black holes

The black hole has always occupied a sort of space in the middle, between science and philosophy. It’s good to see that acknowledged. From ScienceDaily: Erik Curiel studied Philosophy as well as Theoretical Physics at Harvard University and the University of Chicago, and the primary aim of his current DFG-funded research project is to develop a precise philosophical description of certain puzzling aspects of modern physics. “Phenomena such as black holes belong to a realm that is inaccessible to observation and experiment. Work based on the assumption that black holes exist therefore involves a level of speculation that is unusual even for the field of theoretical physics.” However, this difficulty is what makes the physical approach to the nature of Read More ›

According to a new paper, white holes, the theoretical opposite of black holes, may account for dark matter, and may even predate the universe. They may even, according to Carlo Rovelli, explain the direction of time: A black hole is one prediction of Einstein’s theory of general relativity. Another is known as a white hole, which is like a black hole in reverse: Whereas nothing can escape from a black hole’s event horizon, nothing can enter a white hole’s event horizon. … In the 2014 study, Rovelli and his team suggested that, once a black hole evaporated to a degree where it could not shrink any further because space-time could not be squeezed into anything smaller, the dying black hole Read More ›

If you saw it up close? If you were to take a photo of a black hole, what you would see would be akin to a dark shadow in the middle of a glowing fog of light. Hence, we called this feature the shadow of a black hole . Interestingly, the shadow appears larger than you might expect by simply taking the diameter of the event horizon. The reason is simply, that the black hole acts as a giant lens, amplifying itself. Surrounding the shadow will be a thin ‘photon ring’ due to light circling the black hole almost forever. Further out, you would see more rings of light that arise from near the event horizon, but tend to be concentrated Read More ›

Quantum theory specifies that information is never lost but what happens to the information when a black hole vanishes? In the latest paper, Hawking (1942-2018) and his colleagues show how some information at least may be preserved. Toss an object into a black hole and the black hole’s temperature ought to change. So too will a property called entropy, a measure of an object’s internal disorder, which rises the hotter it gets. The physicists, including Sasha Haco at Cambridge and Andrew Strominger at Harvard, show that a black hole’s entropy may be recorded by photons that surround the black hole’s event horizon, the point at which light cannot escape the intense gravitational pull. They call this sheen of photons “soft hair”. Read More ›

Sabine Hossenfelder, author of Lost in Math: How Beauty Leads Physics Astray, explains, Three weeks ago, Steinhauer’s group reported results from a new experiment in which they have now measured the temperature of the fluid black hole: Observation of thermal Hawking radiation at the Hawking temperature in an analogue black hole Juan Ramón Muñoz de Nova, Katrine Golubkov, Victor I. Kolobov, Jeff Steinhauer arXiv:1809.00913 [gr-qc] While the measurement is not very exact owing to the noise in the system, the result agrees with Hawking’s prediction, at least to the precision that the experiment allows to identify a temperature to begin with. The authors also point out in the paper that they see no evidence of a black hole firewall. A black hole Read More ›