I see some possibility of having interesting discussion threads here Joint S&P. It's not something I know a great deal about. (Not a philosophy buff, or even a philosophy of physics buff). I'd like to gather a bunch of links to experiments that may raise conceptual issues. Since I'm not an expert in this line I will do so inexpertly---make a stab at it---and welcome helpful contributions from others.
My view is that the progress of physics can get stuck because of problems with unexamined concepts. Habitual concepts may block progress and need re-understanding. So I'd like links to a grabbag of experiments (and theoretical results as well) that seem to probe and highlight conceptual puzzles.
Also general source material like Wiki articles are OK.
It seems that the 1935 EPR paper triggered a huge amount of experimentation which is still going on after more than 70 years. Showing violation of local realism.
March 4th, 2009 "It's Easier to Observe the Failure of Local Realism than Previously Thought"
June 16th, 2008 "World's Largest Quantum Bell Test Spans Three Swiss Towns"
EPR refers to the 1935 paper of Einstein Podolsky Rosen.
Background in wiki:
Related news I don't have time to evaluate right now:
March 4th, 2009 http://www.physorg.com/news155386974.html
January 14th, 2009 http://www.physorg.com/news151164690.html
The idea that something real and definite underlies what we measure. And idea that spatially separated things can't communicate faster than the speed of light. May have to give up one or the other or both. Presumably they'll keep locality and give up realism, just my guess. Or some more bizarre outcome.
Now about the idea of Time. Rovelli has an essay called "Forget Time" that recently won a FQXi award. Says time is not a fundamental feature of reality. More like temperature. The concept of temperature only emerges macroscopically/statistically when you have a large number of things. If you look closely at a microscopic level temperature (as we are used to thinking of it) does not exist. Not fundamental IOW. Emergent.
The other FQXi first prize winner, Julian Barbour, says the same thing. Time not fundamental. Shows it by elemetary classical analysis.
So the concept of Time is being challenged. Here are links:
Both essays wrestle at a philo level with the concept of time. Both are by world-class experts. It's a good introduction to the problem IMHO, if anyone is looking for one. Ordinary quantum mechanics takes a classical time for granted. The time variable is different from all the others, it is not a quantum observable but is outside the system studied and purely classic. So there is a deep-rooted difficulty in physics waiting to be resolved.
About the idea of spatial dimension
. Usually dimensionality, either of space or spacetime, is taken for granted. Space is set up with some dimension, assumed to be an integer, and assumed to be constant
independent of place, time, and the scale of measurement.
However in mathematically defined spaces such as fractals, dimensionality can have non-integer values, can vary from place to place, and can vary with scale
Of course the real spacetime we live in could be like that---hasn't been ruled out. A number of groups working on this, deriving consequences. Some observational consequences have been proposed. Working towards potentially testable predictions. Here are links to recent work.
An easy introduction is in a recent Scientific American article
Physorg also had something recently:
March 25th, 2009 "Spacetime May Have Fractal Properties on a Quantum Scale"
This listing is preliminary and slap-dash. Maybe we can improve it. Something to go on anyway. Concepts like locality, realism, time, dimensionality can yield seemingly paradoxical expectations, may need to be re-examined at a philosophical level, re-conceived.