physicists cannot agree on how the Universe works

Physics is science - not religion. It's theories fit the facts we know about. We haven't got any theory of quantum gravity yet, nor any evidence that gravity is quantised.

However, if you are looking for evidence that gravity is special in some way, it is notable because it is instantaneous. Zero time passes before its effects take place.

Gravity propages at the speed of light according to 'science':

That's not true.

Except that it isn't. Gravitational waves seem to travel at the same speed as light. There's at least one observation that shows them to equal to on part in 10^15.

That seems to indicate it's /already there/ when any given measurement starts. Do you think gravity is prescient?

And some of the nay-sayers claim gravity travels at the speed of light- ish. I don't believe them, either.

And there are some more gaps in the standard theories about gravity, but I'll let the nay-sayers guess those. After all, I don't have to teach them anything.

Feynman was once asked how long it would take for the effects to arrive if the sun disappeared.

He is said to have replied, “go ahead and try it!”

(Feynman stories are like Patton or Montgomery stories—you have to remember that they were all furiously building legends around themselves.)

And the reason physicists can’t agree is that we’re disagreeable. ;)

Cheers

Phil Hobbs

It is fair for beliefs about mysteries to be different.

More than 21 years ago various persons traveled for a physics talk. A senior physicist asked a student in this hosting country about what she was studying. She said that she was taking lectures on quantum gravity, so this senior physicist said to her that there is not a theory of quantum gravity.

(S.

I maintain that this is still remarkable. Light only travels at light speed

- through a void

- if it is not blocked by an obstacle

Clearly, gravity doesn't suffer the same visual restrictions.

Note, it's not gravity travels at light speed minus a small constant, it's

- gravity travels at exactly light speed, no less

"Scientists Have Slowed Light Down To An Embarrassing 38 Miles Per Hour"

It would be even slower if they sent it through central London.

Lane W wrote in sci.physics, sci.astro, sci.electronics.design:

First of all, there is no "gravity"; strike that term from your physics vocabulary. The correct term is _gravitation_, and it is an effect itself.

Second, you are wrong.

If gravitation would properly be described as the consequence of a force that is acting instantaneously at a distance as Newton's theory indicated to some (Newton himself was not convinced of that; to him it sufficed that his theory worked, and he famously refused to make [up] hypotheses as to how or why ["hypotheses non fingo"]), then this would violate causality. And example that shows this is a thought experiment in which Sol suddenly disappearing: an observer passing by the Sol System would see the planets and other Sol System objects suddenly propagating outwards in straight lines even though they would be oblivious to the fact that Sol would have disappeared because the still see light that Sol emitted before.

General relativity resolves this problem and other problems of Newton's theory by postulating that gravitation is not the consequence of a force, but _a_ consequence of the curvature of spacetime, and that changes in spacetime curvature would not propagate faster than c, but exactly at c. Supporting evidence for that assumption is the measured phase speed of gravitational waves that are emitted when the change in spacetime curvature is not spherically symmetric, so especially when two objects with large masses are in a close orbit around each other, like two black holes or two neutron stars before they merge.

Veritasium: There Is Something Faster Than Light

Also contained in my public playlist "General Relativity":

F'up2 <news:sci.physics>

Science is not a belief system. Scientists do not believe in the things that they consider correct.

Science is not a dead body of knowledge that we accept because our forebears told us so; it is an ongoing process of obtaining knowledge. What was considered correct in the past need not be considered correct later when new information has been obtained. Physics is a science. Therefore, what a physicist, senior or not, said or did not say 21 years ago is merely of historical interest.

Lane W wrote in sci.physics, sci.astro, sci.electronics.design: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ [*facepalm*]

"We all have susceptibility to bias. Search engines on the Internet are /the epitome/ of confirmation bias. And you're gonna use /that/ as evidence that you're /correct?/ /No./"

--Neil deGrasse Tyson, astrophysicist and science communicator (in his "MasterClass" trailer,

First of all, read what you wrote: You are effectively claiming that it is possible for light to not propagate at its own speed. I hope you can agree that your statement is ridiculous nonsense.

Instead, the speed of light varies: it depends on the properties of the space through which it is propagating. The (local) _phase_ speed of light is largest and constant in an ideal _vacuum_ (NOT: "void"); _that_ speed is denoted c (formerly, c₀).[1] (It is then also the same in all inertial reference frames, which special relativity was originally based on.) If the space through which it propagates contains an optical medium, its phase speed can be greater than or less than c.

The case where it is less than c in an optical medium is more common. However, the correct explanation for that is NOT that the light is blocked, but that it puts the electrically charged particles of that medium into motion which causes them to generate their own light, and the interference of them produces light with a smaller phase speed than c.

Finally, light is a quantum-mechanical phenomenon and thus never fully blocked. There is always a non-zero probability for it to propagate through a barrier.

See also my public YouTube playlist "Optics":

_Gravitation_

Gravitational effects should, and "gravitational" waves apparently do, propagate at c instead.

F'up2 <news:sci.physics>

Yes, good point, I wonder how they measured (or concluded) gravity moves at the speed of light, that would need an experiment using stuff (electronics for example and light that does travel at that speed Bit circular reasoning.

But (as I think maybe the case) if light (EM radiation) is a 'state' of Le Sage particles, then all you need to 'stop' light is change the state of those LS particles, most matter can do that (by interacting with the EM field, glass a bit less for some frequencies...

Also Le Sage explains clocks slowing down near a big object (like earth for example) as then more Le Sage particles are intercepted, 'matter' gets less compressed, the 'pendulum becomes 'longer', and 'time', slows down. There must be a point where an object is so dense, big, heavy that all Le Sage particles are intercepted That gets rid of the divide by zero mamaticians like to try all the time, and cover it up with re-normalization. Making light is in Le Sage case nothing but adding some effect (state change) to the Le Sage particles, so simple.

Whatever way you look for all things, we need a 'mechanism' to understand and explain all this stuff. An example: Ohm's law. No current in a vacuum (infinite resistance). But then came the vacuum radio tube, was invented, and there WAS a current in the vacuum, specifically electrons flowing, violating Ohm's law.

In the same way gravity without LS particles or something is nothing but useless babble, There was this guy albert who was into it, and many still parrot his formulas space is curved and bla bla bla. Bit like this:

I did read Feynman objected to Le Sage, but he used simple particles like stones in his model. Even electrons are very complex and we do not know much about those. Same for Le Sage particles.. Not a few weeks go by without CERN finding new things that conflict with what we know so far about elementary particles. I see on

So, a MECHANISM is needed, without that ? nothing, kein stein. I am open to anything better than Le Sage So far have not seen any.

Nice, now test if for gravity speed?

Sorry, but my kitchen laboratory is not equipped to make such measurements.

I tried a few AI opinions. The consensus seems to be that the speed of gravity is the same as light using gravitational waves when observing a neutron star merger:

This was strongly confirmed observationally in 2017 when gravitational waves from a neutron-star merger (GW170817) and electromagnetic radiation from the same event arrived almost simultaneously after traveling roughly 130 million light-years. The observations constrained any difference between the speeds of gravity and light to an extraordinarily small amount."

Unfortunately, the physics is also well above my pay scale.

"Why Do Gravitational Waves Travel Exactly At The Speed Of Light?"

LOL. I have studied (Astro)physics. I am not confused, _you_ are. Read _all_ that I wrote. And stop that mindless crossposting (without Followup-To)!

Yes, but if somebody mentions 'gravitational waves' - I have been to the beach, know about Moon tides ;-)

Beautiful and very clear article! Thank you, keeping the link :-)

Experiments are essential to understanding. Alber E. never did an experiment in his life, his mind was curved in a bad way. He admitted though, at his death bed, that he failed to unite the EM and gravitational forces .. From:

So Le Sage particles that can be modified to carry charge / EM radiation is my simple explanation. I declare it public domain

The No bell price I do not want, too much politics in that.

Simplicity is soooooooo cool!