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Astronauts are not in a zero-G environment . . . gravity exists . . .the astronauts are in free fall while orbiting the earth.

Do things change if the two sides of the clock are connected by wire, through which the bounced signal passes?

This is very helpful. It seems possible to test whether one-way light speed is the same in opposite directions: ethicsblackhole.blogspot.com/2024/05/proposed-test-for-light-speed-symmetry.html

How can the ground accelerate up? Is the Earth getting larger by 9.8 meters per second per second. Seems absurd.

Assertions assertions assertions. Nail your colours to the mast so that we can know for real that you are a crank.

This is the single best video I’ve ever seen summarizing Reimannian , geometry, and general relativity. Absolutely brilliant. Bravo bravo!!

It is important to note, as pointed out in the video, that in Relativity theory, unlike the sound clock, “v” is the velocity of the moving platform with respect to a remote observer. The local observer in a light clock case does NOT experience any time dilation, EVER, unlike the sound clock example. A simple interpretation of time dilation in the light clock case is: the finite speed of light causes changing events on the moving platform to APPEAR to slow down to the remote observer, like a movie running in slow motion. It does not mean that life has slowed down on the observed platform. If the latter is true, how does a time-counter on the moving platform record slower passage of time. I guess I still don’t understand your “mechanistic explanation”.

Why is the presence of the Earth necessary in formulating the Twin Paradox? Why not assume twins of identical mass, no Earth but keep the Fixed Stars, and then reexamine the explanation. I am not sure that it will still hold water.

I don’t get the aversion to absolute simultaneity in modern physics. The existence of STR doesn’t necessarily rule it out and it would make understanding quantum mechanics a whole lot easier. Tim Maudlin is a proponent of the idea that we ought to bring back absolute simultaneity because of what we see in QM, but for whatever reason there seems to be almost an anathema against it.

I understood literally nothing.

Inertial frames are for people who don't know what acceleration means. No, I'm not going to tell you. This is a job for science fiction writers. BTW - the path of a falling object is an ellipse, not a parabola. Yes, they lied to us all.

You're right, there's a ducked up, unintuitive paradox and these physics diddlers can't explain it, and neither can I. 🤦🏻‍♂️

That's the whole point of inertia as a phenomenon. If you apply force and accelerate a thing quickly, you can pancake it. How is that not physical?! You don't need reasoning or knowledge or "feeling". There's always asymmetry. You can start with two objects, and applying force to one without it "knowing" has a physical consequence, and also can be measured, by displacement of the particles that make it up, which we call inertia. So the real question is what causes inertia? It's not what Mach thought, and it must be acceleration relative to spacetime itself, which must be a fabric of sorts, but it's not the same as the famed aether. Still, it's a physical thing, affecting matter and light, and matter affecting it. But the crucial difference between the twins is that one experiencing these effects from true acceleration through spacetime, where faster movement through space is exchanged from slower movement through time, but that's a specious difference that we observe as humans, the path through spacetime is always the same for all things. Besides, for the 0.5c twin, nothing really changes anyway, they're experiencing "time" the same as before. It's relational, and it's also an illusion of sorts, even if they physically aged less than the other twin - both twins move through space+time at the same speed always. The motion of particles in your body that constitutes bodily processes that constitute aging happened slower compared to the other twin, but those particles also moved faster through space than the first twin's. It's about total velocity, not acceleration. Acceleration is necessary to increase that velocity, and a force is necessary for that, and that results in physical effects from inertia, a property that seems to be the result of stuff interacting with spacetime, ie truly accelerating in it locally, whether it's straight or curved.

What curved spacetime??? You mean CGIs of the toilet bowl model of gravity? That's really Einstein. BTW - the bottom or your gravity well should be in the center of the mass, not UNDER IT. Every try thinking instead of letting other people do your thinking for you? The bottom of the well is zero acceleration. Gravitational acceleration and mechanical acceleration are not the same thing. Gravity produces acceleration, gravity is NOT acceleration. Inertial frames just ignore acceleration, pretending it doesn't happen. When an object falls to the ground, it stops moving, calling that acceleration is foolish. Acceleration is the increase in velocity over time. An object laying on the ground is not moving, its velocity is zero and that doesn't. change until FORCE is applied to it, not a CURVE, so gravity is countered by a FORCE, making gravity a FORCE. You people are highly paid to spout this nonsense?

You messed up. Force is an abstract concept but the effects are indeed "felt". Accelerating a body induces physical changes - if you accelerate fast enough you die, your spaceship gets crushed etc. I believe, like Einstein later did, that Mach was wrong and inertia is not the result of spooky action with the rest of the mass of the universe averaged, but with the spacetime itself, which is a real, physical thing. Time dilation happens with increasing velocity, not acceleration. But to achieve these velocities through space one must accelerate through spacetime, and this is intrinsically different than inertial movement - we can indeed "feel" it, but so can any object, in that deformations occur, small or large, depending on the degree of the rate of change (acceleration/deceleration).

So we do have a continuous one-way light source: the sun. If the one way speed of light can vary, wouldn't we expect this to manifest at times as photons stack on each other and moments where they are absent? This would cause the sun to 'flicker' similar to constructive and destructive interference vs the light being a steady stream. Surely some of the sun's light (or any star's) would do this if it was possible.

great graphics and explanations, thanks!

Indeed...but why earth accelerates toward fallen apple?

What if I told you space and time are an illusion? Your mind is shaped by evolution, and you think you can comprehend reality. 😂 Check out Donald Hoffman.

How do you not have more subscribers? These videos are unbelievable. You are amazing at teaching and the videos are such high quality. Amazing work as always!

I tend to agree with Mach on why inertia exists, but wouldn't that imply an infinite universe with infinite stuff in it? How would that work at the edges of the universe, where the averaged out mass of everything in it would not produce equal inertia in all directions, ie towards vs away from the center of all averaged mass. Meaning inertia is anisotropic, which would make light speed anisotropic too? EDIT: In 1920 (Leyden Address) and 1924 (Essay On the Ether) Einstein rejected the Machian idea that inertia arises from matter's spooky action-at-a-distance interaction with all the matter in the universe. It's only been a bit less than 100 years, so it's unsurprising that word has not gotten out. Einstein thought that gravitational and inertial effects resulted from matter's interaction with the local space in which it is embedded, and not from any action-at-a-distance. He was not able to extend GR to encompass this concept before his death, but that doesn't mean that he was wrong. Reference: www.physicsforums.com/threads/is-inertia-truly-uniform-in-all-directions.285262/ So according to Einstein you're wrong at 7:32 - the accelerating objects would feel force in the form of inertia, there's always an asymmetry between accelerating and non-accelerating objects in straight spacetime. I wonder, however, what he meant by interaction with space they're embedded in. What is this space, physically? He therefore thought spacetime was a real thing, regardless of stuff in the universe. In an empty universe, spacetime still exists according to Einstein. But then his idea of spacetime is incompatible with quantum theory...

The animations were great, but in this video, you only questioned other people's statements and still haven't answered the main question! What is the cause of gravity or, as you say, "Earth's acceleration outwards"?

I never believed time dilation

So we're back to square one and you haven't answered the original question! What causes space to flow towards Earth or Earth to accelerate upwards?

What about the explanation given by nick lucid from science asylum

so, factually one way light speed is what varies among frames of reference, not time or space ("lenght")... makes sense, as light is physical "stuff" / "real" (in an all-ever-moving universe) and spacetime isn't (mere abstract coordinates / "thoughts")

as a laymen I think in real inter actions what is shown as a cause of this attraction is a wall of caulk makings only provided by job program dollars to me the simple cause is it is a force easily seen the same as dark matter and dark energy [joking] but to me what force do we really know of what pulls things together and that would be the strong force maybe be the strong force does not stop at its proton wall but .001% carry's over to the next proton they add up over the trillions in any mass[ like stacking magnets] and on a plant mass thats is a lot of pull into the center of the mass Not the earth surface coming up to meet the apple as what happens on the other side of earth with a another apple the earth can,t move in two different directions. and seeing how the strong force is balanced maybe there are a - and a + but in two mass there is not the same balance which accounts for the attraction and for two different masses falling at the same speed maybe there is a auto balance in the two strong forces [or the other forces popping in and out] which no one can see . but you can make any mass fall faster if you add energy so there is that. so sorry for for the rambling but all should go in the trash bin and the trillion of $$$ should go how to look inside matter not paid guess work.

Well this channel has turned out to be a flop.

Does this mean that a pendulum clock depending on acceleration is superior to a light clock in determining time?

Gravitational force is acceleration, the acceleration is gravitation. Seriously? The actual question is that why is there so much trouble in accepting the fallaciousness of the special theory of relativity?

The true cause of the force F exerted by a force field on objects, which contributes to the force field is the dependency of the energy content W in the field overlay on the relative position s of the objects. F=dW/ds. dW/ds is not a gradient. It is a direction derivative and contains all non-local contributions, which depend on the relative position s. This force law applies to gravitational, electric and magnetic forces. The energy density in force fields is given by W/V = (-g²/(8πG), ε0E²/2, μ0H²/2). (V=volume), g=gravitational acceleration, G=gravitational constant, ε0=vacuum permittivity, μ0=vacuum permeability, E=electrical field strength, H=magnetic field strength.

Bro rediscovered Buddhas Tetralemma 🤔

He says that time dilation of the clocks is observer dependent. How then does GPS work? GPS relies on relativistic corrections of the clocks in satellites vs those on the ground - anywhere in the world. Your GPS tells the same time whether you are in free fall, on the ground, or in the space shuttle.

What if you take two or 3 cogged wheels. A kilometer away from each other. As light shines only between the teeth of the first cogged space then through the spinning cogged space a Kilometer apart. Can we use two maybe even 3 spinning coggs to determine the speed of light in one direction? There must be a way of timing that?

But with the SF metric which is r->inf a clearly ininertial RF, you clearly get time dilation in the g.t ST metric?????? So idk understand the same ticking clocks claim

The more of these videos i watch, the less i believe ANYONE understands GR. Ive worked through the math from Lorentz to SF and i still dont understand why still object fall down. The idea of space flowing into a mass makes NO SENSE. Is the space just being endlessly collected under non singularity mass???? Does it break apart and violate the torsion free principle???? I honestly believe no one understand wtf they are talking about

Wow I really understand everything you said in video... Very informative video.. I subscribe your chanel.. Thank you brother❤

Thank you!!!!

I love how in your videos you explain what the symbols used in GR mean in a way that I can understand. Your videos are like a Rosetta Stone for understanding the language of GR.

Уже давно одурели. Это даже не четырехмерное пространство, а четырехмерный континуум, ничего общего с пространством не имеет, к тому же псевдо, некая математическая модель придуманная для описания гравитации. И главный вопрос даже не в том верно ли подобное описание, а... После таких теорий и появляются темные материи и энергии.

I still understand it as the earth being still and spacetime "falling" into it. Why say it the other way around?

But why is earth expanding outwards? Like from the begging when it was a small rock has it been expanding outwards?

UNBELIEVABLE, THIS IS THE BEST DAMN VIDEO I HAVE SEEN IN A LONG TIME , AWESOME WORK.... GOOD FOR YOU 👏👏👏👏

rather I think it shows special relativity is interpretive rather than calculating the fact. I think the symmetry argument just show there is no clock difference when meet.

I'm still confused as to why you couldn't sync two clocks that were right next to each other together, _very slowly_ move one of the clocks a distance away from the other, and then run the test to figure out the one-way speed. Perhaps Vertasium covered this, I haven't watched his video yet.

This must be a flat earther skam Channel. The Sound clock is a complete joke as a devise to measure time. You define time as an integral/derived part of absolute space - doesn’t make Any sence.

I agree and I thought so when I watched it ages ago. In fact the closer you get to C the less the observer-dependant accelerative effects anyway.

That poor monkey