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Category: cosmology – Page 414

I wonder if people who were alive when Galileo first turned his telescope to the heavens in 1610, when he discovered the moons of Jupiter, realized that it was a seminal moment in human history. The discovery changed everything. It showed that not all celestial objects orbit the Earth and set the stage for adoption of the Copernican theory, which holds, of course, that the Earth orbits the sun and not the other way around. From that date onward, telescopes aimed at the sky became a staple of cosmology and a constant source of discovery and wonder for humanity.

It’s quite possible that people living in the distant future will view last year’s announcement of the discovery of gravitational waves as a similar turning point in humanity’s ability to observe and understand the cosmos.

Related: Earth-Sized Telescope May Let Us See Black Hole for First Time.

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April 12 (UPI) — A new composite image captured by researchers at the University of Waterloo in Ontario, Canada, offers proof galaxies are connected by a web of dark matter.

The universe’s cosmic web of dark matter has remained elusive, but Waterloo researchers were able to tease out its existence by tracing a weak gravitational lensing.

Typically, astronomers used gravitational lensing events to study the light from distant galaxies as the beams are warped by massive galactic structures. But the gravity of smaller cosmic objects can bend light, too — including strands of dark matter.

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Researchers in the US say they’ve created a fluid with negative mass in the lab… which is exactly as mind-bending as it sounds.

What it means is that, unlike pretty much every other known physical object, when you push this fluid, it accelerates backwards instead of moving forwards. Such an oddity could tell scientists about some of the strange behaviour that happens within black holes and neutron stars.

But let’s take a step back for a second here, because how can something have negative mass?

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By Leah Crane

Break out the censor’s black bars for naked singularities. Quantum effects could be obscuring these impossible predictions of general relativity, new calculations show.

Albert Einstein’s classical equations of general relativity do a fairly good job of describing gravity and space-time. But when it comes to the most extreme objects, such as black holes, general relativity runs into problems.

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Once upon a time, two black holes collided, releasing energy which undulates across the universe. Little is known about these reverberations — dubbed “gravitational waves” — including how they were formed in the first place. However, a University of Birmingham astrophysicist told Sputnik science may now have the beginnings of an answer.

It’s believed that around 1.3 billion light years away from Earth, two black holes cataclysmically collided, releasing energy — gravitational waves — which undulates across the universe like ripples in a pool.

Gravitational waves had long been speculated upon, and were a major prediction of Albert Einstein’s 1915 general theory of relativity, but the existence of these wrinkles in the fabric of space-time was only confirmed in September 2015.

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Stephen Hawking appeared through the marvel of modern technology as a hologram during an event in Hong Kong last week. He had some harsh words regarding our current climate of disregarding experts.

Stephen Hawking is a real wonder to behold. The now 75-year-old astrophysicist was told that he wouldn’t see past his 25th birthday due to his diagnosis of ALS (amyotrophic lateral sclerosis) or Lou Gehrig’s disease. And, although he is bound to a wheelchair, his mind has wildly surpassed his physical limitations.

Embracing his lack of limitations, Hawking recently appeared as a hologram at an event in Hong Kong last week. During the talk, Hawking fielded questions about exoplanets, black holes, and other topics that firmly fit within his area of expertise. He also made a few enlightening comments about current affairs.

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Quantum gravity is a theoretical attempt to reconcile general relativity and the quantum field theories of particle physics. The theory holds that space and time are both quantized in a way that quantum field theory doesn’t account for. Attempts to find evidence in support of the theory have focused on the gravitational effects of black holes. Now, some are using the data collected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) project that has now detected two instances of gravitational waves from the collision of black holes. And there are hints that the data has the evidence the researchers are looking for.

But Afshordi’s idea overthrows what physicists believed they knew about black holes. In Albert Einstein’s theory of general relativity, the event horizon of a black hole – the surface beyond which there is no escape – is insubstantial. Nothing special happens upon crossing it, just that there is no turning around later. If Afshordi is right, however, the inside of the black hole past the event horizon no longer exists. Instead, a Planck-length away from where the horizon would have been, quantum gravitational effects become large, and space-time fluctuations go wild. (The Planck length is a minuscule distance: about 10-35 metres, or 10-20 times the diameter of a proton.) It’s a complete break with relativity.

When he heard of the LIGO results, Afshordi realised that his so-far entirely theoretical idea could be observationally tested. If event horizons are different than expected, the gravitational-wave bursts from merging black holes should be different, too. Events picked up by LIGO should have echoes, a subtle but clear signal that would indicate a departure from standard physics. Such a discovery would be a breakthrough in the long search for a quantum theory of gravity. ‘If they confirm it, I should probably book a ticket to Stockholm,’ Afshordi said, laughing.

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The past few years have been incredible for physics discoveries. Scientists spotted the Higgs boson, a particle they’d been hunting for almost 50 years, in 2012, and gravitational waves, which were theorized 100 years ago, in 2016. This year, they’re slated to take a picture of a black hole. So, thought some theorists, why not combine all of the craziest physics ideas into one, a physics turducken? What if we, say, try to spot the dark matter radiating off of black holes through their gravitational waves?

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Meanwhile, the Hubble image offered a clue about what dislodged the black hole from its galaxy’s centre. The host galaxy bore faint, arc-shaped features called tidal tales, which are produced by the gravitational tug-of-war that takes place when two galaxies collide. This suggested that galaxy 3C 186 had recently merged with another system, and perhaps their black holes merged too.

What happened next, scientists can only theorize. Chiaberge and his colleagues suggest that as the galaxies collided, their black holes began to circle each other, flinging out gravity waves “like water from a lawn sprinkler,” as NASA described it. If the black holes had unequal masses and spin rates, they might have sent more gravitational waves in one direction than the other. When the collision was complete, the newly merged black hole would have then recoiled from the strongest gravitational waves, shooting off in the opposite direction.

“This asymmetry depends on properties such as the mass and the relative orientation of the back holes’ rotation axes before the merger,” Colin Norman of STScI and Johns Hopkins University, a co-author on the paper, said in the NASA news release. “That’s why these objects are so rare.”

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