Many laymen can't believe that the physicists can make some predictions by pure thought without looking at the experiments. Doesn't the large number of dimensions or the large number of vacua make reasoning impossible? Isn't it clear that mathematics and science must break down when things are hard? Isn't it obvious that science is over? Isn't mathematics another religion, these laymen ask? Maybe it is a religion but it works.
Let me show you an example. Choose your favorite number X between 0 and 99. Add the digits of your favorite number to obtain another number Y. Now you take the difference X-Y. For example, if your number is X=32, the sum of the digits is Y=3+2=5, and you will work with X-Y=32-5=27.
Find X-Y in the table inside the flash applet. There is a symbol next to X-Y. Think about this symbol intensely and click at the crystal ball. Despite the huge landscape of possible symbols in the table, the crystal ball will tell you what symbol you're thinking about. Isn't it amazing?
Maybe, it is amazing. But some of the readers will be even able to figure out why it works. ;-)
Some skeptics who don't trust rational thinking much will think that this is just a coincidence that is not even wrong, and they will publish books about it. Well, you can try it again, and it will reveal the correct symbol again. Some other skeptics will think that it is always the same symbol. But you can click "noch einmail" (once again) and start from the scratch. The crystal ball will determine your symbol correctly even though it will be a different symbol. ;-)
After a well-known mathematician and an achieved applied quantum mechanician explain why the trick works in the fast comments, there will be a third group of skeptics who will argue that 81,90,99 all seem to have different symbols in the table, so it can't be just about the multiples of nine. ;-) Needless to say, the magicians will have an explanation, too. But some people will never believe because they don't want to believe any rational answers.
In quantum gravity, the situation is similar. Many people would find it unbelievable that in such a difficult enterprise, we can say something at all. Why is it exactly string theory that is the only possible theory of quantum gravity in 4 dimensions or higher? Cannot it be cosmic Darwinism, loop quantum gravity, triply special relativity, quadruply special relativity, unified theory of mind and matter, or any other idea? Well, it cannot.
String theorists are using methods somewhat analogous to the crystal ball - this kind of magic is often referred to as mathematics - although the details are more involved. The lesson is that even though something looks impossible to a randomly chosen layman on the sidewalk somewhere at Manhattan or in Waterloo, it doesn't mean that there aren't other people who can actually figure out the right answer.
Previous flash: IQ test.
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