[immijimmi]

questionposter, on 22 January 2012 - 05:51 PM, said:

Actually I have a whole nother realm of a question:

If a photon hits an electron and get's re-emitted and head's towards an observer, is the location of where the photon hit the electron "recorded" within the photon, or is the location that we measure the electron at uncertain within the photon that we measure?
In other words, is it predetermined where we will measure an electron at within a photon?

...What? The reason we see things which photons have bounced off is that the photons that are not absorbed are of a specific frequency or frequencies, which gives us the colour of the object. Put all the photons that enter your eyes together and you get an image. The photons that reached us don't carry an image of the incident. They won't have changed at all. We can't measure anything from this lone photon you're talking about unless we know some other details of the incident. (for example, we could measure when it happened if we knew where, by calculating distance/speed).

[questionposter]

MigL, on 22 January 2012 - 06:30 PM, said:

Re-read the whole discussion.
It seems you are confused about what happens when a measurement is made on a Quantum Mechanical system.
By your misunderstanding, the collapse of the wavefunction when an observation is made, implies that the wave nature of the system becomes an actual point particle.
That is NOT the way it works. Wave function collapse is an 'interpretation' to allow for the multitudes of possibilities represented by the wavefunction and the single observed result.
The wavefunction does not collapse to a particle, and time certainly does not stop.

Except I'm not talking about the wave of a particle, I'm talking about that-which-you-measure, which is a point or single exactly defined result. When you measure a particle, even though the particle itself is a wave, the thing your measuring or seeing is a point, your not actually seeing an entire undefined wave, your somehow only seeing something as a point. Why doesn't someone just see what happens when they plug in "energy=0" for a wave mechanics equation? I'm pretty sure no energy means no wave anyway. So if what we are measuring matches what is generating by what happens when you plug in "energy=0", that what we are measuring is what happens when you plug in "energy=0"
Maybe time doesn't stop from a point of reference, but nothing actually has 0K, so what else happens at 0K and what else is happening that turns a measurement from a wave to a point?
Also, even though something can have a point of reference from itself, is Swan actually suggesting that every object relative to itself has achieved absolute 0? Why are there so many people that say absolute 0 is impossible if its that simple?

This post has been edited by questionposter: 22 January 2012 - 07:13 PM

[D H]

questionposter, on 22 January 2012 - 07:05 PM, said:

Also, even though something can have a point of reference from itself, is Swan actually suggesting that every object relative to itself has achieved absolute 0? Why are there so many people that say absolute 0 is impossible if its that simple?

Individual atoms do not have a temperature. Temperature is a macroscopic phenomenon, not a microscopic one.

You are still mis-mixing and mismatching a number of different concepts.

There is no such thing as absolute rest or absolute motion. Get those notions out of your mind.

[questionposter]

D H, on 22 January 2012 - 07:47 PM, said:

Individual atoms do not have a temperature. Temperature is a macroscopic phenomenon, not a microscopic one.

You are still mis-mixing and mismatching a number of different concepts.

There is no such thing as absolute rest or absolute motion. Get those notions out of your mind.

Ok, but kinetic energy is different than temperature. Temperature is the measure of the average kinetic energy. A single atom doesn't have an average kinetic energy, but it does have just plain kinetic energy.
Also, I'm not saying that you can't measure different motions from different points of reference, but every atom has some kind of kinetic energy. Just how light always travels at C but you can measure different frequencies. A property of kinetic energy is just that it causes things to move in some way shape or form just as a property of gravity is that it gets weaker by f=y/x^2 or a property of electro-magnetism is that it has parity or a property of light is that it travels at C. Some things are just beyond relativity.
And again, why are there so many people who say 0K is impossible if all you have to do is pick up a clock to prove something has 0K?

Actually, because of the uncertainty principal, there HAS to be motion because there will always be uncertainty about a particle's momentum, so a particle can't actually have 0K without I guess either time having been stopping or it just not existing at least as a wave any more.
Also a distinction that somehow people still aren't recognizing is between an actual particle and a measurement. A measurement is different than a particle, that's why they have different definitions in the dictionary. The measurement you make is a point which is not traveling distance over time, where the measurement of a point came from is a particle which does travel distance over time. A measurement doesn't travel distance over time and therefore cannot have kinetic energy or even momentum which is why we don't observe a measurement as a wave, since you need energy to generate a wave.

This post has been edited by questionposter: 22 January 2012 - 08:22 PM

[D H]

questionposter, on 22 January 2012 - 08:12 PM, said:

Ok, but kinetic energy is different than temperature.

Not really. The temperature of an object (if it has one) is just a measure of the average kinetic energy of the individual atoms/molecules in that object. You said so yourself:

Quote

Temperature is the measure of the average kinetic energy.

So which is it: Is temperature something different than kinetic energy, or a measure of the average kinetic energy? You can't have it both ways.

One of the key moves afoot in metrology is to make several of the currently measured physical constants into defined constants. Example: The speed of light is now a defined constant. The latest meeting of the CGPM proposed making the Boltzmann constant k a defined constant, along with several others. Making the Boltzmann constant a defined value would explicitly tie temperature to kinetic energy, by definition.

You appear to still be hung up on the idea of absolute motion. Drop that notion. Galileo (not Einstein) showed that this concept has limited validity. Einstein showed that it has no validity. None, zero, zip, nada. You need to drop this Aristotelian notion before you can make any progress in understanding the physics of the last 400 years.

[Widdekind]

I understand, that "wave-function collapse to a point" is, rigorously, an exaggeration, which has never, actually, been observed. For example, in double slit experiments, the incident photon / electron wave-function "collapses", into one of many phosphor grains, coating the detector screen. But, those phosphor grains are in size, characteristically. Thus, the wave-function "collapses", from a macro- or meso-scopic scale, to a micro-scopic scale, but, by no means, to "a point".

I also understand, that the Schrodinger Wave Equation, is an approximation, to the more rigorous, and relativistically accurate, equations (e.g. Dirac equation, Klein-Gordon equation). Thus, the SWE implicitly embodies simplifying assumptions, whose omission could cause confusion. In particular, in the full relativistic equations, a particle's rest-mass-energy (mc²) defines that particle's intrinsic phase frequency. That could be included in the SWE, as . Thus, a particle with zero KE, or even a negative bonding energy, still has a positive frequency (unless the negative bonding energy exceeds its rest-mass energy, which only occurs, in relativistically deep gravity wells).

I understand, that that phase frequency is physically real, as the phase of wave-functions can be measured, e.g. Aharonov-Bohm effect. Thus, the wave-function, of a particle at rest, is still "spinning its phase", even if "its just sitting there", e.g. in its own rest-frame.

This post has been edited by Widdekind: 22 January 2012 - 10:46 PM

[questionposter]

D H, on 22 January 2012 - 09:24 PM, said:

Not really. The temperature of an object (if it has one) is just a measure of the average kinetic energy of the individual atoms/molecules in that object. You said so yourself:

So which is it: Is temperature something different than kinetic energy, or a measure of the average kinetic energy? You can't have it both ways.

One of the key moves afoot in metrology is to make several of the currently measured physical constants into defined constants. Example: The speed of light is now a defined constant. The latest meeting of the CGPM proposed making the Boltzmann constant k a defined constant, along with several others. Making the Boltzmann constant a defined value would explicitly tie temperature to kinetic energy, by definition.

Having an average of kinetic energies is way different than looking at the kinetic energy of an individual atom.

I'm not saying a specific kinetic energy is constant, I'm saying the fact that there is kinetic energy is constant, which is just like "the force of gravity is not constant, but the fact that all mass-particles have gravity is constant". You could even say that the gravity of Pluto on planet Earth is 0 because you can't feel it even though by the laws of gravity the gravity of Pluto has to be effecting us in some way.

Widdekind, on 22 January 2012 - 10:25 PM, said:

I understand, that "wave-function collapse to a point" is, rigorously, an exaggeration, which has never, actually, been observed. For example, in double slit experiments, the incident photon / electron wave-function "collapses", into one of many phosphor grains, coating the detector screen. But, those phosphor grains are in size, characteristically. Thus, the wave-function "collapses", from a macro- or meso-scopic scale, to a micro-scopic scale, but, by no means, to "a point".

I also understand, that the Schrodinger Wave Equation, is an approximation, to the more rigorous, and relativistically accurate, equations (e.g. Dirac equation, Klein-Gordon equation). Thus, the SWE implicitly embodies simplifying assumptions, whose omission could cause confusion. In particular, in the full relativistic equations, a particle's rest-mass-energy (mc²) defines that particle's intrinsic phase frequency. That could be included in the SWE, as . Thus, a particle with zero KE, or even a negative bonding energy, still has a positive frequency (unless the negative bonding energy exceeds its rest-mass energy, which only occurs, in relativistically deep gravity wells).

I understand, that that phase frequency is physically real, as the phase of wave-functions can be measured, e.g. Aharonov-Bohm effect. Thus, the wave-function, of a particle at rest, is still "spinning its phase", even if "its just sitting there", e.g. in its own rest-frame.

With general relativity, it can't be spinning according to it's own frame of reference, from it's frame of reference everything else would be moving around it. That's why people thought stars revolved around the Earth. I know that a particle does have to be oscillating and moving in order for it to even exist as it does, but that's one of the problems here. This is where QM and GR for some reason don't mix.
Anyway, we can't directly measure things as a wave, which only leaves things as a defined point, unless there's some other shape I'm missing. When you refer to the dimensions of the phosphorus, you are referring to when a photon effects phosphorous atoms and phosphorous atoms themselves occupy 3 dimensional space, but not the measurement of a photon bouncing off of that phosphorous atom itself. A measurement doesn't occupy space, it doesn't move distance over time, it's technically not even a real thing, because by the time you would measure the location of an electron, the electron had already gone into a state in which it has no defined location, unless somehow the measurement and the photon and the electron are still entangled...maybe.
I suppose time stopping isn't logical even if people weren't understanding that I wasn't saying the time of the universe is stopping, but there is a difference between an object and the measurement of that object.

This post has been edited by questionposter: 22 January 2012 - 11:03 PM

[MigL]

But we don't measure to a dimensionless point...
There is a limit to accuracy we can acheive, and it is fairly 'smeared out'.
Also as Widdekind has explaned, put an EM wave through a double slit. Do you measure a point ???

Wish I had more time, gotta run.

[questionposter]

MigL, on 22 January 2012 - 11:09 PM, said:

But we don't measure to a dimensionless point...
There is a limit to accuracy we can acheive, and it is fairly 'smeared out'.
Also as Widdekind has explaned, put an EM wave through a double slit. Do you measure a point ???

Wish I had more time, gotta run.

If you put an EM wave through a double slit, you technically don't even measure the phosphorous, you measure a photon, which is why there should be a distinction between a measurement and the object you measure. A point I think also occupies one dimension.

This post has been edited by questionposter: 22 January 2012 - 11:14 PM

[DrRocket]

questionposter, on 22 January 2012 - 06:47 AM, said:

So if nothing is universal, then from some point of reference I should be able to measure light not traveling at the speed of light, or that something is traveling faster than light, or that gravity get's weaker by the cube of the distance rather than the square of the distance, or that energy=mass times the speed of light quintupled...

Your logic is flawed (non-existent) and your conclusion is false.

questionposter said:

If I pick up a clock, the vibrations generated by my heartbeat move it, even if it's not noticeable. So do the vibrations from motion within the Earth's crust as well as random neutrino and cosmic-ray hits and all the particles HAVE to be moving because they don't have 0K when your not measuring them, which means the particles of the clock are in some way "moving back and forth" due to kinetic energy and definitely due to unnoticeable vibrations that are proven to exist.

The term "clock" in relativity, and in physics in general, does not refer to any specific device, or in fact to any device at all, but rather any means, real or idealized, for measuring time. "Time is what clocks measure".

So, yes, if you have a physical device that is your "clock" then the elementary particles of which it is composed will each be in some quantum state and that state will not be one of 0 energy even if the clock is at 0K -- not all (in fact no two) fermionic particles in a system, according the Pauli exclusion principle, can be in the same quantum state, so they cannot all have 0 energy. But they can be in the lowest allowable set of states and that is what is meant by absolute zero.

[swansont]

questionposter, on 22 January 2012 - 05:32 PM, said:

Ok, now there's a conflict, because in the same page I have "0K is impossible" and "0k is completely possible".

You have misread something or have a misconception if that's what you have taken away from this.

questionposter, on 22 January 2012 - 05:32 PM, said:

The objects making up something in a center-of-mass system are made out of atoms, and atoms are constantly moving in some way because they have energy, so if they have no energy, there would be no wave...oh wait, a point, it's not a wave, and we can't infinitely continuously measure that the point moves distance over time, so how is the point not having 0 kinetic or really 0 of any energy?

Why do you think there is no wave, and you have a point, if there is no energy? The deBroglie wavelength tends to infinity as kinetic energy (and thus momentum) goes to zero. That's the opposite of a point.

[questionposter]

swansont, on 23 January 2012 - 01:37 AM, said:

You have misread something or have a misconception if that's what you have taken away from this.



Why do you think there is no wave, and you have a point, if there is no energy? The deBroglie wavelength tends to infinity as kinetic energy (and thus momentum) goes to zero. That's the opposite of a point.

Because if a wave doesn't have energy, then it's no longer a wave, and when you measure something, we don't measure it as a wave which suggests it may not have energy, and the other part is that a measurement which is a point isn't traveling any distance over time and thus cannot have momentum or I guess kinetic energy.
Also, I thought it was impossible for a particle itself to have 0 momentum because of the uncertainty principal and you would have to add energy into the system to try and force a a particle to a lower energy state beyond it's lowest possible state to 0 which isn't decreasing the energy, it's just forming degenerate matter which definitely has a lot of energy.

This post has been edited by questionposter: 23 January 2012 - 01:57 AM

[Widdekind]

I understand, that a particle can have a momentum expectation value , indicating that the "centroid" of the wave-function is stationary. The HUP demands, however, some "uncertainty", i.e. some mathematical statistical spread, in momentum. Er go, a particle which is "stationary" is a super-position, of numerous momentum states, representing equal amounts of momentum, flowing forward as backward, left as right, up as down.

[swansont]

questionposter, on 23 January 2012 - 01:51 AM, said:

Because if a wave doesn't have energy, then it's no longer a wave, and when you measure something, we don't measure it as a wave which suggests it may not have energy, and the other part is that a measurement which is a point isn't traveling any distance over time and thus cannot have momentum or I guess kinetic energy.
Also, I thought it was impossible for a particle itself to have 0 momentum because of the uncertainty principal and you would have to add energy into the system to try and force a a particle to a lower energy state beyond it's lowest possible state to 0 which isn't decreasing the energy, it's just forming degenerate matter which definitely has a lot of energy.

The wave has an infinite wavelength. Why is a measurement involved here?

HUP says you cannot simultaneously measure momentum and position to arbitrary precision. You can know the momentum as long as you don't know the position. In any event, trying to tie time to motion is misguided.

[questionposter]

swansont, on 23 January 2012 - 01:08 PM, said:

The wave has an infinite wavelength. Why is a measurement involved here?

HUP says you cannot simultaneously measure momentum and position to arbitrary precision. You can know the momentum as long as you don't know the position. In any event, trying to tie time to motion is misguided.

But you technically don't know the position still, all you know is what the photon tells you and by the photon is measured the particles has already gone into a state with an undefined location.
Perhaps there is uncertainty in "where" you will end up measuring the location of the point which can be contained within the photon you measure information from, otherwise what else are your eyes and instruments actually measuring? Are they measuring triangles? Circles? Squares?

This post has been edited by questionposter: 23 January 2012 - 01:21 PM

[swansont]

questionposter, on 23 January 2012 - 01:19 PM, said:

But you technically don't know the position still, all you know is what the photon tells you and by the photon is measured the particles has already gone into a state with an undefined location.

Why is there a photon involved? I though the question was whether something can have zero kinetic energy. I mean, sure, you can say nothing can be at rest because I am going to continually perturb it, but that's not really the same thing, is it?

[questionposter]

swansont, on 23 January 2012 - 01:30 PM, said:

Why is there a photon involved? I though the question was whether something can have zero kinetic energy. I mean, sure, you can say nothing can be at rest because I am going to continually perturb it, but that's not really the same thing, is it?

I suppose no "object" can have 0 kinetic energy (and therefore has to be constantly moving in some way?), but a measurement isn't an object...

[DrRocket]

questionposter, on 22 January 2012 - 08:12 PM, said:

Ok, but kinetic energy is different than temperature. Temperature is the measure of the average kinetic energy. A single atom doesn't have an average kinetic energy, but it does have just plain kinetic energy.

Of course a single atom has an average kinetic energy. When you average over a single data point, that point IS the average.

However, what you are grasping to say is that temperature is normally used to describe the statistical behavior of a large number of particles, and hence temperature is not really germane to the description of a single particle. Also you have to be rather careful when considering a single particle, as kinetic energy is a frame-dependent quantity. In statistical thermodynamics, it is implicitly assumed that one is working in a reference frame in which the net momentum of the system of particles under consideration is zero. In engineering thermodynamics (which considers open systems as well as closed systems) one has to be careful to specify what means by "temperature" so when gas dynamics enters the picture you have "stagnation temperature" or "static temperature" and the two can differ by literally thousands of degrees in problems of practical interest.

You are also confusing the general, classical kinetic theory with quantum theory. They are not the same thing and the classical theory does not consider quantum effects.

questionposter said:

Also, I'm not saying that you can't measure different motions from different points of reference, but every atom has some kind of kinetic energy.

That is simply not true.

The internal energy of a monatomic gas, like hydrogen, in classical statistical thermodynamics is just the translational kinetic energy, and it is very easy to pick a reference frame in which the energy of any single atom is zero.

When you invoke quantum theory the situation is a bit more muddy.

In fact at the quantum level the notion of kinetic energy as distinct from potential energy rather loses meaning. In fact "motion", given the uncertainty in position, is not particularly well-defined.

What you have are quantum states, and "energy" is part of what is necessary to define a quantum state.

questionposter said:

Actually, because of the uncertainty principal, there HAS to be motion because there will always be uncertainty about a particle's momentum, so a particle can't actually have 0K without I guess either time having been stopping or it just not existing at least as a wave any more.

Nope.

You are trying to impose classical notions on quantum mechanics. That doesn't work.

questionposter said:

Also a distinction that somehow people still aren't recognizing is between an actual particle and a measurement. A measurement is different than a particle, that's why they have different definitions in the dictionary. The measurement you make is a point which is not traveling distance over time, where the measurement of a point came from is a particle which does travel distance over time. A measurement doesn't travel distance over time and therefore cannot have kinetic energy or even momentum which is why we don't observe a measurement as a wave, since you need energy to generate a wave.

This makes no sense. Of course a measurement is different from a particle. A measurement is not a physical thing, but rather is an action taken by someone. It is also true, and equally relevant, that a horse is not a political principle.

It is you, not others, who is not recognizing what is going on.

You are also confusing the second law of thermodynamics -- which in one form states that no system not already at absolute zero can reach absolute zero in a finite number of thermodynamic steps -- with the idea that "0K is impossible". The concept of absolute zero is crystal clear -- either in the abstract language of classical thermodynamics or in the slightly more concrete language of quantum mechanics in which it is the lowest possible energy state of a system (which by the Pauli exclusion principle is not a state of zero energy).

[questionposter]

DrRocket, on 24 January 2012 - 01:36 AM, said:

Of course a single atom has an average kinetic energy. When you average over a single data point, that point IS the average.

Then there is always an average above 0. I have yet to see a head line that saying "Scientists Achieve Absolute 0 in a substance" or even something as 'simple' as "Scientists Achieve Absolute 0 With Single Atom".

DrRocket, on 24 January 2012 - 01:36 AM, said:

However, what you are grasping to say is that temperature is normally used to describe the statistical behavior of a large number of particles, and hence temperature is not really germane to the description of a single particle. Also you have to be rather careful when considering a single particle, as kinetic energy is a frame-dependent quantity. In statistical thermodynamics, it is implicitly assumed that one is working in a reference frame in which the net momentum of the system of particles under consideration is zero. In engineering thermodynamics (which considers open systems as well as closed systems) one has to be careful to specify what means by "temperature" so when gas dynamics enters the picture you have "stagnation temperature" or "static temperature" and the two can differ by literally thousands of degrees in problems of practical interest.

You are also confusing the general, classical kinetic theory with quantum theory. They are not the same thing and the classical theory does not consider quantum effects.

Some classical mechanics happens at the atomic level. When you have kinetic energy, atoms are LITERALLY moving. When you push on something, you are LITERALLY pushing on the atoms and giving them kinetic energy and making them move and bump into each other.

DrRocket, on 24 January 2012 - 01:36 AM, said:

That is simply not true.

The internal energy of a monatomic gas, like hydrogen, in classical statistical thermodynamics is just the translational kinetic energy, and it is very easy to pick a reference frame in which the energy of any single atom is zero.

When you invoke quantum theory the situation is a bit more muddy.

In fact at the quantum level the notion of kinetic energy as distinct from potential energy rather loses meaning. In fact "motion", given the uncertainty in position, is not particularly well-defined.

What you have are quantum states, and "energy" is part of what is necessary to define a quantum state.

Energy within an atomic system, such as with hydrogen gas, is quantized. Losing all kinetic energy requires an electron to lose energy past it's ground state (which is always a non-zero momentum above the nucleus) and remain solely in the nucleus, which isn't known to be possible. And then, we can try to force an electron into the nucleus, but that only adds more energy to the system and eventually forms high-energy degenerate matter.
I get that there are frames of reference, but there's also different frame's of reference in which to measure light yet it is always measured at C. Given the proper instruments, we could always measure something is moving because we can never actually achieve a perfectly "still" or "perfectly in uniform motion" system, and this is because everything we can measure light from is made up of atoms which have uncertain momentums.

DrRocket, on 24 January 2012 - 01:36 AM, said:

Nope.

You are trying to impose classical notions on quantum mechanics. That doesn't work.

The Heisenberg Uncertainty Principal is quantum mechanics, not classical mechanics. Even though I already mentioned the quantinization problem, it still holds true that there is uncertainty about the momentum of a particle and thus the energy level of a particle cannot actually solely be at 0. Perhaps it maybe can be "at 0 and at it's next energy level and some energy levels above that" but all simultaneously.
Math is not reality because math is deterministic.

DrRocket, on 24 January 2012 - 01:36 AM, said:

This makes no sense. Of course a measurement is different from a particle. A measurement is not a physical thing, but rather is an action taken by someone. It is also true, and equally relevant, that a horse is not a political principle.

It is you, not others, who is not recognizing what is going on.

You are also confusing the second law of thermodynamics -- which in one form states that no system not already at absolute zero can reach absolute zero in a finite number of thermodynamic steps -- with the idea that "0K is impossible". The concept of absolute zero is crystal clear -- either in the abstract language of classical thermodynamics or in the slightly more concrete language of quantum mechanics in which it is the lowest possible energy state of a system (which by the Pauli exclusion principle is not a state of zero energy).

The laws of thermal dynamics which have already been broken by substances like liquid helium apply to physical objects, not measurements.
Kinetic energy can be defined basically as something that causes acceleration or motion, and atoms have both literal and quantum mechanical motion.
Perhaps you can try to make the net kinetic energy of an object "0" so that you can try to state it has no kinetic energy and isn't traveling in any direction, but the atoms themselves will have to be moving as they cannot exist in a defined location. Only a defined location can have a net energy equal to 0 at least in a vector system. How could an undefined location have it? It doesn't exist a specific location, so it doesn't hold specific kinetic energy.
With a measurement itself however, a measurement, which is the point, isn't traveling distance over time and so can't be moving, so the measurement has 0 kinetic energy.


A measurement has no momentum so that is perhaps why we perceive atoms as points instead of waves since you need momentum to generate a wave.

It's already expected and essentially proven that consciousness has weird effects on matter on the atomic scale, I don't get why the above notion this is such a catastrophe to people.

This post has been edited by questionposter: 24 January 2012 - 02:21 AM

[swansont]

questionposter, on 24 January 2012 - 02:07 AM, said:

The laws of thermal dynamics which have already been broken by substances like liquid helium apply to physical objects, not measurements.

What thermodynamic laws do you think have been broken by liquid Helium?