When is absence of evidence, evidence of absence?

[PCarr]

I'm probably not qualified to make this statement. But it rings so intuitively true: Until we mathematically and experimentally enjoin gravity with other known and quantifiable forces in our universe, out understanding of time and space is, to say the least, utterly immature. With the exception the recent confirmation of frame dragging, we know little more about the phenomenon of gravity than has been verified by experiments confirming Einstein's theories of relativity formulated in the early 1900s.

Not really true. There have been a lot of observational and experimental confirmations. Special relativity is a done deal - confirmed to many decimal points, since it plays an important part in the basis of quantum field theory. Frame dragging by the way, is extremely persuasive evidence for GR, since it is a very tough test. Gravitational lensing is also predicted and very impressive. Black holes were predicted by the general theory decades before they were ever observed. The gravitational effect on clocks in orbit (GPS mostly) is also exactly as GR would predict.

So, our understanding of time as something measured by clocks is extremely good. The clocks have also gotten very good. The next frontier is to ask just what is it that clocks are measuring.

 

[PCarr]

Good heavens, don't forget the shared archetypes... and also the collective unconscious.

Carl Jung - Wikipedia, the free encyclopedia

Nice to see my BA in psych being useful for once.

Paul:

Um. Not sure why it's arrogant to have a hypothesis...

Unidentified Science part 2 is now out as part of API Case Files Episode 2, so I can share it with you. There is a link to the script in the show notes. It's all about how humility is a necessary virtue for scientific investigation of any sort, and the ETH (or any other "H") violates humility. Humility is not timidity, though. We can press forward, but need to set aside confirming the ETH as a goal.

 

[boomerang]

Not really true. There have been a lot of observational and experimental confirmations. Special relativity is a done deal - confirmed to many decimal points, since it plays an important part in the basis of quantum field theory. Frame dragging by the way, is extremely persuasive evidence for GR, since it is a very tough test. Gravitational lensing is also predicted and very impressive. Black holes were predicted by the general theory decades before they were ever observed. The gravitational effect on clocks in orbit (GPS mostly) is also exactly as GR would predict.

So, our understanding of time as something measured by clocks is extremely good. The clocks have also gotten very good. The next frontier is to ask just what is it that clocks are measuring.

Yes, but aren't we still talking about experimental confirmation of Einstein's original work? I'm under the impression that the road to understanding gravity on a sub-atomic scale, as in quantum gravity, has not gone much of anywhere. Or does this amount to asking the wrong questions ?

 

[PCarr]

Yes, but aren't we still talking about experimental confirmation of Einstein's original work? I'm under the impression that the road to understanding gravity on a sub-atomic scale, as in quantum gravity, has not gone much of anywhere. Or does this amount to asking the wrong questions ?

It's an area of active research, and who knows what we'll find on the other side? At present, quantum field theories (like string theory) use an Einsteinian view of time, but some theorists think we might eventually move beyond that. A huge obstacle in the way is that it's basically impossible to do experiments.

 

[manxman]

does this article interest either of you.

This physical breakthrough could change our understanding of spacetime

heres the gist of it, they seem at face value credible physicist's, but im making no claims, just thought it may be of interest.

Physicists have discovered a jewel-like geometric object that dramatically simplifies calculations of particle interactions and challenges the notion that space and time are fundamental components of reality.

“This is completely new and very much simpler than anything that has been done before,” said Andrew Hodges, a mathematical physicist at Oxford University who has been following the work.

The revelation that particle interactions, the most basic events in nature, may be consequences of geometry significantly advances a decades-long effort to reformulate quantum field theory, the body of laws describing elementary particles and their interactions. Interactions that were previously calculated with mathematical formulas thousands of terms long can now be described by computing the volume of the corresponding jewel-like “amplituhedron,” which yields an equivalent one-term expression.

“The degree of efficiency is mind-boggling,” said Jacob Bourjaily, a theoretical physicist at Harvard University and one of the researchers who developed the new idea. “You can easily do, on paper, computations that were infeasible even with a computer before.”

The new geometric version of quantum field theory could also facilitate the search for a theory of quantum gravity that would seamlessly connect the large- and small-scale pictures of the universe. Attempts thus far to incorporate gravity into the laws of physics at the quantum scale have run up against nonsensical infinities and deep paradoxes. The amplituhedron, or a similar geometric object, could help by removing two deeply rooted principles of physics: locality and unitarity.

“Both are hard-wired in the usual way we think about things,” said Nima Arkani-Hamed, a professor of physics at the Institute for Advanced Study in Princeton, N.J., and the lead author of the new work, which he is presenting in talks and in a forthcoming paper. “Both are suspect.”


heres a bunch more physicist's talking the same construct, a much longer article.

Physicists Discover Geometry Underlying Particle Physics | Simons Foundation

 

[Burnt State]

Manxman, you better invite @Soupie to this discussion as the image from the article, which is the amplituhedron is Soupie's avatar. He's obviously an expert in such things and should be able to clear up this entanglement without dropping a sweat.

 

[boomerang]

does this article interest either of you.

This physical breakthrough could change our understanding of spacetime

I admit to having insufficient cerebral bandwidth to even begin to evaluate such models. Here is another one by physicist Garrett Lisi that made a splash some years ago:

http://www.cs.virginia.edu/~robins/A_Geometric_Theory_of_Everything.pdf

 

[PCarr]

I admit to having insufficient cerebral bandwidth to even begin to evaluate such models. Here is another one by physicist Garrett Lisi that made a splash some years ago:

http://www.cs.virginia.edu/~robins/A_Geometric_Theory_of_Everything.pdf

The amplituhedron, as I understand it, is really an improved method for calculating amplitudes, although perhaps it will yield some new insights as well. Space and time are still the 20th century understanding of space and time.

 

[PCarr]

I like this. It explains Bayesian thinking very clearly.

http://nbviewer.ipython.org/github/...al&utm_source=twitter.com&utm_campaign=buffer

 

[trainedobserver]

Those theoretical physicist guys crack me up. Everyone knows it turtles all the way down.

 

[PCarr]

Those theoretical physicist guys crack me up. Everyone knows it turtles all the way down.

Now you're starting to offend my religious beliefs. The scriptures clearly teach that there is but one turtle, the Great A'Tuin.

 

[Randall]

... So, our understanding of time as something measured by clocks is extremely good. The clocks have also gotten very good. The next frontier is to ask just what is it that clocks are measuring.

Unfortunately the next frontier in our understanding of time will get nowhere by approaching time as a measurement. Why? Because clocks don't actually measure anything. What is really happening is that within every functional clock, there is an apparatus of some kind that detects and reports some sort of change. There are no exceptions to this. So ultimately, time itself is nothing more than the changes taking place within a given frame of reference. But I don't simply mean change in a casual sense. I mean all changes as they apply to everything all the way down to the smallest particles.

This situation illuminates serious problems with the way that ideas such as time travel and time dilation are sometimes illustrated. It takes some contemplation, but in the end it reveals that sci-fi like time travel is not possible, and time dilation is not what it is often made out be. There are some hypothetical circumstances that could give the illusion of sci-fi like time travel, but what would actually be happening could not possibly be the real thing.