event horizon tagged posts

New theoretical research by Michael Wondrak, Walter van Suijlekom and Heino Falcke of Radboud University has shown that Stephen Hawking was right about black holes, although not completely. Due to Hawking radiation, black holes will eventually evaporate, but the event horizon is not as crucial as had been believed. Gravity and the curvature of spacetime cause this radiation too. This means that all large objects in the universe, like the remnants of stars, will eventually evaporate.

Using a clever combination of quantum physics and Einstein’s theory of gravity, Stephen Hawking argued that the spontaneous creation and annihilation of pairs of particles must occur near the event horizon (the point beyond which there is no escape from the gravitational force of a black hole)...

Black holes form natural time machines that allow travel to both the past and the future. But don’t expect to be heading back to visit the dinosaurs any time soon.

At present, we don’t have spacecraft that could get us anywhere near a black hole. But, even leaving that small detail aside, attempting to travel into the past using a black hole might be the last thing you ever do.

What are black holes?

A black hole is an extremely massive object that is typically formed when a dying star collapses in on itself.

Like planets and stars, black holes have gravitational fields around them. A gravitational field is what keeps us stuck to Earth, and what keeps Earth revolving around the Sun.

As a rule of thumb, the mor...

In principle, nothing that enters a black hole can leave the black hole. This has considerably complicated the study of these mysterious bodies on which generations of physicists have debated ever since 1916, the year their existence was hypothesized as a direct consequence of Einstein’s Theory of Relativity. There is, however, some consensus in the scientific community on the fact that black holes possess an entropy, because their existence would otherwise violate the second law of thermodynamics. In particular, Jacob Bekenstein and Stephen Hawking have suggested that the entropy – a measure of the inner disorder of a physical system – of a black hole is proportional to its area and not to its volume, as would be more intuitive...

Proposed 15 yrs ago, the bounded L2 curvature conjecture has finally been proved by a group of 3 researchers at the Laboratoire Jacques-Louis Lions (CNRS / UPMC / Université Paris Diderot) and Princeton University. It provides a potentially minimal framework in which it is possible to solve the Einstein equations, which in turn could be a critical step toward the proof of major conjectures, such as Penrose’s cosmic censorship conjectures. This work has appeared in Inventiones Mathematicae Oct14

Even though this yr marks its 100th anniversary, Albert Einstein’s theory of general relativity still holds its share of mysteries. This theory of gravitation stipulates that matter curves spacetime in proportion to the mass of the object...