Everyone loves black holes. Immense gravity, a one-way space-time membrane, the possibility of links to other universes. All lovely stuff. A little trawl of the internets reveals an awful lot of web pages discussing black holes, and discussions about spaghettification, firewalls, lost information, and many other things. Actually, a lot of the stuff out there on the web is nonsense, hand-waving, partly informed guesswork. And one of the questions that gets asked is "What would you see looking out into the universe?" Some (incorrectly) say that you would never cross the event horizon, a significant mis-understanding of the coordinates of relativity. Other (incorrectly) conclude from this that you actually see the entire future history of the universe play out in front of your eyes. What we have to remember, of course, is that relativity is a mathematical theory, and instead of hand waving, we can use mathematics to work out what we will see. And that's what I did.
I have a cosmological post brewing, so I thought I would touch on a slightly different topic, namely the question of "could physics predict a giraffe?" The following has the usual "buyer beware" clauses; I am a physicist, an astrophysicist at that, and not a chemist, or a biologist, and definitely no a philosopher of science, although I may end up annoying all of them. To start with, let's look at the subject, to wit, a giraffe. The reason for the post is because of an article over at The Curious Wavefunction titled Why biology (and chemistry) is not physics. The basic argument is this; Physics is a fundamental science, and identified the basic workings of the Universe. How do nuclei hold themselves together, how does the Universe expand, why do electrons flow through conductors etc etc. That's physics. Now, physics is "reductionist", in that all complex processes can be broken down into a the application of relatively simple underlying phy
After a weekend of great rugby (from the Welsh, the English and Australians were rather blah), I have responded to a good question posted over at The Conversation on distances in the Universe. It's a question that gets raised quite a bit and basically put it goes something like If the Universe began 13.7 billion years ago, when the distance between any pair of points was zero, how can anything be more than 13.7 billion light years away? The answer is the difference between local motions and global motions. Here's the response I posted An excellent question, and one which may not make sense to start with. We know from special relativity, nothing can travel faster than light (recent neutrino claims excepted). But in reality, special relativity says that nothing can go faster than the speed of light **locally**, so in a small box, if I try and race an electron and a photon across the box, the photon will win. With the expanding universe, the question we are a