Question on Spacetime

ZorbaTehZ

Kevster wrote: »

That's not really what I was asking. Im aware of their accuracy, but what I was implying was that I don't 'buy' this notion of time moving at different paces, and that this 'concorde' example with atomic clocks can be explained by one clock simply absorbing slightly more radiation than the other (and therefore decaying faster and giving a different time).

If the experiment was repeated a number of times, I doubt the results would be consistent.

This is absolute nonsense. These experiments have been carried out multiple times and have yielded consistent results. Notwithstanding that, there are countless other experiments that have validated it (even since 1940 - google Bruno Rossi) Time dilation is indisputable.

Kevster

No need to be so melodramatic my friend. In science research, you'll have to get used to being nicer to people if you want to get far, and not being so abrupt. Thank you for your info though. I like your attempt at emphasising the 'have' by bolding it - very creative. Did you want to call me on the phone too to shout at me?

You should be open to more creative thinking instead of shutting down other peoples' views as you have done just now.

Kevin

Morbert

mangaroosh wrote:

It would be more plausible, that the effect of flying at supersonic speeds, had a physical impact on the microwave emissions of the changing electrons, as opposed to the notion that the passage of the "thing" called time actually changed, which itself is a non-sequitur.

In a similar sense that increased pressure on ice lowers its melting point, as opposed to speeding up time.

mangaroosh wrote:

the physical effect of travelling at speed, would have a physical effect on the microwave emissions.

again, however, the assumption that a clock measures something called time is questionable.

Kevster wrote: »

That's exactly the comment/answer I wanted to hear. Thanks dude.

Kevin

But that's not what relativity says. In physics jargon, General Relativity says the laws of physics are invariant under smooth one-to-one spacetime transformations. What this basically means is the laws of Physics are the same in all reference frames (i.e. from all perspectives). So we can't say speed affects a clock because the clock is stationary in its own reference frame.

Also, consider the fact that time dilation is independant of the mechanism of the clock. Whether the clock is built from gears, or vibrating atoms, or photon detection, the time dilation effect will be the same. So if our measurement of time is dependent on whatever physical mechanism we use, then the question of why time dilation does not depend on any particular mechanism must be answered.

If the experiment was repeated a number of times, I doubt the results would be consistent.

Time dilation is one of the most extensively tested phenomena. Furthermore, the local minkowski geometry of spacetime is incorporated into quantum field theory, the most accurate physical theory we have to date. We can predict the creation and annihilation of particles with great success by utilising relativity.

roosh

Morbert wrote: »

But that's not what relativity says. In physics jargon, General Relativity says the laws of physics are invariant under smooth one-to-one spacetime transformations. What this basically means is the laws of Physics are the same in all reference frames (i.e. from all perspectives). So we can't say speed affects a clock because the clock is stationary in its own reference frame.

Unfortunately my understanding of physics is relatively limited (pardon pun), so forgive me if the questions I ask sound pretty basic.

Just with regard to the laws of physics being the same in all reference frames, how would that work with regard to gravity on earth and in space? There is an obvious difference there, and this would have a physical impact on objects in either reference frame.

Also, if one were sitting in a car and it accelerates from any position, there will be a physical effect on objects that differs to someone standing still, similarly is something comes to a stop.

Morbert wrote: »

Also, consider the fact that time dilation is independant of the mechanism of the clock. Whether the clock is built from gears, or vibrating atoms, or photon detection, the time dilation effect will be the same. So if our measurement of time is dependent on whatever physical mechanism we use, then the question of why time dilation does not depend on any particular mechanism must be answered.

The answer to this question has no bearing on the existence of time. Time exists or doesn't exist, independent of this.

The assumption however remains, that time is something which can be measured, and a clock is what is used to measure it. Whereas the contention is that time is the measurement system, in the same way as a metre is not something which can be measured, rather a metre is the unit of measurement.

If clock does not measure time then the issue above is a separate one.

Just a quick question with regard to time dilation experiments, when time dilation is measured, is it measured against a third control clock, for all experiments?

Morbert wrote: »

Time dilation is one of the most extensively tested phenomena. Furthermore, the local minkowski geometry of spacetime is incorporated into quantum field theory, the most accurate physical theory we have to date. We can predict the creation and annihilation of particles with great success by utilising relativity.

The thing is though, that the "problem of time" is such that measurements of time would not necessarily change, as it is merely a confusion of cause and effect. Time could still remain as a measurement system (in its present format) and be used to explain our perception of the universe, it is just the way in which it is regarded that would change.

The effects of "time" dilation would remain, and the uses it is put to, in GPS systems would remain, we would still use clocks to measure things, but the erroneous assumption that they measure "an external phenomenon" called time would change, the consideration of time as something that can be manipulated would change.

Kevster

mangaroosh wrote: »

The thing is though, that the "problem of time" is such that measurements of time would not necessarily change, as it is merely a confusion of cause and effect. Time could still remain as a measurement system (in its present format) and be used to explain our perception of the universe, it is just the way in which it is regarded that would change.

The effects of "time" dilation would remain, and the uses it is put to, in GPS systems would remain, we would still use clocks to measure things, but the erroneous assumption that they measure "an external phenomenon" called time would change, the consideration of time as something that can be manipulated would change.

This is essentially what I have been trying to say, except mangaroosh has herewith said it more clearly than I have. I think we've been all talking about the same thing, but just not 'connecting' each others' views in the right way. I mean, I don't doubt any of what you guys are saying about time and such, but I strongly believe that what managroosh and I have been saying is also true.

Kevin

Morbert

mangaroosh wrote: »

Unfortunately my understanding of physics is relatively limited (pardon pun), so forgive me if the questions I ask sound pretty basic.

Just with regard to the laws of physics being the same in all reference frames, how would that work with regard to gravity on earth and in space? There is an obvious difference there, and this would have a physical impact on objects in either reference frame.

Also, if one were sitting in a car and it accelerates from any position, there will be a physical effect on objects that differs to someone standing still, similarly is something comes to a stop.

Let's consider the case of a "moving" car to answer this question. A person standing still will watch the car drive off some distance and return some time later. Because of this travelling, the car's clock will have ticked more slowly than the person standing still. So what about the driver of the car? He observes the the other person "moving" away from him and returning. So if all perspectives are equally valid, then he should conclude that the other person's clock ticked more slowly than his, right? The thing is, in the drivers frame of reference, there is a "uniform potential field" between himself and the other person, which will make the other person's clock tick faster than his. This means both people agree that the car's clock will tick less time, even though each person's respective clock is observed to have a constant rate of ticking.

So if you "asked" the universe which person definitively moved, there would be no answer. If we can't say which one moved, then we can't say the physics of one clock was affected by speed.

The answer to this question has no bearing on the existence of time. Time exists or doesn't exist, independent of this.

The assumption however remains, that time is something which can be measured, and a clock is what is used to measure it. Whereas the contention is that time is the measurement system, in the same way as a metre is not something which can be measured, rather a metre is the unit of measurement.

If clock does not measure time then the issue above is a separate one.

The thing is though, that the "problem of time" is such that measurements of time would not necessarily change, as it is merely a confusion of cause and effect. Time could still remain as a measurement system (in its present format) and be used to explain our perception of the universe, it is just the way in which it is regarded that would change.

The effects of "time" dilation would remain, and the uses it is put to, in GPS systems would remain, we would still use clocks to measure things, but the erroneous assumption that they measure "an external phenomenon" called time would change, the consideration of time as something that can be manipulated would change.

My post was specifically in response to the claim that "speed affects physical mechanisms." I have already said that I am open to the idea of relativity being an "effective theory", emerging from something more fundamental.

Just a quick question with regard to time dilation experiments, when time dilation is measured, is it measured against a third control clock, for all experiments?

Not that I know of. But clocks in planes is not where most of the evidence for time dilation comes from. Time dilation produces certain phenomena that can be recorded. The time dilation of high speed atoms, for example, can induce a very specific Doppler effect in laser light, which is accurately measured. It can induce longer particle decay times, which can also be detected. These observed effects are not just qualitatively predicted, but quantitatively predicted as well, and provide the bulk of time dilation evidence.

Morbert

Kevster wrote: »

This is essentially what I have been trying to say, except mangaroosh has herewith said it more clearly than I have. I think we've been all talking about the same thing, but just not 'connecting' each others' views in the right way. I mean, I don't doubt any of what you guys are saying about time and such, but I strongly believe that what managroosh and I have been saying is also true.

Kevin

You said you doubted the consistency of the result if the experiment was repeated a number of time. I said that multiple experiments have been carried out to test for time dilation, and it cannot be explained by a physical mechanism like "absorbing more radiation."

[edit-to-expand on a point]-You said in an earlier post "I cannot see how one atomic clock would show a different time unless <snip>", the thing is (and this is what is so great about relativity) if we presume that time, whatever it ultimately is, acts like a 4th dimension, then these "different time" effects follow directly from geometry, and no change of physics needs to be supposed.

Morbert

Just for the hell of it: http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

That's the wiki article on the plane experiments. The ground clock might constitute a control clock that mangaroosh asked about.

Kevster

Thanks for the link, etc. Here's a wild idea: Could the 'time' in all of thes equations not catually be accounting for time as we know it to be?; and instead is accounting/referring to something different (and as yet unmeasured) in the Universe.

The reason why I'm not giving up this argument just yet is because my common sense brain won't stop telling me the following: If I buy two rolex watches - giving one to my little pet dog - and then send him off on a roundtrip to Alpha Centauri, are you guys honestly saying that the time on my and my dog's watches will differ? I just don't see it.

Kevin

Tears in Rain

Kevster wrote: »

The reason why I'm not giving up this argument just yet is because my common sense brain won't stop telling me the following: If I buy two rolex watches - giving one to my little pet dog - and then send him off on a roundtrip to Alpha Centauri, are you guys honestly saying that the time on my and my dog's watches will differ? I just don't see it.

Kevin

That is exactly what they're saying, and it's true, even though it goes against every intuitive bone in your body. It has been shown experimentally again and again and again.

Kevster

lol... ...I'm still clutching at my last few straws here but how can two watches with identical battery-life and design actually show different times, given the previous example I mentioned? I mean, they tick at the same rate, irrespective of how fast you're moving.

Tears in Rain

Kevster wrote: »

lol... ...I'm still clutching at my last few straws here but how can two watches with identical battery-life and design actually show different times, given the previous example I mentioned? I mean, they tick at the same rate, irrespective of how fast you're moving.

Because that's what the laws of physics say what will happen.
It sounds like a weak argument, but all of our physical laws are based on observation, and if what we observe doesn't match up with what we expect from our laws, then the laws need to be modified.

Our only everyday experience is of things moving far below the speed of light, and that means prior to relativity, we had simple rules like 'time flows the same, everywhere'. When we start looking at things, we realise this isn't the case. (Well, relativity wasn't discovered from realising time flowed differently depending on the observer, but it was a consequence of modifying the laws of physics to match the observation).

If you ask 'will the watches really show different times if we move one around', the answer is yes, absolutely, our theories, and our experiments show this. There is no question.

If you ask 'how does this happen, well we can throw (well I can't, but a physicist can) a load of equations at you and say 'well, it follows logically from assuming light travels at the same speed regardless of what inertial frame you're in, and assuming the physical laws are the same regardless of what inertial frame you're in' and you can understand it or not.

If you ask 'why does this happen', there is really no better answer than 'it happens because that's how the world works'. It's a question that doesn't have an answer anymore than asking why F=ma or V=IR or 1+1=2, it's true because it's true.

Fringe

It's been proven many times that the speed of light is constant in all reference frames. In order for this to happen, space and time have to warp. This link gives a nice description. Don't forget to go onto the next page: http://casa.colorado.edu/~ajsh/sr/paradox.html

It completely goes against common sense but that's why it was so hard to grasp when Einstein first came up with it. You'll need to abandon any previous assumptions you've had before you can understand relativity.

Turtwig

"The universe is not only queerer than we suppose, it is queerer than we can suppose."
Truth is stranger than fiction and all that. Common sense applied to reality does not work.

del88

I don't think time exsists as such...it's allways now ..the abstract idea of time allows us to measure the infinite nows of the past and help us predict the infinite nows of the future.....

Tears in Rain

del88 wrote: »

I don't think time exsists as such...it's allways now ..the abstract idea of time allows us to measure the infinte nows of the past and help us predict the infinte nows of the future.....

You sound like you've taken a simple enough idea (time), and turned it into a more complicated abstraction without adding anything of value. You have some metaphysical notion of time not existing, but you recognise there are 'nows' in the future, and 'nows' in the past. You would probably say something that by moving, I'm not actually changing my position with respect to time, but rather altering my position in some future now? It just sounds like a more complicated way of saying "my position changes with respect to time".

Why not stick to the simpler notion of time? We all know what is meant when we say "in ten seconds, I will be over by the door". Even the physicists, who know what you actually mean is "in ten seconds by my watch, but not by yours". Why not regard it as being real?

del88

Tears in Rain wrote: »

Why not stick to the simpler notion of time? We all know what is meant when we say "in ten seconds, I will be over by the door". Even the physicists, who know what you actually mean is "in ten seconds by my watch, but not by yours". Why not regard it as being real?

Not sure how that contradicts what i said.....It's still only a way of predicting change in the futrure and studing change in the past.....
Did time exsist before the big bang...If not why not...

check this guy out

https://www.youtube.com/watch?v=WKsNraFxPwk

Morbert

Kevster wrote: »

lol... ...I'm still clutching at my last few straws here but how can two watches with identical battery-life and design actually show different times, given the previous example I mentioned? I mean, they tick at the same rate, irrespective of how fast you're moving.

You're still thinking along the lines of "speed causing a change in ticking". Relativity is much more fundamental than that. It says the very intervals between ticks are subject to a certain type of geometry. This geometry tells us that the movement of an object through space is connected to its movement throught time. The fewer ticks of one clock are not because that clock has physically slowed. Instead it's because that clock has ticked out a smaller amount of 'proper time' due to its path through spacetime.

Morbert

del88 wrote: »

I don't think time exsists as such...it's allways now ..the abstract idea of time allows us to measure the infinite nows of the past and help us predict the infinite nows of the future.....

"Now" is only a local concept though, even (from what can gather) in Barbour's formalism. Your "now" is different to mine; things that are happening in your "now" might not happen until the future for me.

http://en.wikipedia.org/wiki/Relativity_of_simultaneity

Morbert

del88 wrote: »

Did time exsist before the big bang...If not why not...

Is there a country north of the north pole? If not why not?

del88

Morbert wrote: »

"Now" is only a local concept though, even (from what can gather) in Barbour's formalism. Your "now" is different to mine; things that are happening in your "now" might not happen until the future for me.

http://en.wikipedia.org/wiki/Relativity_of_simultaneity

So everyone is in their own now and if i was to meet you then we woulds share a now for now and then go our seprate ways.....then if we're all in our own now that would mean time is actually running backwards just like a pole stuck in the bed of a river with the water flowing past.....we're the pole and time is the river.....(this is going to get interesting)

del88

Morbert wrote: »

Is there a country north of the north pole? If not why not?

No there's no country north of the north pole beacuse the north pole is a point on the outside of a sphear (the earth) and the term "north" refers to the direction you would face if you where to follow the shortest possible route to that point from any other given point on that sphear..(the earth)

Kevster

...just going to be pedantic here and say that the Earth is in no way a sphere. It's more like an ellipse.

Tears in Rain wrote: »

Because that's what the laws of physics say what will happen.
It sounds like a weak argument, but all of our physical laws are based on observation, and if what we observe doesn't match up with what we expect from our laws, then the laws need to be modified.

Our only everyday experience is of things moving far below the speed of light, and that means prior to relativity, we had simple rules like 'time flows the same, everywhere'. When we start looking at things, we realise this isn't the case. (Well, relativity wasn't discovered from realising time flowed differently depending on the observer, but it was a consequence of modifying the laws of physics to match the observation).

If you ask 'will the watches really show different times if we move one around', the answer is yes, absolutely, our theories, and our experiments show this. There is no question.

If you ask 'how does this happen, well we can throw (well I can't, but a physicist can) a load of equations at you and say 'well, it follows logically from assuming light travels at the same speed regardless of what inertial frame you're in, and assuming the physical laws are the same regardless of what inertial frame you're in' and you can understand it or not.

If you ask 'why does this happen', there is really no better answer than 'it happens because that's how the world works'. It's a question that doesn't have an answer anymore than asking why F=ma or V=IR or 1+1=2, it's true because it's true.

I'll have to agree with you, I suppose, but I've been taught to question everything that I see and is told to me. I don't think that saying "it happens because that's how the world works" is going to make any regular Jow Soap believe you though. in fact, that's more likely for them to not believe what you're saying. Mr. Joe Soap will just assume that it's scientists going crazy again - fabricating laws to suit their own needs.

ZorbaTehZ

The only way to convince you lot I'd say is for you to look at the mathematical derivation of it. Pay particular attention to how time is transformed between the frames and you should see how it follows - in the end quite simply actually.

Podge_irl

Kevster wrote: »

Mr. Joe Soap will just assume that it's scientists going crazy again - fabricating laws to suit their own needs.

Personally, my needs would require a physical law that transforms bad maths ideas into money. Alas, not matter how much I try to fabricate such a law it will never be true.

We "fabricate" laws to suit experiment - you know, things that actually happen.

Morbert

del88 wrote: »

No there's no country north of the north pole beacuse the north pole is a point on the outside of a sphear (the earth) and the term "north" refers to the direction you would face if you where to follow the shortest possible route to that point from any other given point on that sphear..(the earth)

So think of the big bang as a "before pole". Since time is a dimension of spacetime, when we say before, we are referring to a direction towards that pole. If we follow any timelike path in reverse, it will approach this pole. Getting to this pole and saying "what's before it?" is a little like getting to the north pole and saying "What's further north?". It's a question that, while grammatically correct, doesn't make much physical sense.

roosh

Morbert wrote: »

Let's consider the case of a "moving" car to answer this question. A person standing still will watch the car drive off some distance and return some time later. Because of this travelling, the car's clock will have ticked more slowly than the person standing still. So what about the driver of the car? He observes the the other person "moving" away from him and returning. So if all perspectives are equally valid, then he should conclude that the other person's clock ticked more slowly than his, right? The thing is, in the drivers frame of reference, there is a "uniform potential field" between himself and the other person, which will make the other person's clock tick faster than his. This means both people agree that the car's clock will tick less time, even though each person's respective clock is observed to have a constant rate of ticking.

So if you "asked" the universe which person definitively moved, there would be no answer. If we can't say which one moved, then we can't say the physics of one clock was affected by speed.



My post was specifically in response to the claim that "speed affects physical mechanisms." I have already said that I am open to the idea of relativity being an "effective theory", emerging from something more fundamental.

EDIT: just coming back to that. The thing is, we know that flying has a physical effect on the body, and indeed on an aircraft, in that these can actually change in size. It is eminently possible that these same physical effects would impact on the mechanics of a clock, in fact it would be pretty much guaranteed one would think.

So perhaps it might be the effect of altitude, seeing as there are noticebaly different physical effects with differing altitudes.

Morbert wrote: »

Not that I know of. But clocks in planes is not where most of the evidence for time dilation comes from. Time dilation produces certain phenomena that can be recorded. The time dilation of high speed atoms, for example, can induce a very specific Doppler effect in laser light, which is accurately measured. It can induce longer particle decay times, which can also be detected. These observed effects are not just qualitatively predicted, but quantitatively predicted as well, and provide the bulk of time dilation evidence.

EDIT: I don't doubt that the measurements of "time" dilation are not accurate and repeatedly tested, rather whether what is changing is actually time.



cheers for the explanations. Relativity is certainly something that I hope to get my head around further.

Still though, the basic assumption remains, that a clock is used to measure the phenomenon called time.

Examination of this assumption will show that this is not the case.

roosh

Kevster wrote: »

Thanks for the link, etc. Here's a wild idea: Could the 'time' in all of thes equations not catually be accounting for time as we know it to be?; and instead is accounting/referring to something different (and as yet unmeasured) in the Universe.

The reason why I'm not giving up this argument just yet is because my common sense brain won't stop telling me the following: If I buy two rolex watches - giving one to my little pet dog - and then send him off on a roundtrip to Alpha Centauri, are you guys honestly saying that the time on my and my dog's watches will differ? I just don't see it.

Kevin

I wouldn't doubt the results of "time" dilation, insofar as the clocks would register different times - it's remarkably well established.

Question the basic assumption however, that a clock actually measures a phenomenon called time and while the results of time dilation remain, the reason for why it has occured remains unknown - as you mentioned above.

If we take the example of an atomic clock, which measures the emissions of electrons, it is clear that what is being measured is that, and that only - electron emissions.

To say that something else is being measured is a non-sequitur.

Morbert

mangaroosh wrote: »

EDIT: just coming back to that. The thing is, we know that flying has a physical effect on the body, and indeed on an aircraft, in that these can actually change in size. It is eminently possible that these same physical effects would impact on the mechanics of a clock, in fact it would be pretty much guaranteed one would think.

So perhaps it might be the effect of altitude, seeing as there are noticebaly different physical effects with differing altitudes.

If we suppose that a specific interaction between the clock's mechanism and its environment is responsible for slower "ticking", then that effect depends specifically on that interaction. Introducing a clock with a different mechanism (say photons and mirrors), would invoke a different interaction, and hence a different effect. This means that, if physical interactions are responsible for time dilation, there is no reason why clocks which employ different mechanisms should incur the same amount of time dilation, as they are both being affected by their environment differently. Yet time dilation is independent of what clock we use. It's a massive coincidence if interactions between an environment and different clocks slow them all down to the same extent. Instead, it implies an underlying structure to what we call the passage of time.

EDIT: I don't doubt that the measurements of "time" dilation are not accurate and repeatedly tested, rather whether what is changing is actually time.

Still though, the basic assumption remains, that a clock is used to measure the phenomenon called time.

Examination of this assumption will show that this is not the case.

Everyone would agree that time is not directly measured by clocks. This is what Prof. Fink meant when he said time is not an observable. But if time is assumed to be a dimension of spacetime, then clocks quantitatively indicate distance "dt".

antiselfdual

mangaroosh wrote: »

If we take the example of an atomic clock, which measures the emissions of electrons, it is clear that what is being measured is that, and that only - electron emissions.

What property of electron emissions is being measured?