Allright I have a query. From what I understand, despite all the work done at REALLY cold temperatures, it is impossible to get to absolute zero. Now, what if say, you applied negative energy to something. If you applied enough, would it reach Absolute Zero? And What if you KEPT adding negative energy, would it go BELOW Absolute Zero?And what would happen then? As far as I know, we at this present time use less negative energy, then we do antimatter, so this 'experiment' won't become a practical question for a quite a while, if ever.

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Currently, absolute zero is a hard limit and negative temperatures have very little meaning.

Reach absolute zero? Never!

Go below absolute zero? See previous question!

ravens cry: now, what if say, you applied negative energy to something. If you applied enough, would it reach Absolute Zero? And What if you KEPT adding negative energy, would it go BELOW Absolute Zero?And what would happen then? As far as I know, we at this present time use less negative energy, then we do antimatter, so this 'experiment' won't become a practical question for a quite a while, if ever.

dcl: We do not have access to negative energy. It is accessible only to "pair production", in which negative energy is borrowed from space itself to produce, for example, electrons and positrons, that must then be returned to space itself via the process of "pair annihilation". There is no such thing as negative absolute temperature.

Hmmm. . . that isn't what THIS said, but maybe I am reading it wrong, as far as the access to negative energy goes. http://www.phy.duke.edu/~hsg/55/rela...s-jan-2000.pdf
Admittedly 95% of my understanding of negative energy is in that PDF, and 4% of the rest is from Terry Pratchett.

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dcl. I think I'll disagree here. The energy that that occurs in the Heisenberg Uncertainty Principle is real and therefore positive....although it is transient, and has a fleeting existence. Like Cinderella, it must get back to the castle before midnight, or the gown, the chariot and the ballroom fun disappear.
Einstein didn't like the Uncertainty Principle because it meant you could not be omniscient and deterministic about the velocity and positions of particles. I'll link Wiki further down. To further his case against Heisenberg, he expanded the Principle to include mass, energy and time....for a given object with a non-zero rest mass, he argued that you could not determine it's mass exactly to an arbitrary number of significant figures in a very short time interval....and therefore that it's mass/energy was inconstant. The shorter the time interval...the larger the mass fluctuation. He was right in his argument.
It took the insight of Hideki Yukawa to see that the mass/energy uncertainty of Einstein here could be used to create a "Cinderella-like particle", that could appear in a virtual sense, travel a very short distance in a real sense, interact with a nearby real particle, yet get back to it's point of origin within the constraints of the Uncertainty Principle, and nobody would be the wiser. He used it to predict the strong force carrying meson...the pion. It does not require a pair production (though that's possible), as long as the pion annihilates like Cinderella at "midnight"...the time constraint of a short speed of light transit. If pairs are produced , they too must disappear to conserve the hierarchy of conservation laws.
For Yukawa it enabled him to predict from proton/neutron distances, a time of flight, and from that a limiting mass for his virtual pion. It enabled Yukawa to model the strong force as an exchange of virtual particles...force carriers.To make the pion "real" you must agitate the nucleus with sufficient energy to embody it and eject it...say a cosmic ray collision, or an electron beam in an accelerator.
One way to think of it is as a tender of the gold bars at Fort Knox. Your job is inventory. One day you decide to swipe some bars. You pick up a couple, take two steps towards the door, and you've got them briefly (you're strong). You decide better of it, turn around, and restack them on the floor. For a few moments, they were yours, and the floor mass at Fort Knox was diminished, but you returned them before you were ever caught. Nobody was the wiser, even though you never got out the door. The difference is mass is conserved and Fort Knox never lost the gold. In a proton or neutron, the mass/energy must be returned by midnight. Lots of internet babble about harvesting virtual particles, and quantum foam, is unfounded, and like Fort Knox, you don't get energy or mass for free. pete
see:

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A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

trinitree88: The energy that that occurs in the Heisenberg Uncertainty Principle is real and therefore positive.

dcl: That is certainly true in most situations of pair production. But how about Hawking radiation? As I understand it, the energy that is converted into a particle pair just outside the event horizon is said to be borrowed temporarily from space itself as opposed to pair production via conversion of energetic radiation and is called "negative energy". If you know the above to be incorrect in any way, I'll appreciate your explaining what is wrong with it. I'm a physicist, but not a particle physicist.

If we create a particle from negative energy, I would expect it to have negative mass and cause the BH to grow.

This can't be right.

Excuse my ignorance, but BH? Acronyms can be so ambiguous.

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Black hole (BH) but if it starts getting to BHN Bullet Head Nebula then it will be confusing. The artists impression was good and so not right. From sums years ago to create a worm hole a half metre high would take the energy of the sun for a second.

The problem is that a worm hole on our level or even a star requires space to be plastic, malleable so that it can be stretched, pushed dragged or in this case have a hole poked through it. The next diagram is the better diagram as it shows the flat circular nature of the worm hole in the same style as the rubber sheet analogy.

So if it could be done then why is it still wrong on the streets of New York. Well the energy within the gateway would shred who so ever stepped any where near a worm hole that size. The rest position of all that is between that opening and the other end would have a gravitational effect. The light between the gate and a point in the distance where space was stretched beyond the capacity of light to get back to the opening would create a disk of utter darkness.

Now that does not sound like the worm hole every one is familiar with but if a work hole is to work space must be like plastic and poking a hole through from one side to another with the times stretching to balance. For a worm hole to work space must be something, vacuum is not empty.

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"Nature is obliged to let reality determine its laws, whereas mathematics is under no such constraint."

The question is what are you saying? That is not what popular science teaches about worm holes.

The answer:-
How could you be aware of what is intrinsic to your makeup?

Do you 'feel' the strong and the weak nuclear forces within you?

The answer is no but we know they are there ... E=mc^2 tells us the average human has enough fusible energy within them to level a city, do you feel it?

Since you do not feel that energy and yet you know that it is there all the rest must be deduced by a process of logic.

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"Nature is obliged to let reality determine its laws, whereas mathematics is under no such constraint."

This has been discussed before in the forums.

See also Wikipedia: Absolute zero.

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"All your bias are belong to us." Ara Pacis
"A witty saying proves nothing." Voltaire

dcl. The delta t times delta E presupposes you have the sample in hand in order for HUP to apply. With the BH event horizon, you can't reach in there and come back, so Cinderella gets stuck at the ballroom and evaporates, and if you take a piece of restmass, or a photon from this side....well that's already here, not in the BH....so you haven't added anything. Others have taken issue with Hawking radiation, particularly if it appears as particulates, since it presupposes an inherent asymmetry in the infalling of matter/antimatter in order for one to survive out here. This has not been historically my "toot". Pete

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A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

alainprice: If we create a particle from negative energy, I would expect it to have negative mass and cause the BH to grow. This can't be right.

dcl: We only CALL it negative energy, meaning that it is borrowed and must be repaid. I suppose that means that "negative energy" is a misnomer, but it wasn't my idea! Anyway, the mass, being kinda stupid, doesn't know that it's negative and insists on being treated as if it were positive.

ravens cry: If we create a particle from negative energy, I would expect it to have negative mass and cause the BH to grow.

dcl: Again, "negative energy" is only a name. The energy, while it's available, is real. The particles created from the "negative" energy have positive mass. The black hole does not grow because the particle falling into the black hole collides with an antiparticle and the two disintegrate, returning the energy borrowed from space back to space. Disappearance of the antiparticle leaves the mass of the black hole that much less. The original particle was never in the black hole in the first place, so it doesn't count in the transaction.

trinitree88: The delta t times delta E ...

dcl: I do not understand what you're trying to say. The mechanism of Hawking radiation, described in my response to ravens cry, above, is quite different from what you described. What does acronym HUP stand for? I wish people would stop using acronyms without defining them.

If you lend me $ 20, am I borrowing negative twenty dollars or a positive twenty dollars?

Sure, the number can be represented as 20 or -20, but the meaning does not change. There is no negative money, only a lack of positive money. Once the debt is repaid, you become whole again. Who's to say that being whole starts at 0?

Negative energy is a very serious misnomer unless you put it into context with an appropriate example.

Raven didn't say that, I did. The quote is misleading.

That description of Hawking radiation has many flaws.

Firstly, an antiparticle that falls into a black hole will add mass, not substract it. Even if the antiparticle finds its brother and annihilates, the sum of the energy is the same and stays within the singularity.

Secondly, the original particle is said to have borrowed the energy required for creation from the gravitational field of the BH. So yes, it is equivalent to a BH spitting out a sole particle and is the heart of this evaporation process.

Thirdly, how can you justify saying that negative energy can be used to create positive mass? If I borrow negative energy and don't repay it, the whole universe has lost energy, but gained mass. Impossible as far as I know.

Again, now that you explain yourself within a context, your meaning is clear. However, the wording remains misleading.

HUP: Heisenberg Uncertainty Principle
delta t: a small amount of time, or a ridiculously small interval
delta e: an amount of energy, generally small and negligible

alainprice: Sorry, I copied ravens cry's remark from your quotation of his statement without noticing that I was doing so. When I said, "The mass, being kinda stupid", I goofed. I meant to say, "The negative energy, being kinda stupid".

I'm aware that the description involving particle pairs just outside the event horizon is an oversimplification, but the more rigorous analysis involves more quantum field theory than I'm prepared to deal with. I'm led to understand that the particle-pair picture is a rough approximation of what quantum field theory describes.

My answers to your three points are:

1- It's annihilation of the particle or antiparticle falling through the event horizon that returns "negative" energy to its source whether it happens inside or outside the event horizon.

2- The "borrowed" energy that goes into generation of the particle pair is said to have been loaned not from the gravitational field of the black hole but from space itself, suggesting that space has the ability to perform short-term loans of real energy.

3- The "negative" in negative energy is not to be taken too literally. It merely implied that it is loaned and must be returned to its source.

Following your logic, if a particle-antiparticle pair forms(at the EH) and both magically manage to escape, then now there's a doubling of the negative energy being returned to the BH. This again is misleading, as if one of the 2 particles falls in, it is returning positive energy borrowed before(that particle adds back the mass-energy it borrowed).

A reasonable question might be are all forms of energy flavours of heat?

If so then absolute zero is the end of it all.

If not then ... game on!

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"Nature is obliged to let reality determine its laws, whereas mathematics is under no such constraint."

Michael Noonan: A reasonable question might be are all forms of energy flavours of heat?

dcl: I believe your question is similar to asking if all animals are forms of sharks. Heat is a form of energy in the same sense as a shark is a type of animal.