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...you've probably already recognized the "time is a plane and not a line" phenomenon raised in discussing extra time dimensions.

I do, Alamo-Girl; but Green seems to suggest that, however many dimensions there are -- 11 in current string theory -- that only one of them will be a time dimension. It seems the balloon analogy -- of the inflationary universe -- allows for those tiny, crabbed, "curled up" ten spatial dimensions to do all their work in one time dimension -- the one that we can "picture." At least, that appears to be the jist of Green's presentation. Once the universe has expanded sufficiently, the idea is the harmonic signatures of these teensy curled up dimensions become "audible," and therefore observable.

If such observations confirm the mathematical predictions, we're home free -- string theory can be said to have been observed in action.

And yet I have questions, probably idle ones. One is that for string theory to be correct, we must understand that it has been at work regardless of the space/time frame that enables us to recognize it. If the theory is correct, and these ten spatial dimensions altogether specify every particle known and yet unknown in the universe, then obviously, they have always been doing that, "from the beginning." If we add the idea of vacuum fields, or zero point fields, each with its own signature particle, then we are effectively dealing with a universal phenomenon, for fields are understood to be universal. My question is: Where do we put the idea of universality into a framework that calls for only one dimension of time? It seems to me that, in a very real sense, universality carries the idea of that which is timeless, ever persisting at least so long as the universe lasts.

He writes, "...conventional theories do break down when you try to push them all the way back to the beginning. We believe that string theory does not break down, but it still is a very complicated theory when you try to apply it to time zero itself. So far, no string theorist has succeeded in using the theory to peel back the obscuring layers and reveal what happened at the start. But the hope is that we will shortly be able to do that."

I dunno. It may be premature to start numbering time dimensions before we can understand what happened at "time zero." I wonder what the math might have to say about that.

Maybe someone can shed further light on these intriguing issues.

Please correct me if I am wrong but wasn't it Einstein that said time was a creation, a persistant illusion? If you will permit me to be a little metaphysical, I would like to think that the other strings we cannot see are dimensions of the spiritual - angels, demons, our spirit. Since God spoke the world into being (see Genesis 1) would it not also make sense that he controls events in all dimensions through sound? These filaments (strings) are sound in particle form, correct? Another analogy I like to think about is that we are dancing on the strings of God's violin. So to get back to my idea, if time is created but does not seem to apply to God or the spiritual world, then it would make sense to me that time is only one dimension - one that we can sense. What do you think?

Thank you so much for your reply!

Indeed, Greene is only speaking in the interview of the conventional, compactified Kaluza-Klein extra spatial dimensions, but in his presentation on PBS (I think it was) he also spoke of the higher dimensional theories, inter-dimensionality and included Cumrun Vafa in the program (extra time dimensions). For that reason, I believe he is open to the other theories as well.

Plus, he said this in the article:

I think, however, and many physicists agree, that that sense of time flowing that we all feel through memory is actually an illusion. Every moment is as real as every other. Every "now," when you say, "this is the real moment," is as real as every other "now"—and therefore all the moments are just out there. Just as every location in space is out there, I think every moment in time is out there, too.

At bottom, space and time transform. Time is geometric. That is the point of the Lorenz transformation and special relativity. General relativity makes it more complicated because it speaks to the warping of space/time and is even more problematic for causality than special relativity. Nevertheless, where there is space, there is time and vice versa thus each point constitutes a space/time history (Hilbert space) even without an extra temporal dimension. But an extra time dimension itself simplifies a host of other problems (duality, non-locality, superposition, etc.) In all fairness, it does so at the expense of causality (which is already on life support from non-locality anyhoot)! Nevertheless, IMHO it is a much better theory.

But I digress...

I certainly do agree with you that it is premature to count the dimensions or to characterize them in terms of number of spatial and number of temporal or to require that they be in total compactified or higher dimensional!!!

He writes, "...conventional theories do break down when you try to push them all the way back to the beginning. We believe that string theory does not break down, but it still is a very complicated theory when you try to apply it to time zero itself. So far, no string theorist has succeeded in using the theory to peel back the obscuring layers and reveal what happened at the start. But the hope is that we will shortly be able to do that."

For some odd reason, I do not share his confidence in this matter, though it would be interesting to see what they would come up with.