## Death by Higher-Dimensional Bubble

Tonight I should finish a book that I’ve been slowly working my way through since the beginning of August: *The Shape of Inner Space* by Shing-Tung Yau. I was given the book along with a physics award my junior year of high school, and started it during summer vacation after letting it sit on my shelf for over two years (too much to read, too little time; my list of books I want to read currently has almost 130 titles). The reason why it’s taken me so long hasn’t been because I don’t have the time to read it, however, but because the material is so dense and takes so long to understand. I still don’t fully understand several of the concepts presented by the author, the winner of the Fields medal in 1982 and a key figure in the development of the mathematics of String theory through structures called Calabi-Yau manifolds, so it’s definitely one that I will want to re-read in a little while.

For those of you who aren’t that familiar with String theory, the idea is that all matter in the universe, rather than consisting of simple point-like particles, is made up of small strings, the properties of which determine their identity and interactions with other strings. While this is a little bit confusing, and scientists still aren’t completely sure what consequences may arise from these circumstances, the theory helps to unify many existing theories and other observed phenomena. Where the Standard model fails to accurately explain gravity (seemingly the most obvious, but actually the least important of four “fundamental forces“), the interaction is a direct result of String theory (don’t ask me to explain why, I don’t know). However, despite all of its successes, there has been no hard proof to date that supports String theory, and the search for such evidence continues today.

Another interesting consequence of Sting theory is that it would probably require the universe to exist with ten dimensions, but last time I checked, we only live in four (three spacial dimensions and time, along which we can only move in one direction, and at a constant “speed”). So where do the other six go…?

This is where the work of Yau and a number of other mathematicians and theoretical physicists comes in. Yau was one of the mathematicians responsible for proving the existence of Calabi-Yau manifolds, which manage to compact several dimensions into a long, thin shape. If you’re not sure where this is going, imagine wrapping one of these manifolds so that their ends touch, creating a thin loop of many dimensions, or a string. Now imagine that such a loop is the same as the strings in String theory…

So the universe may be a four-dimensional space made up of tiny strings of six-dimensional spaces. Kind of hard to imagine, but mathematically, it seems to make sense (even though I can’t explain it). While this setup is stable for the time being (we don’t live in ten-dimensions, right?), if the forces that hold the six-dimensions of the strings together (they would really like to “get out” into the whole universe) slacked even a little bit (and at any one of these individual strings), things would change quite a bit. The escaping dimensions would form a ten-dimensional bubble whose expansion would almost instantly reach the speed of light as it moves through our four-dimensional universe. Any and all existing matter “run over” by that bubble would be violently reorganized into ten dimensions, decimating everything. And our only way to observe things is with light, we wouldn’t even be able to observe the bubble before it destroyed the Earth and all of its matter. That’s a fun thought…

Fortunately, the likelihood of an actual bubble forming is very very low. Using more math that I can’t understand or explain, it’s been calculated that the universe would probably last e^(10^120) years, which is a ridiculously long time. According to Google and other web-based calculator applications, e^(10^120) is approximately equal to infinity. So we should be good for a long time.

Hey, it’s interesting to think about though.