Misconceptions in gravitational physics

Post author:The Physics Detective
Post published:15th June 2019
Post category:Black holes Gamma ray bursts Gravity Hawking radiation Singularities Time
Post comments:39 Comments

I think it’s safe to say that there are some misconceptions in physics. The issue of course, is how many. That’s where I part company with your average physicist. He’ll tell you that whilst we don’t understand everything, we do understand some things, such as black holes. Only he doesn’t. Take a look at the Wikipedia black hole article. It says this: “a black hole is a region of spacetime exhibiting gravitational acceleration so strong that nothing - no particles or even electromagnetic radiation such as…

Firewall!

Post author:The Physics Detective
Post published:15th December 2018
Post category:Black holes Cosmology Gamma ray bursts Gravity Singularities
Post comments:56 Comments

The black hole firewall is a relatively recent idea. On Wikipedia you can read how it “was proposed in 2012 by Ahmed Almheiri, Donald Marolf, Joseph Polchinski, and James Sully as a possible solution to an apparent inconsistency in black hole complementarity”. Their proposal is known as the AMPS firewall, and the title of their paper is black holes: complementarity or firewalls? They cannot all be true They start by saying “we argue that the following three statements cannot all be true: (i) Hawking radiation is…

The information paradox

Post author:The Physics Detective
Post published:8th December 2018
Post category:Black holes Cosmology Hawking radiation Singularities Trouble with physics
Post comments:0 Comments

The information paradox was first mooted by Stephen Hawking in 1976. For an introduction to the subject, see Brian Koberlein’s black holes tell no tales or do they? Then see Hawking’s paper on the breakdown of predictability in gravitational collapse. Hawking said information is lost down a black hole because the quantum emission is completely random and uncorrelated. He also said “this means there is no S matrix for the process of black-hole formation and evaporation”. The S-matrix is the scattering matrix which is to do…

The Hawking papers

Post author:The Physics Detective
Post published:1st December 2018
Post category:Black holes Cosmology Hawking radiation Singularities
Post comments:10 Comments

You can find a list of Stephen Hawking’s publications on the Hawking.org website. It starts with his 1965 PhD thesis. This is said to have “borrowed from Roger Penrose's theorem which described a 'spacetime singularity' being present in the centre of black holes”. Penrose was one of Hawking’s PhD examiners. Seven out of Hawking’s first ten papers concerned singularities. Singularities and the geometry of spacetime One of Hawking’s early papers was singularities and the geometry of spacetime dating from 1966. At 91 pages it’s curiously long.…