Have a look at this New Scientist article.
This is the first totally new (for me) physics concept that I have seen on New Scientist for a while now.
I get the just of it and I was hoping to hear the opinions of some actual physicists.
What do you guys think? Could this pave the way to a theory of everything? Is this actually that new?
Old news. Physical systems have been described in terms of phase space since before Einstein. Usually it’s described in 6-dimensional terms, not 8, but that’s a natural enough extension, once you’ve got Special Relativity.
fine, physical systems have been described in terms of phase space.
but have they descibed space time as being curved and dependant on the viewers perspective? and the curvature being caused by momentum space?
I have often heard that space time is invariant or something, and what that means is that it does not depend on the perspective of the viewer. but this idea contradicts that.
Doesn’t M-Theory posit 11 dimensional space? And IIRC, regular String Theory posits 8 or10 dimensional space. So no, nothing new there.
I’ll let the ‘actual physicists’ type 'dopers answer though…I’m more a Science Channel junkie.
-XT
I realise now that I wasn’t clear about what is new here.
It is the suggestion that space time is not absolute, as relativity says it is.
I’m not sure what you mean by the statement that relativity says that spacetime is absolute. I can think of ways to translate that into technical terms by which that statement is true, but I can also think of ways to translate it by which that statement is false.
What does it even mean that spacetime is absolute? It can be bent, twisted, compressed or expanded, even punched through…at least theoretically (well, the bent part isn’t theoretical afaik, since gravity does that).
-XT
The article suggests that curved momentum space would mean that different observers would disagree about the space-time interval between two events, which is a disagreement with SR and GR, in which theories s-t interval is invariant.
No idea whether this is a good idea or not. New Scientist has a reputation for exaggerating and/or being completely misleading when it reports on new stuff, but on the other hand, Smolin is no crank.
You’d have to dig into the original journal article to really say. I hadn’t read far enough to get to the part where they say that four-interval isn’t invariant in this model; that would be a significant change. And since position and momentum are quantum-mechanical conjugates, this might touch on quantum gravity.
What I’d really want to know, though, is whether this new model makes any predictions differing from relativity, which could be tested with present or imminent technology. New physical models that deviate only at undetectable or undefined levels are a dime a dozen.
The New Scientist article does quote people making the connection to quantum gravity, and does provide a possible test (regarding observations of gamma-ray pulses) - we’ll see.
Actually I’d take someone saying ‘spacetime is absolute’ as a crude way of stating the diffeomorphism invariance of general relativity.
I would say sapcdetime can be ‘bent’ (as a crude way of stating in can have intrinsic curvature) but I would say that ‘twisting’ (i.e. torsion) of spacetime occurs only in extensions of general relatvity and I would disagree that there’d be an obviouis interpretation of spacetime being compressed, expanded or punch through.
IANAP, but the article represents a new tact at creating a background for a quantum field theory of gravity and one of tghe co-authors Lee Smolin in the World of quantum gravity is virtually a celebrity and seen as one of top people in that area so it’s definitely and idea that theoreticla phsyicists workign in the field of quantum gravity will not ignore.
The paper on which the article is based is linked to at the end and the point about the ‘non-absoluteness’ of spacetime is this: