psēlaphaō wrote:Is this helpful?:

http://math.ucr.edu/home/baez/physics/Q ... icles.html

We are really using the quantum-mechanical approximation method known as perturbation theory. In perturbation theory, systems can go through intermediate "virtual states" that normally have energies different from that of the initial and final states. This is because of another uncertainty principle, which relates time and energy.

In the pictured example, we consider an intermediate state with a virtual photon in it. It isn't classically possible for a charged particle to just emit a photon and remain unchanged (except for recoil) itself. The state with the photon in it has too much energy, assuming conservation of momentum. However, since the intermediate state lasts only a short time, the state's energy becomes uncertain, and it can actually have the same energy as the initial and final states. This allows the system to pass through this state with some probability without violating energy conservation.

Some descriptions of this phenomenon instead say that the energy of the system becomes uncertain for a short period of time, that energy is somehow "borrowed" for a brief interval. This is just another way of talking about the same mathematics. However, it obscures the fact that all this talk of virtual states is just an approximation to quantum mechanics, in which energy is conserved at all times. The way I've described it also corresponds to the usual way of talking about Feynman diagrams, in which energy is conserved, but virtual particles can carry amounts of energy not normally allowed by the laws of motion.

(General relativity creates a different set of problems for energy conservation; that's described elsewhere in the sci.physics FAQ.)

lucek wrote:

DavidMcC wrote:

lucek wrote:

DavidMcC wrote:
Wrong. Ever heard of the uncertainty principle (delta E * delta t = h bar)?
Without that temporary violation of E-conservation, there would be no point in postulating virtual particles in the first place!

Dave your track record on this thread is pretty impressive. Virtual partials always conserve energy and momentum.

Don't be silly.
What bit of "virtual particles temporarily fail to conserve total energy" do you not understand?

Not on any scale beyond the one point of space. Keep in mind Dave we were talking about the scale of galaxies. Over time or over distance virtual partials average out. They in fact do conserve energy of space time.

Dave can you really do some reading, either what you are replying to or to the science.

lucek wrote:

DavidMcC wrote:

lucek wrote:

DavidMcC wrote:
Wrong. Ever heard of the uncertainty principle (delta E * delta t = h bar)?
Without that temporary violation of E-conservation, there would be no point in postulating virtual particles in the first place!

Dave your track record on this thread is pretty impressive. Virtual partials always conserve energy and momentum.

Don't be silly.
What bit of "virtual particles temporarily fail to conserve total energy" do you not understand?

Not on any scale beyond the one point of space. Keep in mind Dave we were talking about the scale of galaxies. Over time or over distance virtual partials average out. .
...

hackenslash wrote:

lucek wrote:Negative energy and negative mass are still quite hypothetical.

Ah, not really. They're pretty standard fayre in physics. Virtual pair production is pretty nailed to the wall by now, and there you have negative energy and negative mass (if the energy is negative, so's the mass, via E=mc2).

For experimental evidence of this, see Casimir Effect.

hackenslash wrote:It should be noted also that there are repulsive solutions to Einstein's equations, and repulsive gravity is a strong Dark Energy contender.

hackenslash wrote:See later post, where I retracted.

lucek wrote:...
Dave your track record on this thread is pretty impressive. Virtual partials always conserve energy and momentum.
....

Dave can you really do some reading, either what you are replying to or to the science.

DavidMcC wrote:

psēlaphaō wrote:Is this helpful?:

http://math.ucr.edu/home/baez/physics/Q ... icles.html

We are really using the quantum-mechanical approximation method known as perturbation theory. In perturbation theory, systems can go through intermediate "virtual states" that normally have energies different from that of the initial and final states. This is because of another uncertainty principle, which relates time and energy.

In the pictured example, we consider an intermediate state with a virtual photon in it. It isn't classically possible for a charged particle to just emit a photon and remain unchanged (except for recoil) itself. The state with the photon in it has too much energy, assuming conservation of momentum. However, since the intermediate state lasts only a short time, the state's energy becomes uncertain, and it can actually have the same energy as the initial and final states. This allows the system to pass through this state with some probability without violating energy conservation.

Some descriptions of this phenomenon instead say that the energy of the system becomes uncertain for a short period of time, that energy is somehow "borrowed" for a brief interval. This is just another way of talking about the same mathematics. However, it obscures the fact that all this talk of virtual states is just an approximation to quantum mechanics, in which energy is conserved at all times. The way I've described it also corresponds to the usual way of talking about Feynman diagrams, in which energy is conserved, but virtual particles can carry amounts of energy not normally allowed by the laws of motion.

(General relativity creates a different set of problems for energy conservation; that's described elsewhere in the sci.physics FAQ.)

Thanks, psēlaphaō. Perhaps lucek does not recognise that way of looking at it (see bolded bit).

psēlaphaō wrote:

DavidMcC wrote:

psēlaphaō wrote:Is this helpful?:

http://math.ucr.edu/home/baez/physics/Q ... icles.html

We are really using the quantum-mechanical approximation method known as perturbation theory. In perturbation theory, systems can go through intermediate "virtual states" that normally have energies different from that of the initial and final states. This is because of another uncertainty principle, which relates time and energy.

In the pictured example, we consider an intermediate state with a virtual photon in it. It isn't classically possible for a charged particle to just emit a photon and remain unchanged (except for recoil) itself. The state with the photon in it has too much energy, assuming conservation of momentum. However, since the intermediate state lasts only a short time, the state's energy becomes uncertain, and it can actually have the same energy as the initial and final states. This allows the system to pass through this state with some probability without violating energy conservation.

Some descriptions of this phenomenon instead say that the energy of the system becomes uncertain for a short period of time, that energy is somehow "borrowed" for a brief interval. This is just another way of talking about the same mathematics. However, it obscures the fact that all this talk of virtual states is just an approximation to quantum mechanics, in which energy is conserved at all times. The way I've described it also corresponds to the usual way of talking about Feynman diagrams, in which energy is conserved, but virtual particles can carry amounts of energy not normally allowed by the laws of motion.

(General relativity creates a different set of problems for energy conservation; that's described elsewhere in the sci.physics FAQ.)

Thanks, psēlaphaō. Perhaps lucek does not recognise that way of looking at it (see bolded bit).

Hmm. What do you think is meant by the underlined and italicized part?

DavidMcC wrote:_____
A thought on mass-energy equivalence:
In the absence of creation or destruction of space (which is in pretty well all experiments that can be done in labs), the principle should hold good, because the energy of space itself is not converted one way or the other. However, if space itself has energy (the so-called zero-point energy), and particle are excitations of space, then the theory should not be so simple. This could explain why "dark energy" has such different effects from "dark matter".

lucek wrote:

DavidMcC wrote:_____
A thought on mass-energy equivalence:
In the absence of creation or destruction of space (which is in pretty well all experiments that can be done in labs), the principle should hold good, because the energy of space itself is not converted one way or the other. However, if space itself has energy (the so-called zero-point energy), and particle are excitations of space, then the theory should not be so simple. This could explain why "dark energy" has such different effects from "dark matter".

No words Dave. You leave me with no words at all.

I'm hoping that this was fallacious.

DavidMcC wrote:

lucek wrote:

DavidMcC wrote:_____
A thought on mass-energy equivalence:
In the absence of creation or destruction of space (which is in pretty well all experiments that can be done in labs), the principle should hold good, because the energy of space itself is not converted one way or the other. However, if space itself has energy (the so-called zero-point energy), and particle are excitations of space, then the theory should not be so simple. This could explain why "dark energy" has such different effects from "dark matter".

No words Dave. You leave me with no words at all.

I'm hoping that this was fallacious.

Well, if you have no words, nor do I, and that is the end of it.
I know, what if you find the words to argue against the concept of the energy of space, because that is the only defence of mass-energy equivalence in cosmology (as opposed to in stars, nuclear bombs and high energy physics experiments, where it does hold, because no space is being created or destroyed).

lucek wrote:

DavidMcC wrote:

lucek wrote:

DavidMcC wrote:_____
A thought on mass-energy equivalence:
In the absence of creation or destruction of space (which is in pretty well all experiments that can be done in labs), the principle should hold good, because the energy of space itself is not converted one way or the other. However, if space itself has energy (the so-called zero-point energy), and particle are excitations of space, then the theory should not be so simple. This could explain why "dark energy" has such different effects from "dark matter".

No words Dave. You leave me with no words at all.

I'm hoping that this was fallacious.

Well, if you have no words, nor do I, and that is the end of it.
I know, what if you find the words to argue against the concept of the energy of space, because that is the only defence of mass-energy equivalence in cosmology (as opposed to in stars, nuclear bombs and high energy physics experiments, where it does hold, because no space is being created or destroyed).

I was more referring to you saying that space containing energy might be a reason why a universe wide outward force is different then matter that doesn't or only weakly interacts with anything except via gravity.

If I take it to mean that the energy of particles affects their behavior then I'd say duh, if I take it to mean you think dark energy and dark matter are the same or two sides of the same coin I can only face palm, other then that I don't know what to take from your statement.

DavidMcC wrote:

lucek wrote:

DavidMcC wrote:

lucek wrote:
No words Dave. You leave me with no words at all.

I'm hoping that this was fallacious.

Well, if you have no words, nor do I, and that is the end of it.
I know, what if you find the words to argue against the concept of the energy of space, because that is the only defence of mass-energy equivalence in cosmology (as opposed to in stars, nuclear bombs and high energy physics experiments, where it does hold, because no space is being created or destroyed).

I was more referring to you saying that space containing energy might be a reason why a universe wide outward force is different then matter that doesn't or only weakly interacts with anything except via gravity.

That is not what I said, lucek. Read my posts in the LQG thread (page 6, et seq.) and you will see that you misinterpretted me in this.

If I take it to mean that the energy of particles affects their behavior then I'd say duh, if I take it to mean you think dark energy and dark matter are the same or two sides of the same coin I can only face palm, other then that I don't know what to take from your statement.

This also has nothing to do with what I said in the LQG thread.

lucek wrote:

DavidMcC wrote:

lucek wrote:

DavidMcC wrote:
Well, if you have no words, nor do I, and that is the end of it.
I know, what if you find the words to argue against the concept of the energy of space, because that is the only defence of mass-energy equivalence in cosmology (as opposed to in stars, nuclear bombs and high energy physics experiments, where it does hold, because no space is being created or destroyed).

I was more referring to you saying that space containing energy might be a reason why a universe wide outward force is different then matter that doesn't or only weakly interacts with anything except via gravity.

That is not what I said, lucek. Read my posts in the LQG thread (page 6, et seq.) and you will see that you misinterpretted me in this.

If I take it to mean that the energy of particles affects their behavior then I'd say duh, if I take it to mean you think dark energy and dark matter are the same or two sides of the same coin I can only face palm, other then that I don't know what to take from your statement.

This also has nothing to do with what I said in the LQG thread.

I freely admit then I have no clue what the fuck you are on about then. I also have yet to see why you thought it important to bump this thread with it. If you won't even clarify what appears to just be ramblings then I must wonder the value of this discourse.

That said, Good by Dave.