Proving String Theory?

Question

Why is String Theory considered unprovable? Isn't the whole point of a theory the ability to predict an outcome under certain conditions?

Answer 1

The energy scales at which it would be possible to see the stringy nature of particles is much greater than is presently experimentally accessible.

Answer 2

That was the original idea. However, we can't see strings unless we build a particle accelerator the size of a galaxy, so until then, it's effectively unprovable.

The problem with string theory is that while it makes good predictions when it comes to particle physics, physicists can't figure out a way to make it predict something that's not already predicted by the other theories. In fact, some are wondering if it can be made to predict any result that appears in our particle accelerators, and if that were true the theory would be unfalsifiable.

The reason why physicists like string theory is because it's a consistent theory of quantum gravity. Many brilliant physicists have labored unsuccessfully for decades in pursuit of this goal, and they have come up with two major theories, the other being loop quantum gravity, which suffers from similar problems as string theory in this context.

Another reason why it's so compelling to many theoretical physicists, is that string theory has revealed some remarkable mathematical relationships, which imply a larger mathematical structure to string theory that hasn't been explored. Most string theorists have taken these mathematical relationships as a sign that they're headed in the right direction. However, some leading theoretical physicists, like Roger Penrose, doubt this.