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Archive for October 20th, 2008

This post in “Science After Sunclipse” reminded me of one of the most beautiful ideas to come out of the continuing attempts to combine String Theory and Cosmology. The idea of Robert Brandenberger and Cumrun Vafa, dubbed more recently as “String Gas Cosmology”, is a wonderfully creative attempt to explain why our world has three spatial directions. There is no other theory on the market where the dimensionality of space could be determined dynamically, or at least come out as a result of a calculation, rather than being put in as an input, so in String Theory this is a natural question to ask. The idea for an answer,  provided by String Gas Cosmology, could be stated naturally and simply, which is what I try doing in this post. As usual, one has to remember that the devil is in the details, and those at the moment provide a real challenge for the idea.

One of the beautiful aspects of this approach is even asking the question: why four dimensions?  famously, the dimension of spacetime in string theory is larger than the observed one, in the simplest scenarios 10 or 11 spacetime dimensions, depending on details. We of course only see 3 spatial directions to move in, and can only make sense out of one time direction. Isn’t that a clean Popperian falsification of String Theory?

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Where in the world is….

 By the time you start reading this post, I will be squirming in my seat trying to get a little bit of extra leg room, or I will have landed already. In any case, just to add some meaningful content and to avoid complaining about cramped conditions in airplanes, I thought I would give you a picture I took from an airplane a few years ago. And all you have to do is figure out where in the world this picture was taken.

Hint: there are geographic features in the photo that are visible…

Where was this picture taken?

Where was this picture taken?

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