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homerwho
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Is instantaneous limited to our in ability to continue to count time faster.
Speed (relative to something) is quantifiable in math terms. What else is there? If you mean can we measure speed to infinite precision then certainly not.homerwho said:Summary: Is instantaneous something that is quantifiable?
Is instantaneous limited to our in ability to continue to count time faster.
Kind of. There are digital and analog methods to measure "speed".homerwho said:Summary: Is instantaneous something that is quantifiable?]]
Is instantaneous limited to our in ability to continue to count time faster.
homerwho said:Yes it makes sense. Can assumptions be made on a change that it happened instantly?
Yes, the physics of velocity is bound by the physical laws relating to spacetime as humans currently understand them. Math is purely conceptual, so it is not bound by those same limits. The measurement of speed (the OP's original question), and perhaps the measurement of any physical phenomenon, is the joining or alignment of the physics of spacetime with conceptual math. So both the physical and the conceptual must be bound by those limits to make that joining feasible in a definite manner.sophiecentaur said:Maths is not 'real' and only applies in some cases.
I don't agree with that definition. I'd say "instantaneous" means "happens in zero time". And I'd say that based on that definition, all events are instantaneous by definition of the word "event".sepcurio said:This has many concepts associated with it. "Instantaneous" implies two events happening at the same time...
However, in Classical physics there are many things that, for all practical purposes, can be considered to happen instantaneously.
No, speed is often measured over a time duration, but not always. And the units it is expressed in do not require/imply it needs to be.There is also the more philosophical concept of memory and comparison. When motion is measured, there has to be some memory (not necessarily biological) of where is "was" and a comparison of that to where it "is."
Maybe, but just to make sure we're clear and agreeing: you can measure instantaneous velocity.Paul Colby said:When reading the OP and replies I get the feeling people are equating quantifiable with measurable...
Velocity of the center of mass of an object is quantified even if the measurement of such is always of limited precision.
No, radar guns measure speed from doppler shift of reflected radio waves. They are single-point/instantaneous measurements.Paul Colby said:One can certainly infer an approximate "instantaneous" velocity from measurement. Most quantities I can think of are actually inferred from measurements. How direct these are depends on the methods and models employed. Take velocity. What comes to mind? Radar gun? Two consecutive position measurements? None of these are instantaneous but arguments can be made about the rate of change of the velocity over the measurement period being small or negligible.
Well, you might want to review how these things actually work. Measuring a doppler shift in under a period of the radiation shifted ain't happening.russ_watters said:No, radar guns measure speed from doppler shift of reflected radio waves. They are single-point/instantaneous measurements.
...now you are talking about the nature of light: Photons are not little (or long), continuous waving strings that you can break apart into pieces of a wave, or it isn't like watching a peak and waiting for the next peak and measuring how long it took to arrive. Photon emission, absorption and reflection are instantaneous processes/events.Paul Colby said:Well, you might want to review how these things actually work. Measuring a doppler shift in under a period of the radiation shifted ain't happening.
Good heavens, not at RF frequencies. My point is instantaneous measurement implies unlimited bandwidth. Nothing has infinite bandwidth. IMO you are paving over the measurement time which is always finite and non-zero.russ_watters said:And radar guns measure photon energy.
Late edit to the previous post; the principle for radar guns uses beat frequency/wave interference, and not a direct energy measurement. Apologies.Paul Colby said:Good heavens, not at RF frequencies. My point is instantaneous measurement implies unlimited bandwidth. Nothing has infinite bandwidth. IMO you are paving over the measurement time which is always finite and non-zero.
I argue even this has finite measurement time and uncertainties. Idealization is fine. Any method can be refined until the model requires fixing. The thing about measurement is it's not all theoretical. Bit of a mix.russ_watters said:You could theoretically bounce a single photon off an object and measure its energy on return.
) ...that measure speed from centrifugal force.
Can you list them? Are you confusing error and signal propagation delay with measurement time?Paul Colby said:I argue even this has finite measurement time and uncertainties.
Yeah, you are confusing the time to take or process the measurement with the nature of the measurement. By this logic, weight has a time parameter as well.Paul Colby said:Centrifugal force is not an instantaneous measurement. Just looking at the thing takes some time.
Paul Colby said:Centrifugal force is not an instantaneous measurement. Just looking at the thing takes some time.
Exactly.sepcurio said:We're talking about two different things here. One is the measurement of an instantaneous point in time. The other is the the time it takes to analyze or evaluate that information. Two different things.
That's a response time error. That doesn't change the instantaneous nature of the measurement itself. It's like not waiting for a scale to settle before reading a weight. It doesn't mean weight has a time parameter.Paul Colby said:Nope. You're neglecting the measurement time. A governor will average over time just based on its own inertia.
This has nothing to do with integration time or sampling rate. The device makes one reading.Paul Colby said:Okay, and Analog to digital, the modern day version of looking, has a finite integration time. When you find one that doesn't please send me the spec.
What you say make absolutely no sense to me. And, it's not the sampling rate it's the time it takes for a sample which is always finite.russ_watters said:This has nothing to do with integration time or sampling rate. The device makes one reading.
Is weight a single point or time-integrated measurement?Paul Colby said:What you say make absolutely no sense to me. And, it's not the sampling rate it's the time it takes for a sample which is always finite.
Actually it may be the latter, or it can be considered a time-integrated interaction. Weight is the interaction of mass and gravity via an as-yet-to-be discovered gauge boson, and that interaction takes time. But this is off topic...russ_watters said:Is weight a single point or time-integrated measurement?