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Einstein's Other Theory of Everything

nautil.us

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Re: Einstein's Other Theory of Everything

#111

Post by imglorp »

Pompidou wrote: post #106
imglorp wrote: post #102

Earlier quoted context omitted.

Given how easy it seems to reproduce, someone had better explain this effect if it's not what is claimed there... PS: this looks like anyone could reproduce or refute it in their basement for a few hundred dollars given all the details in the slides. I'm hoping some amateurs step in.

"Gem test" 1 and 2 on john brandenburg 's youtube channel : https://www.youtube.com/watch?v=hqbOnqZtz3Y https://www.youtube.com/watch?v=RSRbLA6dhtk

It all seems to suffer from some of the issues the EM Drive saw: the proposed effect is tiny and very, very difficult to tease apart from environmental and system noise. I hope I'm wrong.

Re: Einstein's Other Theory of Everything

#112

Post by tgarrett »

pdonis wrote: post #92
tgarrett wrote: post #73

Earlier quoted context omitted.

Hi greysphere, you are definitely correct that one primary thing preventing velocity of the electron from exceeding than the speed of light is the presence of gamma in the relativistic force law, aka \partial_t (m_e \gamma v ) = q_e(E + v \times B), although the LHS doesn't quite equal \gamma m_e a, since \gamma also depends on v... In general I think it's fine to use Coulomb's law as an approximation in this case be…

> so the electron is now bound to the proton This is extremely unlikely unless the relative motion is very slow, or, to put it another way, the total center of mass energy is very close to the rest energy of electron + proton, so there is a significant probability amplitude for capture into a bound hydrogen atom. The post I originally responded to was obviously not considering such a case since it claimed the electro…

If the electron starts with zero energy at infinity (e.g. a parabolic orbit, a natural default assumption), and some of the potential energy is converted into free EM radiation due to acceleration of the electron as it is falling down the potential well, then it will become bound to the proton. My reading of phkahler's original statement is that the electron will wind up going faster than the speed of light (which is incorrect, due to gamma) due to falling down the potential well, and not due to having non-zero kinetic energy at infinity...

Re: Einstein's Other Theory of Everything

#113

Post by pdonis »

tgarrett wrote: post #110
pdonis wrote: post #88

Earlier quoted context omitted.

> our universe also includes QM and that makes BH physics much more subtle In some ways, yes, but none of that changes the particular thing I said about BH physics.

In pure GR an infalling observer will sail past the EH and not notice anything unusual since spacetime is locally Minkowski (ignoring tidal forces, which is valid e.g. for humans falling into supermassive BHs). If the (GR+QM) firewall hypothesis is correct (a big if), an infalling observer will instead be promptly incinerated within a Planck's length of the EH. The intuition one builds from a pure GR understanding of…

> If the (GR+QM) firewall hypothesis is correct (a big if)

A big if indeed, but if that hypothesis is correct, then the GR solution that applies is no longer the standard black hole solution. The "firewall" is not vacuum--more precisely, it does not have a vanishing stress-energy tensor. Which means "the intuition one builds from a pure GR understanding" for the "firewall" case will need to be a pure GR understanding of a different solution from the standard BH, and of course such an understanding can be perfectly correct.

In other words, if you're going to talk about a "firewall" solution, then saying "well, GR doesn't model that correctly because it's not a standard GR black hole" is simply wrong. GR can model lots of other things besides standard (vacuum solution) black holes. You just have to use the correct GR model for the actual stress-energy tensor that is present. Of course statements about a standard vacuum black hole will not be correct for a different non-vacuum solution; but that is not contradicting anything I said, because the post I was responding to was assuming a standard vacuum black hole, and my statement was correct for that case.

The real question is whether such a "firewall" model, with a nonzero stress-energy tensor, would even have an event horizon. As far as I know nobody has actually answered that question; the treatments I have seen have simply assumed that there is one without taking into account the fact that the "firewall" stress-energy tensor is non-vanishing. If there is an event horizon in such a model, then my statement would still be correct for that model, since my statement was based on general properties of event horizons.

Re: Einstein's Other Theory of Everything

#114

Post by niederman »

tbrownaw wrote: post #109
motohagiography wrote: post #72

Earlier quoted context omitted.

interesting, content to be wrong based on an absolute ignorance of the topic. my laymans read of photon entanglement had to do with how it was described in quantum key distribution, where entangled photons maintained a kind of polarization state between each other over a long distance, where the observation of one of them caused a state change at the other "end". this idea of remote causality was what implied that th…

> maintained a kind of polarization state between each other over a long distance, where the observation of one of them caused a state change at the other "end". this idea of remote causality Operating on one half of an entangled pair does not transmit information to the other half. Therefore, the is no action or causation. Choices of vocabulary which imply otherwise are incorrect. It also doesn't work by "hidden var…

Whether there is any kind of action on the entangled counterpart is not actually answered by quantum mechanics, and depends on the interpretation. For example, in the Copenhagen interpretation there is an action (measuring one half of the pair causes the others waveform to instantly collapse), but in the Many Worlds interpretation there is no causal action, because observation is just a new entanglement between the observer and the entangled pair system.

Re: Einstein's Other Theory of Everything

#115

Post by passion__desire »

Levitating wrote: post #9
dr_dshiv wrote: post #3

An alternative to the “ball on rubber sheet” model of gravity is “twisting a lump out of a sheet of silly putty.” You get the same curvature without relying on gravity to serve as a model of gravity (which always bothered me a bit) For clarity, here’s what I mean: if you flatten out some silly putty (or pizza dough should work) then pinch and twist together some of the sheet into a lump, that pulls along the surround…

That's a pretty clever model. Do you know any videos demonstrating it?

A new way to visualize General Relativity

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

This uses Adobe tools to visualize and take advantage of video format.

Re: Einstein's Other Theory of Everything

#116

Post by wruza »

NooneAtAll3 wrote: post #96
wruza wrote: post #83

Earlier quoted context omitted.

I think it’s a good model because it poses the same question: an object is in a field gradient of otherwise forceless space, so what ? In 0g a mass on a rubber sheet won’t attract an object, so why would real gravity “lines” attract an object that doesn’t try to move across it? There’s no supergravity for “gravity sheet” to work either. Afaiu, the answer is that moving through time in a gravitational gradient makes y…

in 0g, object that does not leave contact with the curved (by-whatever-means) rubber sheet will behave the same way "using gravity" in the experiment is convenience of the experiment - gravity is freely abundant to use, both as a source of curvature and source of "making objects not leave the sheet" if you want to hold the sheet by yourself, and hold the objects to the sheet by yourself - you are free to do it, enjoy…

in 0g, object that does not leave contact with the curved (by-whatever-means) rubber sheet will behave the same way

An inert object will sit on it kissing it and never go anywhere. The curvature of a sheet doesn’t matter cause there’s no “down” and no forces. If you push it “in” a little and release, the sheet tension will push it back out but not “to” the well. You may start accelerating the system to create gravity-like situation, but that’s the point.

Re: Einstein's Other Theory of Everything

#117

Post by gradschoolfail »

ls-lah_33 wrote: post #44

I'm surprised Sabine doesn't mention the way fermions are treated in Loop Quantum Gravity [1][2]. My understanding is they are treated as "non-local" or open loops of gravitational force, and thus entry and exit points in space-time. This makes them conceptually similar to the "wormhole model" of matter that Einstein and Rosen originally described. [1] https://arxiv.org/pdf/gr-qc/9404010 [2] https://arxiv.org/pdf/101…

My understanding is that this is the way fermions are treated in any modern theory of quantum gravity, and not specific to LQG?

Re: Einstein's Other Theory of Everything

#118

Post by xscott »

IgorPartola wrote: post #52
the__alchemist wrote: post #24

Earlier quoted context omitted.

I think the balls on sheet is an OK compromise. The reason for me is, it's tough (but not impossible as you point out) to visualize functions over 3D space. Your sponge does that and I like it! (You could also use color-coding, vector-gradients etc) The ball and sheet uses a spacial dimension as the function value, and that's the dimension the needs gravity to work acts on. So, if you accept that as a compromise, it'…

I like to explain it all as graph paper where the squares get bigger or smaller depending on what’s near them.

That helps explain curvature of space, but it doesn't explain any of the motion.

When you see those stretched rubber sheets, they rarely/never show the grid lines moving. So let's say you place a small *stationary* object at a specific grid point (coordinate), and there's a large object that deforms the grid itself. Nothing about that visual provides any new intuition about why the small object would leave it's current grid position and move towards the larger one.

The visual tries to explain gravity by appealing to your existing notion of gravity.

Re: Einstein's Other Theory of Everything

#119

Post by gus_massa »

XorNot wrote: post #97
pdonis wrote: post #89

Earlier quoted context omitted.

> electrons orbiting protons don't emit synchrotron radiation Not in atoms, no. But I mentioned scattering, which is a different scenario.

And I have absolutely no idea what you think this explains. Which is the point of physics you know: to convey actionable concepts about the behavior of experiments. Not be cryptic and vague.

It explains what happens if the electron goes too fast and instead of getting "trapped" it just changes it direction a little.

Re: Einstein's Other Theory of Everything

#120

Post by carapace »

photonthug wrote: post #85
carapace wrote: post #82

Earlier quoted context omitted.

Gravity is one of the fundamental forces, there's no recursion in it's definition, indeed we don't "define" it we describe it. The actual description of gravity isn't hard to understand, it's just really strange. There is no good reason to introduce confusing and intrinsically incorrect models.

> There is no good reason to introduce confusing and intrinsically incorrect models. Well, teaching is the usual reason, otherwise physics with trig would all just wait for calculus, and calculus wouldn't get covered before real analysis, etc. Incorrect, or more charitably "useful, prerequisite, & intentionally not rigorous" models are a pretty standard tool for walking students closer to real understanding. Clearly…

> > There is no good reason to introduce confusing and intrinsically incorrect models.

> Well, teaching is the usual reason,

Introducing confusing and intrinsically incorrect models is the opposite of teaching.

> "useful, prerequisite, & intentionally not rigorous" models are a pretty standard tool for walking students closer to real understanding.

The funnel model of gravity isn't useful, prerequisite, or rigorous.

> Unpacking this to a first approximation it actually sounds like you're looking ...

A bunch of projection on your part follows.

I'm sorry to be rude, but to me you seem to be intelligent yet deeply confused.

I'm going to bow out of this thread now, again I apologize.

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