B Is time dilation just a problem with our clocks?

[russ_watters]

I'm not trying to argue or be rude. I hope everyone understands that. I am merely saying that our time measuring devices ARE affected by gravity and movement based on laws, simply because gravity affects matter and light. Can we all agree on that? Therefore I'm saying the mechanism is affected.

No.

Sorry if this is going over old ground, but I think a more assertive approach may be more pointed and easier to recognize (I think the apparently more common phrasing/framing can be misleading):

There is a well known equation for predicting the tick rate of a pendulum clock based on changes in gravitational acceleration. There is no such equation for a quartz clock, spring clock, atomic clock, motorized clock, radioactive decay clock, etc. The tick rates of these clocks are not affected by gravity. The fact that no mechanism exists to explain the differing tick rates - besides actual varying time rates at different speeds and gravitational accelerations - is why it must be concluded that it is time itself that varies, not just faulty clocks.

 

[russ_watters]

Gravity affects all matter my friend. The atomic clock is the most accurate clock avaliable. And it is still affected. Gps satellites must constantly be calibrated back to Earth time.

Peter answered "yes" to all of these, but because of the way the answers were split, it implied something to me that is not true, which was the reason for my previous post. In the sense that local measurements/calculations can detect/explain the effect of gravity on a pendulum clock, the claim that the atomic clock is also affected by gravity is false, not true. The atomic clock is "affected" by time dilation, which is measured between frames. The pendulum clock is affected by gravitational acceleration, which can be measured locally. That's why I prefer answering "no" to the question of whether gravity affects clocks. It depends on what you are referring to and in the context of Relativity (the laws of the universe are the same in all inertial frames), I believe the answer should be "no" (for a good clock). It's time itself that is different between frames: the clock is just along for the ride.

 

[PeterDonis]

There is a well known equation for predicting the tick rate of a pendulum clock based on changes in gravitational acceleration. There is no such equation for a quartz clock, spring clock, atomic clock, motorized clock, radioactive decay clock, etc.

I think this can be phrased in a way that makes the difference even more evident. The well known equation for the tick rate of a pendulum clock expresses that tick rate in terms of...the tick rate of those other kinds of clocks. In other words, to use the concept of "tick rate" at all, we need to have the concept of an "ideal" clock, one whose tick rate is not affected by any environmental factors like changes in the gravitational field. When we say the tick rate of other clocks, like a pendulum clock, is affected by changes in the environment, we mean that we can see the change by comparing those other clocks to an ideal clock. But in order to make that comparison, we have to have an ideal clock--we have to have at least one kind of clock which we treat as not being affected by changes in the environment.

But if we then take two such ideal clocks, and send them on different paths through spacetime between the same pair of events, they will, in general, register different elapsed times. That means that even ideal clocks are "affected by gravity" in the sense that their elapsed times depend on the paths they take through spacetime.

The atomic clock is "affected" by time dilation, which is measured between frames. The pendulum clock is affected by gravitational acceleration, which can be measured locally

Yes, this is a good way of describing the distinction between a non-ideal clock and an ideal clock. An ideal clock is only affected by the length of the path it takes through spacetime, which is a global property; a non-ideal clock is affected by other things, which are locally measurable properties.

 

[russ_watters]

I think this can be phrased in a way that makes the difference even more evident. The well known equation for the tick rate of a pendulum clock expresses that tick rate in terms of...the tick rate of those other kinds of clocks. In other words, to use the concept of "tick rate" at all, we need to have the concept of an "ideal" clock, one whose tick rate is not affected by any environmental factors like changes in the gravitational field. When we say the tick rate of other clocks, like a pendulum clock, is affected by changes in the environment, we mean that we can see the change by comparing those other clocks to an ideal clock. But in order to make that comparison, we have to have an ideal clock--we have to have at least one kind of clock which we treat as not being affected by changes in the environment.

Agreed. So my point was that while we have/know a specific mechanism that causes a pendulum clock to vary vs an "ideal' clock, there are no known mechanisms for those other types of clocks that would explain-away time dilation (and in fact, if we could build a precise enough pendulum clock or generate a high enough speed or gravitational potential, it would still be noticed to be subject to time dilation as well).

But if we then take two such ideal clocks, and send them on different paths through spacetime between the same pair of events, they will, in general, register different elapsed times. That means that even ideal clocks are "affected by gravity" in the sense that their elapsed times depend on the paths they take through spacetime.

So, while I get what you mean, I just feel that to someone like the OP there may not be a clear enough difference between that and the previous passage. As long as we can make sure that they are clear that that "affected by gravity" means something different for the atomic clock than for the pendulum clock, I guess that would be ok. But I prefer not having a difference because I'm not sure in other, similar contexts we'd use that framing. Consider:

If I'm jogging in place on a barge in a river, would you say that the speed of the river affects how fast I can run? If so, I've found a loophole that should enable me to fill that barge with Olympic medals. Point being, "the speed I can run" is always measured between me and the surface I'm running on. Similarly, I propose "the tick rate of my clock" should always be stated with respect to its local frame of reference. For a cesium clock, that's always 9x10^9 hz. For a pendulum clock, you have to calculate it based on local gravity/acceleration.

Yes, this is a good way of describing the distinction between a non-ideal clock and an ideal clock. An ideal clock is only affected by the length of the path it takes through spacetime, which is a global property; a non-ideal clock is affected by other things, which are locally measurable properties.

Exactly.

 

[Dale]

t in order to make that comparison, we have to have an ideal clock--we have to have at least one kind of clock which we treat as not being affected by changes in the environment.

Muons seem to qualify. They were subjected to accelerations of something like 10^18 g and still kept time as we would expect from ideal clocks in relativity

 

[PeterDonis]

Muons seem to qualify.

Yes, agreed.

 

[Edriven]

Muons seem to qualify. They were subjected to accelerations of something like 10^18 g and still kept time as we would expect from ideal clocks in relativity

Thank you, I will research this topic more.

 

[Dale]

Thank you, I will research this topic more.

OK, here is a reference to help get you started.

Bailey et al., “Measurements of relativistic time dilation for positive and negative muons in a circular orbit,” Nature 268 (July 28, 1977) pg 301.

 

[Edriven]

OK, here is a reference to help get you started.

Bailey et al., “Measurements of relativistic time dilation for positive and negative muons in a circular orbit,” Nature 268 (July 28, 1977) pg 301.

There are a lot of factors involved but it seems plant life happens is not affected.
http://www.nasa.gov/vision/earth/technologies/aeroponic_plants.html

 

[Nugatory]

There are a lot of factors involved but it seems plant life happens is not affected.
http://www.nasa.gov/vision/earth/technologies/aeroponic_plants.html

That shows that plants grow differently and better under conditions of weightlessness. This effect is so large as to overwhelm (by many orders of magnitude) the relativistic effects that we've been discussing in this thread.

Thus, plant growth is a poor clock to use if we're trying to measure relativistic effects in Earth orbit. We need a clock that is accurate to tiny fractions of seconds.

 

[Dale]

There are a lot of factors involved but it seems plant life happens is not affected.
http://www.nasa.gov/vision/earth/technologies/aeroponic_plants.html

Even on Earth with constant gravitational influence it would be difficult to use plant growth to measure the amount of time required to bake a cake let alone the amount of time for a muon to decay.

 

[Edriven]

That shows that plants grow differently and better under conditions of weightlessness. This effect is so large as to overwhelm (by many orders of magnitude) the relativistic effects that we've been discussing in this thread.

Thus, plant growth is a poor clock to use if we're trying to measure relativistic effects in Earth orbit. We need a clock that is accurate to tiny fractions of seconds.

Thank you. I am merely looking at plants that have a short measurable life to see how it might affect life compared to life on Earth. I do agree with you. At what speed and time do you think would have to be obtained to see any results of time dilation on plants or humans?

 

[Edriven]

Even on Earth with constant gravitational influence it would be difficult to use plant growth to measure the amount of time required to bake a cake let alone the amount of time for a muon to decay.

Thank you. I was merely wondering how it would affect life. Plants might be a good subject, because of short life span and it is easily comparable to Earth life. What do I think the limits are to this time change to affect life?

 

[PeterDonis]

Plants might be a good subject

No, plants are a very poor subject, like any living thing, because there are so many factors other than the geometry of spacetime that can affect how they grow. If we really want to measure the geometry of spacetime, we need to use things that aren't affected by anything else. DaleSpam gave the decay of muons as an example; as far as we can tell, nothing else affects this except the geometry of spacetime--what path through spacetime the muons take. So they make a good test case for studying the effects of that.

 

[Edriven]

No, plants are a very poor subject, like any living thing, because there are so many factors other than the geometry of spacetime that can affect how they grow. If we really want to measure the geometry of spacetime, we need to use things that aren't affected by anything else. DaleSpam gave the decay of muons as an example; as far as we can tell, nothing else affects this except the geometry of spacetime--what path through spacetime the muons take. So they make a good test case for studying the effects of that.

I'm just wondering if time dilation isn't limited to the quantum world. A large change, requires objects to be moving very fast. Thus, its influence approaches 0, when placed in celestial world. Also gravity doesn't seem to work in quantum world. It's power approaches 0 when discussing atoms. Is this a proper comparison? Longest time for a human in space 747 days produced only a change in age of 20 milliseconds. For a human this is not even noticeable, but light can cover a lot of ground in that little time. Notice all accurate clocks except the basic clock can account for time dilation because they work in the quantum world. The proper place for time dilation to have the most effect. https://en.m.wikipedia.org/wiki/Sergei_Avdeyev

 

[PeterDonis]

I'm just wondering if time dilation isn't limited to the quantum world.

It isn't. SR and GR are classical theories.

gravity doesn't seem to work in quantum world

No, that's not correct. What is correct is that (1) we don't have a good theory of quantum gravity, and (2) we can't do experiments in the regime where we expect quantum gravity effects to be important. But effects on quantum systems of classical gravitational fields have been measured; see, for example, this:

http://www.nature.com/news/bouncing-neutrons-probe-dark-energy-on-a-table-top-1.15062

 

[Nugatory]

I'm just wondering if time dilation isn't limited to the quantum world. A large change, requires objects to be moving very fast. Thus, its influence approaches 0, when placed in celestial world.

We see it at work in the precession of the orbit of Mercury, and Mercury has a mass of more than $3\times{10}^{23}$ kilograms. So no, we aren't limited to very small objects here.

 

[Edriven]

We see it at work in the precession of the orbit of Mercury, and Mercury has a mass of more than $3\times{10}^23$ kilograms. So no, we aren't limited to very small objects here.

https://www.quora.com/Can-100-years-on-Earth-be-equal-to-about-500-years-on-Mercury-due-time-dilation
According to mr Toth, it would only have a difference of 76 seconds per 100 years from Earths time. That's not a lot. Most people wouldn't be able to gain those 76 seconds.

 

[Edriven]

It isn't. SR and GR are classical theories.
No, that's not correct. What is correct is that (1) we don't have a good theory of quantum gravity, and (2) we can't do experiments in the regime where we expect quantum gravity effects to be important. But effects on quantum systems of classical gravitational fields have been measured; see, for example, this:

http://www.nature.com/news/bouncing-neutrons-probe-dark-energy-on-a-table-top-1.15062

Thank you. Interesting article.

 

[Edriven]

https://www.quora.com/Can-100-years-on-Earth-be-equal-to-about-500-years-on-Mercury-due-time-dilation
According to mr Toth, it would only have a difference of 76 seconds per 100 years from Earths time. That's not a lot. Most people wouldn't be able to gain those 76 seconds.

Also this difference could only be measured by a quantum world clock.

 

[Dale]

I'm just wondering if time dilation isn't limited to the quantum world.

There is no reason to think that it doesn't apply microscopically.

Your plant data point illustrates the difference between good science and bad science. Plant growth, as a clock, is known to be susceptible to a wide variety of effects. Including light, temperature, soil composition and texture, nutrients, atmosphere, moisture, and gravitational acceleration. So, an experiment to test relativistic effects on plant growth would need to control for all of these non relativistic factors. If it did not control for them then it would not be a very good experiment.

Did the data you are thinking of have such controls?

 

[Edriven]

Thank you. Interesting article.

Gentlemen, it seems to me that we agree on the changing of the clock. It has been proven. My example is 3 observers (with decent vision, a wrist watch and an atomic clock): one stays on earth, one orbits Earth, and one on Mercury. A strobe is placed on the moon that flashes once per second. Assuming that the Mercury observer can see the strobe on the moon, they all make observations and record them during their journeys. They all spend a good deal of time in these observation posts. They eventually meet on Earth and discuss their findings. Neither observer appears any older than the other. Their crops in space grew better than on earth. All 3 observers report that their wrist watches and the strobe kept perfect time, while their atomic clocks only varies by milliseconds. So what should we conclude? Time was slowed down or the atomic clock lost calibration?

 

[Edriven]

There is no reason to think that it doesn't apply microscopically.

Your plant data point illustrates the difference between good science and bad science. Plant growth, as a clock, is known to be susceptible to a wide variety of effects. Including light, temperature, soil composition and texture, nutrients, atmosphere, moisture, and gravitational acceleration. So, an experiment to test relativistic effects on plant growth would need to control for all of these non relativistic factors. If it did not control for them then it would not be a very good experiment.

Did the data you are thinking of have such controls?

Please see my explanation below

 

[russ_watters]

All 3 observers report that their wrist watches and the strobe kept perfect time, while their atomic clocks only varies by milliseconds. So what should we conclude? Time was slowed down or the atomic clock lost calibration?

That doesn't resemble reality: wrist watches don't keep very good time and an atomic clock does. The atomic clock's variation would match very closely with the predictions of Relativity if someone was keeping track of its location/speed, so it would be clear that the variation was not a calibration issue.

 

[PeterDonis]

We see it at work in the precession of the orbit of Mercury

Perihelion precession isn't really due to time dilation. It's due to the fact that, to the first post-Newtonian order, the "force" of gravity has a velocity-dependent component that is not present in Newtonian gravity.

 

[PAllen]

Gentlemen, it seems to me that we agree on the changing of the clock. It has been proven. My example is 3 observers (with decent vision, a wrist watch and an atomic clock): one stays on earth, one orbits Earth, and one on Mercury. A strobe is placed on the moon that flashes once per second. Assuming that the Mercury observer can see the strobe on the moon, they all make observations and record them during their journeys. They all spend a good deal of time in these observation posts. They eventually meet on Earth and discuss their findings. Neither observer appears any older than the other. Their crops in space grew better than on earth. All 3 observers report that their wrist watches and the strobe kept perfect time, while their atomic clocks only varies by milliseconds. So what should we conclude? Time was slowed down or the atomic clock lost calibration?

Change the experiment such that the atomic clocks vary by years (make one of the observers be in a rocket accelerating away from Earth at 1g for a year - per earth, then turning around and accelerating at 1 g for a year back). Then the age of the people will vary by over a year on meet up.

 

[PeterDonis]

it seems to me that we agree on the changing of the clock.

We agree that clocks that travel on different paths through spacetime between the same pair of events can, in general, register different elapsed times, because of the geometry of spacetime. But not all of the things you mention are due to that effect, and sometimes you appear to be saying that the effect is not even present.

Neither observer appears any older than the other.

No, this is not correct; the three observers will all have different elapsed times from the start (where they all are together on Earth before the two traveling observers depart, to Earth orbit and Mercury) to the end (where they all meet up back on Earth again).

Their crops in space grew better than on earth.

As has been pointed out multiple times now, this is not due to relativistic time dilation; it's due to other factors that have a much greater impact on plant growth. Please do not keep using this example; this forum is for discussing relativity, not plant biology.

So what should we conclude? Time was slowed down or the atomic clock lost calibration?

You can easily rule out the second possibility: just compare the rates of the atomic clocks when they meet back up. If they are all sitting on Earth again, at rest relative to each other, and they all tick at the same rates again, then they kept their calibration fine.

The first possibility is correct, but it is not best viewed as "time slowing down". It is best viewed as spacetime geometry: different paths through spacetime between the same pair of events can have different lengths. This is no different than the fact that different paths on the Earth's surface between the same two points can have different lengths. It's just geometry.

 

[Dale]

Moderators note: several posts involving personal speculation have been deleted.

 

[Janus]

Gentlemen, it seems to me that we agree on the changing of the clock. It has been proven. My example is 3 observers (with decent vision, a wrist watch and an atomic clock): one stays on earth, one orbits Earth, and one on Mercury. A strobe is placed on the moon that flashes once per second. Assuming that the Mercury observer can see the strobe on the moon, they all make observations and record them during their journeys. They all spend a good deal of time in these observation posts. They eventually meet on Earth and discuss their findings. Neither observer appears any older than the other. Their crops in space grew better than on earth. All 3 observers report that their wrist watches and the strobe kept perfect time, while their atomic clocks only varies by milliseconds. So what should we conclude? Time was slowed down or the atomic clock lost calibration?

The logical conclusion is that wrist watches, plant growth and human biological aging aren't accurate enough methods of time measurement to detect a time difference of only milliseconds over an extended observation period. If they were, they would show the same time difference as the atomic clocks. Time dilation has nothing to do with what type of clock was used to make the measurement. As has been stated above, its due to differing paths through space-time.

I'll try to illustrate by an analogy. Two men start at the same point and begin traveling in different directions at an angle to each other. After each has traveled a set distance as measured by themselves, they check on the progress of the other, with each one judging said progress as being in the direction they, themselves, are traveling. Both will note that the other man has made less progress in the direction in which he is walking. It doesn't matter what method the men use to make the measurement. Tape measure, laser ranger, etc. As long as they are accurate enough so that the difference in their progress is greater than any error in their measurement method.

If one of the men then changes direction so that he is paralleling the other man's path, he will find that in terms of progress in the direction he is walking, he will be behind the other man.

This is the same type of effect that happens in Relativity, but with one of the spatial directions replaced with the time dimension, And for each man the "direction" of time is always in the direction he himself is traveling. Time dilation is not about some outside influence affecting clocks, it's about the very nature of Space and Time and how they interrelate to each other.

 

[darkchild]

I used to have difficulty with the concept of time dilation similar to what is expressed in the OP. The problem is that physics theory, or the way it is discussed or taught, is not explicit about definitions of terms. The key, as someone posted early on, is that "time is what a clock measures." In everyday speech, time is an abstract concept, so neither gravity nor any other physical mechanism can alter it. With that meaning in mind, the concept of time dilation seems absurd. In physics, however, it seems to be (only implicitly?) defined as the operation of clocks, and the operation of clocks is obviously affected by physical phenomena, so time dilation makes more sense in this sense.

Having majored in physics myself, I'm intrigued by the fact that some people seem to intuitively pick up on these implicit ideas, while others (like myself) do not. Who knows, maybe they were taught explicitly. When I look at physics threads, I see people who are discussing physics theory from inside physics theory (everything they say refers back to theory) trying to communicate with people, often laypeople, who are discussing it from outside — from a position that prioritizes their knowledge of and experience with the natural world, seeking to fit the theory in with that. The latter don't understand, and the former throw more theory at them, which may not solve the problem because the latter may lack the thought paradigm necessary to make sense of the theory. I'm certain that much of the reason people struggle to grasp physics is due to the weak bridge between these two paradigms. It's certainly the reason I struggled, and still struggle.

Physics would be much easier to understand if there was some type of movement to directly address the transition from the layperson's physical-world perspective to a physics-theory perspective. Explicit definitions, explanations for why things are modeled the way they are (rather than just expecting people to accept unrealistic-looking models without comment) and their pros and cons, explanations of why the theory defies intuition, and less reliance on explanatory metaphors. Also, better distinction between facts and non-facts. I have noticed an off-putting attitude from some posters (on this forum and others) to the effect that "this is the way things are; if you disagree, you are a crackpot," but the fact of the matter is that some details of physics models are quite arbitrary, so no, it's not quite true that such a model is simply the way things are, and saying so is likely to confuse. The whole purpose of physics is to describe the natural world; if people don't see a correspondence between the two, the discipline is failing in a crucial way.

Kudos to the earlier poster who recognized that the OP probably has a different (but not necessarily wrong) way of viewing relativity. That's the kind of engagement that promotes understanding of physics.

 

[PeterDonis]

In everyday speech, time is an abstract concept, so neither gravity nor any other physical mechanism can alter it. With that meaning in mind, the concept of time dilation seems absurd.

But this abstract concept of time turns out not to work. For example, if this abstract concept of time were correct, the clocks on the GPS satellites would not have to be adjusted in order to put out time signals that match clocks on Earth.

laypeople, who are discussing it from outside — from a position that prioritizes their knowledge of and experience with the natural world, seeking to fit the theory in with that

But this viewpoint assumes that laypeople have a consistent conception of their knowledge of and experience with the natural world, which is often not true; not that people explicitly seek out inconsistency, but that they've never been forced to consider all the implications of their unexamined beliefs. Also, it assumes (implicitly) that people's knowledge and experience with the natural world covers a wide enough range of phenomena to be applicable when modern physics is being discussed. That is certainly not true; nobody's everyday experience includes phenomena in which relativity is significant, and while many aspects of our everyday experience ultimately depend on quantum phenomena, the connection is not obvious and is not part of people's knowledge of and experience with those phenomena. (Btw, I'm not trying to point fingers here: what I've said in this paragraph describes me before I learned about relativity and QM.)

Studying physics, particularly relativity and QM, forces people to face up to the limitations of their everyday knowledge and experience, and to confront the fact that many of their unexamined beliefs and assumptions, based on the limited range of phenomena in their everyday experience, are actually wrong. Those beliefs and assumptions work reasonably well as approximations in the limited domain of everyday experience, but they break down outside that domain.

IMO one of the first things anyone who wants to learn about modern physics should do is to accept the fact that their intuitions will not work. But I do agree that people won't see the need to do this just from being given reams of theory. They need to be confronted with experimental results that simply do not match their intuitions.

The whole purpose of physics is to describe the natural world; if people don't see a correspondence between the two, the discipline is failing in a crucial way.

But if you define "the natural world" as "the world most people are familiar with from their everyday experience", which is what your statement that I quoted earlier implicitly does, then there is not a correspondence between the two. That's the problem. People come into relativity and QM expecting their intuitions to work, and they don't. They expect "time" to work the way it works in everyday experience, and then they find out that it doesn't. Well, it doesn't. There's no way around that.

Now, if someone asks, "Why doesn't time work the way it seems to work in everyday experience?", then we've made progress. We can at least try to answer that question--although "why" questions in physics always end up bottoming out somewhere; there is always a point where the answer is "because that's the way we've found things to be". But we can at least explain about proper time, and how it depends on the particular path you take through spacetime, and how people who take different paths through spacetime can have different elapsed proper times when they meet up again, and show experimental results that confirm that yes, this happens. But the person has to start by asking the question--by at least admitting the possibility that time doesn't work the way it seems to work in everyday experience. The person who keeps on saying, "But time should work this way!" in the face of all the evidence that it doesn't--well, there isn't much we can do here at PF for that person, except to keep them from interfering with the discussion.

 

[bligh]

Replying to oct 20 2015 reply to me blighcapn re Time dilatation, my comments and your's about views from inside professional physics and outside such as mine.
I use logic as my base. A physical theory can be correct as it is stated, but when aspects of it are presented to the public as dogma, such as BBT, Time dilatation, Bending space and the like I compare it to all the information at hand. Doing so, I found that my "theory" that is totally consistent with physics as I know it and with logical consistency, at least to me, is far more superior and more consistent. Granted it begins with a strong metaphysical base, but I have found that almost all modern physics fits, with the exceptions mentioned above.
When I have reponded to other posts in the past, one of the bull dogs on the watch detail has kicked me off. I am very pleased to have found my way back into these discussions. So, If you are a mentor or a guard dog, please tell that other one to back off. Sorry, can't remember his name.
BTW, are you familiar with Alton Arp, Al Kelly, Thomas E. Phipps Jr. and Lenard Ashmore, Lee Smolin? How about Fritz Zwicky? These gentlemen have some very good ideas and should not be so marginalized.
Thanks to you, Darkchild
bligh

 

[PeterDonis]

Doing so, I found that my "theory" that is totally consistent with physics as I know it and with logical consistency, at least to me, is far more superior and more consistent.

Do you have a mainstream reference (peer-reviewed paper or textbook) for your "theory"? If you don't, it's a personal theory and off limits for discussion here. The only reason I didn't give you a warning for this particular post is so that I could respond as I have just done, so you would understand why your previous posts were deleted and why future posts from you along these same lines, without references, will also be deleted.

When I have reponded to other posts in the past, one of the bull dogs on the watch detail has kicked me off.

That's because you gave references that were not valid. Al Kelly is not a valid reference.

are you familiar with Alton Arp, Al Kelly, Thomas E. Phipps Jr. and Lenard Ashmore, Lee Smolin? How about Fritz Zwicky? These gentlemen have some very good ideas and should not be so marginalized.

If you can find valid references by these gentlemen (peer-reviewed papers or textbooks) that support whatever claims you are making, by all means post links to them. But don't just throw names around without being able to back them up with valid references. That will get you a warning and a deletion. Again.

 

[darkchild]

But this abstract concept of time turns out not to work. For example, if this abstract concept of time were correct, the clocks on the GPS satellites would not have to be adjusted in order to put out time signals that match clocks on Earth.

It does work. It is intended for dealing with change, and people do that successfully with it all the time. You are illustrating what I meant about discussing physics from the outside vs. the inside. I distinguished time in physics vs. time in everyday speech — a metatheory level distinction— and here you are dragging us back into the domain of physics again. Physics theory has no bearing on the workaday concept of time, just as the physics concept of work has no bearing on the workaday concept of work (aside from probably being derived from it). They are two separate concepts with different purposes and purviews; neither is any more "correct" than the other because there is little meaningful basis upon which to compare them as such (common use of time has nothing to do with satellites or relativity). You, a mentor, can cause confusion by eliding such distinctions.

Besides that, an accurate and experimentally verifiable physics in which time is invariant is possible, so time as it is conceptualized in existing physics theory isn't correct in any absolute sense even when considered solely in the realm of physics. It is a mere model, one possible representation of physical reality; it is not a fact, and presenting it as such is misleading.

I don't know if you understood anything from my previous post. It was a criticism of communication, particularly physics pedagogy, formal and informal (like what mentors provide on this forum). I mentioned the way laypeople think as a starting point to discuss how to get them to understand physics (and the failure to do so). It wasn't a promotion of an intuitive approach to physics.

 

[Dale]

here you are dragging us back into the domain of physics

And correctly so. This is Physics Forums.

This thread is closed.