Ontology of time

[Iggy]

Iggy,

I mean that clocks in orbit are traveling at higher velocity relative to earth's center than clocks on the surface, and they slow down compared to the latter

I agree, but I still don't understand your idea of velocity because you didn't define it like I asked and you didn't answer, "how do you decide if something has high velocity?" Let me put it this way, when you say something like this:

 

Relativity has shown (and I accept) that clocks at high speed "tick" slower. I assume that all physical processes including the human aging process "proceed" more slowly at high speed.

if one of those clocks is in the Andromeda galaxy and the other is in the Milky Way then which has a higher speed and therefore ticks slower? Is it the one in the Andromeda galaxy or the one in the Milky Way? I'm assuming you don't intend to compare both to the center of the earth again.

 

You say that not all inertial frames are equal... you say the rest frame is the only "accurate" frame -- so how do you decide which is which? Which galaxy has a higher velocity and slower clocks?

 

How do you decide what velocity an inertially moving body has?

 

How do you define velocity so that you can say "this thing has a high velocity and its clock will tick slow"?

Edited July 29, 2011 by Iggy

[tar]

Owl,

 

I think "outward" from the big bang, as if it was an explosion is not a correct way to look at it.

 

In some ways we are still "where" the big bang occurred.

 

And if you notice, the cosmic background radiation is out there in all directions, not just in one direction.

 

If there were such a center, away from which everything was moving, we could probably identify which direction that was. Things would look different if we looked "in" or "out" or "across". But since things look about the same in all directions (if we kind of ignore the MilkyWay), we are still "at" the site of the big bang.

 

Regards, TAR2

[owl]

TAR,

You are off topic.

Iggy,

The clock in orbit, say on a GPS, ticks slower than one on the surface, because of its relatively higher velocity (they call it "time dilation")... and the gravitational difference (which requires adjustment), so relativity makes the corrections to give travelers (and their clocks) accurate positioning information. That is my point...clocks ticking slower with no need to claim that something called time slows down.

 

The above does not concern itself with earth's velocity relative to our galactic center or our whole system relative to Andromeda. This is a red herring. Nobody cares, and it's off topic, how our clocks' velocities, on the surface or in orbit, compare to the velocity of clocks in to Andromeda Galaxy.

[swansont]

TAR,

You are off topic.

Iggy,

The clock in orbit, say on a GPS, ticks slower than one on the surface, because of its relatively higher velocity (they call it "time dilation")... and the gravitational difference (which requires adjustment), so relativity makes the corrections to give travelers (and their clocks) accurate positioning information. That is my point...clocks ticking slower with no need to claim that something called time slows down.

What is the mechanism that causes the clock to slow down? How do you get the Lorentz transformations from this mechanism? Show your work.

[owl]

What is the mechanism that causes the clock to slow down? How do you get the Lorentz transformations from this mechanism? Show your work.

We know that a lot of situations will slow down a clock. Among them are traveling at different velocities. This is not a mechanism, but it does require differences in acceleration... a force... to get them into different velocities. Putting them in different gravitational environments will change their rate of ticking too... Still not a "mechanism" but certainly a difference in force field.

 

The ontological question this thread poses is, "What is time that 'it' slows down "dilates" in the above circumstances?

 

Show how time is verified to be such an entity. I don't believe that it is... i.e., that there is no difference between "time dilation" (assuming that time is something) and clocks slowing down (observable/empirical.)

I have no problem with the Lorentz transformations (LT) making sense of the differences between clocks as above so that we end up in the same moment in a plane heading toward a mountain and in a GPS telling the plane where it is in relation to the mountain.

(In other words, please don't keep citing LT as a proof of time dilation.)

[swansont]

We know that a lot of situations will slow down a clock. Among them are traveling at different velocities. This is not a mechanism, but it does require differences in acceleration... a force... to get them into different velocities. Putting them in different gravitational environments will change their rate of ticking too... Still not a "mechanism" but certainly a difference in force field.

 

Yes, it's not a mechanism. So the issue is unanswered by you.

 

The ontological question this thread poses is, "What is time that 'it' slows down "dilates" in the above circumstances?

 

Show how time is verified to be such an entity. I don't believe that it is... i.e., that there is no difference between "time dilation" (assuming that time is something) and clocks slowing down (observable/empirical.)

I have no problem with the Lorentz transformations (LT) making sense of the differences between clocks as above so that we end up in the same moment in a plane heading toward a mountain and in a GPS telling the plane where it is in relation to the mountain.

(In other words, please don't keep citing LT as a proof of time dilation.)

You're the only one in the conversation insisting that time is an entity. I don't see why I have to provide a description, since I'm not supporting that thesis. I observe that whatever it is, it behaves in a predictable manner, as described by relativity. If you want to discuss the ontology, go ahead. But as long as you continue to mention the physics — and, most importantly, misrepresent it — I will be calling you on it. You do this whenever you insist there is some objective measurement that is "truth," and/or that some measurements are illusions. You have yet to come up with an objective test that describes how to tell them apart.

[Iggy]

How do you decide what velocity an inertially moving body has?

 

How do you define velocity so that you can say "this thing has a high velocity and its clock will tick slow"?

Iggy,

The clock in orbit, say on a GPS, ticks slower than one on the surface, because of its relatively higher velocity (they call it "time dilation")... and the gravitational difference (which requires adjustment), so relativity makes the corrections to give travelers (and their clocks) accurate positioning information. That is my point...clocks ticking slower with no need to claim that something called time slows down.

 

The above does not concern itself with earth's velocity relative to our galactic center or our whole system relative to Andromeda. This is a red herring. Nobody cares, and it's off topic, how our clocks' velocities, on the surface or in orbit, compare to the velocity of clocks in to Andromeda Galaxy.

You have said that clocks and rulers which are not at rest give bad measures of time and distance. You have said that clocks and rulers which are at rest give the correct and accurate results. How do you know if something is at rest?

 

You honestly can't answer this?

[tar]

Owl,

 

OK, trying to get back on topic.

 

Time is something. Like distance is something. You can measure them both.

 

I am not thinking it makes any sense that time slows down, or that distances shorten.

 

Once you establish a unit of either, based on some example, then you should stick to your units and your examples, and measure everything else, in regards to them.

 

If the speed of light in a vacuum is 186,000 miles per second, measured as 186,000miles per second in any inertial frame of reference, with all the instruments involved moving in concert through space and time, then we know what a second is, and we know what a mile is. Neither one is going to change, as long as everything we are measuring is moving as we are moving.

 

If on the other hand, the thing we are measuring is moving, relative to the frame we have established, say a clock, moving away from us at .886C, then it makes sense that by the time the second hand ticks to the next position, the clock will be 165000 miles away, and due to photon lag, we won't see the tick till the photons get back to us, which I think would be, by our stay at home clock reckonings, 1.886 seconds later. So it would appear that the moving clock is ticking .53 the speed of our clock. But nowhere, here, does it seem to me that time slows down. It is moving right along for us, and moving right along for the clock speeding away. If the traveling clock where to turn around and head back, I would think the ticks would appear to be ticking faster as the frequency would be appropriately blue shifted.

 

It would seem that the clocks should be back in snyc upon return. After all, we were moving away from it, as fast as it was moving away from us, and we were moving toward it, as fast as it was moving toward us, on the way back.

 

As Iggy might say, "which clock was at rest?"

 

Regards, TAR2

[Iggy]

If the speed of light in a vacuum is 186,000 miles per second, measured as 186,000miles per second in any inertial frame of reference, with all the instruments involved moving in concert through space and time, then we know what a second is, and we know what a mile is. Neither one is going to change, as long as everything we are measuring is moving as we are moving.

 

If on the other hand, the thing we are measuring is moving, relative to the frame we have established, say a clock, moving away from us at .886C, then it makes sense that by the time the second hand ticks to the next position, the clock will be 165000 miles away, and due to photon lag, we won't see the tick till the photons get back to us, which I think would be, by our stay at home clock reckonings, 1.886 seconds later. So it would appear that the moving clock is ticking .53 the speed of our clock. But nowhere, here, does it seem to me that time slows down. It is moving right along for us, and moving right along for the clock speeding away. If the traveling clock where to turn around and head back, I would think the ticks would appear to be ticking faster as the frequency would be appropriately blue shifted.

You are confusing together signal delay, classical doppler shift, and time dilation. When the clocks reunite they do not read the same. Time dilation is an additional factor to doppler shift and signal delay.

[owl]

TAR:

Time is something. Like distance is something. You can measure them both.

 

If event duration of physical processes is "something", then I agree. It "takes time" for things to move, and everything moves.

 

Distance is the space between things, but that doesn't make the space into "something" just because we can apply numbers and distance units to how far apart things are.

 

I am not thinking it makes any sense that time slows down, or that distances shorten.

 

I agree. Clocks slow down... for many reasons. Other physical processes slow down too... probably including the aging process in humans at high velocities.

When two objects get closer together, there is a shorter distance between them (to state the obvious.) Seeing an immutable meter rod as 1/8th of a meter long would be an optical distortion due to extremely high velocity.

 

As Iggy might say, "which clock was at rest?"

 

In the GPS clocks' case (in orbit), as I've been saying, it is traveling at higher velocity relative to earth's center than clocks on the surface, so the slowing down effect requires sophisticated adjustments for positioning accuracy in "real time," i.e., the same actual moment (now) for both sets of clocks. Relativity provides the equations, which work extremely well.

(I don't know how much gravity has to do with the difference, but that is another question.)

Edited August 4, 2011 by owl

[michel123456]

If event duration of physical processes is "something", then I agree. It "takes time" for things to move, and everything moves.

 

Distance is the space between things, but that doesn't make the space into "something" just because we can apply numbers and distance units to how far apart things are.

(...)

 

Think more.

[swansont]

Seeing an immutable meter rod as 1/8th of a meter long would be an optical distortion due to extremely high velocity.

 

Which leads to the inevitable question that you perpetually ignore: how can you tell who is moving and who is at rest, to tell "truth" from "illusion"? You HAVE to address this. Really: rule 1 of speculations says you have to. It's the price of admission, to keep things above the level of bald assertion.

[owl]

Which leads to the inevitable question that you perpetually ignore: how can you tell who is moving and who is at rest, to tell "truth" from "illusion"? You HAVE to address this. Really: rule 1 of speculations says you have to. It's the price of admission, to keep things above the level of bald assertion.

I am trying to avoid constant repetition here.

EVERYTHING IS MOVING, everywhere.

So, we must define our 'universe of discourse', our focus in each case. If we want to measure a certain object, it is best to minimize variables for maximum control of one them, as in any experiment. (I started my higher education with a B.S. degree and understand the scientific method.)

Flying by an object at near light speed and trying to measure it (if we even could) would not minimize those variables. It would complicate the hell out of the experimental results, if there were such an experiment, which there is not... yet. So here we have thought experiments from extreme frames as alternatives to up close examination of what is being measured.

 

(Like the 'thought experiment' measuring the distance and travel time between sun and earth from a "photon's frame of reference." Bad idea. I think it was asserted here that "for a photon" there is no distance between sun and earth and no travel time. Then someone said... (paraphrased), no, that's not an inertial frame. Oh well, just an illustration of what an extreme frame of reference "sees.")

 

If the frame is very close to at rest with earth, for instance, as in orbit or on the surface using various measurement techniques, this will eliminate the possible (probable, I think) introduction of error due to perhaps unknown variables involved in a super high speed frame relative to earth.

The measurement of earth (and its shape) would not be done, for instance, from galactic center or from Andromeda with an expectation to minimize all unknown variables. If I may not say that this is obvious, please explain how "all thiings being equal" (variable control) applies in the situations above.

 

There is no absolute "at rest", to answer your question. There is only relatively at rest... with whatever is the object of investigation/measurement. And there are preferred frames of reference which minimize unknown variables. I can give many examples. If you are examining the properties of a microscopic organism, for example, you want it under an electron microscope on your lab bench, not flying through the lab at near 'C.'

I hope you get my point without further elaboration.

Edited August 4, 2011 by owl

[tar]

Iggy,

 

I know I am confusing things. One has to have the same assumptions, go by the same rules, and use the same conventions, to actually know what another "means" by various statements.

 

But lets say a close to light speed experiment were to accidently take a path that countered the path and rotation of the milkyway, the path of the sun, and the motions of the Earth. The experiment, might then be at rest compared to the average motion of surrounding galaxies. In which case, if the experiment was as rest, the Earth would be moving close to light speed in its rest frame, and OUR clocks would slow?

 

Regards, TAR2

[Iggy]

Flying by an object at near light speed and trying to measure it (if we even could) would not minimize those variables. It would complicate the hell out of the experimental results

Relativistic factors can be measured at low velocity.

 

There is no absolute "at rest", to answer your question. There is only relatively at rest... with whatever is the object of investigation/measurement. And there are preferred frames of reference which minimize unknown variables.

 

If you are relatively at rest with an object then the object has zero momentum. Perhaps you can understand that 'zero momentum' is not the only correct momentum for an object.

 

If you are relatively at rest and very near a GPS clock then you measure the rate of its clock at 1 second per second. Since you feel it necessary to compare the GPS clock to the center of the earth you should understand that 'one second per second' is not the only correct measure of the clock's rate.

 

If you and all your measurement equipment are at rest with points A and B then the distance [math]\overline{AB}[/math] is impossible to measure.

 

Iggy,

 

I know I am confusing things. One has to have the same assumptions, go by the same rules, and use the same conventions, to actually know what another "means" by various statements.

 

But lets say a close to light speed experiment were to accidently take a path that countered the path and rotation of the milkyway, the path of the sun, and the motions of the Earth. The experiment, might then be at rest compared to the average motion of surrounding galaxies. In which case, if the experiment was as rest, the Earth would be moving close to light speed in its rest frame, and OUR clocks would slow?

 

Regards, TAR2

I think the earth is moving about 600 km/s relative to the microwave background and the gravitational potential of earth's surface with respect to the Milky Way is 130 GJ/kg so the time dilation wouldn't be much... our clocks would run slow by a factor of 0.999997 in that frame if my quick calculations are correct.

[swansont]

I am trying to avoid constant repetition here.

EVERYTHING IS MOVING, everywhere.

So, we must define our 'universe of discourse', our focus in each case. If we want to measure a certain object, it is best to minimize variables for maximum control of one them, as in any experiment. (I started my higher education with a B.S. degree and understand the scientific method.)

Flying by an object at near light speed and trying to measure it (if we even could) would not minimize those variables. It would complicate the hell out of the experimental results, if there were such an experiment, which there is not... yet. So here we have thought experiments from extreme frames as alternatives to up close examination of what is being measured.

 

(Like the 'thought experiment' measuring the distance and travel time between sun and earth from a "photon's frame of reference." Bad idea. I think it was asserted here that "for a photon" there is no distance between sun and earth and no travel time. Then someone said... (paraphrased), no, that's not an inertial frame. Oh well, just an illustration of what an extreme frame of reference "sees.")

 

If the frame is very close to at rest with earth, for instance, as in orbit or on the surface using various measurement techniques, this will eliminate the possible (probable, I think) introduction of error due to perhaps unknown variables involved in a super high speed frame relative to earth.

The measurement of earth (and its shape) would not be done, for instance, from galactic center or from Andromeda with an expectation to minimize all unknown variables. If I may not say that this is obvious, please explain how "all thiings being equal" (variable control) applies in the situations above.

 

There is no absolute "at rest", to answer your question. There is only relatively at rest... with whatever is the object of investigation/measurement. And there are preferred frames of reference which minimize unknown variables. I can give many examples. If you are examining the properties of a microscopic organism, for example, you want it under an electron microscope on your lab bench, not flying through the lab at near 'C.'

I hope you get my point without further elaboration.

 

Time dilation and length contraction are not due to measurement error. Predictions have nothing at all to do with measurement error.

[owl]

Time dilation and length contraction are not due to measurement error. Predictions have nothing at all to do with measurement error.

How does this square with the fact that a meter rod can not be both 100 cm and 12.5 cm, the latter as seen from high speed frame of reference?

[Cap'n Refsmmat]

How does this square with the fact that a meter rod can not be both 100 cm and 12.5 cm, the latter as seen from high speed frame of reference?

It doesn't have to, since that's not a fact. The rod's spacetime interval stays constant between reference frames, though.

[swansont]

How does this square with the fact that a meter rod can not be both 100 cm and 12.5 cm, the latter as seen from high speed frame of reference?

Answered in another thread. The premise on which this is based is false. Length is not an invariant quantity.

[owl]

It doesn't have to, since that's not a fact. The rod's spacetime interval stays constant between reference frames, though.

(I'm wishing that all three of my ontology threads were in one, since time, spacetime, and the philosophy of realism vs idealism... or frame of reference based "Reality", if you prefer, are so intertwined.)

 

Since I, and many others (ISASS, in spacetime thread) do not accept "spacetime" as a given, as in relativity, using the word as an established fact is not appropriate for a discussion which disputes "spacetime intervals." It assumes a premise in dispute.

 

If space is 3-D volume and time is event duration of physical processes (not an entity woven together with 'space'), as is my argument,... and if objects have intrinsic, objective properties (realism), independent of how they are seen from different perspectives (also my argument), then solid rods and the quite rigid earth and most other objects do not vary in shape and length with whatever perspective from which they are observed.

 

Interrupted, tho not finished. Back later.

[tar]

Iggy,

 

Well thanks for that. My experiment would have no chance of finding rest (compared to the background radiation.)

 

But that does give us a rest frame to work with, doesn't it?

 

But why is it impossible to determine the distance between A and B if all your equipment, and both points are at rest?

 

Can't you put a mirror on B, bounce a light beam from A off of it, measure the seconds that elapse for the beam to return, use the fact that every second corresponds to 186,000 miles, and figure just how far A and B are from each other?

 

Regards, TAR2

[Iggy]

Well thanks for that. My experiment would have no chance of finding rest (compared to the background radiation.)

 

But that does give us a rest frame to work with, doesn't it?

 

At rest relative to the CMB.

 

...edit...

 

The CMB frame is the local frame in which the universe appears to be expanding at equal velocity in every direction. It is, like you said, the frame where all of the peculiar velocities o fgalaxies nearby tend to cancel out. Because that frame is used in cosmology to give a meaningful notion to 'cosmic time' and space as well (spatial hyperslices) it is sometimes mistaken for a privileged frame.

 

...edit...

 

But why is it impossible to determine the distance between A and B if all your equipment, and both points are at rest?

 

Can't you put a mirror on B, bounce a light beam from A off of it, measure the seconds that elapse for the beam to return, use the fact that every second corresponds to 186,000 miles, and figure just how far A and B are from each other?

 

Bouncing light there and back would measure the distance, but light is not at rest with A and B.

 

Since I, and many others (ISASS, in spacetime thread) do not accept "spacetime" as a given, as in relativity, using the word as an established fact is not appropriate for a discussion which disputes "spacetime intervals." It assumes a premise in dispute.

 

If space is 3-D volume and time is event duration of physical processes (not an entity woven together with 'space'), as is my argument,... and if objects have intrinsic, objective properties (realism), independent of how they are seen from different perspectives (also my argument), then solid rods and the quite rigid earth and most other objects do not vary in shape and length with whatever perspective from which they are observed.

 

Nature has chosen the space-time interval to be invariant and nature has chosen spatial distance to be variant. It doesn't matter if you like space-time or not, and it doesn't matter if you really want spatial distances to be invariant or not.

 

These facts follow from your definition of space and time. If you arbitrarily decide to ignore them then you are arbitrarily deciding to ignore the nature of the world around you.

Edited August 6, 2011 by Iggy

[Cap'n Refsmmat]

Since I, and many others (ISASS, in spacetime thread) do not accept "spacetime" as a given, as in relativity, using the word as an established fact is not appropriate for a discussion which disputes "spacetime intervals." It assumes a premise in dispute.

One can use spacetime intervals without assuming spacetime "exists." Simply use [math]s^2 = \Delta x^2 - c^2 \Delta t^2[/math] and pretend s means something else.

 

Regardless, you have been arguing against relativity without understanding it. I have been explaining its predictions. These predictions explain the results of experiments very well. If you want to come up with your own hypotheses:

 

If space is 3-D volume and time is event duration of physical processes (not an entity woven together with 'space'), as is my argument,... and if objects have intrinsic, objective properties (realism), independent of how they are seen from different perspectives (also my argument), then solid rods and the quite rigid earth and most other objects do not vary in shape and length with whatever perspective from which they are observed.

...you had better come up with evidence to support them. How do you account for observed time dilation and length contraction?

[swansont]

Since I, and many others (ISASS, in spacetime thread) do not accept "spacetime" as a given, as in relativity, using the word as an established fact is not appropriate for a discussion which disputes "spacetime intervals." It assumes a premise in dispute.

I was under the impression that you were interested in what time "is" rather than contending that it does not exist. If time and spatial dimensions exist, you have spacetime.

[tar]

but light is not at rest with A and B.

 

Iggy,

 

Why not? If a photon sees no time pass as it goes from A to B, and sees no distance traveled as it goes from A to B and has no Mass to move from A to B, I would say that is as "restful" as you can get. Since point A and point B are "glued" together by the photon traveling between them, and the impulse getting from A to B is what defines space and time, then the photon, the graviton, and anything else that connects point A and B at 186,000miles per second, is not a candidate for moving or being at rest, or having a relative velocity to any one particular other thing. Is it?

 

Regards, TAR2