While researching the interesting topic of active versus passive transformations in physics, I stumbled upon this fascinating paper by Witten from 2014.

In it, Witten discusses Einstein's efforts with Bergmann in 1938 to develop a unified theory of graviation and electromagnetism from the idea of a 5th dimensions, in the spirit of Kaluza–Klein theory. The main new idea that Einstein and Bergmann introduced was the "compactification" of the 5th dimension to a short length scale relative to the famililar 4 dimensions of space–time.

Apparently, Einstein balked at this idea and instead advocated that the 5th dimension be "wrapped" like a circle (whatever that means, apparently he worked out some calculation scheme). Witten criticises this last "misstep" but praises the "modern" conception of compactification.

If anbody is wondering, the resultant "scalar–tensor" theory turned out to be wrong because it incorrectly predicts the existence of a "massless scalar field". My understanding does not extend so far as to know why exactly that is inconsistent with experiment. Perhaps @johncarlosbaez can clarify?

In any case, some fascinating history.

https://arxiv.org/pdf/1401.8048

RE: https://legal.social/@malteengeler/117302396327854999

Rereading "The Dispossessed" right now. I think it is clicking thisn time around.

Amazing reminder to myself how your cognitive set can completely flip your perception of the world.

Not that I need a reminder, having just written a book about the central roles of reference frames and relativity in the appearance of things.

RE: https://mastodon.social/@BenRiceM/116980424345560765

Don't fuck with Israeli weapons manufacturers (Elbit Systems), they will have you royally fucked up.

Why do I find this initiative "depressing and distressing"?

There are many reasons, not least of which is the current grift-laden fire hose of "AI tools" that will wash away decades of solid and hard fought wins in the software engineering industry.

I take it as given that the reader understands the rapacious and brazen theft of intellectual property that underscores the current AI grift.

I also take as given that the reader understands the horrific environmental, moral, economic and societal impacts of the AI grift. Entire biological and digital ecosystems are being destroyed in front of our eyes.

It may not be as clear to some folks, but it's also important to understand some deeper context to the AI grift:

(A) It is not a new grift and its origins can be traced back to the Greek myth of the Oracle of Delphi and more "recently" to the "Mechanical Turk", a chess playing automaton of the 18th century.

(B) There exists no scientific basis for the claim that AI resembles or surpasses human intelligence (whatever that is) in any form. The AI grift of the 21st century is solely rooted in the acceleration of digital information processing brought about by computer hardware acceleration, and has nothing to do with advances in understanding either human intelligence or AI algorithms. This acceleration has allowed computer models, such as LLMs, to acquire and compute resources at an unprecedented scale, thereby making feasible the advent of chat bots and the like.

(C) The core mathematical and conceptual tools that underlie the workings of modern neural networks have not changed for more than 50 years. People like Stephen Grossberg developed the basic paradigms of reinforcement learning in the 1950s!

Make of this what you will.

But I personally find the fact that arguably the greatest mathematician who has ever lived has put his name to an AI initiative, involving stake holders from some of the key players in the current AI grift economy, one of the most depressing and distressing things I have encountered lately, and that's saying something.

https://sair.foundation

A great side story from the same wikipedia entry:

"Einstein and Rosen accordingly submitted a paper entitled Do gravitational waves exist? to a leading physics journal, Physical Review, in which they described their wave solutions and concluded that the "radiation" that seemed to appear in general relativity was not genuine radiation capable of transporting energy or having (in principle) measurable physical effects.[8] The anonymous referee, who—as the current editor of Physical Review recently confirmed, all parties now being deceased—was the combative cosmologist, Howard Percy Robertson, pointed out the error described below, and the manuscript was returned to the authors with a note from the editor asking them to revise the paper to address these concerns. Quite uncharacteristically, Einstein took this criticism very badly, angrily replying "I see no reason to address the, in any case erroneous, opinion expressed by your referee." He vowed never again to submit a paper to Physical Review. Instead, Einstein and Rosen resubmitted the paper without change to another and much less well known journal, The Journal of the Franklin Institute.[9] He kept his vow regarding Physical Review."

The existence of gravitational waves was a hotly debated topic after Einstein introduced general relativity.

Indeed, Einstein and Rosen concluded in 1936 that gravitational plane waves do not exist, but this conclusion turned out to be wrong.

It was Richard Feynman who came up with a thought experiment that eventually led to a rigorous mathematical foundation for the understanding of gravitational waves and their physical effects on material objects.

Feynman's argument is called the "sticky bead" thought experiment. Quoting from the Wikipedia page:

"Feynman’s gravitational wave detector: It is simply two beads sliding freely (but with a small amount of friction) on a rigid rod. As the wave passes over the rod, atomic forces hold the length of the rod fixed, but the proper distance between the two beads oscillates. Thus, the beads rub against the rod, dissipating heat."

https://en.wikipedia.org/wiki/Sticky_bead_argument

@johncarlosbaez How familiar are you with gauge theory gravity?

I find it very interesting in view of certain considerations that follow from the ideas in my book.

https://en.wikipedia.org/wiki/Gauge_theory_gravity

Questions for physics folks

Do physicists consider General Relativity to be a superior description of nature compared to Newton's laws in terms of its intrinsic ability to account for "fictitious forces", such as centrifugal and Coriolis "forces"?

Correspondingly, is it a correct statement to say that Newton's laws of motion only strictly apply in inertial frames of reference and therefore GR provides a more parsimonious account of the concept of "force"?

I've tried to find historical references that remark upon the ad hoc nature of the addition of "fictitious forces" to Newton's laws but it doesn't seem to me that physicists of the 17th - 19th centuries were overly concerned by these issues.

Is that a fair appraisal?

Note that I am not asking whether GR is a better description of nature than Newton's laws in general but rather with specific reference to the "fictitious forces" and the question of whether physicists actually considered them a fundamental issue that required a better or more parsimonious solution.

cc @johncarlosbaez

Opening lines of the Chernobyl miniseries:

"It's not that we'll mistake them for
the truth. The real danger is that
if we hear enough lies, then we no
longer recognize the truth at all.
What can we do then? What else is
left but to abandon even the hope of
truth, and content ourselves
instead... with stories."

This is now the existential threat the fascist regime of the USA has become to the entire world.

If we are not actively fighting this regime and others like it, we are the enemy of truth.

My book "The Appearance of Things: How the Principle of Relativity Shapes Our Visual World" will be released in eBook, paperback and hardcover versions on September 8.

You can find it here https://www.amazon.com/dp/B0HCVLM6T9 and here https://www.amazon.com/dp/1764711513

I've opted to make it available exclusively through Amazon, which I think is a pretty shitty thing to have to do. But the reality is that this approach gives me by far the best chance to grow an audience. This restriction will last (at least) 3 months. I hope to eventually be able to release the book more widely after this initial period.

Anybody who knows me knows that I despise the world of corporate technology. The good news is that your support will help me get the book out to the folks who need to read it. So please consider purchasing, sharing or discussing the book.

Thanks in Advance!

Why the fuck should I pay for content on a streaming service to which I already subscribe?

What a fucking capitalistic dystopian shit show the world has become.

The Zone of Interest is an absolutely chilling movie, particularly in light of what's happening in contemporary America.

https://www.youtube.com/watch?v=Orh20527gVI

h/t @wlumley

Yellow, green, red and blue pegs hanging on a line, with pixel samples along each peg shown. How do we perceive the pegs as solid "body" colours when the pixel samples differ markedly?

Simultaneous contrast (from local edges) and assimilation (from remote edges) induced into physically identical grey rings.

I made two attempts to adjust the intensity of the ring not the right to match the appearance of the ring on the left.

Both increasing and decreasing the intensity of the right ring leads to poorer matches to my eye/brain.

Which of the three right rings matches best for you? And how good is the match on a scale of 1-10, 10 being "identical" and 1 being "as different as black and white"?

The two rings are identical, but the one on the right stands out from the background much more strongly, in addition to appearing metallic or lustrous compared to the matte or dull ring on the left.

Simultaneous contrast this apparently works to enhance figure-ground separation.

Standard models of perception that map intensity to a continuum of grey shades ranging from black to white (absolute gamut) predict that the induced brightness and darkness from the background should cancel and the rings should appear identical.

Why have I never before noticed the perceptual multi-stability of the Mac Finder icon?

A primer on "Mid-Level Vision" by Bart Anderson.

https://www.cell.com/current-biology/fulltext/S0960-9822(19)31593-3

Anderson has been at the forefront of research on surface perception for decades now. He's shown over and over how subtle manipulations to images can transform our percepts in dramatic ways.

The figure here shows how the covariation of shading with object boundary conditions triggers either a perception of a 3-D corrugated surface of uniform albedo with variable illumination (left) or a 2-D surface with variable albedo and uniform illumination.

Relates to this discussion too https://mathstodon.xyz/@TonyVladusich/114244329572487584.

I find this work by David L. Wiltshire fascinating and elegant: it may be that dark energy does not actually exist and that measurements of the expansion rate of the universe are better fit by a model based on space-time warping at cosmological scales, consistent with the strong equivalence principle at the heart of Einstein's theory of General Relativity.

https://arxiv.org/pdf/0809.1183