|Ken Novak's Weblog
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Gravitrons, dimensions, string theory
This is an odd topic... but the Nova show on string theory and its implications was good to watch. There are some ideas that combine in a provocative way:
- string theory predicts 11 dimensions (10 spatial dimensions and time)
- a 3d+time universe is a membrane, or "brane" in the multi-dimensional reality
- "parallel universes" can exist, as branes differing in the 7 other dimensions
- the other 7 dimensions may cause the distance between our 3d universe and parallel universes to be very short
- while most particles can't traverse all the dimensions, gravitons can
- atom-smashing experimenters are looking for evidence of gravitons leaving our universe into parallel universes
If experimenters can send gravitons into other universes, they could arrive in small amounts of time, since other branes can be very close to ours.
The odd idea is this: if there is life in the other universes, communication might be possible via graviton transmission. And distances might be quite small, so it might be possible without the long delay of interstellar light transmission.
Just an odd connect-the-dots thought. Here's a little reference material from a Nova interview:
.. [G]ravity, and in particular the graviton -- the quantum of gravity that carries the gravitational force -- should always be able to move off into extra dimensions. String theory puts this on a much more concrete basis and tells you exactly why a graviton can move in the higher dimensional space, whereas the stuff we're made out of may not be able to move in those extra dimensions. ..
You can think of gravitons as closed loops of string that are floating around in the higher dimensional space, whereas you and I are the ends of open strings that are tied to branes and cannot move around in the higher dimensional space.
.. Not too many years ago people who talked about large extra dimensions would have been considered crackpots, to put it lightly. What's really changed is that people have realized that there are very hard-core, rigorous concepts coming out of string theory that allow you to talk about the possibility of visible extra dimensions, extra dimensions that you can see with experiments in a rigorous way. So we've turned something that used to be fantasy into hard science that we can go out and do experiments on right now. That's the real excitement about extra dimensions. It's not just something that we talk about, it's something we can do real experiments on right now.
The key to testing extra dimensions in experiments has to do with gravity. The simplest way that you can see evidence for an extra dimension is to try to produce a high-energy graviton, the quantum of gravity, which could then move off into the extra dimensions. In a particle accelerator we try to collide very high-energy particles and hope occasionally to produce a high-energy graviton that moves off into extra dimensions and disappears.
.. This fact has not been lost on people that do experiments or on theorists. We are really expecting a watershed in the history of physics through this kind of discovery. It will change all of our thinking about the universe and thus all of our thinking about experiments that we do after that.