Is Acceleration Relative??? Dialect is WRONG!!!

Recently youtube channel called Dialect published video about the problems of special relativity. The main problem according to creator is the definition of absolute acceleration in current physics. In this video I will talk about this issue and argue it is not the case and we can indeed define absolute acceleration without any circular conflict like referencing it back as relative to the inertial frame.

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[dialectphilosophy]

Hey there! Someone pointed us to this video recently and we really enjoyed it! First off, we think it’s very important to have and maintain open dialogues about topics like these and think it’s great that you have brought forth concerns and criticisms.

As for our response, we’d stress two main things. First, we’re hardly the first people to argue against the definability of absolute motion: Einstein argued against it not only in that 1914 paper but also in a 1918 paper as well, stating there that it made no sense to the consistently thinking individual. Then of course others such as Herman Weyl, Mach, Leipzig, etc. all argued the same thing.

As to defining interial frames via conservation of momentum, this unfortunately suffers from the same circularity of definition. How is it you could possibly measure the true mass of the object without first invoking an inertial frame? Or likewise, how could you possibly measure the true velocity of an object without first invoking an inertial frame? As for rotating your spring, this implies you have already constructed a frame by which you have laid out a notion of euclidean space complete with Euclidean angles. Where and how and with what did you do this? You could only have constructed such a notion of space with instrumentation that could itself ever have changed when rotated, but there’s no way of knowing whether your instrumentation changed when rotated unless you have some further layer of instrumentation of which you are certain does not change when rotated. This of course leads to the absurdity of infinite regress of instrumentation.

Indeed, when you think it through carefully, you will see that no apparatus despite how cleverly conceived will ever overcome this issue — because at the end of the day, it’s about epistemological uncertainty. It’s a philosophical realization that’s unfortunately difficult for the more practical-minded physicist to grasp, or if, when they do, a realization they tend to dismiss as pedantic. But ultimately we’re going to see such considerations become utterly crucial when we seek to realize the physical meaning of theories like relativity. So we hope you’ll stay tuned to our channel.

Great job again and keep up the good work!

[jessstuart]

Dealing with accelerating (non-inertial) reference frames was the primary motivation for Einstein's General Theory of Relativity (1915).

[mayatrash]

I'm a physicist and I must say, I think dialect is still correct, even though is arguments are novel and not perfect. Mach was right. Everything is defined relative to other things. There is no calibration of anything without a zero point. There is even no symmetry if there is no equilibrium. This holds for anything. If this would be solvable the ground state problem in quantum field theory would not be a millenium problem - I suppose it's not solvable.

Every respectable physicists knows that we never have any way of measuring energy, just energy differences. And the same argument can be made for anything.

[maximusideal]

I love your concise and precise summary of Dialect's points.

[RangQuid]

I think the conservation of linear momentum is not enough to define an inertia frame, you also need the conservation of angular momentum. Because a ball rotates on a fixed axis has zero momentum but a non-zero angular momentum. But this definition intrinsically assumes that spacetime itself is uniform and isotropic.

[christianlibertarian]

I have watched that exact Dialeckt video. It definitely seemed off on the acceleration issue, but I couldn't figure out why. Thanks for clearing it up for me.

[marsglorious]

This guy was lucky to have a critic as kind and illuminating as you.

[filker]

I made a similar argument in the comment section of the Dialect video in question, and got a similar answer. My observation is that even if you can't calibrate the accelerometer in an accelerating frame of reference (which I don't believe is correct), the fact that you are accelerating will be obvious
My physics background is old - my father is a theoretical physicist but my last physics course in college was more than 40 years ago.

[AnyVideo]

I think Ive finally been able to clarify this discrepancy.

A big realization of GR was that _intertial_ mass and _gravitational_ mass are exactly the same thing. Forever, Newtonian physics took this fact for granted and it would take a much deeper theory to realize the two could be different but aren't for a natural reason.

Getting back to this question, there are indeed two notions at play: acceleration and "proper" acceleration. For example, a simple case in SR demonstrates that viewing an object with constant proper acceleration from your own rest frame results in diminishing acceleration. Consider likewise using polar coordinates to describe motion and sure enough what we believed to be acceleration in our coordinates experiences no proper acceleration.

What is now the underlying connection is that using light to define your coordinate spaces (and also the connection between local tangent spaces in GR) now gives you a definition of acceleration which coincides with proper acceleration. Since we've evolved to understand our world on this manner (space is Euclidean by equal time travel in all directions by light-ray) we overlook this coincidence.

Just remember, if you have a manifold, the choices of coordinate maps and metric is always up to the mathematician/physicist. Local tangent spaces on curved space are unrelated to eachother naturally and it is through observation we may conjecture a natural metric for spave time. And only once you have a metric can you begin to define invariants which everyone can agree upon such as whether or not a path is a geodesic.

[bazzaar]

The number of times otherwise inteligent people forget the simple expedient of changing the orient tation of a measurement device to check for an unexpected offset. Dialect looks kind of silly ploughing on after this clanger.

[juleskurianmathew]

When an accelerometer is kept on ground, there is a downward deflection. This is due to gravity. So the calibration here is already made! Now if that accelerometer starts to accelerate horizontally, there will be horizontal deflection. Both these deflections correspond to relative acceleration; not absolute acceleration. Earth is in acceleration wrt local universe. When accelerometer was at rest wrt ground, it is still in acceleration wrt local universe! And what should the deflection on accelerometer, which is difference of accelerations of accelerometer and earth correspond to? Its relative acceleration! I think dialect is correct.

[barakenat]

Perfect video! Dialect almost confused me but then I realized exactly what you explain. I wouldn't need 4 springs. Just rotate the string and see if its length is changing. In the twin paradox, even if the outgoing twin was moving in constant acceleration and at zero time turns back in constant deacceleration, a string in his direction of motion would at that single point change its length while on the earth that same string will stay the same length all the time.

[asyncasync]

Gravitational pull is almost uniform, but you still have gravitational tidal forces that can tell you the direction.

[_UnknownEntity]

From the two videos of Dialect that popped up on my feed, what I've seen is, whoever is behind that content starts off by stating an incorrect interpretation of something (e=mc² for example), and then the rest of that video is based entirely off of that axiom.

[victormd]

I still honestly dont understand one thing:

Figuring out if momentum is conserved is the same as finding the center of mass of the whole universe and seeing if it moves in uniform motion. However, supposing for a moment the center of the universe is exactly one meter above you and you begin to spin around it's axis you'll see that it is still fixed (thus momentum is conserved) but now everything is spinning around you ( and thus, are being accelerated toward you ). How can you know if it is you who is rotating or if the things are truly rotating through an axis through their center of mass?

[APaleDot]

Excellent explanation. As someone trying to learn about relativity, this dialogue is really patching up some weak spots in my understanding!

[alejosanchez]

First, we need a frame-independent definition of force, but we can't have that, so an inertial frame is more of a choice. In an inertial frame, the fundamental interactions (which are also a choice) are the only interactions that can change the momentum of a body. And so, our frames are approximately inertial frames.

[DrJamTastic]

Acceleration is defined by an unobservable geometry. Gravity is the force (not pseudoforce) that leads objects to move away from geodesic paths (as defined by an arbitrary geometry). The fact that we can choose a geometry in which this force disappears is the strong equivalence principle. We say "gravity is just geometry" but it is rather that it is relative; gravity can't be distinguished from geometry. This is why we refer to the current form of GR as a "geometric *model* of gravity.

[iliaadamanthark]

Ok, so tell me, if some planet just cross our planet at 99% the speed of the light.
Will the person on that planet be the younger one (experience slower time), or it is us that is younger?

Which planet accelerate according to absolute acceleration?

[philoso]

If you have experience calibrating a tilt meter on so call horizontal surface but not knowing it is true or not, you know what I mean when it comes to accelerometer calibration. We orientate the accelerometer under calibration in all theta and phi angles and record all data-angle data points then take a vector sum (average) to a calibrated reference.