Sounds too good to be true, right? And it is.
They are testing the equivalence principle. But
But what’s that got to do with string theory? If you read their paper, you will notice that the word “String Theory” appears in only one obscure sentence in the introduction, referring to a very specific form of string theory [with an extremely light spin-zero field, called the dilaton], implying that their work might be relevant for string theory if we lived in a stringy universe that had such a field. Not even the conclusion, much less the bulk of the paper, mentions strings or string theory. That’s because the paper has nothing to do with testing string theory; it is merely testing Einstein’s theory of gravity. More.
Is it possible, however, that an announced finding can be jimmied to make it look like support for string theory?
See also: Science Fictions