Uncertainty… principle?
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22-04-2014, 06:03 PM
RE: Uncertainty… principle?
(22-04-2014 05:03 PM)Chas Wrote:  That is Heisenberg's Uncertainty Principle, yes. The concept has been extended to wave phenomena, but that's not what he was talking about.

The concept of uncertainty was more general than Heisenberg's conception, but those are isomorphic - the maths are the same.

Well, sure; though with the caveat that generally speaking basal uncertainty and observer effects are conflated... The position/momentum relation was the first to be observed, and the maths were generalised, that is true.

But yeah, the "limits" mentioned in the OP are more incumbent on the means of observation. A photograph is not bound by quantum limitations. It's trivial to overcome that specific limit - with a film camera! After all, a long-exposure photograph is just the superposition of "instantaneous" images.

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22-04-2014, 06:40 PM
RE: Uncertainty… principle?
(22-04-2014 06:03 PM)cjlr Wrote:  
(22-04-2014 05:03 PM)Chas Wrote:  That is Heisenberg's Uncertainty Principle, yes. The concept has been extended to wave phenomena, but that's not what he was talking about.

The concept of uncertainty was more general than Heisenberg's conception, but those are isomorphic - the maths are the same.

Well, sure; though with the caveat that generally speaking basal uncertainty and observer effects are conflated... The position/momentum relation was the first to be observed, and the maths were generalised, that is true.

But yeah, the "limits" mentioned in the OP are more incumbent on the means of observation. A photograph is not bound by quantum limitations. It's trivial to overcome that specific limit - with a film camera! After all, a long-exposure photograph is just the superposition of "instantaneous" images.

Yup.

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28-04-2014, 02:26 AM
RE: Uncertainty… principle?
(22-04-2014 02:43 PM)living thing Wrote:  Is it not possible that the notion of an instantaneous momentum is yet another abstraction in our minds that helps us understand the behaviour of things out there?

Thanks again for your kind remark. Have a good day!
Consider the empirically supported law of conservation of energy.

Energy cannot be created or destroyed, but only converted from one form to another.

Kinetic energy is energy in the form of movement. If you have momentum then you have kinetic energy. If you take a snap shot so quick in time such that delta t = 0, you see everything as if it is motionless. You can see the position (and shape) of things in space but you of course cannot see motion.
There is something else that you also cannot see and that is the energy and forces in play. You must remember that energy must be conserved. So either this kinetic energy has transformed into mass or potential energy or heat energy...
You need to account for it, even though you can't see it.

Lets say that we haven't stopped time. Time is going along at the usual rate. A one kilogram object is moving at 10m/s. Momentum = mass x velocity thus momentum of this object is 10kg.m/s. Kinetic energy is 1/2m.v^2 = 50kg.m^2/s^2 = 50J.
Now if velocity were to change, lets say it halved to 5m/s^2. Then Kinetic energy would decrease to 1/2.1.5^2 = 12.5J then we have lost 37.5J of energy, so where does the energy go? We need to account for it. Maybe it turned into heat, this could be possible if friction were causing the object to slow down. Or maybe it turned into potential energy, this would be possible if the object were traveling away from a large gravitational source (such as the Earth).

But in your example the only thing that has changed is the journey of time. You have frozen time. The energy was not transferred to heat or potential energy merely because time was frozen.

I would suggest that the energy is still there (because we can't account for any change and it is impossible for energy to not be conserved), since the object hasn't changed mass then I would say that it has an instantaneous velocity.

If the object had no forces acting on it then its kinetic energy remains constant. Its speed remains constant even though time has stopped.
If the object was subject to force, either it was accelerating or decelerating then you may need to use some math to work out its instantaneous velocity.

But there you go. Just because time stops it doesn't mean that momentum or kinetic energy disappears. Since there is momentum or kinetic energy then the object in frozen time has an instantaneous velocity even though you can't see it.
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28-04-2014, 04:24 AM (This post was last modified: 28-04-2014 04:45 AM by living thing.)
RE: Uncertainty… principle?
Hello again Stevil, thank you for another informative response. I hope you will not mind if I rearrange your text in order to simplify my replies; I’m not trying to change any meaning in your words but if you feel I have, please do correct me.

(28-04-2014 02:26 AM)Stevil Wrote:  If the object had no forces acting on it then its kinetic energy remains constant. Its speed remains constant even though time has stopped.
I don’t think it does.

When I take a photograph of a scene around me, the universe keeps going but the things in the picture stop moving. Things don’t move when time is stopped and, if they go from moving to not moving, that can hardly be described as a constant speed. Constant speed means that equal distances are traveled over equal non-zero periods of time, but it does not mean that things move during the zero length of an instant.

(28-04-2014 02:26 AM)Stevil Wrote:  But there you go. Just because time stops it doesn't mean that momentum or kinetic energy disappears. Since there is momentum or kinetic energy then the object in frozen time has an instantaneous velocity even though you can't see it.
I hate to say this, but I think you’re begging the question. In order for me to accept that the object has an instantaneous velocity even though I can’t see it, I must accept the premise that momentum and kinetic energy still occur during the zero length of an instant, but that is the conclusion that you are trying to draw.

However, when I do manage to freeze frame scenes, the most notorious feature common to all of them is the lack of motion in the objects contained; momentum and kinetic energy are clearly absent from those time-frozen scenes. So I cannot take your premise as a truth; in my mind, it seems far more likely that the notion of an instantaneous velocity is an abstract idea in our minds that helps us understand the behaviour of things around us. Although I may be wrong, so please don’t take my words too seriously.

(28-04-2014 02:26 AM)Stevil Wrote:  Consider the empirically supported law of conservation of energy.

Energy cannot be created or destroyed, but only converted from one form to another.
Of course, because energy is change.

I don’t think energy can be created or destroyed; there was never less than there is now, and there will never be more than there is now. Which leads to an interesting question: what happened 13.8 billion years ago?

Thanks once more for your helpful contribution to the thread.

(Edit: a few more years ago, he he)
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28-04-2014, 07:15 AM
RE: Uncertainty… principle?
(28-04-2014 04:24 AM)living thing Wrote:  Hello again Stevil, thank you for another informative response. I hope you will not mind if I rearrange your text in order to simplify my replies; I’m not trying to change any meaning in your words but if you feel I have, please do correct me.

(28-04-2014 02:26 AM)Stevil Wrote:  If the object had no forces acting on it then its kinetic energy remains constant. Its speed remains constant even though time has stopped.
I don’t think it does.

When I take a photograph of a scene around me, the universe keeps going but the things in the picture stop moving. Things don’t move when time is stopped and, if they go from moving to not moving, that can hardly be described as a constant speed. Constant speed means that equal distances are traveled over equal non-zero periods of time, but it does not mean that things move during the zero length of an instant.

(28-04-2014 02:26 AM)Stevil Wrote:  But there you go. Just because time stops it doesn't mean that momentum or kinetic energy disappears. Since there is momentum or kinetic energy then the object in frozen time has an instantaneous velocity even though you can't see it.
I hate to say this, but I think you’re begging the question. In order for me to accept that the object has an instantaneous velocity even though I can’t see it, I must accept the premise that momentum and kinetic energy still occur during the zero length of an instant, but that is the conclusion that you are trying to draw.

However, when I do manage to freeze frame scenes, the most notorious feature common to all of them is the lack of motion in the objects contained; momentum and kinetic energy are clearly absent from those time-frozen scenes. So I cannot take your premise as a truth; in my mind, it seems far more likely that the notion of an instantaneous velocity is an abstract idea in our minds that helps us understand the behaviour of things around us. Although I may be wrong, so please don’t take my words too seriously.

(28-04-2014 02:26 AM)Stevil Wrote:  Consider the empirically supported law of conservation of energy.

Energy cannot be created or destroyed, but only converted from one form to another.
Of course, because energy is change.

I don’t think energy can be created or destroyed; there was never less than there is now, and there will never be more than there is now. Which leads to an interesting question: what happened 13.8 billion years ago?

Thanks once more for your helpful contribution to the thread.

(Edit: a few more years ago, he he)




I think what everyone here is missing is the time cube principle.
http://www.timecube.com/

Let me know when you guys get through the second page. Laugh out load
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28-04-2014, 07:46 AM
RE: Uncertainty… principle?
Momentum (or what behaves at the macro scale as momentum) appears to be a fundamental property at the quantum level we are able to analyse. In particular, "spin"[1] seems to be intrinsic to particles to such as electrons. We know it is a quantum property because when we try to work backwards from the amount of energy we think the spin is composed of we find that the electron must be travelling faster than the speed of light in order to attain it.

As for your thought experiment about freezing a moment in time and observing that there is no motion and therefore no kinetic energy, I'm not sure I have clear answer to that. However, the answer I think begins with this "spin" property and also must take into consideration uncertainty in time. The uncertainty principle is not limited to ordinary space. We also find that particles and interactions and events have an uncertainty in time that may exclude your thought experiment from matching reality at this quantum level. We might imagine that we can freeze time and deduce something about what we think energy must be through that process of imagination, but there is no evidence that the thought experiment could correspond to reality. The experiment may boil down to "If this impossible thing were true then...".

[1] https://en.wikipedia.org/wiki/Spin_(physics)

Give me your argument in the form of a published paper, and then we can start to talk.
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28-04-2014, 08:08 AM
RE: Uncertainty… principle?
We were uncertain if my sister was going to be principal, then they offered her the job, even though she's still doing her PhD. She's a very certain principal, and that's a certainty. She was an uncertain principal only briefly.

That is all.
Carry on.

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28-04-2014, 10:54 AM
RE: Uncertainty… principle?
(28-04-2014 04:24 AM)living thing Wrote:  
(28-04-2014 02:26 AM)Stevil Wrote:  If the object had no forces acting on it then its kinetic energy remains constant. Its speed remains constant even though time has stopped.
I don’t think it does.
You are wrong. Newton's First Law.
Quote:When I take a photograph of a scene around me, the universe keeps going but the things in the picture stop moving. Things don’t move when time is stopped and, if they go from moving to not moving, that can hardly be described as a constant speed. Constant speed means that equal distances are traveled over equal non-zero periods of time, but it does not mean that things move during the zero length of an instant.
You are confused. There are no 'things' in your photograph.
Quote:
(28-04-2014 02:26 AM)Stevil Wrote:  But there you go. Just because time stops it doesn't mean that momentum or kinetic energy disappears. Since there is momentum or kinetic energy then the object in frozen time has an instantaneous velocity even though you can't see it.
I hate to say this, but I think you’re begging the question. In order for me to accept that the object has an instantaneous velocity even though I can’t see it, I must accept the premise that momentum and kinetic energy still occur during the zero length of an instant, but that is the conclusion that you are trying to draw.

However, when I do manage to freeze frame scenes, the most notorious feature common to all of them is the lack of motion in the objects contained; momentum and kinetic energy are clearly absent from those time-frozen scenes. So I cannot take your premise as a truth; in my mind, it seems far more likely that the notion of an instantaneous velocity is an abstract idea in our minds that helps us understand the behaviour of things around us. Although I may be wrong, so please don’t take my words too seriously.
You are confused. There is no momentum or change in momentum in your photograph.

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Science is not a subject, but a method.
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28-04-2014, 12:39 PM
RE: Uncertainty… principle?
Hello Hafnof, how's it going?

Do you think that an object can change its location or its orientation, in relation to some other object, during a time increment of zero units?
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28-04-2014, 12:41 PM
RE: Uncertainty… principle?
Hello Chas, how are you? Once again, I appreciate your skepticism. I do have a question, though. Do you think that styling your text in bold face makes you more correct?

Newton’s first law of motion describes how an object’s state of motion will not change unless acted upon by an external force; if the object has traveled a specific distance in a specific direction over the last non-zero interval of time, an equal interval of time later it will have covered an equal distance in the same direction. Newton’s first law of motion says absolutely nothing about the distance covered by an object during a zero length instant.

Of course there are things in my photograph, don’t be silly. There are plenty of chemical pigments arranged on a sheet of paper.

And I know there is no momentum or change in momentum in my photograph, that was exactly my argument. It is you who seems to be confused.

Thank you for enlightening me.
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