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The Large Scale Structure of Space-Time by Stephen Hawking and George Ellis.
Cambridge Core - Cosmology, Relativity and Gravitation - The Large Scale Structure of Space-Time - by Stephen Hawking and George Ellis.
ebooks  books  astronomy  planetary  science  theoretical  physics  mathematics  cosmology  time  relativity  reference  university  cambridge  gravitational 
9 weeks ago by asaltydog
The Large Scale Structure of Space-Time - Wikipedia
The Large Scale Structure of Space-Time is 1973 book about the theoretical physics of spacetime by Stephen Hawking and George Ellis.
books  astronomy  planetary  science  theoretical  physics  mathematics  cosmology  time  relativity  reference  gravitational 
9 weeks ago by asaltydog
Dark Energy Stars
“Event horizons and closed time-like curves cannot exist in the real world for the simple reason that they are inconsistent with quantum mechanics. Following ideas originated by Robert Laughlin, Pawel Mazur, Emil Mottola, David Santiago, and the speaker it is now possible to describe in some detail what happens physically when one approaches and crosses a region of space-time where classical general relativity predicts there should be an infinite red shift surface. This quantum critical physics provides a new perspective on a variety of enigmatic astrophysical phenomena including supernovae explosions, gamma ray bursts, positron emission, and dark matter.,”
georgechapline  relativity  singularity  star  theoreticalphysics  quantummechanics  astrophysics  boseeinsteincondensate  blackholes  darkenergy  arxiv 
october 2018 by danhon
How Do You Take a Picture of a Black Hole? With a Telescope as Big as the Earth - The New York Times
near the core, that fog forms a great glowing Frisbee that rotates around a vast dark sphere. This is the supermassive black hole at the core of the Milky Way, the still point of our slowly rotating galaxy. We call it Sagittarius A*, that last bit pronounced “A-star.” The black hole itself is invisible, but it leaves a violent imprint on its environment, pulling surrounding objects into unlikely orbits and annihilating stars and clouds of gas that stray too close.

the inaugural run of the Event Horizon Telescope (E.H.T.), a virtual Earth-size observatory designed to take the first picture of a black hole. The E.H.T. uses a technique known as very long baseline interferometry (V.L.B.I.), in which astronomers at observatories on different continents simultaneously observe the same object, then combine the collected data on a supercomputer. The E.H.T.’s director, Shep Doeleman, a radio astronomer with the Harvard-Smithsonian Center for Astrophysics, likes to call the E.H.T. “the biggest telescope in the history of humanity.” It has the highest resolution of any astronomical instrument ever assembled. It’s sharp enough to read the date on a nickel in Los Angeles from New York, to spot a doughnut on the moon and, more to the point, to take a picture of the black hole at the center of our galaxy — or, at least, its shadow.

The effort to get that picture speaks well of our species: a bunch of people around the world defying international discord and general ascendant stupidity in unified pursuit of a gloriously esoteric goal. And in these dark days, it’s only fitting that the object of this pursuit is the darkest thing imaginable.

The physicist Werner Israel put it better when he described a black hole as “an elemental, self-sustaining gravitational field which has severed all causal connection with the material source that created it, and settled, like a soap bubble, into the simplest configuration consistent with the external constraints.”

what a black hole would look like if illuminated by the glow from the superheated matter swirling around it. He did his calculations by feeding punch cards into a primitive computer. He drew the results by hand. His black-and-white images looked like twisted depictions of a black Saturn, with a ringlike accretion disk warped like taffy.

That this shadow might be visible from Earth depended on an astonishing set of circumstances. Earth’s atmosphere happens to be transparent to the electromagnetic radiation — in this case, certain microwaves — shining from the edge of the black hole, even though it blocks radiation of slightly longer and shorter wavelengths. The interstellar gunk lying between Earth and the galactic center also becomes transparent at those frequencies, as do the clouds of superheated matter just outside the black hole, blocking a view of the event horizon. Later in life, Fulvio Melia compared this alignment to the cosmic accidents that give us total solar eclipses. The moon is just the right size, in just the right orbit, at just the right distance from Earth that now and then it blocks the sun entirely. Fulvio wasn’t religious, but these coincidences were so unlikely that he couldn’t help but feel that the black-hole shadow was meant to be seen. The universe had arranged for humans to see to the nearest exit.

it’s hard to reconcile two conflicting theories if you can’t find something wrong with either one, and quantum theory, like general relativity, has passed every test. As a result, scientists have been looking for ever-more-extreme situations in which to test these theories. That led them to black holes.

To avoid poisoning one another’s minds — so that no one could accidentally nudge another group into seeing a black-hole shadow that wasn’t really there — these groups worked in isolation, making images using different algorithms and techniques, trying hard to discredit anything that looked too sharp, too clean, too likely to be the product of wishful thinking.
telescope  astronomy  scientist  world  project  Physics  law  research  relativity  quantum 
october 2018 by aries1988
One of the Greatest Scientists of the 20th Century You've Probably Never Heard Of
Fr Georges Lemaitre, who published the mathematics of an expanding universe in 1927 (before Hubble)
astronomy  physics  science  relativity  belgium  catholicism  religion 
september 2018 by pozorvlak
Home - SXS - Simulating eXtreme Spacetimes
The SXS project is a collaborative research effort involving multiple institutions. Our goal is the simulation of black holes and other extreme spacetimes to gain a better understanding of Relativity, and the physics of exotic objects in the distant cosmos.
simulation  physics  relativity  gravity 
september 2018 by trewbot

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