Is relativistic velocity a noticeable effect?

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Offline MikeS

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Is relativistic velocity a noticeable effect?
« on: 26/09/2011 16:13:12 »
If the Universe is expanding at a significant fraction of the speed of light then we are moving at a significant fraction of the speed of light.
Relativistic speed dilates time.  If the speed of the expansion is increasing then time is constantly dilating.  How should we interpret this in terms of what we observe?

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Offline imatfaal

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Is relativistic velocity a noticeable effect?
« Reply #1 on: 26/09/2011 16:39:02 »
You need to get your frames of reference and relative velocities down pat.  Time dilation works on two frames - within your own frame time is never dilated, looked at from another frame then it often is.  What frame exterior to the universe are you looking from?  Relative speeds between galaxies and clusters within the universe is accounted for in cosmological working where precision is required.
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Offline MikeS

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Is relativistic velocity a noticeable effect?
« Reply #2 on: 26/09/2011 17:25:33 »
If we look at a galaxy far far away and observe it to be receding at a relativistic speed then time has slowed down for it but to an individual in that galaxy they will see time progressing as normal.
If that individual observes our galaxy then they will observe time here as being slowed, while we think time is passing as normal.  So, if time has dilated at a distance and here then it must have dilated throughout the observable universe.

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Offline Soul Surfer

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Is relativistic velocity a noticeable effect?
« Reply #3 on: 26/09/2011 23:50:21 »
You are tending to think of time as some sort of absolute thing like a clock ticking throughout the universe.  This is wrong.  Time is a local phenomenon and not absolute.
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Offline MikeS

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Is relativistic velocity a noticeable effect?
« Reply #4 on: 27/09/2011 07:18:07 »
You are tending to think of time as some sort of absolute thing like a clock ticking throughout the universe.  This is wrong.  Time is a local phenomenon and not absolute.

Yes, that is how I think of time.  Time is an effect of 'something' in the universe, so it seems natural that the universe has an average 'passage' of time which can vary at any locality.

Even if this is incorrect the universe can be thought of as made up of an infinite number of space-time coordinates.  Any two of which, if they are of great distance and relative to each other are moving apart at relativistic speed.  Therefore, time must be dilating everywhere.  Whether time is absolute or not the result is the same.  Taking an average of all the 'local' times gives an 'average' time.


If my thinking on this is wrong then I would like to understand why.
« Last Edit: 27/09/2011 07:20:41 by MikeS »

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Offline Soul Surfer

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Is relativistic velocity a noticeable effect?
« Reply #5 on: 27/09/2011 09:32:21 »
Time is just a convenient way of expressing the progression of events locally and how the rest of the universe appears from this local point of view it is nothing more than this it is most definitely not the big clock that keeps the computer going.
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Offline MikeS

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Is relativistic velocity a noticeable effect?
« Reply #6 on: 27/09/2011 09:39:37 »
Time is just a convenient way of expressing the progression of events locally and how the rest of the universe appears from this local point of view it is nothing more than this it is most definitely not the big clock that keeps the computer going.

Is this a personal viewpoint or is there evidence (references) that this is true?

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Offline MikeS

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Is relativistic velocity a noticeable effect?
« Reply #7 on: 27/09/2011 09:45:05 »
If we look at a galaxy far far away and observe it to be receding at a relativistic speed then time has slowed down for it but to an individual in that galaxy they will see time progressing as normal.
If that individual observes our galaxy then they will observe time here as being slowed, while we think time is passing as normal.
  So, if time has dilated at a distance and here then it must have dilated throughout the observable universe.

Surely, this is a prediction of Relativity?

We can not know that our clocks have slowed other than by an observation over a great distance.
« Last Edit: 27/09/2011 09:55:00 by MikeS »

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Offline imatfaal

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Is relativistic velocity a noticeable effect?
« Reply #8 on: 27/09/2011 10:25:48 »
Time is dilated relative to somewhere else and is reciprocal - you cannot look at individual circumstances and sum to the whole.  If you take the universe as a frame then you need to step out - and you cannot.  If you take the milky way as your frame then other galaxies will be time dilated.  this has been shown by the evolution of primordial galactic clusters and their constituents in the distant sky being slower than those closer.
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Offline simplified

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Is relativistic velocity a noticeable effect?
« Reply #9 on: 27/09/2011 13:00:25 »
Time is dilated relative to somewhere else and is reciprocal - you cannot look at individual circumstances and sum to the whole.  If you take the universe as a frame then you need to step out - and you cannot.  If you take the milky way as your frame then other galaxies will be time dilated.  this has been shown by the evolution of primordial galactic clusters and their constituents in the distant sky being slower than those closer.
That is not surprising if distance between galaxies increases.Because photons of first event arrive faster than photons of second event to us. [:D]

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Offline imatfaal

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Is relativistic velocity a noticeable effect?
« Reply #10 on: 27/09/2011 13:24:01 »
Time is dilated relative to somewhere else and is reciprocal - you cannot look at individual circumstances and sum to the whole.  If you take the universe as a frame then you need to step out - and you cannot.  If you take the milky way as your frame then other galaxies will be time dilated.  this has been shown by the evolution of primordial galactic clusters and their constituents in the distant sky being slower than those closer.
That is not surprising if distance between galaxies increases.Because photons of first event arrive faster than photons of second event to us. [:D]

Note; I said slower, rather than at an later time.  After all other known effects are taken into account the slower pace is still there
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Offline jartza

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Is relativistic velocity a noticeable effect?
« Reply #11 on: 27/09/2011 18:05:27 »
I would say that if we look at a clock that "moves" away from us at speed 0.5 c, because of expansion of space, and a clock that moves away from us at speed 0.5 c, then we see the clock that "moves" is running faster than the clock that moves.

Because: "moving" can reach speeds like 5 c, while moving is always slower than 1 c.

If we look at a galaxy that is "moving" at speed 0.9 c, and moving at zero speed, then we see no Lorentz contraction in the galaxy. Or do we see?


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Offline simplified

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« Reply #12 on: 27/09/2011 18:13:34 »
Time is dilated relative to somewhere else and is reciprocal - you cannot look at individual circumstances and sum to the whole.  If you take the universe as a frame then you need to step out - and you cannot.  If you take the milky way as your frame then other galaxies will be time dilated.  this has been shown by the evolution of primordial galactic clusters and their constituents in the distant sky being slower than those closer.
That is not surprising if distance between galaxies increases.Because photons of first event arrive faster than photons of second event to us. [:D]

Note; I said slower, rather than at an later time.  After all other known effects are taken into account the slower pace is still there
Was I saying that 'later time'?
Photons of start of the event arrive by short way to us,photons of finish of the event arrive by long way.It increases time of our observing of flow of the event.
Even if it is taken into account,that is not the obligatory proof of twin paradox  . Only following experiment can be such proof:  a first clock and a second clock have synchronized on a satellite. Then the second clock travels to the earth (dominant mass),it exists long time on the earth, then travels back to insignificant mass(people check the result on the satellite ). The result of such experiment is  main thing to  proof of the paradox. [:P]
« Last Edit: 27/09/2011 18:50:49 by simplified »

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Offline MikeS

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Is relativistic velocity a noticeable effect?
« Reply #13 on: 28/09/2011 17:44:54 »
Time is dilated relative to somewhere else and is reciprocal - you cannot look at individual circumstances and sum to the whole.  If you take the universe as a frame then you need to step out - and you cannot.  If you take the milky way as your frame then other galaxies will be time dilated.  this has been shown by the evolution of primordial galactic clusters and their constituents in the distant sky being slower than those closer.
[/quote}

"you cannot look at individual circumstances and sum to the whole." 
Why not?  Everywhere in the universe must be subject to the passage of time.  Can you quote any references please?

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Offline imatfaal

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Is relativistic velocity a noticeable effect?
« Reply #14 on: 28/09/2011 17:59:40 »
Mike It's not called relativity just cos that's a nice name.  Measurements and calculations depend on the frame of reference.  there is no "fullgod frame" from which everything can be judged (h/t tar2 at SFN) and in which time is absolute and measurements are "correct".  A local frame on earth has no time dilation - the same point viewed from our observatory on pluto sees earthbound clocks running slow, from the edge of the oort cloud they seem slower still; which is correct?  They all are - so which are you going to put into your sum? 

Relativity Special General and Cosmological - Wolfgang Rindler
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Offline imatfaal

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Is relativistic velocity a noticeable effect?
« Reply #15 on: 28/09/2011 18:09:11 »
Time is dilated relative to somewhere else and is reciprocal - you cannot look at individual circumstances and sum to the whole.  If you take the universe as a frame then you need to step out - and you cannot.  If you take the milky way as your frame then other galaxies will be time dilated.  this has been shown by the evolution of primordial galactic clusters and their constituents in the distant sky being slower than those closer.
That is not surprising if distance between galaxies increases.Because photons of first event arrive faster than photons of second event to us. [:D]

Note; I said slower, rather than at an later time.  After all other known effects are taken into account the slower pace is still there
Was I saying that 'later time'?
Photons of start of the event arrive by short way to us,photons of finish of the event arrive by long way.It increases time of our observing of flow of the event.
Even if it is taken into account,that is not the obligatory proof of twin paradox  . Only following experiment can be such proof:  a first clock and a second clock have synchronized on a satellite. Then the second clock travels to the earth (dominant mass),it exists long time on the earth, then travels back to insignificant mass(people check the result on the satellite ). The result of such experiment is  main thing to  proof of the paradox. [:P]

No you said photons "arrive faster" - as all photons travel at c, and faster means travelling at greater velocity I decided you meant something possible. 

After all things are taken into account (the greater distance to travel for photons emitted by the end of the event etc) then these stellar evolutions seem to take longer when the galaxy is moving with high relative velocity - this timing difference is correctly explained by time dilation due to rel vel. 

on the twin paradox - there is no paradox, only a misunderstanding of sr leading to people not being able to reconcile the strange results of relativistic velocities; no experiment is needed to prove or disprove the twin paradox as there is no paradox

here is a link to the physics faq twin paradox which shows in multiple ways why it isn't a problem
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Offline MikeS

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Is relativistic velocity a noticeable effect?
« Reply #16 on: 29/09/2011 07:37:12 »
Mike It's not called relativity just cos that's a nice name.  Measurements and calculations depend on the frame of reference.  there is no "fullgod frame" from which everything can be judged (h/t tar2 at SFN) and in which time is absolute and measurements are "correct".  A local frame on earth has no time dilation - the same point viewed from our observatory on pluto sees earthbound clocks running slow, from the edge of the oort cloud they seem slower still; which is correct?  They all are - so which are you going to put into your sum? 

Relativity Special General and Cosmological - Wolfgang Rindler

My point being that from any distant reference frame time on Earth is dilated (as you mention).  The only place you can not see this directly is in the time frame of the Earth.  We can not see it because we are in that dilating time frame.  When we look outside the Earth's time frame and see all other distant time frames as dilated then that is evidence that our own time frame is dilated.

What is wrong with this argument?
« Last Edit: 29/09/2011 07:42:53 by MikeS »

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Offline yor_on

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Is relativistic velocity a noticeable effect?
« Reply #17 on: 29/09/2011 14:47:08 »
Mike, my turn on it is this. There is a universal 'time'. That 'universal' time is proven each time you ala startrek 'teleport' to that other frame of reference which clock was so slow before, according to you. Presto, as soon as you're there its 'time' will be yours, no difference measurable. And if you had a defined 'life span' counted in heartbeats, then you will find it to be the same, no matter where you go, or how 'fast' you go.

So yes, there is a 'universal clock'. But, as Soulsurfer pointed out, it's always a 'local one' and also the one that defines all other 'clocks' you can find measuring other frames. It's not related to the 'whole of the universe' as a ocean might be seen as related to the fish, it's more of a 'same' very local 'beat'. If it wasn't that way you wouldn't have a time dilation as the clock then shouldn't differ at all, no matter at what 'frame' you measure it, relative yours. But it is indeed 'universal' in that that you never will find it to give you a different beat relative, for example, your heartbeats.

SpaceTime is like a mosaic, we see the pieces represented as different 'beats' or 'clocks' relative the piece we are at, but as soon as we go there the piece will fit our clock. And there is nowhere you will live any longer. You can't change your metabolic rate by falling towards the event horizon for example. Not as measured locally, and you won't get any more heartbeats to dispose of :)
==

And it's directly related to the way radiation 'ticks', invariantly. As long as 'c' will be found to be a 'constant' locally, this will be true. And the really weird thing to consider here, that too many ignores, is that 'c' doesn't care where you are, or how fast you go. Locally the speed of light in a vacuum always will give you the same value, be it measured from a speeding rocket, or at a neutron star.

« Last Edit: 29/09/2011 14:59:21 by yor_on »
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Offline imatfaal

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Is relativistic velocity a noticeable effect?
« Reply #18 on: 29/09/2011 17:45:15 »
Mike It's not called relativity just cos that's a nice name.  Measurements and calculations depend on the frame of reference.  there is no "fullgod frame" from which everything can be judged (h/t tar2 at SFN) and in which time is absolute and measurements are "correct".  A local frame on earth has no time dilation - the same point viewed from our observatory on pluto sees earthbound clocks running slow, from the edge of the oort cloud they seem slower still; which is correct?  They all are - so which are you going to put into your sum? 

Relativity Special General and Cosmological - Wolfgang Rindler

My point being that from any distant reference frame time on Earth is dilated (as you mention).  The only place you can not see this directly is in the time frame of the Earth.  We can not see it because we are in that dilating time frame.  When we look outside the Earth's time frame and see all other distant time frames as dilated then that is evidence that our own time frame is dilated.

What is wrong with this argument?

Everything is dilated - so nothing is dilated.  There is no universal time; if everything is wrong by 1.5times then everything is correct (and you can ignore the factor).  to get the dilation to be apparent you need a set basis, and that set basis is everywhere (it is here, it is on pluto, it is on α-centuri and on the intergalactic equivalent of scotch corner - barnard's star). if we transfer our laboratory from earth to a space port orbiting barnard's star we would still see the same thing - so the easiest and most logical thing to do is to call that zero/baseline/normal.  to measure a galactic effect you need to be well o/s the galaxy - to measure a local galatic cluster effect... to measure a universal effect you need to be outside the universe, and at present that is an impossibility even to comprehend
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Offline simplified

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Is relativistic velocity a noticeable effect?
« Reply #19 on: 30/09/2011 18:18:46 »
Time is dilated relative to somewhere else and is reciprocal - you cannot look at individual circumstances and sum to the whole.  If you take the universe as a frame then you need to step out - and you cannot.  If you take the milky way as your frame then other galaxies will be time dilated.  this has been shown by the evolution of primordial galactic clusters and their constituents in the distant sky being slower than those closer.
That is not surprising if distance between galaxies increases.Because photons of first event arrive faster than photons of second event to us. [:D]

Note; I said slower, rather than at an later time.  After all other known effects are taken into account the slower pace is still there
Was I saying that 'later time'?
Photons of start of the event arrive by short way to us,photons of finish of the event arrive by long way.It increases time of our observing of flow of the event.
Even if it is taken into account,that is not the obligatory proof of twin paradox  . Only following experiment can be such proof:  a first clock and a second clock have synchronized on a satellite. Then the second clock travels to the earth (dominant mass),it exists long time on the earth, then travels back to insignificant mass(people check the result on the satellite ). The result of such experiment is  main thing to  proof of the paradox. [:P]

No you said photons "arrive faster" - as all photons travel at c, and faster means travelling at greater velocity I decided you meant something possible. 

After all things are taken into account (the greater distance to travel for photons emitted by the end of the event etc) then these stellar evolutions seem to take longer when the galaxy is moving with high relative velocity - this timing difference is correctly explained by time dilation due to rel vel. 

on the twin paradox - there is no paradox, only a misunderstanding of sr leading to people not being able to reconcile the strange results of relativistic velocities; no experiment is needed to prove or disprove the twin paradox as there is no paradox

here is a link to the physics faq twin paradox which shows in multiple ways why it isn't a problem
'Good theory does not need new experiments' sounds like 'good dictator does not need honest elections'. [:D]

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Offline MikeS

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« Reply #20 on: 03/10/2011 08:32:49 »
Mike It's not called relativity just cos that's a nice name.  Measurements and calculations depend on the frame of reference.  there is no "fullgod frame" from which everything can be judged (h/t tar2 at SFN) and in which time is absolute and measurements are "correct".  A local frame on earth has no time dilation - the same point viewed from our observatory on pluto sees earthbound clocks running slow, from the edge of the oort cloud they seem slower still; which is correct?  They all are - so which are you going to put into your sum? 

Relativity Special General and Cosmological - Wolfgang Rindler

My point being that from any distant reference frame time on Earth is dilated (as you mention).  The only place you can not see this directly is in the time frame of the Earth.  We can not see it because we are in that dilating time frame.  When we look outside the Earth's time frame and see all other distant time frames as dilated then that is evidence that our own time frame is dilated.

What is wrong with this argument?

Everything is dilated - so nothing is dilated.  There is no universal time; if everything is wrong by 1.5times then everything is correct (and you can ignore the factor). to get the dilation to be apparent you need a set basis, and that set basis is everywhere (it is here, it is on pluto, it is on α-centuri and on the intergalactic equivalent of scotch corner - barnard's star). if we transfer our laboratory from earth to a space port orbiting barnard's star we would still see the same thing - so the easiest and most logical thing to do is to call that zero/baseline/normal.  to measure a galactic effect you need to be well o/s the galaxy - to measure a local galatic cluster effect... to measure a universal effect you need to be outside the universe, and at present that is an impossibility even to comprehend

For an object traveling at relativistic speed their clocks run slower according to a distant observer.  This effect is reciprocal.  If the effect is reciprocal then how can we observe it?
Surely, we canít.  In which case how do we know the effect is real?  We can compare the passage of time at the present with the passage of time in the past to see if there is any difference.  How would this difference manifest itself?  It would show as a red or blue shift in the photons reaching us now that were emitted in the past.

A red shift would indicate that time is contracted now and was dilated in the past.
Explanation.  Light has a certain frequency  and wavelength.  Light emitted in the past had that same specific frequency and wavelength.  As time contracts, a second becomes, by comparison, shorter.  Fewer cycles arrive in a shorter second and their wavelength is longer.  This is a red-shift.  This red-shift is due to time contraction now in comparison to the past.  If the time contraction is continuous then the red-shift will increase.

A blue shift would indicate that time is dilated now and was contracted in the past.
Explanation.  Light has a certain frequency  and wavelength.  Light emitted in the past had that same specific frequency and wavelength.  As time contracts, a second becomes, by comparison, longer.  A greater number of cycles arrive in a longer second and their wavelength is shorter.  This is blue shift.  This blue-shift is due to time dilation now in comparison to the past.  If time dilation is continuous then the blue-shift will increase.



"Everything is dilated - so nothing is dilated."
You could argue that point if it didn't leave any evidence of change.  If time is continually dilating then it must have been more contracted in the past.  This would show as light from the past being red-shifted, which it is.

"There is no universal time;"
I really do not understand that argument.  Time, the same as gravity must exist everywhere in the universe.  Its dilation/contraction varies at different localities just the same as the strength of gravity varies.  If everywhere has a passage of time then the universe must have an average passage of time.

"to measure a universal effect you need to be outside the universe",
Yes, I believe if you were outside the universe you would see all clocks speeding up and you could measure this. 
If we knew that the time dilation/contraction red-shift was the only component of the cosmological red-shift then we could measure this and calculate time dilation/contraction.
Unfortunately, time dilation/contraction red-shift is 'mixed' up with the expansion red-shift (Hubble)and we have no way of knowing what proportion of the total red-shift either contributes.

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Offline damocles

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« Reply #21 on: 03/10/2011 10:06:17 »
Might I suggest that we are looking at this issue on the wrong scale of distance and time. I am not a particle physicist, but it seems to me that the ball for direct proof of special relativistic time dilation is in their court, in the first instance.

Possible experimental approach: Do a fairly typical particle type experiment to produce some very short-lived particles, moving fast, no doubt, but nowhere near the speed of light.

Now repeat the experiment in a setup where the same particles are moving close to the speed of light in the laboratory frame.

The average lifetime of the first population of particles, as measured in the LAB frame should be significantly shorter than the average lifetime of the second lot, as measured in the LAB frame.
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Offline CPT ArkAngel

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« Reply #22 on: 03/10/2011 12:04:53 »
Yes Damocles, it has been proved. What i don't know it is if the reverse frame experience has been done.

A simple experience would be to synchronize two atomic clocks on earth. An astronaut takes one of the clock on the International Space Station. A year later, an astronaut takes the other clock to the space station and compares their time. After separating the effects of general relativity and special relativity, what is the effect of special relativity?

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Offline JP

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« Reply #23 on: 03/10/2011 15:45:00 »
Might I suggest that we are looking at this issue on the wrong scale of distance and time. I am not a particle physicist, but it seems to me that the ball for direct proof of special relativistic time dilation is in their court, in the first instance.

Possible experimental approach: Do a fairly typical particle type experiment to produce some very short-lived particles, moving fast, no doubt, but nowhere near the speed of light.

Now repeat the experiment in a setup where the same particles are moving close to the speed of light in the laboratory frame.

The average lifetime of the first population of particles, as measured in the LAB frame should be significantly shorter than the average lifetime of the second lot, as measured in the LAB frame.

You're right that this would be an easy test case of SR, and indeed it has been tested!
http://en.wikipedia.org/wiki/Time_dilation_of_moving_particles

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Offline simplified

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« Reply #24 on: 03/10/2011 16:46:36 »
A traveling tiny mass (relatively of dominant mass) has a slowed time, this is proved.
 A traveling dominant mass (relatively of tiny mass) has a slowed time, this is not proved!

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Offline damocles

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« Reply #25 on: 03/10/2011 22:30:53 »
Yes Damocles, it has been proved. What i don't know it is if the reverse frame experience has been done.

A simple experience would be to synchronize two atomic clocks on earth. An astronaut takes one of the clock on the International Space Station. A year later, an astronaut takes the other clock to the space station and compares their time. After separating the effects of general relativity and special relativity, what is the effect of special relativity?

The problem with this is that general relativity is probably far more complex and less well-established than special relativity; if any anomaly were found in this experiment, which theory would it challenge? Or perhaps it would challenge neither, but a hidden assumption that the effects of the two theories could be separated and combined in an additive fashion?

A traveling tiny mass (relatively of dominant mass) has a slowed time, this is proved.
 A traveling dominant mass (relatively of tiny mass) has a slowed time, this is not proved!

mass does not enter into the treatment of time dilation in special relativity; there does not seem to be a need to treat these two cases separately, and it goes against ockham's razor to find any real need to do so. (We would never say, for example, that it has been proved for Tuesdays but not for Fridays).
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Offline yor_on

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« Reply #26 on: 03/10/2011 22:45:05 »
As I see it special relativity is about light speed and treat the universe from there. General relativity is the description of gravity, linking it to lights speed in a vacuum. And they are not separate, in reality both goes together, everywhere.
==

It's not that mysterious if you accept that we have one constant 'c' that defines a border. that border will be the exact same in Einsteins definition, no matter your (relative) speed or 'gravity'. The next step he did was to in cooperate 'gravity' into it. He realized that 'gravity' not only was a expression from invariant mass, but also from accelerations, and as I think of it, also from the geometry of space. He then linked those descriptions into SpaceTime where 'time' is a definition having two faces. One 'invariant locally', never changing its pace. and one defined from the 'time dilations' we observe comparing our 'invariant time pace' to other 'frames of reference', as a speeding spaceship. Gravity is in his descriptions a form of acceleration, in that it can produce the same 'time dilation' as a acceleration. The really tricky part, to me that is, is to see how different 'relative uniform motions' can produce time dilations on their own, relative a observer. And that one still hurts my head, sometimes it feels as if I can see why, but then it moves away from me again :).. But it has to be right, although the universe would look simpler to me if it was only gravitation/mass and accelerations that produced it.

Take a look here.
clocks so accurate that they lose or gain less than one second every 3.7 billion years.

But please ignore the Mail Online statement that you 'gain a longer life span'. That's so phreakin 'not it' that I almost want to write them a angry letter :) you only gain a 'longer life' relative the 'universe', but counting your heartbeats they will deliver you the same wherever you are, and measuring them against your wrist watch they will be the exact same. That one seems to be the most common misunderstanding of Einsteins theory of relativity there is.
« Last Edit: 03/10/2011 23:14:31 by yor_on »
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Offline JP

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« Reply #27 on: 03/10/2011 23:11:52 »
As I see it special relativity is about light speed and treat the universe from there. General relativity is the description of gravity, linking it to lights speed in a vacuum. And they are not separate, in reality both goes together, everywhere.

Special relativity is one special, simple case of general relativity.  General relativity is about comparing observations between observers undergoing arbitrary accelerations (or in the presence of gravitational fields, which are equivalent to accelerations).  GR does this by modeling space-time as curved.

Special relativity is what you get when space-time isn't curved (no gravity/accelerations between observers) or when you only care about a tiny region of space-time (very small volume of space in a very short time) in which case the curved space-time looks pretty much flat.

They both postulate the speed of light being constant.  GR needs more postulates about gravity and accelerations.

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« Reply #28 on: 03/10/2011 23:16:34 »
Well JP, I will stand by my definitions.

By the way NIST Pair of Aluminum Atomic Clocks Reveal Einstein's Relativity at a Personal Scale This one is the source of the link I gave above. And what it says should help you understand what a 'time dilation' really is. You need to consider that if you were there you would see those clocks desynchronize in front of your eyes. If you at the same time measured your heartbeats against your wrist watch you would find it to be 'invariant', no matter if you laid on the floor, or stood up while observing those clocks.

A 'time dilation' will always be a description between frames of reference, but nowhere will it influence your own 'intrinsic/inherent' time flow. You don't age 'slower' (although you you will see the universe 'speed up'.) by staying in a gravity well as a neutronstar, or laying close to the Earths surface, you have only one 'life span' of heartbeats, whatever. It's quite simple.


=

Dam*, this one was harder to write than I thought :)
Had to reread it to get it right.
« Last Edit: 04/10/2011 00:21:05 by yor_on »
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Offline MikeS

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« Reply #29 on: 04/10/2011 08:31:32 »
As I see it special relativity is about light speed and treat the universe from there. General relativity is the description of gravity, linking it to lights speed in a vacuum. And they are not separate, in reality both goes together, everywhere.
==

It's not that mysterious if you accept that we have one constant 'c' that defines a border. that border will be the exact same in Einsteins definition, no matter your (relative) speed or 'gravity'. The next step he did was to in cooperate 'gravity' into it. He realized that 'gravity' not only was a expression from invariant mass, but also from accelerations, and as I think of it, also from the geometry of space. He then linked those descriptions into SpaceTime where 'time' is a definition having two faces. One 'invariant locally', never changing its pace. and one defined from the 'time dilations' we observe comparing our 'invariant time pace' to other 'frames of reference', as a speeding spaceship. Gravity is in his descriptions a form of acceleration, in that it can produce the same 'time dilation' as a acceleration. The really tricky part, to me that is, is to see how different 'relative uniform motions' can produce time dilations on their own, relative a observer. And that one still hurts my head, sometimes it feels as if I can see why, but then it moves away from me again :).. But it has to be right, although the universe would look simpler to me if it was only gravitation/mass and accelerations that produced it.

This is my take on the cause.

Why is gravity the same as acceleration and why are the effects of this the same as traveling near to the speed of light?

1)   Why is gravity the same as acceleration? 
All mass creates a gravitational field.
The field is stronger on the surface of the Earth (mass) weakening further away. 
A gravitational field dilates time.
Time dilation is greatest on the surface of the Earth with the passage of time becoming faster the greater the distance.
Acceleration contains a time factor.  Therefore, changing the passage of time (time contraction) is the same as an acceleration.
Mass, by continually moving from a state of high time dilation to low time dilation is continually accelerating (in space-time).  This is an affect of gravity.

2)   Why is traveling (at a constant velocity) near to the speed of light the same as acceleration?
          To accelerate to any speed that is an appreciable fraction of the speed of light             
            requires a large amount of energy.  The energy goes toward infinity as the   
            speed of light is approached.  Due to energy equivalence E = mc2 mass also 
            tends toward the infinite.   So even if the object is not accelerating but is 
            traveling at a significant fraction of the speed of light then it has enough mass   
            to produce a gravitational field and this is equivalent to acceleration.

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« Reply #30 on: 04/10/2011 14:34:43 »


mass does not enter into the treatment of time dilation in special relativity; there does not seem to be a need to treat these two cases separately, and it goes against ockham's razor to find any real need to do so. (We would never say, for example, that it has been proved for Tuesdays but not for Fridays).
[/quote]Day of result of clever experiment will be a holiday of science.
Illegibility is not a science. [:P]

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Offline yor_on

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« Reply #31 on: 15/10/2011 03:06:55 »
Well Mike, gravity do dilate 'time'. To Einstein this was about 'frames of reference' and how to define a same time for a 'frame'. The idea was to have some defined distance, and then send a light pulse from the exact middle of that distance to its endpoints, where you would have two 'clocks' getting synchronized, as I understands it. That would give a same 'frame of reference' time-wise, relative the clocks.

Another way, that I'm fond of, is to define all 'frames of reference' as slightly different. And as those atomic clocks showed, there most probably is no point in a positional system with the same values, when you count up all the values defining them, as position, gravity/mass, relative motion, and so 'time'.

If we only discuss gravity, I think the same will be applicable, although you then can have two 'points' defined to be the same, even if not positionally, as we can manipulate gravity by accelerations, and just kismet, sort of.

But the reason gravity dilate time seems to be the same reason accelerations do, and that reason must hinge together with 'c' and the way a 'room time geometry' get distorted with motions. So Einstein defined two types of 'accelerations', one as in motion, another as in invariant mass.
 
« Last Edit: 15/10/2011 06:05:12 by yor_on »
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« Reply #32 on: 16/10/2011 06:48:49 »
Does the same acceleration make traveler be younger(relatively of motionless twin) after long travel than after short travel?If the same acceleration does different results then what is main cause of slowing of time?
« Last Edit: 16/10/2011 10:07:27 by simplified »

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« Reply #33 on: 20/10/2011 16:41:00 »
The further a galaxy is away from us the faster it is receding and there is no limit on that speed. Galaxies can be observed which are moving away from us faster the speed of light. And this does not violate the 1st postulate of relativity.

As to the question Relativistic mass increase at slow speeds, Gerald Gabrielse, Am. J. Phys. 63(6), June 1995

I can e-mail that to anyone who wishes to read it, or I culd temporarily post it somewhere on my website for your viewing pleasure. :)

Best wishes

Pete

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Offline damocles

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« Reply #34 on: 20/10/2011 18:29:19 »
...(snip)...Galaxies can be observed which are moving away from us faster the speed of light. ...(snip)...

Umm... there is a problem here, at the very least a semantic one. I would not have been fazed by "... There is evidence for the existence of galaxies which ...", But "...Galaxies can be observed which ..." is surely impossible by definition! For something "to be observed", light from some part of the em spectrum must have left it and reached us or our instrument to be detected, because that is the basic definition of "observed". If an object is receding from us faster than the speed of light, how could that possibly happen?
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Offline imatfaal

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« Reply #35 on: 21/10/2011 13:36:16 »
                         
...(snip)...Galaxies can be observed which are moving away from us faster the speed of light. ...(snip)...

Umm... there is a problem here, at the very least a semantic one. I would not have been fazed by "... There is evidence for the existence of galaxies which ...", But "...Galaxies can be observed which ..." is surely impossible by definition! For something "to be observed", light from some part of the em spectrum must have left it and reached us or our instrument to be detected, because that is the basic definition of "observed". If an object is receding from us faster than the speed of light, how could that possibly happen?


Agree - there exist gaps between galaxies that according to our theories are increasing faster than light speed.  The furthest we can observe is the CMB and the distance to that is not increasing at above light speed. 
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Offline damocles

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« Reply #36 on: 21/10/2011 14:59:55 »
But I wonder if that can work. Because if I see object A moving South at speed 0.9c and object B moving North at 0.8c, then special relativity tells us that their relative speed is not vA +vB, but vA + vB - vA.vB/c2

That is, they are moving apart not at 1.7c but at 1.7 - 0.72 = 0.98c
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Offline JP

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« Reply #37 on: 21/10/2011 15:14:04 »
There's 2 reasons why it can happen.

First, special relativity tells you that the space between objects can't increase at faster than the speed of light, but in special relativity, space itself is static.  In general relativity, nothing in static space can move apart faster than the speed of light, but if space itself is expanding, they can. 

Think of it as two ants on the surface of a balloon.  Each ant has a built in speed limit--the fastest it's legs can move.  If the balloon isn't being inflated, they can move apart at some maximal speed determined by their individual maximal speeds.  If you inflate the balloon while they're moving apart, the space between them increases at faster than the rate they'd expect just based on their own maximal speeds--because the balloon itself has expanded.  But if they look down at the patch of balloon right below them, they're still moving over it at their maximal speed.  Similarly, nothing can move over a small patch of space faster than the speed of light, but over large regions, the expansion of space can cause things to move apart faster than the speed of light.

Second, the light reaching us from distant galaxies is light they emitted a while ago.  If they are receding at faster than the speed of light, then light they're emitting now will never reach us--they've gone beyond the visible horizon of the universe.

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Offline MikeS

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« Reply #38 on: 22/10/2011 06:59:12 »
What does the creation of space mean?  What is it that is being created?

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« Reply #39 on: 23/10/2011 18:22:10 »
What does the creation of space mean?  What is it that is being created?
The space is totality of distances. Distance  is ability of reduction and increasing . [:P]
« Last Edit: 23/10/2011 18:46:49 by simplified »

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Offline simplified

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« Reply #40 on: 23/10/2011 18:41:37 »
I would say that if we look at a clock that "moves" away from us at speed 0.5 c, because of expansion of space, and a clock that moves away from us at speed 0.5 c, then we see the clock that "moves" is running faster than the clock that moves.

Because: "moving" can reach speeds like 5 c, while moving is always slower than 1 c.

If we look at a galaxy that is "moving" at speed 0.9 c, and moving at zero speed, then we see no Lorentz contraction in the galaxy. Or do we see?


I don't see. Gravitation of our galaxy does not make kinematic slowing of time of such very far galaxy.
« Last Edit: 23/10/2011 18:43:19 by simplified »

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Offline damocles

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« Reply #41 on: 23/10/2011 23:30:27 »
I would say that if we look at a clock that "moves" away from us at speed 0.5 c, because of expansion of space, and a clock that moves away from us at speed 0.5 c, then we see the clock that "moves" is running faster than the clock that moves.

Because: "moving" can reach speeds like 5 c, while moving is always slower than 1 c.

If we look at a galaxy that is "moving" at speed 0.9 c, and moving at zero speed, then we see no Lorentz contraction in the galaxy. Or do we see?


I don't see. Gravitation of our galaxy does not make kinematic slowing of time of such very far galaxy.

It is important to remember that the Lorentz contraction is a 1-dimensional thing: it applies only in the direction of motion: towards or away. It is also the case that our observation of the extent of something is a two-dimensional thing: we can observe up, down, left, right, but not towards, away. So we have no means of directly observing whether the contraction applies or not (to the component of motion directly away from us) when we look at distant galaxies. The two dimensions of observation and the one dimension of contraction are orthogonal.
« Last Edit: 23/10/2011 23:33:23 by damocles »
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Offline jartza

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« Reply #42 on: 24/10/2011 11:29:57 »
I would say that if we look at a clock that "moves" away from us at speed 0.5 c, because of expansion of space, and a clock that moves away from us at speed 0.5 c, then we see the clock that "moves" is running faster than the clock that moves.

Because: "moving" can reach speeds like 5 c, while moving is always slower than 1 c.

If we look at a galaxy that is "moving" at speed 0.9 c, and moving at zero speed, then we see no Lorentz contraction in the galaxy. Or do we see?


I don't see. Gravitation of our galaxy does not make kinematic slowing of time of such very far galaxy.

It is important to remember that the Lorentz contraction is a 1-dimensional thing: it applies only in the direction of motion: towards or away. It is also the case that our observation of the extent of something is a two-dimensional thing: we can observe up, down, left, right, but not towards, away. So we have no means of directly observing whether the contraction applies or not (to the component of motion directly away from us) when we look at distant galaxies. The two dimensions of observation and the one dimension of contraction are orthogonal.


I was thinking about a large mirror to help us see what the side of a receding galaxy looks like.

But now I can see that universe is transparent enough, so we can see that receding galaxies are not packed together in the towards-away dimension.

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Offline damocles

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« Reply #43 on: 24/10/2011 13:11:01 »
Perhaps I am partly blind, but I do not "see" any way we can know about the towards, away dimension of a distant object by direct observation if we are unable to change our position. Even the normal artist's rules of perspective are not really knowing, because they make assumptions about the shapes of the objects we are looking at. How can we possibly "see" that distant galaxies are not packed close together in layers (apart from different red shifts, etc,, which is again making assumptions)?
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Offline simplified

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« Reply #44 on: 24/10/2011 14:53:38 »
I would say that if we look at a clock that "moves" away from us at speed 0.5 c, because of expansion of space, and a clock that moves away from us at speed 0.5 c, then we see the clock that "moves" is running faster than the clock that moves.

Because: "moving" can reach speeds like 5 c, while moving is always slower than 1 c.

If we look at a galaxy that is "moving" at speed 0.9 c, and moving at zero speed, then we see no Lorentz contraction in the galaxy. Or do we see?


I don't see. Gravitation of our galaxy does not make kinematic slowing of time of such very far galaxy.

It is important to remember that the Lorentz contraction is a 1-dimensional thing: it applies only in the direction of motion: towards or away. It is also the case that our observation of the extent of something is a two-dimensional thing: we can observe up, down, left, right, but not towards, away. So we have no means of directly observing whether the contraction applies or not (to the component of motion directly away from us) when we look at distant galaxies. The two dimensions of observation and the one dimension of contraction are orthogonal.


I was thinking about a large mirror to help us see what the side of a receding galaxy looks like.

But now I can see that universe is transparent enough, so we can see that receding galaxies are not packed together in the towards-away dimension.
Very interesting idea. If speed reduces distance then the farthest galaxies are ten times closer.  [:)]
Relativity is ridiculous theory.

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Offline Pmb

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« Reply #45 on: 24/10/2011 18:13:29 »
Quote from: damocles
[...(snip)...Galaxies can be observed which are moving away from us faster the speed of light. ...(snip)...
It's well known among Astro physicists that there is an event horizon, which means that galaxies exist beyond that horizon. Galaxies which are closer to the horizon can be observed.
« Last Edit: 24/10/2011 18:15:59 by Pmb »

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Offline JP

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« Reply #46 on: 25/10/2011 00:53:29 »
Relativity is ridiculous theory.

Fortunately for Einstein's ghost, it's better than the even more ridiculous alternatives!

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Offline thebrain13

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« Reply #47 on: 25/10/2011 06:27:42 »
I pretty much just spent all day thinking about relativity in an attempt to logically explain why the math works.

To my surprise I was able to do it using different logic and math. I just thought I'd show how the end of it worked out. (1/2(c+v)(c-v)+1/2(c-v)(c+v))=1/d^2 If you solve for d, you get the correct equation for time dilation(woo hoo!)

However I'd like to point out, my logic is a bit "etherian" if you will. The logic I used is based on the idea that time dilation is dependent on an observers motion relative to its surroundings compared to another objects motion relative to the other objects surroundings. So if there was an object traveling 3 times the speed of light in an area where everything travels 3 times the speed of light, and you were at rest relative to your surroundings, there would be no time dilation between you and the distant speedy object.






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« Reply #48 on: 26/10/2011 19:25:12 »
Relativity is ridiculous theory.

Fortunately for Einstein's ghost, it's better than the even more ridiculous alternatives!
Relativity convinces people to not make some  useful experiments. Therefore it is less ridiculous but  more dangerous for development. [:(]

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Offline JP

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« Reply #49 on: 26/10/2011 20:29:52 »
Relativity is ridiculous theory.

Fortunately for Einstein's ghost, it's better than the even more ridiculous alternatives!
Relativity convinces people to not make some  useful experiments. Therefore it is less ridiculous but  more dangerous for development. [:(]

On the contrary, it prevents people from wasting time with ridiculous experiments, thus freeing them up to make scientific progress.  Relativity has been supported by so much experimental and observational evidence that it's definitely a highly accurate model, even if it turns out to only be approximately correct. 

By the way, when experiments are done that seem to rigorously show that relativity might have a problem, they're taken very seriously, as is evident from the recent faster-than-light neutrino result.