So, I largely understand the different kinds of string theories that physicists across the world have propounded. An incredibly rudimentary form of boiling it down would be to say that they have a different number of dimensions to them – 5, 9, 10, 11 and from what I have heard/read, even 26.
But i have a few questions that i hope the community can answer in simpler form:
(1) What are the differences and similarities between these different versions or types of string theory?
(2) Why have we picked the numbers 5, 9, 10, 11 and 26? Why not pick let’s say 17 or 22?
(3) Following on from the same thread as above, do we know whether there is an upper bound to the number of dimensions that the string theory can have? What stops it from being, say 49? Or 10^9?
(4) If string theory is incapable of measurement or physical verification, what tells us we are not simply reverse engineering our belief / bias and fitting things into our theorem?
I am sorry if these questions are silly. But i would really be grateful if someone can these aspects for me! Thank you so much!
In: 1
This feels more like something for r/AskPhysics than ELI5 tbh.
But regarding point 4, string theories are falsifiable, but we will need much more advanced engineering before being able to carry these experiments.
Also, there are many different parameters that can be adjusted for various string theories (think fundamental constants) that all give rise to our current models. So we will probably need quite a lot of experiments before we can pinpoint which one is the correct one.
Can’t speak to the other points, sorry
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