Strings theory full#

Parallel universes: theories and evidence.How the universe could possibly have more dimensions.

Strings theory full#

Still, theorists continue to probe at the edges, hoping to someday give a full name to the 'm' in M-theory. String theorists usually work in one of the five usual regimes, since they've been so well studied for decades, and the additional dimension and the introduction of branes makes the already-fiendish mathematics of string theory that much worse. ' Brane' is just a fancy word for multidimensional vibrating things, with the letter 'd' signifying the dimension, giving us everything from 1-branes (strings) to 2-branes (sheets) to 3-branes (blobs) and more.įor the most part, these branes lie low and mostly just act like strings, with the eleventh dimension not playing much of a role in the grand cosmic symphony.īeyond that, there isn't much known about M-theory. What's more, the fundamental object of reality is no longer the string but the d-brane. And that real deal requires not 10 but 11 dimensions in our universe. One curious feature of M-theory (the little that we know about it, that it) is that what we consider string theory appears to be just a low-energy approximation of the real deal. But M-theory revealed that all those islands actually shared the same, much larger, planet all along. We used to think of the five string theories as separate planets, with our theoretical and mathematical explorations confined to little islands on those planets. M-theory is like an uber-theory of strings, showing how all five string theories are really just small corners of a much larger, and much more mysterious, theory. What is that 'somewhere new'? Edward Witten suggested calling it 'M-theory', with the 'm' open to interpretation (e.g., 'mother,' 'mystery' or 'membrane') until such time as we actually understand it. By attempting both dualities on the five string theories, sometimes you get links to one of the other five, and sometimes you get dualities to somewhere new. That deeper thing can be guessed at by following all the dualities. These dualities suggest that the five string theories are all related, somehow, and are probing something much, much deeper. Type IIA and Type IIB string theories are related by such a duality. Sometimes strings can wind around a tiny, curled-up dimension a certain number of times with a certain momentum, but the duality of that has the number of windings and the momentum flipped. But if you take, say, Type 1 string theory and ramp up its interaction strength, you end up with the weaker version of SO(32) heterotic.Īnd there's more. For example, something we don't know about strings is how strongly they like to interact. It turns out that there are interesting connections, called dualities or symmetries, among the five theories. In the talk, he offered a radical suggestion: perhaps the five string theories weren't so different after all. Related: The history and structure of the universe (infographic)Īnd then 1995 happened, when prominent theoretical physicist Edward Witten gave a talk at the annual string theory conference. And so the five string theories represent five different approximations, with no way of being able to decide which one is best. We only have approximations that we hope - but can't prove - are close to the actual theory. They obviously couldn't all be correct descriptions of nature, but which one was the 'real' string theory, and which were the phonies? The problem was (and still is today) that string theory isn't complete - there's no such thing as the final equations of string theory, something that could be printed on a t-shirt, that describes the theory in the same way that we have the Einstein equations for gravity or the Maxwell equations for electromagnetism.

And some theories were combinations of other theories.įor reference, in case you're curious, the names of the five string theories are: Type 1, Type IIA, Type IIB, SO(32) heterotic, and E8圎8 heterotic. Some theories only allowed vibrations to travel in one direction on the strings, while others allowed both.

Some theories only had closed loops of strings, while others allowed open, wiggling strings. But when it comes to physical theories, details matter, and the five competing string models differed in the details. And in all the theories, the ways strings vibrate give rise to the richness of our physical world, from the forces of nature to the building blocks of matter to physical constants themselves.