measuring time with a ruler

[michel123456]

Time is what a clock measure.

Distance is what a ruler measure.

 

Then a question arises: is it possible to measure time with a ruler?

 

For example, following Galileo's experiment: putting a ruler inclined and making a small sphere rolling upon it.

When the sphere passes by over a line of the ruler, one unit of time has passed.

Of course the problem arises that if my lines on the ruler are equidistant, I will measure time as accelerating.

But although unconventional, that would be a way to measure time with a ruler.

Isn't it?

[JustinW]

or you could measure distance with a clock. I don't know... It was just the first thing that popped into my head while reading the question.

 

It makes scence to me, but you could only start measuring once the sphere reached terminal velocity. Not to mention it would have be one hell of a long ruler or time would stop. (figuratively speaking)

[Schrödinger's hat]

Well once you have known distances and (predictably) moving objects, you've made yourself a clock.

 

Ditto goes for known times.

 

If you were very quick (or c was slow) you might be able to do a direct measurement of time with a ruler using relativity, but only someone else's time.

 

Other interesting and relevant fact:

c is now defined as a ratio. So distances are actually measured with clocks (and light, or some other speed of light phenomenon).

We do this because our clocks are very very good, while our distance related apparatus are merely very good.

Edited December 2, 2011 by Schrödinger's hat

[md65536]

For example, following Galileo's experiment: putting a ruler inclined and making a small sphere rolling upon it.

When the sphere passes by over a line of the ruler, one unit of time has passed.

Of course the problem arises that if my lines on the ruler are equidistant, I will measure time as accelerating.

No, you would measure the sphere to be accelerating.

The reason you can measure time this way is that the ball is moving in a precise, consistent, known way. It is known that it is accelerating, and the rate of acceleration is known (as a function of g and the angle of the ramp; they would need to be precisely fixed and/or known in order to use this to tell time precisely). So you can create a formula to describe the movement of the sphere, and find t from that, and if everything's accurate you'll find t to behave just as expected. Changing the spacing of your tick marks doesn't affect time, nor does the angle of the ramp, though they'll affect the formula and measurements.

 

 

Perhaps you can create some useful time-like property measured by equal spacing of lines on the ruler, but that isn't time (as measured in consistent intervals by other clocks).

[michel123456]

If you were very quick (or c was slow) you might be able to do a direct measurement of time with a ruler using relativity, but only someone else's time.

 

Other interesting and relevant fact:

c is now defined as a ratio. So distances are actually measured with clocks (and light, or some other speed of light phenomenon).

We do this because our clocks are very very good, while our distance related apparatus are merely very good.

 

Theoretically you could use a ruler to measure C, indeed. If C was much slower that could be a very simple experiment.

 

So I was wondering, when you make wooden ruler, and put it simply like that on your desk, it does not measure time. If you light it, theoretically it becomes a clock, with the only problem that light goes too fast: you cannot observe the rays reaching the first line of the ruler, then the second line, and so on. The ruler seems to be lighted all at once.

 

Also, you could take the ruler and make it slide on an inclined plane. That would be the reverse of Galileo's type of experiment. So that a moving ruler would transform in a clock.

Then, you could state that the ruler does not measure time because the ruler is comoving with you in spacetime. If you choosed another FOR in spacetime, the ruler would be a clock for this FOR.

 

And if the above is correct, one could make a statement following which the ruler is a clock for all FOR different from the ruler's FOR. IOW the ruler is not a clock only for its own FOR.

[Schrödinger's hat]

And if the above is correct, one could make a statement following which the ruler is a clock for all FOR different from the ruler's FOR. IOW the ruler is not a clock only for its own FOR.

 

You'd need to know something about its motion as well.

Either its velocity/momentum in your frame or its acceleration or semi-major axis of its orbit or similar.

If you had very precise instruments (or c was slower) you could compare its length to a reference ruler which is co-moving, or check its colour somehow (arguably measuring redshift requires a clock of some kind too). This would tell you its velocity without having to have access to a separate clock.

[dimreepr]

Time is what a clock measure.

Distance is what a ruler measure.

 

Then a question arises: is it possible to measure time with a ruler?

 

For example, following Galileo's experiment: putting a ruler inclined and making a small sphere rolling upon it.

When the sphere passes by over a line of the ruler, one unit of time has passed.

Of course the problem arises that if my lines on the ruler are equidistant, I will measure time as accelerating.

But although unconventional, that would be a way to measure time with a ruler.

Isn't it?

 

time isn't quantifiable. its purely a measure imposed by us.the only way time could be measured is useing planks min length to describe a unit, and even then its diferent for every body in the universe.

Edited December 3, 2011 by dimreepr

[md65536]

And if the above is correct, one could make a statement following which the ruler is a clock for all FOR different from the ruler's FOR. IOW the ruler is not a clock only for its own FOR.

 

I think you're hiding flawed logic in a fog of vagueness. Relativity is not so flimsy, and it's easier understood when you state everything clearly.

 

First of all, I don't think "a ruler is a clock" is meaningful. How is it a clock? The answer to that question is what makes it a clock (or not a clock, depending on how you answer). Eg. it's not just a ruler that makes a clock, but a ruler and a light source and a light detector, or some other combination. In this case, the ruler moving against an incline makes your clock. Even if you're not moving relative to the ruler, it is still moving relative to the incline, so it can still be used as a clock in the ruler's frame.

 

Second, clocks measure proper time. (I suppose you could build an apparatus that doesn't, and still behaves like a clock... then maybe you could call it something like "a clock with a limited domain" or something like that???) The universe is consistent, so if one observer observes that a device accurately measures proper time (and is thus a clock), then all observers will observe observations that are consistent with that (everyone will agree that the device measures proper time).