# A photonic clock

Discussion in 'Physics & Math' started by Quantum Quack, Sep 21, 2004.

1. ### Quantum QuackLife's a tease...Valued Senior Member

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In another thread discussing absolute time and what it is, an idea occurred that if we construct a clock that derives it's tick rate from lights velocity, a photonic clock, wouldn't that acheive a state of absolute time.

If all clocks where ever they were, were ticking at the rate that was determined by lights velocity (299792kpsec) then wouldn't we establish absolute time? After all lights velocity is deemed invariant to all observers in absolutum........there for the tick rate achieved using this invariant would also be invariant thus absolute.

Care to discuss

3. ### James RJust this guy, you know?Staff Member

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You said, elsewhere:

That is not true. An observer in relative motion would see the same distance contracted in the direction of motion, and therefore a light beam would take less time to cover the distance from that observer's point of view. That observer's clock rate would therefore be different.

5. ### Quantum QuackLife's a tease...Valued Senior Member

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JamesR, Thanks for taking the time to respond but I think we are at cross purposes here, let me clarify the clock a little

We have a solid enclosed box of a ridgid alloy.
Inside this box we have a light emitting diode or laser that transmits light to a destination 1 meter away inside our enclosed box, for all intents and purposes no other light can enter and the pressure inside the box is allowed to be equal to the outside.

The light emited by the diode is measured and it's velocity is determined as 'c'. the device then uses this light to calibrate it's clock which is located outside the box ( digital L.E.D. clock ) The second tick rate is determined soley by the light inside the box. ( not atomically but only by light)

Now because the light ray is invariant regardless of the velocity of the box the tick rate would be constant.....or maybe that is what has to be agreed upon?
So we have this 1 meter cube with a clock visable on the outside.

The question I guess is would this clock indicate absolute time regardless of where it is in the universe ( space ) and if we had a million of the same clocks would they all tick at the same rate?

The clock is a independent and closed time system based only on the velocity of light inside that system..

In this system there is always only one observer being the destination of that 1 meter length of light distance, inside the box this observer determines the tick rate based only on that observation.

7. ### Quantum QuackLife's a tease...Valued Senior Member

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think of it like a smaller version of the M and M device used to measure for aether. self contained self referencing based on light velocity.

8. ### James RJust this guy, you know?Staff Member

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Only if they were not moving relative to each other. An observer sitting on top of one of these clocks watching another identical one flying past would see the second clock running slower than his own clock.

Yes. That's why the rate at which the clock ticks doesn't vary for an observer sitting on top of the clock, no matter how fast the clock goes. However, the points of view of other observers watching this clock are not based only on the velocity of light inside the clock, but also on the motion of the entire clock relative to the external observer.

9. ### Quantum QuackLife's a tease...Valued Senior Member

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JamesR I am a little confused here obviously, I was under the impression that the velocity of light is invariant to all observes regarless of frame.
The velocity in side all of our clocks are identicle are they not?

If the velocity inside our clocks are identicle then the tick rate has to be identicle.
If the tick rate is not identicle then the postulate fails. simply because the tick trate is only gained by the speed of light which is invariant.

Now if a passing observer reads a different tick rate then the postulate is flawed, and I don't think it is.

10. ### Quantum QuackLife's a tease...Valued Senior Member

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if the clock was run by atomic reference means then what you are saying is correct but the clock is run by light reference means, and this is the very important distinction.

By using light as your reference then absolute time can be achieved, or should I say this is the contention anyway.

11. ### Quantum QuackLife's a tease...Valued Senior Member

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BTW i am not referring to other light effects such as accelleration of two light sources causing the clocks to be read differently due to the delay of that information due to the distance of separation. of course the dely due to exterenal light effect would effect the reading over large distances. But this is outside our time system.

12. ### Quantum QuackLife's a tease...Valued Senior Member

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Lets digress a little and simplify.

Say our clocks don't just show tick rate they also show the velocity of the light inside the box.

ten clocks scattered over ten galaxies all show what velocity of light inside the box on their clocks. ( 299792kms is my guess)

now one box flys past another box and what velocity figure is showing on both boxes.....(299792kps is also my guess) an observer on box A sees box B's reading as 299792kps and observer on box B sees A's velocity figure as 299792kps.

so both observers agree that the velocity inside the boxes is identicle.

Now if this is the case and I hope that you will confirm or rebut then the tick rate will also be identicle.

13. ### James RJust this guy, you know?Staff Member

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Yes.

No, because as far as a moving outside observer is concerned, the clock is not the same size as it was when it was stationary, so the light inside has a different distance to travel. Therefore, the time it takes to make one tick can vary.

Remember, if you vary both length and time you can still keep speed constant. In fact, relativity says that must happen.

14. ### Quantum QuackLife's a tease...Valued Senior Member

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jamesR I think you may have missed my later posts

15. ### Quantum QuackLife's a tease...Valued Senior Member

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JamesR you must be thiniking "bloody clocks and their stupid tick rates ..enough to give you the sh*ts yes?"

well when the clocks assembly dillates isn't that exactly what is happening, distance and time both dilating in synch.?

16. ### Quantum QuackLife's a tease...Valued Senior Member

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the velocity of light inside clock B must be determined as 'c' by clock A and the velocity of light inside A must be determined as 'c' by clock B.
Clock A determines it's own light as 'c' but if it could measure clock B's light it would also be 'c' and vica versa.

So all clocks would agree that their velocities and all other clocks inner velocities are identicle no matter how you look at it.
so by usinfg light in a self referencing system we achieve a unifiorm standard.

You know sometimes I find it beneficial to try and argue the other persons case just to see how it fits, try to find agreement. I find that the issue is still what is being used to guage time, we are using light not matter. and as light is constant then so is time for light. and seeing as we are measuring light time then we have an absolute reference for that time which is light.

for matter time is variable but light stays constant regardless of that matter.
So for me to argue your case would mean that the postulate would fail and that light is variant after all......

17. ### Quantum QuackLife's a tease...Valued Senior Member

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The distance may increase but so to has the time available to cover that distance the space of that object dilated in space AND time. so v=c all ways regardless of reference frame.

18. ### James RJust this guy, you know?Staff Member

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Yes.

Yes.

Yes.

Not a uniform time standard. Only a uniform speed standard.

Muddy thinking, I'm afraid. Only the speed of light is constant. Time is not constant, as I keep saying. Therefore, no absolute standard. Speed is made up of time and distance, neither of which is constant by itself, but which give a constant when put together.

19. ### Quantum QuackLife's a tease...Valued Senior Member

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my view is ...this is incorrect and contradictory because speed is what?
distance and time. not just distance and not just time.

and

my view again.....this is incorect for the same reasons as the previous.

Speed is distance vs time. the velocity of light is distance vs time.

The light in the box has speed that is constant and therefore must have both distance and time proportionally identicle.

velocity must equal 299792 kms distance and time must equate to acheive this figure. thus time relative to distance is constant.The velocity is maintained thus the tick rate must also.

20. ### James RJust this guy, you know?Staff Member

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Tick rate is time only. Velocity is distance and time. If both time and distance both change, speed can stay the same.

For example, suppose we have v=d/t.

Suppose I multiply d by 5 and t by 5. What does that do to v?

Having v the same doesn't mean t and d are the same.

21. ### Quantum QuackLife's a tease...Valued Senior Member

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I hope you find this as interesting as I do .......

the tick rate is based on the speed which is the combination of distance relative to time ( inside our box) Because the speed is used to generate the tick rate it should be constant

Velocity and speed are the same thing yes?

it takes our light always a certain amount of time, to travel the meter and even though the meter is changing the time is also thus the speed remains the same. whether dilated or not, after all isn't this the postulate at work?

it still takes 1 second to travel 299792 ks no matter what.

therefore the one second for all our boxes is the same length of time.

22. ### Quantum QuackLife's a tease...Valued Senior Member

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t and d are proportionally the same...... so the speed result is maintained.

23. ### Quantum QuackLife's a tease...Valued Senior Member

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say for arguements sake we exagerate our d and t figures

box A , d= x meters, and t = x time then v = c
Box B , d = x*1.2 meters and T = x *1.2 time then v =c