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Category: physics – Page 224

(8 April 2020 — ESA) Astronomers have assumed for decades that the Universe is expanding at the same rate in all directions. A new study based on data from ESA’s XMM-Newton, NASA’s Chandra and the German-led ROSAT X-ray observatories suggests this key premise of cosmology might be wrong.

Konstantinos Migkas, a PhD researcher in astronomy and astrophysics at the University of Bonn, Germany, and his supervisor Thomas Reiprich originally set out to verify a new method that would enable astronomers to test the so-called isotropy hypothesis. According to this assumption, the Universe has, despite some local differences, the same properties in each direction on the large scale.

Widely accepted as a consequence of well-established fundamental physics, the hypothesis has been supported by observations of the cosmic microwave background (CMB). A direct remnant of the Big Bang, the CMB reflects the state of the Universe as it was in its infancy, at only 380 000 years of age. The CMB’s uniform distribution in the sky suggests that in those early days the Universe must have been expanding rapidly and at the same rate in all directions.

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Astronomers have detected two stellar corpses whirling around each other, and they might be producing gravitational waves.

White dwarf stars are what become of stars like our sun after they run out of fuel and turn into leftover hot cores. For many years, researchers have predicted that there should be binary, or two-object, systems made up of white dwarf stars. According to general relativity, two such masses orbiting each other should emit energy in the form of gravitational waves, which are ripples or disturbances in the fabric of spacetime.

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O,.,o.

Physicists have conducted the most high-energy test of the speed of light yet, and found that it is still constant, everywhere in the Universe, even in gamma rays spewed out of sources such as exploding stars.

This means that, even at the highest energies we can detect, one of the pillars of Albert Einstein’s theory of special relativity still stands firm.

“How relativity behaves at very high energies has real consequences for the world around us,” said astrophysicist Pat Harding of Los Alamos National Laboratory in New Mexico.

Continue reading “Physicists Have Tested The Speed of Light at The Highest Energies Yet” | >

Shoot a rifle, and the recoil might knock you backward. Merge two black holes in a binary system, and the loss of momentum gives a similar recoil—a “kick”—to the merged black hole.

“For some binaries, the kick can reach up to 5000 kilometers a second, which is larger than the escape velocity of most galaxies,” said Vijay Varma, an astrophysicist at the California Institute of Technology and an incoming inaugural Klarman Fellow at Cornell University’s College of Arts & Sciences.

Varma and his fellow researchers have developed a new method using gravitational wave measurements to predict when a final black hole will remain in its host galaxy and when it will be ejected. Such measurements could provide a crucial missing piece of the puzzle behind the origin of heavy black holes, said Varma, as well as offer insights into galaxy evolution and tests of general relativity. He is lead author of “Extracting the Gravitational Recoil from Black Hole Merger Signals,” published March 13 in Physical Review Letters and co-authored with Maximiliano Isi and Sylvia Biscoveanu of the Massachusetts Institute of Technology.

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A long-held mystery in the field of nuclear physics is why the universe is composed of the specific materials we see around us. In other words, why is it made of “this” stuff and not other stuff?

Specifically of interest are the responsible for producing heavy elements—like gold, platinum and uranium—that are thought to happen during neutron star mergers and explosive stellar events.

Scientists from the U.S. Department of Energy’s (DOE) Argonne National Laboratory led an international nuclear physics experiment conducted at CERN, the European Organization for Nuclear Research, that utilizes novel techniques developed at Argonne to study the nature and origin of heavy elements in the universe. The study may provide critical insights into the processes that work together to create the exotic , and it will inform models of stellar events and the early universe.

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The obvious drawback of solar panels is that they require sunlight to generate electricity. Some have observed that for a device on Earth facing space, which has a frigid temperature, the chilling outflow of energy from the device can be harvested using the same kind of optoelectronic physics we have used to harness solar energy. New work, in a recent issue of Applied Physics Letters, from AIP Publishing, looks to provide a potential path to generating electricity like solar cells but that can power electronics at night. For more information see the IDTechEx report on Energy Harvesting Microwatt to Megawatt 2019–2029.

An international team of scientists has demonstrated for the first time that it is possible to generate a measurable amount of electricity in a diode directly from the coldness of the universe. The infrared semiconductor device faces the sky and uses the temperature difference between Earth and space to produce the electricity.

“The vastness of the universe is a thermodynamic resource,” said Shanhui Fan, an author on the paper. “In terms of optoelectronic physics, there is really this very beautiful symmetry between harvesting incoming radiation and harvesting outgoing radiation.”

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Any device that sends out a Wi-Fi signal also emits terahertz waves —electromagnetic waves with a frequency somewhere between microwaves and infrared light. These high-frequency radiation waves, known as “T-rays,” are also produced by almost anything that registers a temperature, including our own bodies and the inanimate objects around us.

Terahertz waves are pervasive in our daily lives, and if harnessed, their concentrated power could potentially serve as an alternate source. Imagine, for instance, a cellphone add-on that passively soaks up ambient T-rays and uses their energy to charge your phone. However, to date, waves are wasted energy, as there has been no practical way to capture and convert them into any usable form.

Now physicists at MIT have come up with a blueprint for a they believe would be able to convert ambient terahertz waves into a , a form of electricity that powers many household electronics.

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