Group items tagged

Event Horizon - a modern myth?

GR is valid on large scales and is, therefore, a simplification of the unknown GUT. As such, the mathematical solutions obtained in GR are strictly speaking valid only within GR. Certainly, the solution called black hole is an extremely heavy object and at the same time extremely small - a point without geometrical extension. The latter is heavily in conflict with the validity range of the underlying theory and, hence, makes lots of people (including experts unlike me) question the concept of black holes despite the fact that something has been "observed" which fits into this concept. Regarding the movie: Event Horizon might be a myth but it emphasizes what Sante said in on of his presentations: Don't use a black hole for travelling, take the worm hole instead. The constructor of Event Horizon created a black hole not considering that the damn thing has no exit...where did he think the Event Horizon would end?

In a surprise announcement earlier today (July 13), the European Southern Observatory said that monster black holes - those giants of millions or billions of solar masses, thought to lurk at the hearts of most galaxies - have a mechanism to become active other than galaxy collisions.

"A new study combining data from ESO's Very Large Telescope and ESA's XMM-Newton X-ray space observatory has turned up a surprise. Most of the huge black holes in the centers of galaxies in the past 11 billion years were not turned on by mergers between galaxies, as had been previously thought." and "The process that activates a sleeping black hole - turning its galaxy from quiet to active - has been a mystery in astronomy. What triggers the violent outbursts at a galaxy's center, which then becomes an active galactic nucleus? Up to now, many astronomers thought that most of these active nuclei were turned on when two galaxies merged, or when they passed close to each other and the disrupted material became fuel for the central black hole. Results of the new study indicate this idea may be wrong for many active galaxies." very interesting indeed

"In an effort to help solve the black hole information paradox that has immersed theoretical physics in an ocean of soul searching for the past two years, two researchers have thrown their hats into the ring with a novel solution: Lasers. Technically, we're not talking about the little flashy devices you use to keep your cat entertained, we're talking about the underlying physics that produces laser light and applying it to information that falls into a black hole. According to the researchers, who published a paper earlier this month to the journal Classical and Quantum Gravity (abstract), the secret to sidestepping the black hole information paradox (and, by extension, the 'firewall' hypothesis that was recently argued against by Stephen Hawking) lies in stimulated emission of radiation (the underlying physics that generates laser light) at the event horizon that is distinct from Hawking radiation, but preserves information as matter falls into a black hole."

Another great presentation at this conference!! Plus I always wanted to enter the numerical computations of orbit around black holes.... with Luzi we had a project on formation flying around black holes .... revolutionary idea (of course we did not do it!!!)

nice movie, and song :) we should definitely implement GR orbits in pagmo !

I agree Marek, yet was it practical for Apollonio to study conic sections more than 1500 years before Kepler found his three laws? And here is a good paper to start with: http://prd.aps.org/abstract/PRD/v77/i10/e103005, making an analogy between the periodic table and the taxomony of all orbits around a black hole.

S. Hawking argues black holes might not exist: "The absence of event horizons mean that there are no black holes - in the sense of regimes from which light can't escape to infinity." Physicists will likely appreciate...

Using random nanostructuring highly absorptive materials were made which are of interest for photovoltaic or thermovoltaic applications

Yes! Black Metal... definitely something the ACT should look into

Black Metal...sounds like something for the ACT Magic Cards. But apart from that - is it possible to shift the PV type of absorption into gamma ray spectrum?

Nice web story on setting up the event horizon telescope network of up to 20 telescopes across the globe to observe the black hole at the galaxy's center

Vortices in the South Atlantic are mathematically equivalent to black holes, say physicists, an idea that could lead to new ways of understanding how currents transport oil and garbage across oceans Black holes are regions of spacetime in which gravity is strong enough to prevent anything escaping, even light.

A British company has produced a "strange, alien" material so black that it absorbs all but 0.035 per cent of visual light, setting a new world record. To stare at the "super black" coating made of carbon nanotubes - each 10,000 times thinner than a human hair - is an odd experience.

Finally! Nowadays blacks were always too bright for my taste...

"No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it." I will keep waiting for my darkness-emitting diodes...

Kip Thorne looks into the black hole he helped create and thinks, "Why, of course. That's what it would do." This particular black hole is a simulation of unprecedented accuracy. It appears to spin at nearly the speed of light, dragging bits of the universe along with it.

"A near-record supermassive black hole discovered in a sparse area of the local universe indicate that these monster objects - this one equal to 17 billion suns - may be more common than once thought, according to UC Berkeley astronomers."

impressive achievement - extremely absorbant feather almost as black as our most "black" material

20 billion sun masses black hole!!

Nice visualization of the structure of the accretion disk surrounding a black hole

Deepest X-ray Image Ever Reveals Black Hole Treasure Trove An unparalleled image from NASA's Chandra X-ray Observatory gives astronomers the best look yet at the growth of black holes over billions of years beginning soon after the Big Bang.

Black-body radiation can give rise to a net attractive force between tiny objects. That is the claim made by physicists at the University of Innsbruck in Austria, who have calculated the strength of this new force between a speck of dust and a hydrogen atom. Under some cirmustances this force could be stronger than gravitation. Read the paper here: http://prl.aps.org/abstract/PRL/v111/i2/e023601

After this lunch lecture probably not as ground breaking as I thought earlier but still an interesting read... "The new solution involves supertranslations, something that I have yet to get my head properly around. But it seems to rely on the well known fact that an "image" of infalling matter seems to get imprinted onto the "surface" of a black hole."

"we conclude that HE 0437-5439 was most likely a compact binary ejected by the Milky Way's central black hole" reminds me a bit of Francesco's proposal to get rid of Mercury for the stability of our solar system ... what was the proposal: "get rid of the sucker?"

In Interstellar, the science-fiction film out this week, Matthew McConaughey stars as an astronaut contending with a supermassive black hole called Gargantua. The film's special effects have been hailed as the most realistic depiction ever made of this type of cosmic object. But astrophysicists have now gone one better - this is a really cool visualisation done by researchers in Cornell.

Wow, impressive! Simulating eXtreme Spacetimes (SXS) software, very quick merging process though 17ms.. Observable?

Mind-blowing!

A new class of exotic materials could find its way into next-generation technologies that efficiently convert waste heat into electrical current according to new research. Both the exotic materials and the means by which they generate electricity rely on a hybrid of advanced concepts-including string theory combined with black holes combined with cutting-edge condensed matter physics.

Sounds spooky