Posts tagged ‘physics’

March 26, 2011

The greatest story ever told (well the first anyway)

by Joshaniel Cooper

Let me prefix this by saying that the early universe was a very boring place. There was a lot of energy, (at one point too much to even allow the formation of matter)  and everything was very ordered with no interesting features. The proof of this comes from the recently measured cosmic microwave background radiation which found that at the point it was created (about 370 000 years after the big bang). The differences in temperature between any points in the universe were around one part in 100 000 (i.e. if it was 100 000K then the max temperature difference would be 1K). A rough idea of the second law of thermodynamics would also make this clear that it is required – if everything gets less ordered with time (entropy increases) then the start of the universe must have been a very well ordered place.

February 26, 2011

Falling Into a Black Hole, Part 1

by Nathaniel Virgo

A little while ago I read Leonard Susskind’s book The Black Hole War (subtitle: My Battle with Stephen Hawking to make the World Safe For Quantum Mechanics).  It’s an interesting and mostly quite readable popular science book about the black hole information paradox.  Susskind thinks that information isn’t destroyed when stuff falls into a black hole, and his book is about why.

The first part of the book has some useful thought experiments about black holes, some of which I’ll take you through below.  After that it starts to talk about string theory, whereupon it becomes as utterly incomprehensible as any other book on the subject.

However, I think Susskind makes an important logical error just before he turns to string theory.  I think that if you correct this error then it leads to a much more elegant resolution of the information paradox — one that doesn’t require the use of string theory.  I won’t get as far as talking about that in this post, but I will point out the error I think Susskind makes, and show how resolving it leads to a simpler explanation of what happens when something passes an event horizon.

February 18, 2011

Reunweaving The Rainbow

by Lucas Wilkins

(* Warning — Some readers may find this massively pedantic *)

A while ago I did some research into rainbows. I’d been reading about Newton and his rings, and thinking about what people say about him and his opinion on the number of colours in a rainbow. In which way these “principal colours” were important to him is a little unclear (“because they pass into one another by insensible gradation” !?!!?!, link), but it seems to me that he understood the relation between the continua of pitch and hue and their (somewhat arbitrary) relation to the respective discrete scales rather well. Anyway, I thought I would have a go at asking how many colours there are in a rainbow, perhaps there would be a sensible answer… I gave up pretty quickly, because I noticed something else.

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