A light clock that might work

Just another clock but this time not using distance of travel as a determiner.
Instead only the intensity or strength of the light is measured which will give a measurement that can be computed to velocity.

I'll use the same diagram I used in another thread "light clock revisited":

<img src=http://www.paygency.com/lightclock1.jpg>

But instead of mirrors we have sensors that measure light intensity.
The clock was calibrated on earth and is traveling at 0.8'c'

Now I would like to ask how time and length transforms would effect the invariant intensity of a common light source?

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keeping in mind that time has no relevance to the measuring of intensity, so time dilations are no longer a factor. [unless some one woudl like to suggest otherwise?]

 

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Why would intensity liberate you from time dilation/length contraction? Intensity is simply the amount of light, per second, the receiver detects. Intensity is not invariant under SR.

 

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Intensity is the amount of light "hitting" our sensor at any given moment. Time is not required to determine intensity. Maybe I need another word for it. Strength, brightness, etc.....

As time is not needed in the equation to determine distance we are able to use light as an absolute time reference.

Thed, would what you are saying be like comparing voltage with ampheres; pressure with current flow?

 

If I am not mistaken if we look at our leading arm [A] then as the clocks velocity increases the length contracts under transform and of course the time dilation factor accomodates the velocity aspect to retain invariants.
However the intestity of the light would remain coinstant regardless of the contraction I would propose becasue intesity is not directly related to velocity.

Thus as length contracted the light would become brighter. And if this was the case then the discrepancy would indicate the contracted state of the clocks arm therefore give an absolute time reference.

Thed it is not surprising that SR does not place the "cross" of invariance on light intensity because if it did I would suggest that SR fails.

 

Another simple way of gettng past this light velocity issue is to use optical geometry.

If an object is say 10 meters in diameter at zero distamce then it's reflected diameter could be only 5 meters in diameter depending on distance.....as the distance contracts the reflected objects image will increase in diameter.THus again our light clock can be use to achieve absolute time [universal Earth time]

 

I have tried to delete this post due to it's obvious mistake

 

At any given instant, there is zero light energy received on the sensor.
Intensity is a measure of light power - energy received per unit time.

 

Pete,by measuring intensity over time aren't you just measuring the change in intensity. If you take a snap shot in a frame no longer than 1 milli second you still get an intensity reading..... yes? or if you reduce the time even further etc wouldn't you still get the same, intensity reading?

The other interesting question popped up today and that was if we took our light clock with a common light source would the light source maintain it's brightness at relativistic velocity or become dimmer due to dilations etc...

If dilation is atomic slowing then I would think that the light would get dimmer.
So whilst the velocity issue is dealt with by the transforms what happens to the brightness of our light?

 

QQ,

Thought you might find this interesting.

http://www.edpsciences.org/articles/epl/pdf/2001/03/6393.pdf

***************************************************
ABSTRACT:

G. Sardin

Applied Physics Department, University of Barcelona - Barcelona, Spain

Gsardin@fao.ub.es

(Received 7 April 2000; accepted in final form 20 November 2000)

Abstract
An electromagnetic speed-meter made of a three-dimensional frame is proposed, which allows measuring speeds independently of any external reference. The device is constituted by three orthogonal light beams and uses the motion-induced aberration of light or Bradley aberration. The frame is formed by three orthogonal beams which stand for the three axes. On the top of each axis arm of the frame a diode laser is fixed whose divergent beam impinges on a convergent lens which focalizes the light on an optoelectronic position detector of high resolution, placed on the base of each arm. The shift of each beam spot due to aberration of light is recorded, from which the motion of the frame is derived. Furthermore, if it is settled on a spacecraft its motion can be controlled in a way to record no aberration shift on any axis, indicating that the spacecraft is then at rest in the cosmic space. Since the referential frame does not use any external reference, it can be taken as a universal frame from which absolute speeds can be defined.

PACS
06.30.Gv - Velocity, acceleration, and rotation.
07.87.+v - Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.).
95.55.-n - Astronomical and space-research instrumentation.

********************************************

Others have argued that this will not work however. My point is your thoughts are not totally unique.

 

Thanks MacM,

In a way it all stems for the question : "if you were in a fast traveling spacecraft between stars, how would you know how fast you were going?"
And if an absolute time reference is achieved even if one is constructed such as an absolute universal Earth frame the issues of absolute time becomes clearer.

 

Pete, thi squestion about intesity/time....if I apply 100 kgs of force to a brick wall. Can I say:
I apply a force of 100kgs or
I am applying a force of 100 kgms.

I understand that in all instances it involves time but I wonder whether time is relevant to the measurement except to qualify changes in intensity.

100 kgs applied for 10 seconds then 120 kg applied for another 10 seconds etc etc....

 

You misunderstand - to measure intensity, you need to measure energy over time - intensity is a measure of the rate of change in energy collected.

Yes.
If I collect 1 millijoule in 1 millisecond, that's the same intensity as 1 joule in 1 second, or 1 nanojoule in 1 nanosecond, etc.

However, 0 joules in 0 seconds tells me nothing.

 

I'm not sure about force.
It's units are mass x distance / time², (ie neither kg nor kg.s are units of force) but I haven't followed through all the variations to determine if it is a true instantaneous measure (I think it is, but that's just my intuition speaking).

 

ok ...you have drawn a distinction between intensity and force.....hmmm..terminology issue again.....

"is the intensity of gravity or magnetic attraction/repulsion determined over time?"
Intuitively the answer would be time is irrelevant or no.....
Brightness or intensity of light would always be a measure made in the 'now' and compared with measurements made over time...I would think.

The measure of velocity inherantly requires the passage of time but the strength of that light or object would be a "now" based measurement.


A car collided with mine with a force of 1000kg impacting at the front.
A photon hit my eyes that was so intense I was momentarilly blinded....

the brightness of my desk light dimmed as my room on board my ship accelerated to 0.9c

 

Can you suggest how you could measure light intensity at an instant?
I can't think of a way... I've tried, and I think it's impossible. I think you always need measurements at different times and or places to get a meaningful measure of intensity


Think of light as waves, then think of water waves as an analogy.
Can you examine a single point at a single time in a body of water and tell whether there are any waves passing that point, and whether those waves are ripples or 10m swells?


Now think of light as particles, then think of a stream of bullets from one or more machine guns striking a target as an analogy.
Can you examine the target at one instant only and tell the intensity of the machine gun fire? (assume the bullets are very very short)

 

Pete say we attach an osciliscope to a high pressure balloon in a wind storm and take a reading over 1 minute. The read out would show a wave form over the one minute. We print it all out on a sheet of paper that is about 2 meters long.

At any given point along the wave we can tell the pressure of the balloon. Be as detailed as you like or as general as you like.

the read out is a center of time document as it was created showing how the "now' was changing.

You use the example of photonic bullets.
If we had equipment sensitive eneough we could measure the impact intensity of a single photon [if one believes in photons in the first place...which I don't as you know]

 

An instantaneous pressure doesn't tell you anything about the wave itself. The wave power depends on how the pressure changes.
For example, continuous unchanging high pressure means a wave of zero intensity.


A single photon tells you the frequency of the signal - but that's all.
Don't you think that a signal with 10 billion photons per second is more intense than a signal with 1 photon per second?

 

Pete, do you remember that diagram where I showed a "Now" axis and time peeling away.

here it is:
<img src=http://www.paygency.com/dilatedtimeaxis.jpg>

Now If we disregard the dilation issue raized and just for a minnie focus on what is happening when light hits our reflector.

As soon as the light has touched the reflector it becomes a memory or exists in the past.

The strength of that impact also exists in the past.

An ongoing ociliscope pattern is describing the changes in intensity over time.
At any point in the graph one can determine what the intensity WAS....not what the intensity is.....if the graph is flat and has been for a while then we can only PREDICT that the intensity will stay the same and the signal will be recorded as flat.

If I hit a nail with a hammer with a force of or intensity of 10 tons persqinch then at what point in time am I recording?

If we went into the macro world you would see a graph over time and that graph would show how the intensity on the top of the nail increased suddenly to 10 tons starting from zero relative to it's ambience.

The intensity of a light signal over time is extrapolated into a form of graphic history of the impact in the NOW.

So therefore intensity can be measured at any given moment from this history.

 

I should have said that intensity in the past can only be measured at any given moment as even the osiliscope takes time to function.
But here is another little diag that shows my point:

<img src=http://www.paygency.com/trillionth.jpg>

The intensity read from the NOW axis is not passage of time related.