations, and new technologies have allowed us to analyze the Big Bang and take photos of black holes. But the hypothetical EmDrive rocket engine threatened to upend what we knew about physics… if it worked. After the latest round of testing, we can say with a high degree of certainty that it doesn’t.

If you have memories from the 90s, you probably remember the interest in cold fusion, a supposed chemical process that could produce energy from fusion at room temperature instead of millions of degrees (pick your favorite scale, the numbers are all huge). The EmDrive is basically cold fusion for the 21st century. First proposed in 2001, the EmDrive uses an asymmetrical resonator cavity inside which electromagnetic energy can bounce around. There’s no exhaust, but proponents claim the EmDrive generates thrust.

The idea behind the EmDrive is that the tapered shape of the cavity would reflect radiation in such a way that there was a larger net force exerted on the resonator at one end. Thus, an object could use this “engine” for hyper-efficient propulsion. That would be a direct violation of the conservation of momentum. Interest in the EmDrive was scattered until 2016 when NASA’s Eagelworks lab built a prototype and tested it. According to the team, they detected a small but measurable net force, and that got people interested.

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Apr 5, 2021

NASA’s Sonification Project Lets You Listen to Stars and Black Holes

Posted by in category: cosmology

When we think about objects in space, like galaxies and black holes, our only frame of reference are the images we’ve seen, taken by the Hubble Space Telescope and similar instruments. Now, thanks to NASA’s new data sonification series, we can translate data signals of these objects into audio.

Apr 3, 2021

String theorist Michio Kaku: ‘Reaching out to aliens is a terrible idea’

Posted by in categories: cosmology, information science, quantum physics

Michio Kaku is a professor of theoretical physics at City College, New York, a proponent of string theory but also a well-known populariser of science, with multiple TV appearances and several bestselling books behind him. His latest book, The God Equation, is a clear and accessible examination of the quest to combine Einstein’s general relativity with quantum theory to create an all-encompassing “theory of everything” about the nature of the universe.

The physicist on Newton finding inspiration amid the great plague, how the multiverse can unite religions, and why a ‘theory of everything’ is within our grasp.

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Apr 2, 2021

Episode 44 — ESA’s Upcoming Euclid Dark Energy Survey

Posted by in categories: cosmology, space travel

Great new episode with Michael Seiffert, the NASA project scientist for the U.S. contribution to the European Space Agency’s Euclid spacecraft. Seiffert talks candidly about what it takes to strike a balance between risk and reward in the design of this upcoming $1 billion dollar dark energy mission.

Fascinating new chat with Michael Seiffert, the NASA project scientist for the U.S. contribution to the European Space Agency’s Euclid spacecraft. Due for launch in the second half of 2022, we discuss how this new space telescope will help astronomers finally understand the mystery of dark energy and maybe even dark matter.

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Apr 1, 2021

Far from science fiction, space elevators may be nearing deployment

Posted by in categories: cosmology, engineering

I’ll believe it when I see it. But this is a skyhook which can be made with existing materials.

With one end of a steel cable hovering in Earth’s orbit and the other end somewhere in outer space, the concept of a futuristic floating “space elevator” promises to amplify humans’ ability to explore the universe — and scientists engineering an improved take on the 19th-century idea say the one-time fantasy is close to becoming a reality.

“Technical-wise, it’s kind of ready,” said George Zhu, a professor of mechanical engineering at York University and a coauthor of a new study on the idea. “It just has small engineering [adjustments], and there’s no fundamental difficulty to do that.”

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Apr 1, 2021

Simulating the Universe a Trillionth of a Second After the Big Bang

Posted by in categories: computing, cosmology

The Big Bang remains the best way to explain what happened at the beginning of the Universe. However, the incredible energies flowing during the early part of the bang are almost incomprehensive to our everyday experience. Luckily, computers aren’t so attached to normal human ways of thinking and have long been used to model the early universe right after the Bang. Now, a team from the University of Göttingen have created the most comprehensive model of what exactly happened in that very early stage of the universe – one trillionth of a second after the Big Bang.

Just because a computer can model it doesn’t really mean it is easy to explain, however. The model includes clumps of energy weighing grams, but which are one millionth the size of a single proton. These energy structures defined what would eventually become the structure of the universe today, with tiny variations in the original structure resulting in entire galaxies or complete voids, depending on the presence or absence of matter.

Throwing this much computing power at a physical space one millionth the size of a proton was no mean feat. “It is probably the largest simulation of the smallest area of the Universe that has been carried out thus far” says Professor Jens Niemeyer, who leads the group carrying out the research.

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Apr 1, 2021

The Closest Star Cluster to Earth is Being Dismantled in Front of our Eyes

Posted by in categories: computing, cosmology, mapping

Star clusters are interesting inhabitants of the sky. They vary in sizes, distances, and number of stars, but almost all are spectacular to look at. And most of them are in the process of being torn apart. That is certainly the case for the Hyades star cluster – the closest one to Earth at only 153 light years away. The problem is, there is something causing a lot more destruction than would be expected given the mass and energy in the surrounding space. Now, a team of scientists from ESA have a theory as to what the cause of the destruction might be – a mysterious dark matter sub-halo.

This novel theory extends from findings gleaned from data collected by GAIA, ESA’s star mapping satellite. The GAIA team expected to see what are called “tidal tails” trailing and leading the star cluster as it moves throughout the galaxy. These tails are formed when some stars are forced to the outer edges of the cluster, and then pulled by the gravitational pull of the galaxy itself, pushing some stars forward in their journey through the galaxy, while other stars are pulled further behind.

The GAIA team did find tidal tails on either side of the Hyades cluster when they observed it. However, they were extraordinarily long – thousands of light years across the galaxy, each holding thousands of stars. Observing them in their entirety was only possible because of the GAIA data and a computer model that Dr. Tereza Jerabkova, an ESA research fellow, developed with her colleagues.

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Apr 1, 2021

New theory suggests uranium ‘snowflakes’ in white dwarfs could set off star-destroying explosion

Posted by in categories: cosmology, materials

A pair of researchers with Indiana University and Illinois University, respectively, has developed a theory that suggests crystalizing uranium “snowflakes” deep inside white dwarfs could instigate an explosion large enough to destroy the star. In their paper published in the journal Physical Review Letters, C. J. Horowitz and M. E. Caplan describe their theory and what it could mean to astrophysical theories about white dwarfs and supernovas.

White dwarfs are small stars that have burned up most of their nuclear fuel—they are typically much cooler than they once were and are very dense. In this new effort, Horowitz and Caplan used data from the Gaia space observatory to theorize that sometimes small grains of uranium could begin to crystalize (due to enriched actinides), forming what they describe as snowflakes. They suggest this could happen because of the differing melting points of the material involved. They further suggest that if this were to occur, it could lead to splitting of atomic nuclei, resulting in a series of fission reactions as the solids become enriched in actinides. And if such reactions were to raise the temperature of the interior of the star by igniting carbon, the result would likely be merging of atomic nuclei and eventually a very large fusion reaction that would result in a large explosion—likely large enough to destroy the star.

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