Archive for November 26th, 2008

Alright, time to discuss some physics again. A while back I outlined the basic dichotomy of quantum gravity. In brief: we have classical general relativity as an excellent description of all observed gravitational phenomena, but when we go to extremely short distances we need to have a good description of quantum gravity. There are two possibilities: either the description of gravitational phenomena by the machinery of general relativity (metric, the principle of equivalence, etc.) holds all the way down to those extremely short distances, or it doesn’t. If it doesn’t, which is my own prejudice, classical general relativity and its variables are never to be quantized, there is no range of energies (or distance scales) which is described by quantum metrics obeying a quantum version of Einstein’s equations.

This situation is similar to the hydrodynamical description of fluid motion: it is a classical effective field theory, which breaks down long before quantum mechanics is needed. We can observe granularity in the fluid on distance scales much larger than those relevant to quantum mechanics. From that perspective, quantizing Einstein’s equations makes as much sense as quantizing the Navier-Stokes equations, which is to say not too much sense.



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Turkey day

debbies-turkey Turkey day is upon us. If you want to have some holiday fun, go and read the blog of all cakes gone bad where I got the picture shown here. They have some really dreadful looking stuff out there.

Also, because I like reading some science fiction, especially if its written by Iain M. Banks, I can not resist linking to Chad Orzels essay on why Science fiction can be good for science. This does not count as work…

And if you really need a play by play blogging of Thanksgiving, why not go all in and read one from the New York Times blog? I’m not sure I have the stomach to read it, but hey, it’s the holidays and I’m just giving you links that you might want to read. The disclaimer is that I don’t certify their value, I don’t even have to read them before posting them here…

Also, I’ll be on Holiday for the next couple of days, so if I stop posting, don’t panic. There are other blogs to read out there. If I’m lucky, Moshe will keep you entertained while I rest a bit.

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