String theory hype is still coming fast and furious, so much so that the latest edition of This Week’s Hype needs to be a double issue. Today we learn that Black holes and pulsars could reveal extra dimensions, solving that thorny problem of testing string theory:
String theory, which attempts to unify all the known forces, calls for extra spatial dimensions beyond the three we experience. Testing the theory has proved difficult, however.
Now John Simonetti of Virginia Tech in Blacksburg and colleagues say black holes orbited by neutron stars called pulsars could do just that – if cosmic surveys can locate such pairings. “The universe contains ‘experimental’ setups we cannot produce on Earth,” he says.
The source of the hype isn’t really new though, they were featured a few years ago in an earlier edition of This Week’s Hype.
I have to say this sort of hype worries me a bit. Since string theory is a theory of anything at all, it won´t take long until any random astronomical signal to be consider evidence of string theory. Is the black-hole radiation loss going to be precisely predicted by the theory so that in the who-knows chance some experimental group see this it could be confronted? No, of course not. So, if we see nothing, situation stays as it is, string-theory is the marvelous theory of zero predictions. If on the other hand we see anything (at all) we can´t really precisely fit to general relativity, sure enough that´s string theory being “confirmed”.
Peter,
It seems like a simple idea that could provide a test although there is some “work” to be done in discovering a system with the appropriate properties. As a layman, I cannot see the difficulties. Where does the idea break down?
This would be a fascinating development if true (about the black holes and pulsars), but it won’t do much for string theory. We can have extra spatial dimensions without any string theory.
abbyyorker,
It’s the same problem as every other “test” of string theory. String theory predicts nothing about these supposed extra dimensions, they could be any size whatsover and have all sorts of different properties. So, even if there are extra dimensions, and you manage to get yourself a pulsar and a black hole with just the right properties to see evidence for them, this in no sense “tests” string theory.
Dear Peter,
I just started following your blog.
In two recent posts you showed how a) Ed Witten stated that String Theory is testable, and that b) Ed Witten deserves an endowed chair.
So why is it that you are surprised when other physicists hype string theory as testable?
Is only Ed Witten allowed to state that string theory is testable, and if so, why? What rules/laws are you following?
Brandon,
There’s no contradiction between someone being a great physicist, deserving of an endowed chair, and at the same time being over-enthusiastic about some idea, to the point of making claims for it that are not really supportable. If believing or saying something not quite true disqualified one from an endowed chair, we would have extremely few professors occupying such chairs.
In this particular case, I’d suspect that Witten, given a chance to revise and extend his remarks, might have something a bit different to say today about this (and even back then probably would have liked to add appropriate caveats). But, no matter what, nothing can change the fact of the matter that he has a fantastic list of achievements to his name, and is a scientist of the highest accomplishment.
Note also that we don’t have a single known example of pulsar-black hole binary.