String theory is interesting and a worthwhile research topic. But I often wish that popular science articles about string theory were less hype and would also inform the readers of the shortcomings of the approach. Here is a reminder 1/10 #physics
String theory, as a theory of quantum gravity and a unification of the forces, has zero experimental evidence speaking for it. 2/10
String theory predicts additional dimensions of space which have not been seen. String theorists therefore conjectured that the unseen new dimensions are very small and compact, so they are unlike the dimensions we are familiar with - for unknown reasons. 3/10
String theory predicts supersymmetric partner particles which have not been observed. To avoid that the theory conflicts with observations, string theorists assumed that the supersymmetric particles are so massive that we have not yet seen them. 4/10
Even after making the supersymmetric particles heavy, the theory still conflicts with observation, because supersymmetry enables particle-interactions which have not been seen. Theoretical physicists then invented a new symmetry (“R-symmetry”) to make the problem go away. 5/10
String theory in its original formulation didn’t have a positive cosmological constant. When the cosmological constant was measured and came out positive, string theorists had to make yet another amendment to make the theory fit observations. 6/10
String theory does not give back Einstein’s theory of general relativity. It gives general relativity plus some hundred additional fields called axions. These fields have not been seen. This requires theorists to invent a way to hide these fields after the Big Bang. 7/10
Despite claims that string theory is a theory of everything that unifies quantum gravity with the standard model, no one has been able to actually find a construction that reproduces the standard model from string theory. 8/10
Just because string theory is *a* theory of quantum gravity does not mean it is *the* theory of quantum gravity that correctly describes our universe. 9/10
No, I did not say that string theory is wrong. No, I did not say that string theory is useless. No, I did not say that string theory is religion, or pseudoscience, or red cabbage. I merely summarized well-known facts that are often “forgotten” in articles on the topic. 10/10
11/10 Typo: I meant R-parity, not R-symmetry. Merry Christmas everyone.
