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Well to be totally honest, they don't teach under grads about either, or at least they didn't in my course. There are two reasons for that: 1) a lot of this sort of cutting edge theoretical work requires a context of good background knowledge to truly appreciate, and 2) much of it is still highly speculative, and they have too much proven, experimentally supported science to get in to most undergraduate courses as it is, without including things like string theory.

So, i can't tell you anything you can't easily read on the net about M-theory. I was never taught about P-branes and D-branes, so i have about as much appreciation of the wiki article as any of you lot (IMG:http://media.profileheaven.com/images/style_emoticons/default/smile.gif)

The QM "many worlds" thing is an interpretation of quantum mechanics. That is to say, it's one possible description of the real-world, practical consequences of quantum theory. I THINK it posits an alternative to the idea of wave function collapse. In QM, wave functions describe matter, and the square of their absolute values, the probability of a system occupying that allowed state. When an event occurs, and is measured, the distribution of wave functions collapses to a single wave function - the actual state of the system. There is a degree of random chance involved in this - see radioactive decay - where the probability distribution indicates the likelihood of collapse to any given state. The many worlds theory is essentially that whilst collapse appears to occur, in fact every single possible quantum possibility DOES occur, each in separate universe. In other words, whilst we're aware of only one outcome, every outcome still happens.

(IMG:http://media.profileheaven.com/images/style_emoticons/default/blink.gif)

So it doesn't really solve any problem?

That depends whether you see wave function collapse as a problem. Some people do! As i say, this is less about a scientific theory to describe a particular phenomenon, and more about an interpretation of a scientific theory, and what it means in the context of reality as we know it. The quantum mechanical description of the universe has been experimentally verified; it's implications are still being debated.

The quantum mechanical description of the universe has been experimentally verified

What does this sentence mean?
Bear in mind you're talking to a guy who scraped a B at physics A-level by 1/10th of a percent.

Well basically QM models are used to make predictions about the properties of given physical systems. Then, those same properties are measured experimentally. The predicted and measured values are found to be highly congruent.

Meh (IMG:http://media.profileheaven.com/images/style_emoticons/default/shrug.gif)

This topic went downhill the second you came along and put science into it (IMG:http://media.profileheaven.com/images/style_emoticons/default/mad.gif)

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