eli5: Why does there need to be 11 additional dimensions for the string theory to work?
In: 5
Imagine looking a map of all the flights of airplanes every day (or use Google and just do it). You’d notice all the flights in the Northern Hemisphere bow upwards, towards the North Pole rather than just being a straight line from city to city. Same with the Southern Hemisphere, only dipping towards the South Pole. Why?
If you’re just a lay person looking at this you *can see it’s happening*, you can *describe* the process, but you can’t *justify it*. In fact, if you tried modeling it and predicting it, it would be really hard to do using math. Why?
Because the problem I set up assumes a 2-dimension map, using X and Y coordinates. The *reality* is that the Earth is a sphere and you need a 3-dimension system to really understand what’s happening and suddenly the paths of the planes make sense (google “Great Circles”) and suddenly if you use 3-dimension math to model the paths of the planes the math isn’t even really difficult anymore, it’s actually easy, high-school level calculations. So understanding flight paths is an inherently 3D process, trying to force this down to 2D is both hard and sometimes impossibly complicated.
The point being, you and I are string theory laypeople, we don’t understand *why* string theory does what it does or how to use it but just like going from 2D to 3D makes air travel understandable, going from 4D to whatever-they-say-nowD in String Theory makes the math solvable, it makes it simpler and easier to solve. It also makes *sense* (sort of) of why it does what it does.
So we’re not going *into* string theory saying 17-Dimensions, duhhhh, we’re looking at string theory and *applying* 11 extra dimensions and seeing that it all makes much more sense now and kind of un-complicates itself.
Assuming you know what the hell String theory is in the first place though.
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