Relativity of Motion discussion from “What is Time”

[modest]

Moderation Note: The first 111 posts of this thread have been moved from 3650 in favor of having their own topic here.

 

Modest:

 

 

Starting slow is good. I will first distinguish between apparent velocity and actual velocity. What we observe, even the image of our hand in front of our face,has signal delay, as light brings the image to the eye(and travels via the optic nerve signal to the visual cortex, where "I see my hand.")

So, as for the velocity of a particle, its apparent velocity will change with with different points from which it is considered, but its actual velocity will not.

So, applying this principle to my inquiry/challenge in previous posts:

 

Likewise "clocking" one earth revolution will give different apparent elapsed times at different altitudes, as you say, (as clocks "tick" slower or faster) but the actual duration of one earth rev will not change because of these differences in measurement.

OK so far?

Michael

 

I think you may have, yes, I'm quite sure you didn't understand my question the way I intended. This is probably my fault. I didn't ask it very clearly.

 

The speed of something like Haley's comet is not an absolute thing. It has a certain speed relative to Earth's equator and a different speed relative to the north pole. It has a different speed again relative to the sun or relative to the Milky Way. The concept of "speed" or "velocity" means that two things are being compared. The very concept inherently demands it. Do you see what I mean? It isn't enough to say that Haley's comet is going 20 thousand m/s (or whatever the number might be). You have to specify relative to what that velocity exists.

 

Do you agree with that? You really should. I'm not trying to trap you here. The above should make good sense on its own merits.

 

~modest

[Michael Mooney]

I thought we were "going slow" (and brief in each post) enough for you to give me a direct answer to:

 

"...but the actual duration of one earth rev will not change because of these differences in measurement.

OK so far?"

 

Do you agree (contradicting your previous statements) or not?

 

So, tho it seems like a diversionary tactic (for covering your backside) I will answer your comet velocity question in the context of my understanding in hope that you will reciprocate, and answer mine, repeated above.

 

 

The speed of something like Haley's comet is not an absolute thing. It has a certain speed relative to Earth's equator and a different speed relative to the north pole. It has a different speed again relative to the sun or relative to the Milky Way. The concept of "speed" or "velocity" means that two things are being compared. The very concept inherently demands it. Do you see what I mean? It isn't enough to say that Haley's comet is going 20 thousand m/s (or whatever the number might be). You have to specify relative to what that velocity exists.

 

I know you are absolutely convinced that "everything is relative," but I am asking you to suspend that belief long enough to actually hear me out.

If everything in the cosmos disappeared except Haley's comet... so there was nothing left for relative velocity reference as in your scenario above, regardless of whatever arbitrary units of time and distance (devised by Earthlings, after all) the comet would still be traveling through space (sans its previous orbit, of course) at the same rate of distance traveled per unit of time.

That's my "final answer." The comet has an absolute/objective velocity (at whatever distance per whatever elapsed time) regardless of your mandatory doctrine that it absolutely must be measured "relative" to other bodies.

 

Your turn to answer mine.

Michael

[freeztar]

If everything in the cosmos disappeared except Haley's comet... so there was nothing left for relative velocity reference as in your scenario above, regardless of whatever arbitrary units of time and distance (devised by Earthlings, after all) the comet would still be traveling through space (sans its previous orbit, of course) at the same rate of distance traveled per unit of time.

How would you know? How would you measure the distance?

In fact, to measure it at all would require an observer. And then, you'd have to put that observer somewhere in space, relative to the comet. Otherwise, without observers, the comet could be imagined to be static.

[Michael Mooney]

How would you know? How would you measure the distance?

In fact, to measure it at all would require an observer. And then, you'd have to put that observer somewhere in space, relative to the comet. Otherwise, without observers, the comet could be imagined to be static.

 

Consider it another "thought experiment" based on a philosophy that the cosmos and all its parts have an existence and a dynamic including rates of rotation/orbit, trajectories and velocities of movement independent of homosapien science and its measurements.

 

Clearly there would be no "observer" if Haley's comet was the only body left in the universe. But its "velocity" would continue the same (with trajectory tangent to its previous orbit)), going nowhere at the same rate as it was traveling when everything else disappeared.

OK?

Michael

[freeztar]

Consider it another "thought experiment" based on a philosophy that the cosmos and all its parts have an existence and a dynamic including rates of rotation/orbit, trajectories and velocities of movement independent of homosapien science and its measurements.

 

Clearly there would be no "observer" if Haley's comet was the only body left in the universe. But its "velocity" would continue the same (with trajectory tangent to its previous orbit)), going nowhere at the same rate as it was traveling when everything else disappeared.

OK?

Michael

 

But as Modest pointed out, to have a velocity, you must have two reference points. Otherwise, velocity has no meaning.

 

Velocity is a vector quantity, which means that it has both magnitude and direction. A comet traveling without an observer or any other frame of reference can not, logically, have a direction. The whole idea of direction becomes meaningless. Hence, the whole idea of velocity becomes meaningless.

 

Does this make sense?

[freeztar]

OK, I'll bite. How can both of the following statements be true?:

A:

Earth's periods of rotation and orbit vary with the point from which they are "clocked."

B:

"The Earth does not physically speed up or slow down due to our clocks."

In statement B, I was making the point that a clock, out in space, does not *dictate* the time it takes for one Earth rotation. This would be preposterous and it would mean that every time we sent a clock into space, our days here would become shorter (faster) for us on Earth. Obviously this is not the case.

 

Nonetheless, the two clocks will measure the duration of one Earth orbit differently. On its surface, it seems paradoxical: How can a planet appear to have two different rates of rotation? The paradox, as shown by Einstein et al., is not actually a paradox at all, when using SR. If you fully understand the Twin Paradox and agree with the solution to the paradox, then it should become clearer.

 

I've said dozens of times that I do understand relativity, both general and special, and understand that the resulting equations provide a vast improvement in the accuracy of all that relativity encompasses without the invention/riefication of either space or time or both together (as an actual bendable, dilating, malleable medium.)

It is clear from previous posts that you do understand the basics of relativity theory, but it is also clear that you do not fully understand relativity theory or its implications. Though, I think you are getting closer to that "aha!" moment.

 

As far as reification goes, I think it's important to know that giving properties to time, such as dilation, is merely a useful way of conceptualizing the strangeness of it all. Time, whatever "it" is, does not actually dilate, like a pupil. Spacetime does not "bend" like a plastic ruler. Though, using mathematics, it is an easy way to visualize what is happening. See here: Curvilinear coordinates - Wikipedia, the free encyclopedia

 

We say "spacetime is curved" not because we actually believe there is an "entity" called spacetime which can be bent and curved, but because the mathematics that deal with measuring events in spacetime follow curved geodesics. In other words, these descriptions that we give to space and time arise from the math (and the corresponding mathematical nomenclature), not from an underlying belief regarding their ontological reality.

 

Maybe if you understood Doctordicks equations better (I don't, btw) his perspective on relativity from a *universal* "frame of reference" and a time-transcending presentism (my "universal now") you would understand better my perspective/philosophy as well.

 

First, I'm not sure you really understand what DD is trying to demonstrate with his equations. From what I can gather, he is trying to do away with implicit assumptions in physics using a modified version of Schroedinger equation. I don't think he is promoting a "universal now", but I'll let him speak to that.

 

Second, I'm quite sure everyone understands your idea of "universal now". It is the common sense explanation that nearly all of us have prior to studying and understanding relativity. Craig mentioned this above. This is the reason people keep harping on your understanding of relativity. For, once it is understood, the idea of a "universal now" becomes obsolete. It is all relative, there is no absolute (with the exception of a preferred reference frame-as I mentioned in a previous post).

 

" ...that the cosmos and all its parts have an existence and a dynamic including rates of rotation/orbit, trajectories and velocities of movement independent of homosapien science and its measurements."

You may delete "velocities" from the above without disturbing the sense of the statement.

If we consider the "lonesome comet" thought experiment above, and we throw out velocity, then we must also throw out rotation, orbit, and trajectory. None of these have any meaning in isolation.

 

Here's a good way to think about it. Imagine that it is night time and you are standing on the Earth. Every star, galaxy, the sun, the moon, and all extraterrestrial forms of light suddenly disappear, the sky is pitch black. How would you determine that the Earth was still rotating?

[modest]

OK, I'll bite. How can both of the following statements be true?:

A:

Earth's periods of rotation and orbit vary with the point from which they are "clocked."

B:

"The Earth does not physically speed up or slow down due to our clocks."

 

EDIT: this was my original statement A:

The duration of one earth rotation is shorter in the Dead Sea than on Mt. Everest.

 

I would tend to agree with Michael that both statements cannot be true, but this depends on what the second statement means. It doesn't specify for whom, or relative to what, the earth is supposed to be speeding up and slowing down. As I've been saying, it is meaningless to say that something has a velocity with respect to nothing at all.

 

In fact, the earth does physically speed up and slow down with respect to an observer changing altitude. The value, for example, of the velocity of Mt Everest relative to the north pole in meters per second will change depending on the gravitational potential from which it is considered (or, in which it exists. It can't very well exist in a vacuum). It will actually, really, and physically change in every meaningful way. The earth is no different from a large clock in this respect. The speed at which the minute hand goes around the clock (or that a mountain goes around the earth) actually, physically changes from one reference frame to another.

 

I think what Freeztar was saying was that the velocity (again, for example, of Mt Everest relative to the pole) does not change for a static observer if another observer changes altitude. That is certainly true and not at all incompatible with statement A above.

 

Michael, I have watched you accuse 1) a theory you don't understand, and 2) many people on this forum of reifying space. You now say that Haley's comet has an absolute velocity relative to space... relative to what you call no-thing-ness with emphasis. What logic could you hold to now? What, pray tell, is your velocity relative to nothing right now? What is nothing's velocity relative to you? After all the things you've said about the reification of space... wow!

 

~modest

[freeztar]

To clarify, I made my statement because it seemed like Michael was interpreting what Modest said, about different durations for Earth's orbit at sea level vs. Mt. Everest, as meaning that the clock actually forces/dictates/causes the difference. In other words, it's not because of a clock's readout that causes the change in rotational speed, it is the other way around (gravity causing time to move at different rates for different observers at different z (altitude) positions relative to the center of the Earth).

[modest]

Yeah, that makes sense.

 

Michael,

 

I think, at the end of the day, it is not so much a meaningful difference. Is the observer slowing down or is the earth speeding up? It depends on which way you look at it. Say, for example, that a person is falling into a black hole. As they look out at the universe everything will start speeding up. When the person gets close to the horizon they will see earth rotate billions of times in a few seconds. Is the person slowing down while falling into the hole or is the universe speeding up as it rises higher and higher in gravitational potential from the infalling observer's perspective. It's both. It is two different descriptions of the same physical situation.

 

Now, if Michael wants to say that earth never changes its speed then he will always have to consider Earth's speed relative to some fixed reference frame which never changes. The only problem with that is that it makes the question meaningless: "Does the speed at which earth rotates change from one frame to another if you only consider one frame?" That's a meaningless question.

 

So, yeah, as Q often quotes from Alice in Wonderland: "Either the well was very deep, or she fell very slowly, for she had plenty of time as she went down to look about her and to wonder what was going to happen next."

 

It's not that the clock speeds up or slows down as it is moved in altitude *or* that the earth speeds up or slows down as it becomes more distant or less distant from the clock's perspective. It's not an either / or thing: it's both, and on this I will quote Einstein in case Lewis Carroll doesn't hold the appropriate sway:

 

In terms of the theory of relativity the case may not be construed in such a way that possibly it is after all the surroundings (of the train) that experienced the change in velocity. We are not dealing here with two different, mutually exclusive hypotheses about the seat of the motion, rather with two ways, equally valid in principle, of representing the same factual situation.

Twin Paradox

It's, again, not that the clock speeds up and slows down *or* the earth speeds up and slows down. It is both depending on perspective. To argue it one way or the other is to argue the importance in admissibility of one valid perspective over another.

 

~modest

[watcher]

When the person gets close to the horizon they will see earth rotate billions of times in a few seconds. Is the person slowing down while falling into the hole or is the universe speeding up as it rises higher and higher in gravitational potential from the infalling observer's perspective. It's both. It is two different descriptions of the same physical situation.

 

i think you have perfectly revealed the fundamental objection of Michael to the assertion of relativity....

 

differing descriptions, perspective and frame of ref, even discrepancy of measurements doesn't give earth's orbit two motions at the same time. that is absurd. if that is the case, order in the universe will not be possible, the universe will be chaotic.

[watcher]

it's like being in the freeway at moderate speed, the faster one's makes you feel at rest, and the slower one you overtook makes you feel in motion.

 

so, are you at rest or in motion? you can't be both.

the earth's orbit cannot be both speeding and slowing down.

and yet it is so from different perspectives. but we can't say either that the space contraction and time dilation is just an optical illusion, it is physically real. anybody can explain this?

[Buffy]

...differing descriptions, perspective and frame of ref, even discrepancy of measurements doesn't give earth's orbit two motions at the same time. that is absurd....

Take this one more step: you're then saying that everything is an illusion, and there is never a correct perspective of the truth because no one can perceive the "universal" perspective. In essence you need to be outside the system in order to see the "truth."

 

So since such a view is unobservable and has no implications for our reality, why is it necessary to try to introduce it?

 

Reality is the leading cause of stress amongst those in touch with it, :)

Buffy

[watcher]

Take this one more step: you're then saying that everything is an illusion, and there is never a correct perspective of the truth because no one can perceive the "universal" perspective. In essence you need to be outside the system in order to see the "truth."

 

actually i w as seeking for an explanation, but since you reply this way, perhaps it is a tacit acceptance that you did believed that earth has two motions as a result of relativity.

 

i said it is absurd that earth have two motions. if this is the result of relativity, then maybe field concept is a wrong concept, just like newton's particle concept was incomplete. perhaps there's a more better concept model of reality that may describe reality more precisely ( closer to universal perspective?). one that has say ,,, no absurdities?

 

So since such a view is unobservable and has no implications for our reality, why is it necessary to try to introduce it?

 

obviously i don't share this limiting beliefs of yours. consider the vaccum, how can one say an unobservable entity like it has no implication to our reality when it is the ground state? if you're happy with relativity with all its absurdities and accept and depend it as "this is the way the world is", then i don't. i share einstein conviction that the world is comprehensible. absurdities are symptomatic that something was wrong with the theory.

 

Reality is the leading cause of stress amongst those in touch with it, :)

Buffy

 

watch out, you might get a phone call from Reality's lawyer and sue you for misrepresentation , LOL

[Buffy]

i said it is absurd that earth have two motions. if this is the result of relativity, then maybe field concept is a wrong concept, just like newton's particle concept was incomplete. perhaps there's a more better concept model of reality that may describe reality more precisely ( closer to universal perspective?). one that has say ,,, no absurdities?

So you're saying that Relativity is completely wrong about its prediction that the two observers will not have different perceptions?

 

If you wish to deny the validity of actual experiments demonstrating this aspect of relativity, you're going to have to provide some explanation for why those experiments all consistently provided incorrect observations.

So since such a view is unobservable and has no implications for our reality, why is it necessary to try to introduce it?

obviously i don't share this limiting beliefs of yours. consider the vaccum, how can one say an unobservable entity like it has no implication to our reality when it is the ground state?

Unfortunately you have misunderstood the point here. You are seeking to avoid inconsistency, yet reconciling the fact that Relativity consistent with the observations at all points within the universe means that any sort of ability to view things from the "universal" point of view--that frame of reference that is such a pesky annoyance of Relativity--must be outside the universe, and thus can never be perceived.

 

Your example of quantum foam is not at all relevant here, because while it "creates something from nothing" its operation is fully consistent with the Universe as it is. It's not "popping in from outside the Universe."

 

Thus there are only two possibilities here: either Relativity is wrong, or there's no way to perceive the Universal perspective, and thus, it's not applicable within the Universe.

 

What you see as constraining, I find quite liberating, which really ends up begging the question: even the Universal point of view were possible to perceive, what would you do with it?

...absurdities are symptomatic that something was wrong with the theory.

Not if it's a problem of perception being limited!

 

If you think you understand quantum mechanics, you don't understand quantum mechanics, :)

Buffy

[watcher]

So you're saying that Relativity is completely wrong about its prediction that the two observers will not have different perceptions?

 

If you wish to deny the validity of actual experiments demonstrating this aspect of relativity, you're going to have to provide some explanation for why those experiments all consistently provided incorrect observations.

 

no, but i do say that the predictions of relativity cannot explain by the theory of relativity. since the theory is a mathematical concept and purely derived from observed behavior of nature.

 

the word field is an invention by maxwell to name that mysterious spooky action at the distance between charges. ie. the invisible force that connects matter/particle. einstein followed suit and called the invisible force gravitational field.

 

the field is a myth, but the math is not.

 

Unfortunately you have misunderstood the point here. You are seeking to avoid inconsistency, yet reconciling the fact that Relativity consistent with the observations at all points within the universe means that any sort of ability to view things from the "universal" point of view--that frame of reference that is such a pesky annoyance of Relativity--must be outside the universe, and thus can never be perceived.

 

outside the universe is a relative term. would you consider non-local phenemena as outside the universe. if so what is its relation to a say our local universe?

 

you see, you are creating your own criteria as how the universe ought to be according to your worldview. and that is to overcome relativity, one must transcend the universe. LOL.

 

Your example of quantum foam is not at all relevant here, because while it "creates something from nothing" its operation is fully consistent with the Universe as it is. It's not "popping in from outside the Universe."

 

is there a physical law that forbids the quantum vaccum as a candidate for an absolute reference to formulate a universal principle. is not the quantum vacuum the same through out the universe? if it is unperceptible , then we have to assume that if there is any variation it is fine and smooth enough to compare to our local universe. ergo, not a bad point of reference. since it is unchanging compare to what relativity uses. the inertial frame

 

Thus there are only two possibilities here: either Relativity is wrong, or there's no way to perceive the Universal perspective, and thus, it's not applicable within the Universe.

 

relativity is incomplete. we have abandoned perception a long time ago in formulating our scientific worldview. as Einstein said, have faith in your imagination.

 

What you see as constraining, I find quite liberating, which really ends up begging the question: even the Universal point of view were possible to perceive, what would you do with it?

 

to answer the question whether earth or any particle for that matter have two motions at once.

 

Not if it's a problem of perception being limited!

 

If you think you understand quantum mechanics, you don't understand quantum mechanics, :)

Buffy

 

who said that? feyman? 30 years ago? you don't really expect me to believe that this was a statement of absolute timeless truth for all of humanity, do you?

 

to believe and hold on to such is self limiting.

[modest]

i think you have perfectly revealed the fundamental objection of Michael to the assertion of relativity....

 

I have a feeling Michael will disagree :)

 

anybody can explain this?

 

Yes we can! :hyper:

 

so, are you at rest or in motion? you can't be both.

 

In fact, and trust me on this, you can't be "at rest" and you can't be "in motion". Those are not whole and complete concepts. You must be at rest relative to something or in motion relative to something. The concept demands it—saying "I'm going 25 km/h is elliptical for saying "I'm going 25 km/h relative to X". Yes? Yes. :) There: I'm in agreement relative to myself, so I must be right

 

the earth's orbit cannot be both speeding and slowing down.

 

you are saying: "both speeding up and slowing down" relative to what? It can certainly be speeding up relative to one thing and slowing down relative to another. There seems nothing wrong with saying that earth is speeding up relative to someone near a black hole and slowing down relative to someone in empty space far from any mass. The problem that seems to be going around is that people want "velocity" and "time" or "duration" to be properties of a single entity regardless of necessary conditions these words require.

 

actually i w as seeking for an explanation, but since you reply this way, perhaps it is a tacit acceptance that you did believed that earth has two motions as a result of relativity.

 

Nothing wrong with the dialectic method, me thinks.

 

~modest

[watcher]

In fact, and trust me on this, you can't be "at rest" and you can't be "in motion". Those are not whole and complete concepts.

 

 

that is what i am saying. relativity is incomplete. based on your explanation, what it accomplished is to make this motion kinda counterintuitive and mysterious.

 

and this is the problem of relativity, it does not have a explanatory power to resolve the mystery of motion. imho