Thursday, October 17, 2013

Physics World turns 25

The IOP's member magazine "Physics World" turns 25 and has an anniversary issue out. It's full of interesting articles, some more information about the content is on the Physics World Blog, and you can download the issue for free here. It contains a contribution from me on one of the "five biggest unanswered questions in physics" -- "Can we unify quantum mechanics and gravity?"

For the download you apparently have to agree to end up on a newsletter email list. If you don't want that but would like to read my piece, send a brief note to hossi at nordita dot org.

5 comments:

Uncle Al said...

"what is the gravitational field of a quantum superposition?" Nice! "violations of certain symmetries" Do opposite shoes (single crystal test masses' enantiomorphic unit cells) violate the Equivalence Principle? ECKS spacetime torsion (chiral) does not postulate the Equivalence Principle. Chirality is the strong arrow of time, too,

http://www.nature.com/nature/journal/v463/n7278/full/nature08680.html
http://pra.aps.org/abstract/PRA/v82/i4/e043811

If trace broken symmetries are forever parameterized problems, then reality was not perfectly symmetric at the starting line. What is incredible given 10^500 string theory vacua as the alternative?

Zephir said...

Of course the quantum gravity is not just about "quantization of gravity". It should connect the predictions of quantum mechanics at the quantum scale with the predictions of general relativity at the large scales, which isn't possible without avoiding of phenomena at the human observer scale. The scope of quantum gravity theory is therefore much wider - it's a theory of everyday phenomena and artifacts, like the plants and Bee itself...

johnduffieldblog said...

Let's have a look then:

And if you know one thing about quantum gravity, it is probably that no-one knows how it works.
I do.

According to general relativity, our universe started in a singularity.
Not true.

Since gravity was strong in the early universe
No it wasn't. The energy density was uniform. There wasn't any gravity.

General relativity also predicts singularities when matter collapses into black holes
No it doesn't. People say it does, but they're wrong. So is the information paradox.

And it must make testable predictions
No it doesn't. It just has provide a calculation method that matches existing experiment.

Holography
Junk.

I think that this experimental guidance is essential to constructing the theory of quantum gravity, and is the route to making progress.
I don't.

Since gravity is really a consequence of space–time being curved
No it isn't.

The nature of time and its uni-directional arrow are puzzles
No they aren't.

The tunnel’s construction site might not look like much
Sorry about all this Sabine, but it isn't a tunnel. It's people shovelling dirt back and forth, and it's going to stay that way until they understand how electromagnetism relates to QED and then to gravity.

Zephir said...

@JohnDuffield: I essentially do agree. The articles like these just conserve the state of omnipresent ignorance of mainstream physics. IMO the strictly formal lowdimensional approach to physics did hit its limits already.

This is doesn't mean, that the mainstream theorists cannot gradually achieve better understanding of reality - but the speed of this understanding will be highly suboptimal and unnecessarily expensive (and apparently lower, than the speed of understanding of various citizen scientists, who don't need to take any money for it).

This situation already happened in computer industry, where the various "twaddlers" and "cake eaters" (i.e. high level language programmers) essentially embraced the niche of "real" "hard core" programmers, who did use the deterministic low level programming languages.

johnduffieldblog said...

I don't know if I agree about the low dimensional, Zephir, but I do agree there's some kind of problem in physics. I don't think it's at all like IT though. I work in IT, and one of the things you have to do is "get under the maths" by breaking it down into primitive steps. It's as if theoretical physicists just don't know how to do this, like they have no training in and no understanding of fundamental physics. They just don't know how gravity works. Or electromagnetism. And without that, IMHO they are lost when it comes to quantum gravity.