Uncertainty… principle?
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22-04-2014, 10:56 AM
Uncertainty… principle?
Next time you’re in a moving vehicle driven by someone else, if you happen to have a camera with you that allows you to change the shutter speed, and especially if you’re bored enough to do it, you can perform a little experiment. Once the vehicle is moving relatively fast in relation to the ground, take two pictures of the scene outside, one with a high shutter speed and the other with a low shutter speed.

Depending on where exactly you perform the experiment, the pictures taken will be different, of course. But I am almost sure that you will be able to notice something. In the high-speed photograph, the location of individual objects in the scene will be fairly easy to resolve, but it will be difficult to get a sense of how fast the vehicle was moving when the picture was taken. In the low-speed photograph, however, the reverse will seem to be true. Things, especially those nearest to the camera, will become trails, giving a sense of motion to the picture, but the location of individual objects in the scene, unless they are far from the camera, will become difficult to discern.

The reason for this is simple: the shorter the exposure time, the less motion the camera captures. In the high-speed photograph, the shutter is open for a very short interval, meaning that things in the photographed scene do not move much during the film’s or digital chip’s exposure; the location of things in the scene is fairly precise. In the low-speed photograph that time is longer, allowing things to cover greater distances during the captured interval. That’s why they become trails.

In my view, this experiment illustrates a two-sided notion. From one angle, that things only occupy a precise location in relation to other things during the “length” of a zero length instant; as soon as non-zero intervals of time are considered, things don’t occupy a precise location. Unless, one might think, they have absolutely no motion in relation to their surroundings. But everything is constantly moving in relation to most of the things in their surroundings, no thing is ever absolutely still in relation to everything else. Thus, during any non-zero interval of time, things don’t occupy a precise location. From the opposite angle, motion does not occur during a zero length instant. The distance covered by a moving object is proportional to the length of time during which that motion is considered; if the time increment is zero, the distance covered is zero too.

By changing the exposure time, you can take photographs that show the locations of things or the motion of things, but the precision gained in one direction is precision lost in the other, because the location of things is only precise during a zero length instant, while the motion of things only happens during a non-zero length interval. In general, I don’t think you can measure a quantity and the rate at which it is changing during the same measurement and up to an arbitrarily high degree of precision, because if a quantity is changing during the interval while we measure it, then its value is not precisely defined during that measurement.

Now, even though we are talking about macroscopic objects, the idea of not being able to simultaneously learn the location of things and the rate of their motion reminds me a lot of some other notion that is often called “uncertainty principle”. However, in my view it appears as a consequence, not as a principle. It is a consequence of the fact that change only happens over time.

Or maybe they are completely unrelated observations, so if you like calling it a principle, I am happy with your choice of words.

Have a good day!
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22-04-2014, 11:26 AM
RE: Uncertainty… principle?
(22-04-2014 10:56 AM)living thing Wrote:  Next time you’re in a moving vehicle driven by someone else, if you happen to have a camera with you that allows you to change the shutter speed, and especially if you’re bored enough to do it, you can perform a little experiment. Once the vehicle is moving relatively fast in relation to the ground, take two pictures of the scene outside, one with a high shutter speed and the other with a low shutter speed.

Depending on where exactly you perform the experiment, the pictures taken will be different, of course. But I am almost sure that you will be able to notice something. In the high-speed photograph, the location of individual objects in the scene will be fairly easy to resolve, but it will be difficult to get a sense of how fast the vehicle was moving when the picture was taken. In the low-speed photograph, however, the reverse will seem to be true. Things, especially those nearest to the camera, will become trails, giving a sense of motion to the picture, but the location of individual objects in the scene, unless they are far from the camera, will become difficult to discern.

The reason for this is simple: the shorter the exposure time, the less motion the camera captures. In the high-speed photograph, the shutter is open for a very short interval, meaning that things in the photographed scene do not move much during the film’s or digital chip’s exposure; the location of things in the scene is fairly precise. In the low-speed photograph that time is longer, allowing things to cover greater distances during the captured interval. That’s why they become trails.

In my view, this experiment illustrates a two-sided notion. From one angle, that things only occupy a precise location in relation to other things during the “length” of a zero length instant; as soon as non-zero intervals of time are considered, things don’t occupy a precise location. Unless, one might think, they have absolutely no motion in relation to their surroundings. But everything is constantly moving in relation to most of the things in their surroundings, no thing is ever absolutely still in relation to everything else. Thus, during any non-zero interval of time, things don’t occupy a precise location. From the opposite angle, motion does not occur during a zero length instant. The distance covered by a moving object is proportional to the length of time during which that motion is considered; if the time increment is zero, the distance covered is zero too.

By changing the exposure time, you can take photographs that show the locations of things or the motion of things, but the precision gained in one direction is precision lost in the other, because the location of things is only precise during a zero length instant, while the motion of things only happens during a non-zero length interval. In general, I don’t think you can measure a quantity and the rate at which it is changing during the same measurement and up to an arbitrarily high degree of precision, because if a quantity is changing during the interval while we measure it, then its value is not precisely defined during that measurement.

Now, even though we are talking about macroscopic objects, the idea of not being able to simultaneously learn the location of things and the rate of their motion reminds me a lot of some other notion that is often called “uncertainty principle”. However, in my view it appears as a consequence, not as a principle. It is a consequence of the fact that change only happens over time.

Or maybe they are completely unrelated observations, so if you like calling it a principle, I am happy with your choice of words.

Have a good day!

I sometimes wonder how animals with different life spans perceive time.

[Image: dobie.png]Science is the process we've designed to be responsible for generating our best guess as to what the fuck is going on. Girly Man
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22-04-2014, 11:41 AM
RE: Uncertainty… principle?
(22-04-2014 11:26 AM)Dom Wrote:  I sometimes wonder how animals with different life spans perceive time.
Apparently, the brain of a fly analyses incoming information at a higher frame rate than ours do, so I suppose they see our hand approaching in slow motion; I guess that is how they always manage to get away.

But you'd have to ask a fly.
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22-04-2014, 11:48 AM
RE: Uncertainty… principle?
(22-04-2014 11:41 AM)living thing Wrote:  
(22-04-2014 11:26 AM)Dom Wrote:  I sometimes wonder how animals with different life spans perceive time.
Apparently, the brain of a fly analyses incoming information at a higher frame rate than ours do, so I suppose they see our hand approaching in slow motion; I guess that is how they always manage to get away.

But you'd have to ask a fly.

I wish I could - I have been wondering about such things all my life. Consider

[Image: dobie.png]Science is the process we've designed to be responsible for generating our best guess as to what the fuck is going on. Girly Man
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22-04-2014, 11:54 AM
RE: Uncertainty… principle?
The "real" uncertainty principle is based on the wave property of quantum stuff. You can either have a wave spread out over a long distance with a well-defined wavelength or you can have a pulse of energy with a well-defined position but a weird mix of wavelengths. This property is not restricted to quanta but also applies to larger scale waves:

Simple:




More accurate:



Give me your argument in the form of a published paper, and then we can start to talk.
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22-04-2014, 12:10 PM
RE: Uncertainty… principle?
Hello, Hafnof, and thanks for two very interesting videos.

(22-04-2014 11:54 AM)Hafnof Wrote:  The "real" uncertainty principle...
Would you mind going to the thread called "Gathering perspectives" and letting me know there what exactly you understand by "real"?

But please don't get me wrong, I never referred to the idea I've described as "the uncertainty principle", I just said that it reminded me of it and that it (the idea I described, not necessarily the "real" uncertainty principle) appears in my view as a consequence.

Waves have a spatial component (their wavelength) and a temporal component (their frequency). Seeing how we are talking about the inability to learn spatial information and temporal information from the same measurement, I'd say we are both talking about the same phenomenon.

But how would I know? Please don't take my view as an opposition to yours, but as an attempt to complement it.

Thanks again for your valuable addition to this thread. Have fun!
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22-04-2014, 01:15 PM
RE: Uncertainty… principle?
The two are totally unrelated.

The Uncertainty Principle is about measuring position and momentum, primarily of sub-atomic particles, nothing else.

Skepticism is not a position; it is an approach to claims.
Science is not a subject, but a method.
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22-04-2014, 01:42 PM
RE: Uncertainty… principle?
(22-04-2014 01:15 PM)Chas Wrote:  The two are totally unrelated.

The Uncertainty Principle is about measuring position and momentum, primarily of sub-atomic particles, nothing else.
Nothing else? If you say so.

What is your opinion on Hafnof's contribution? He's brought up an example of the "real" uncertainty principle, at least the way he seems to use that word, showing up in the frequency vs. wavelength in a wave. Is there anything you would like to say about that?

Thanks Chas, your skepticism is always appreciated.

Enjoy!
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22-04-2014, 02:05 PM
RE: Uncertainty… principle?
(22-04-2014 01:42 PM)living thing Wrote:  
(22-04-2014 01:15 PM)Chas Wrote:  The two are totally unrelated.

The Uncertainty Principle is about measuring position and momentum, primarily of sub-atomic particles, nothing else.
Nothing else? If you say so.

What is your opinion on Hafnof's contribution? He's brought up an example of the "real" uncertainty principle, at least the way he seems to use that word, showing up in the frequency vs. wavelength in a wave. Is there anything you would like to say about that?

Thanks Chas, your skepticism is always appreciated.

Enjoy!

They are isomorphic - that is, they are describing the same phenomenon.
Your picture-taking example is not.

Skepticism is not a position; it is an approach to claims.
Science is not a subject, but a method.
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22-04-2014, 02:06 PM
RE: Uncertainty… principle?
The photo thing is a good way to explain the principle, but it's different, it's like explaining gravity by using a trampoline with weights. Not the same, but helps to get the idea, I'll probably use it when the opportunity arises Thumbsup

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