# Naked Science Forum

## Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Ignorant Enthusiast on 12/09/2013 14:21:31

Title: Does time dilatation explain quantum effects?
Post by: Ignorant Enthusiast on 12/09/2013 14:21:31
I was reading a book the other day (Why E = MC squared) and there was some talk about time dilation, namely that if you could build a spaceship that could travel at 99.99999999% the speed of light you could travel to the Andromeda galaxy in 50 years, while 3000000 years or so would pass on earth. And this made me wonder, if as you made the trip you could watch earth as you speed away from it, would everything on Earth appear to be moving in super fast forward? After all if your time is running 60,000 slower than earth's time wouldn't everything on Earth appear to be moving 60,000 times faster to you?

If that is the case, then consider the following, while you are making your trip to Andromeda scientist run an experiment on Earth that makes a car travel from 1 location to another at 10% the speed of light. If you on your spaceship observed this car, would it appear to you to be travelling at 6000 times the speed of light due to your own local time dilation?

If this is the case (that to us it appears to be travelling much faster than the speed of light) then could the same phenomenon explain things such as instant information exchange between pairs of quantum entangled particles? If the information that one particle passes to the other is travelling in a slower frame of reference than ourselves, but close the the speed of light, then wouldn't our time dilation make it appear to travel faster than the speed of light to us?

Or am I completely misunderstanding time dilation?
Title: Re: Time Dilation Question
Post by: Bill S on 12/09/2013 22:21:11
As another "ignorant enthusiast" I would have to think about that for some time to have a chance of thinking of an answer, but the first thing that comes to mind is that observing this phenomenon would give the observer clear evidence that he/she was in motion.
Title: Re: Time Dilation Question
Post by: Ignorant Enthusiast on 12/09/2013 22:49:34
True, but with a sufficiently powerful telescope it would be an observable phenomena, if not the effect of seeing something travel faster than the speed of light at the very least we would observe the earth complete 3000000 orbits of the sun in our 50 year trip, which again would confirm that we were the ones in motion.

Indeed time dilation should be an observable thing anyway, the ISS travels fast enough so that time dilation happens, albeit only a very small amount, but with suitably accurate atomic clocks (one on the ISS and one remaining on earth) then eventually the crew of the ISS should notice that their clock is running slower than the one on earth, telling them that they are travelling at a faster relative speed than the clock on earth.
Title: Re: Time Dilation Question
Post by: alancalverd on 13/09/2013 00:30:24
Suppose you were travelling away from earth at "very close" to c. Say it takes you a year and a second to travel one light year. Then when you had reached 1 light year distant and looked back, you would see events that occured one second after you left, and after 2 light years' travel, events that occured a second later. So you wouldn't see time compressed, but expanded as you travel. When you reach your destination, you will see earth events in their normal time sequence but delayed by 50 years. But the moment before you land, you will see events that took place 50 years and 50 seconds ago.

Time dilatation is indeed observable and a relativistic correction is applied to the clocks used for GPS.
Title: Re: Time Dilation Question
Post by: jeffreyH on 13/09/2013 01:57:12
Say you are at 99.9% light speed and travelling away from earth. Assume for a moment that 'time dilation' (I hate that term) did not exist. The photons following you from events on earth would appear to move slower from your perspective and when measured would record a slower speed for light. However because all observers record the same value for the speed of light you must be 'slowed down' in order for this to be true. What actually happens is all particle reactions occur more slowly because of the energy trade-off with your momentum. So all the particles that make up you and your spaceship environment are reacting at a slower rate than those of people on earth. This does not only happen at velocities but also under the influence of gravitation. This is because gravity is a momentum potential.
Title: Re: Time Dilation Question
Post by: Ignorant Enthusiast on 13/09/2013 06:41:33
Fair enough alancalverd, so what happens if you make the return journey back to Earth? Surely you would have to see events on Earth unfold in fast forward at some point? So if our scientists tested their superfast car on earth at that point, would we observe something that appears to be travelling faster than light?
Title: Re: Time Dilation Question
Post by: jeffreyH on 13/09/2013 06:50:50
In travelling close to light speed your perceptions would slow so you wouldn't see things speed up. Your interaction with the universe would be slowed.
Title: Re: Time Dilation Question
Post by: Ignorant Enthusiast on 13/09/2013 07:55:25
But surely jeffreyH, at some point things would have to speed up. If you have made the round trip to Andromeda in 100 years and 6,000,000 years have passed on Earth at some point, even if it's as you slow from light speed as you approach Earth things would have to seem to speed up wouldn't they? Using the orbit of the Earth around the sun as an example, if you spent all 100 years counting how many times Earth orbits the sun wouldn't you have to end up with 6,000,000 by the time you returned to Earth, after all that is what the people (assuming there are any left in six million years) on Earth have experienced, or does it not work like that? If the people on Earth have witnessed 6,000,000 orbits of the sun does our traveler at close to light speed who was watching the whole time not have to come up with the same figure?
Title: Re: Time Dilation Question
Post by: imatfaal on 13/09/2013 11:20:41
In travelling close to light speed your perceptions would slow so you wouldn't see things speed up. Your interaction with the universe would be slowed.

Nope.  You are always at rest within your own frame - thus your own wrist watch, brain, bodily functions etc all proceed at a normal pace.  Whether due to gravitational potential or relative velocity - you never notice the change to yourself, only to those in other frames.  You can calculate the change that they would perceive in you - but never observe it.

Travelling toward an object at relativistic speed would blue shift (increase the frequency, decrease the time between peaks and shorten the wavelength) any em radiation  that you encountered.
Title: Re: Time Dilation Question
Post by: alancalverd on 13/09/2013 15:18:23
Fair enough alancalverd, so what happens if you make the return journey back to Earth?

Use the same analysis. We leave Andromeda at time t=0 when we have just observed an event that took place on earth 50 years previously. After one year and a day we are at a point where we observe events that took place 49 years previously. That's the "blue shift".

Now how do we know how fast the car was travelling? Our experimenter on earth will have told us the length of the test track, and will transmit a signal every second. To make it simple, let's say the car travels 100m in 100s. So we receive 100 time pulses, after which we see that the car has travelled 100m. The effect of the blue shift has indeed been to increase the frequency with which we perceive the time signals c ompared with our clock, but whilst the car may appear to have been travelling faster than 100m/s by our clock, it hasn't done so by his clock - and that is the one we use to measure speed.
Title: Re: Time Dilation Question
Post by: Bill S on 13/09/2013 16:37:34
Nice one, I E!  This is the sort of problem I have wrestled with for years, but I have not considered this one.  I shall probably print out this thread to give the aging brain cells a chance.
Title: Re: Time Dilation Question
Post by: jeffreyH on 13/09/2013 19:26:45
In travelling close to light speed your perceptions would slow so you wouldn't see things speed up. Your interaction with the universe would be slowed.

Nope.  You are always at rest within your own frame - thus your own wrist watch, brain, bodily functions etc all proceed at a normal pace.  Whether due to gravitational potential or relative velocity - you never notice the change to yourself, only to those in other frames.  You can calculate the change that they would perceive in you - but never observe it.

Travelling toward an object at relativistic speed would blue shift (increase the frequency, decrease the time between peaks and shorten the wavelength) any em radiation  that you encountered.

I do understand all that already. The poster was missing the point that light speed is constant. You would simply be passing through all the photons that had not caught up with you yet when on the return journey. You cannot break through the speed of light so no speeding up would occur from the traveler's frame of reference.
Title: Re: Time Dilation Question
Post by: jeffreyH on 13/09/2013 19:50:03
But surely jeffreyH, at some point things would have to speed up. If you have made the round trip to Andromeda in 100 years and 6,000,000 years have passed on Earth at some point, even if it's as you slow from light speed as you approach Earth things would have to seem to speed up wouldn't they? Using the orbit of the Earth around the sun as an example, if you spent all 100 years counting how many times Earth orbits the sun wouldn't you have to end up with 6,000,000 by the time you returned to Earth, after all that is what the people (assuming there are any left in six million years) on Earth have experienced, or does it not work like that? If the people on Earth have witnessed 6,000,000 orbits of the sun does our traveler at close to light speed who was watching the whole time not have to come up with the same figure?

You can't outrun photons, that is simply a thought experiment. On your journey back you would just experience photons at the same rate you did when travelling away. If you COULD break light speed then theoretically, yes, you could see a speeding up but what sort of time dilation would this involve. Negative? However you can still only travel in a positive direction of time and never arrive back at earth before the first photon that set of with you.
Title: Re: Does time dilatation explain quantum effects?
Post by: Pmb on 14/09/2013 08:12:18
Quote from: Ignorant Enthusiast
After all if your time is running 60,000 slower than earth's time wouldn't everything on Earth appear to be moving 60,000 times faster to you?
You would measure clocks on Earth to be running slower and observers on Earth would measure your clock to be running slower.

What most people miss when they're considering this problem what happens to the clocks on board the ship when it turns around. The Earth observers will determine the clocks to run slow depening on the speed of the ship. However the earth clocks will run at a rate which depends not only on the speed of the ship but also according to the position of the earth in the ships gravitational field. If the earth is high in the "apparent" gravitational field that exists in accelerating frames of reference then gravitational time dilation must be taken into account. When all these affects are considered then it all works out as described in the grandfather paradox.
Title: Re: Does time dilatation explain quantum effects?
Post by: alancalverd on 15/09/2013 00:06:12
However the earth clocks will run at a rate which depends not only on the speed of the ship but also according to the position of the earth in the ships gravitational field.

Are you sure of that statement? Suppose there are two ships travelling at different speeds with respect to earth. Which one determines the rate of the earth clock?

The essence of relativity is that no clock (or indeed anything else) knows that it is moving if it is not accelerating. You can only detect relative motion.

Those who claim that understood relativity, automatly acknowledge that they understood nonsense

Yet, remarkably, we dulwitted selfdelusionists manage to build particle accelerators, nuclear reactors, PET scanners, electron microscopes, Cerenkov detectors and GPS systems, to name but a few things, that actually work exactly as predicted by relativistic physics. Magic, just like the transit of Venus, computed by guesswork and observed by sheer luck. Long may the luck continue.
Title: Re: Does time dilatation explain quantum effects?
Post by: Pmb on 15/09/2013 03:18:32
Quote from: alancalverd
Are you sure of that statement?
Yes. And to make sure I was on track I talked to a GR expert or two and then found it described as such in a modern physics text. This isn't my first rodeo you know. :)

Note: I'm looking for that text right now. After I scan that portion into a PDF file would you like a copy of it?
Title: Re: Does time dilatation explain quantum effects?
Post by: alancalverd on 15/09/2013 07:47:52
If I read you correctly, you are saying that the frequency of an atomic clock depends on the speed with which things are approaching it. Thus two atomic clocks that are stationary with respect to one another, and initially in sync with each other, would lose sync if another body was to move between them.

The paradox here is that an observer moving from A to B would see a red shift of A and an equal blue shift of B with respect to his own clock, from which he would calculate that A and B remain in sync, yet the very fact of his presence and motion would destroy that synchronism.
Title: Re: Does time dilatation explain quantum effects?
Post by: imatfaal on 15/09/2013 11:26:31
niebieskieucho's hijack regarding alternative theories which replace einstein's relativity has been moved to new theories.  please don't invade mainstream threads with speculative ideas - post those in new theories.  thanks

imatfaal
Title: Re: Does time dilatation explain quantum effects?
Post by: jeffreyH on 15/09/2013 14:40:07
If I read you correctly, you are saying that the frequency of an atomic clock depends on the speed with which things are approaching it. Thus two atomic clocks that are stationary with respect to one another, and initially in sync with each other, would lose sync if another body was to move between them.

The paradox here is that an observer moving from A to B would see a red shift of A and an equal blue shift of B with respect to his own clock, from which he would calculate that A and B remain in sync, yet the very fact of his presence and motion would destroy that synchronism.

You could argue that the relationships are basically pythagorean. But pythagoras on steroids.

http://www.science20.com/hammock_physicist/whats_wrong_relativity
Title: Re: Does time dilatation explain quantum effects?
Post by: alancalverd on 15/09/2013 15:46:20
But in my example A, B and the observer are all in a straight line. What PmB implied was that B would see A's clock blue-shifted simply because someone was travelling form A to B, which seems at the very least improbable.
Title: Re: Does time dilatation explain quantum effects?
Post by: Pmb on 15/09/2013 16:15:24
Quote from: alancalverd
If I read you correctly, you are saying that the frequency of an atomic clock depends on the speed with which things are approaching it.
No. By the way, it's redundant to speak of atomic clock rather than just using the word clock since that term implies a clock which keeps accurate and precise time regardless of its environment. I.e. the rate of the "clock" does not depends on it's temperature of the clock, it.  When you speak of a special kind of clock, such as an atomic clock, the reader often forms the opinion that time dilation only applies to special kinds of clocks and not to time itself.

What I've said is that the rate of time passing will depend on the position of an inertially moving clock is located in an observer's frame of reference when that observer is accelerating in addition to the rate at which it runs due to its speed. This is because according to an accelerating observer this clock is in a gravitational field. The relationship between the time as recorded by the accelerating observer dt and the proper time measured by the clock dT is

dt/dT = 1/sqrt[1 + 2*Phi/c2 - (v/c)2]

This is the general Lorentz factor for an observer in a time orthogonal spacetime.

Whew! May I have my cup of hot cocoa now? :)
Title: Re: Does time dilatation explain quantum effects?
Post by: Pmb on 15/09/2013 16:19:40
But in my example A, B and the observer are all in a straight line. What PmB implied was that B would see A's clock blue-shifted simply because someone was travelling form A to B, which seems at the very least improbable.
No. That is not at all what I was saying. Please read if over again more carefully and my new post too.
Title: Re: Does time dilatation explain quantum effects?
Post by: jeffreyH on 15/09/2013 21:58:02
But in my example A, B and the observer are all in a straight line. What PmB implied was that B would see A's clock blue-shifted simply because someone was travelling form A to B, which seems at the very least improbable.

This is pythagorean as in the equivalence of squared values, not triangles.
Title: Re: Does time dilatation explain quantum effects?
Post by: alancalverd on 16/09/2013 00:31:05
But in my example A, B and the observer are all in a straight line. What PmB implied was that B would see A's clock blue-shifted simply because someone was travelling form A to B, which seems at the very least improbable.
No. That is not at all what I was saying. Please read if over again more carefully and my new post too.

What piqued my skeptical interest was
Quote
However the earth clocks will run at a rate which depends not only on the speed of the ship but also according to the position of the earth in the ships gravitational field.
- no mention of acceleration.

The reason for considering atomic clocks is because they are presumed to be reproducible everywhere and unaffected by acceleration, unlike mechanical clocks.
Title: Re: Does time dilatation explain quantum effects?
Post by: Pmb on 16/09/2013 01:41:04
Quote from: alancalverd
What piqued my skeptical interest was
Quote
However the earth clocks will run at a rate which depends not only on the speed of the ship but also according to the position of the earth in the ships gravitational field.
- no mention of acceleration.
Think of the earth as being a clock, or having a clock on it. Call this clock earthclock. Now consider applying the equivalence principle to the ship's clock. Call this clock shipclock. Let each clock be an idea clock (which is what you were trying to do by using atomic clocks). The speed of the earth can change as measured from the ship's frame of reference by accelerating towards the earth. This happens when the ship's rockets fire.

I was saying that the rate at which the earthclock runs depends on the speed of the earthclock and the location of the earthclock in a gravittional field (from gravitational time dilation). The rate of the earthclock is as measured by the ship clock.

Note: the only reason I said that you don't need the qualifier "atomic" on the earthclock is because it's already assumed. All clocks in SR are assumed to be ideal clocks unless otherwise stated.

Are we clear now?
Title: Re: Does time dilatation explain quantum effects?
Post by: Ignorant Enthusiast on 16/09/2013 10:40:20
Now how do we know how fast the car was travelling? Our experimenter on earth will have told us the length of the test track, and will transmit a signal every second. To make it simple, let's say the car travels 100m in 100s. So we receive 100 time pulses, after which we see that the car has travelled 100m. The effect of the blue shift has indeed been to increase the frequency with which we perceive the time signals c ompared with our clock, but whilst the car may appear to have been travelling faster than 100m/s by our clock, it hasn't done so by his clock - and that is the one we use to measure speed.
This is close to what I was asking, if it could appear to us that something could be travelling faster than light due to it being in a different frame of reference to us, without actually travelling faster than light in reality.  Which I am assuming is the case judging by your answer of "whilst the car may appear to have been travelling faster than 100m/s by our clock".
Title: Re: Does time dilatation explain quantum effects?
Post by: alancalverd on 16/09/2013 11:22:01
The rate of the earthclock is as measured by the ship clock.

Ah, it's all semantics. Being a feet-of-clay experimental scientist, I would call that the apparent rate of the earthclock, knowing that the "true" rate is exactly the same as the ship clock because they are both ideal clocks from my workshop!

And I'm afraid that not every reader of this forum knows that we are only talking about ideal clocks unless we say so!
Title: Re: Does time dilatation explain quantum effects?
Post by: Pmb on 16/09/2013 14:51:27
Quote from: alancalverd
Ah, it's all semantics. Being a feet-of-clay experimental scientist, I would call that the apparent rate of the earthclock, knowing that the "true" rate is exactly the same as the ship clock because they are both ideal clocks from my workshop!
When you make a statement like the that you're in effect saying that time dilation is only apparent since the clock isn't "really" slowing down, the slowing down is only "apparent." What is real or not is what you can measure and you can measure the earthclock to be running slower so this is not apparent at all.
Quote from: Pmb
And I'm afraid that not every reader of this forum knows that we are only talking about ideal clocks unless we say so!
So instead of saying "atomic clock" use the term "ideal clock" instead. I think it will make things much clearer. Otherwise readers will want to know why you have to use an atomic clock instead of an ordinary clock.
Title: Re: Does time dilatation explain quantum effects?
Post by: alancalverd on 16/09/2013 15:18:21
Au contraire! If I'm on the ship I can see pulses from the earthclock arriving slightly further apart than the pulses from the shipclock, but knowing they are both atomic clocks and being wise to relativity, I know that the earthclock is not really running slower. Indeed by knowing that fact and no other, I can calculate my speed away from earth by measuring the apparent rate of the earthclock.

If we didn't distinguish between real and apparent rates, we would believe that the universe contains an infinite number of different elements! Fortunately we can identify the hydrogen spectrum from its pattern and deduce from the shift of its apparent center frequency that a galaxy is moving with respect to us, which makes astrophysics a lot simpler.

I'm perfectly happy to tell anyone why I'm using an atomic clock! From my present point of view it's very far from ideal because I can't wear it on my wrist, and less than 100 years ago an ideal clock would have been a ship's chronometer, but neither my wristwatch nor a chronometer could be relied on to behave like a standard cesium clock once the rocket engine starts.
Title: Re: Does time dilatation explain quantum effects?
Post by: Pmb on 16/09/2013 15:37:29
Quote from: alancalverd
Au contraire! If I'm on the ship I can see pulses from the earthclock arriving slightly further apart than the pulses from the shipclock, but knowing they are both atomic clocks and being wise to relativity, I know that the earthclock is not really running slower. Indeed by knowing that fact and no other, I can calculate my speed away from earth by measuring the apparent rate of the earthclock.
You're confusing the effects due to Doppler shift and those due to time dilation. The arrival rate is caused by both of them acting together. However if you were to have an object moving so close to a wall that they are almost touching then you can exchange signals with that wall and track time by the rate at which spots were left on the wall by the moving clock. The rate at which spots are left will be soley due to the rate at which the clock is ticking and the speed it is moving. Doppler effects won't play a role. I'm surprised that you don't know this by now.

Quote from: alancalverd
I'm perfectly happy to tell anyone why I'm using an atomic clock!
And waste time in each post doing so for no good reason. If you were to do a survey of SR texts you'll notice that almost all of them will state what an ideal clock is, using an atomic clock as an example, then they never mention it again. And for very good reason.
Title: Re: Does time dilatation explain quantum effects?
Post by: jeffreyH on 16/09/2013 22:04:35
If there was a theoretical point in the spacetime continuum where a global rest frame could be found then would an object residing there be older than the apparent age of the universe? A conundrum.