Momentum

[greebo]

Spar had it right with spontaneous particle creation, there is a non-zero probability that virtual particles -- which can spontaneously trigger even from the energy of a total vacuum -- can collapse into "real" (stable, or mostly stable) particles. And get enough of those happening in just the right way, there's supposed to be a probability that it can also put into motion any arbitrary collection of particles as well. (I mean, it's already technically created *this* universe once, from the original singularity subject to these quantum effects, if you want to think about it that way).

I still don't get what this has to do with the number of lives we're living, but I guess we're already past the point where this is being discussed.

 

although quantum effects also have to follow the laws of thermodynamics, so it's incredibly unlikely you'll get spontaneous local entropy increase/organization.

It's rather likely that thermodynamics is following quantum mechanics. Still, I agree that this is so enormously unlikely, that it's not worth to use it as an argument or justification for anything.

 

what is space/time, is quantum physics logically sound? Stuff like that.

No offense meant, but anybody who uses the terms quantum physics and logical (edit: in one sentence, that is) probably hasn't had enough to do with it.

[sparhawk]

I still don't get what this has to do with the number of lives we're living, but I guess we're already past the point where this is being discussed.

 

Without rereading the thread I think the argument was like that. If the universe repeats infinite times, we are also living infinite lives with all variations. An argument AGAINST this is that in such a universe you should of course also see strange things like complex objects spontanously appearing, because in infinity the probabillity of such events tends to 1.

 

No offense meant, but anybody who uses the terms quantum physics and logical probably hasn't had enough to do with it.

 

The more I read about the math involved in quantum, strings, etc. the more I'm convinced that this is not the right way to explain it. Maybe it's just because I don't understand enough of it, but from my programming exprience I have learned one thing. If you add more and more extensions and extra conditions to keep it in line, it's time to redesign it. It doesn't get better, only more complex. Occam's Razor applied.

[Ishtvan]

The more I read about the math involved in quantum, strings, etc. the more I'm convinced that this is not the right way to explain it.

 

There's a big difference between quantum and string theory. Quantum theory makes predictions that we can prove in experiments and use in devices (e.g., the laser in your CD drive). String/M/whatever theory is essentially academic masturbation at this point. It hasn't been able to make predictions and prove them even in huge high energy experiments.

 

I think quantum also has some crazy experiments to rival relativity. Take for example the Casimir effect: If you take two reflective plates with a small separation between them, you create a resonant cavity that supports a finite number of optical modes inside (like a laser cavity). Now, vacuum photons are popping into existence briefly in this system. The space between the plates only allows creation of photons that satisfy the reflective boundary conditions (i.e., the resonant modes). The space outside the plates doesn't have this requirement, so more vacuum photons manifest outside the plates than inside the plates.

 

Because there are more vacuum photons outside the plates than inside, you get more radiation pressure pushing the plates together than pushing the plates apart, so a force is generated that tends to push the plates together. Sound crazy? Well we must live in a crazy world, because the experiment was done and the effect verified. This is an example of generating "vacuum energy" since the plates do work going together, but you can't make a useful engine from it because you have to put work back in to pull the plates apart again.

[Order of the Hammer Bureaucrat]

I was fascinated by this Casimir effect back in the days. Now that we gradually slid to Free Energy discussions, what do y'all think about those Irish spinning their magnets over at Steorn? I've got plenty of such people bookmarked in my "weird tech" bookmarks folder, all are scams and/or shady. Remains to be seen what will come of these guys.

 

If only we could find a place with some lower potential, something very low. If only heaven and hell existed, then we could surely run some heat engines or some other potential harvesting devices between them and generate energy for earth (USA)

[Crispy]

If only heaven and hell existed, then we could surely run some heat engines or some other potential harvesting devices between them and generate energy for earth (USA)

Haha. Someone should write a novel based around that concept. Devil energy, now coming to a grid near YOU!

 

Why only USA?

[Order of the Hammer Bureaucrat]

Because it likes consuming energy. at the moment. China etc will catch up.

[sparhawk]

There's a big difference between quantum and string theory. Quantum theory makes predictions that we can prove in experiments and use in devices (e.g., the laser in your CD drive). String/M/whatever theory is essentially academic masturbation at this point. It hasn't been able to make predictions and prove them even in huge high energy experiments.

 

Yeah, I know. I don't deny the experiments (assuming they work of course), but I was more refering to the math that is supposed to explain why it works. Maybe I get more understanding when I enter that part (if ever because it's rather hard to do this on your own at home). In special relativity it helped. When I read the accounts which are usually given in the layman books, I always had the feeling that maybe this is just a missinterpretation (time delation and length contraction) which I think can easily happen. But after learning about the math, and reading a rather detailed account of the Michelson-Morley experiment, it's much more understandable. So I hope to get a similar understanding about QM later.

 

I think quantum also has some crazy experiments to rival relativity. Take for example the Casimir effect: If you take two reflective plates with a small separation between them, you create a resonant cavity that supports a finite number of optical modes inside (like a laser cavity). Now, vacuum photons are popping into existence briefly in this system. The space between the plates only allows creation of photons that satisfy the reflective boundary conditions (i.e., the resonant modes). The space outside the plates doesn't have this requirement, so more vacuum photons manifest outside the plates than inside the plates.

 

I seem to remember reading briefly about this experiment. Rather interesting. Do you have an article where this is explained in more detail? Same problem as above. Laymen articles and books, try to simplyfy so much, that the important facts are missing. It's ok, because many people are not interested or may not understand deeper thoughts about it, but I find this unsatisfactorly.

 

Because there are more vacuum photons outside the plates than inside, you get more radiation pressure pushing the plates together than pushing the plates apart, so a force is generated that tends to push the plates together. Sound crazy? Well we must live in a crazy world, because the experiment was done and the effect verified. This is an example of generating "vacuum energy" since the plates do work going together, but you can't make a useful engine from it because you have to put work back in to pull the plates apart again.

 

Well, if you attach some strings to these plates with pulleys, then it should be possible to make it work. Problem is that the forces are probably rather small, right?

[Nyarlathotep]

Because it likes consuming energy. at the moment. China etc will catch up.

Plus, everyone knows that Washington, D.C. is the legendary city on the hill from Revelations--just ask Bush!

 

Well, if you attach some strings to these plates with pulleys, then it should be possible to make it work. Problem is that the forces are probably rather small, right?

No, the problem is there is no such thing as free energy. It takes the same amount of energy (not counting losses) to overcome the vacuum pull and reset the plates. So yes, you could make a vacuum energy battery, for example, but never a free energy device. The vacuum energy extractable is indeed small, but I do have to wonder if more advanced designs could eventually exceed the energy density of chemical batteries (this is my uneducated hypothesis, mind you).

[Ishtvan]

@Spar: I don't know of a good technical but not too technical explanation. I think I first read about it in a quantum textbook. The Wikipedia article as actually not that bad.

 

No, the problem is there is no such thing as free energy. It takes the same amount of energy (not counting losses) to overcome the vacuum pull and reset the plates. So yes, you could make a vacuum energy battery, for example, but never a free energy device. The vacuum energy extractable is indeed small, but I do have to wonder if more advanced designs could eventually exceed the energy density of chemical batteries (this is my uneducated hypothesis, mind you).

Supposedly some people are trying to use this effect to compress something inbetween the plates and initiate fusion that way (they aren't using real plates though, they're using crafted charge distributions in a plasma). It seems kind've questionable though, because the force is only significant when the plates are very close together (~10 nm), so you'd have a very thin layer of fusion fuel to work with, and you'd still have to confine it somehow in the transverse direction.

 

Something I was wondering about is whether it's possible to modulate the reflectivity of the plates at the vacuum-photon wavelengths to turn the effect on and off. I'm guessing that it would take more energy to change the reflectivity than the energy you'd get out of the compression though. Or maybe reflectivity works completely differently in the quantum optics regime, I don't know enough about that to say.

[sparhawk]

@Spar: I don't know of a good technical but not too technical explanation. I think I first read about it in a quantum textbook. The Wikipedia article as actually not that bad.

 

Don't worry about technicallity. If I don't understand it, I have to learn it. I'm on my way doing exactly this, even if it may take some time. I'm not in a hurry, I have a job and everything, so I don't have to meet some deadlines anyway.

[demagogue]

Well, while we're on this free-for-all of interesting science stuff ...

 

The most interesting thing I've read about applications of quantum physics lately (was it already posted here? can't remember) is the experiments in freezing things near to absolute zero with lasers. http://web.mit.edu/newsoffice/2007/super-cool.html

 

The idea is, thermal behavior is one of the main things that keeps quantum effects from manifesting on a macro-level. But if you freeze it to near enough absolute zero, quantum effects are the only real controlling thing left.

 

"You always learn in high school physics that large objects don't behave according to quantum mechanics because they're just too hot, and the thermal energy obscures their quantum behavior," said Thomas Corbitt, an MIT graduate student in physics and lead author of the paper."Nobody's demonstrated quantum mechanics at that kind of (macroscopic) scale."

 

To see quantum effects in large objects, they must be cooled to near absolute zero. Such low temperatures can only be reached by keeping objects as motionless as possible. At absolute zero (0 degrees Kelvin, -273 degrees Celsius or -460 degrees Fahrenheit), atoms lose all thermal energy and have only their quantum motion. [...]

 

In their upcoming paper, the researchers report that [using special lasers] they lowered the temperature of a dime-sized mirror to 0.8 degrees Kelvin.

 

The team continues to refine the technique and has subsequently achieved much lower temperatures. But in order to observe quantum behavior in an object of that size, the researchers need to attain a temperature that is still many orders of magnitude colder, Mavalvala said.

 

[...]

 

As the researchers get closer and closer to reaching the cold temperature they need to see quantum behavior, it will get more difficult to reach the final goal, Mavalvala predicted. Several technical issues still stand in the way, such as interference from fluctuations in the laser frequency.

 

"That last factor of 100 will be heroic," she said.

 

Once the objects get cold enough, quantum effects such as squeezed state generation, quantum information storage and quantum entanglement between the light and the mirror should be observable, Mavalvala said.

 

If all of this goes well, with a little luck we may be able to literally see, if not Schrodinger's cat, full-on quantum weirdness on a macroscopic scale in our lifetime! I thought it was a very cool idea.

 

(By the way, I'm not sure you learn what that first sentence says in high school physics. I mean, I don't know what high school he went to...)

Edited June 2, 2007 by demagogue

[Order of the Hammer Bureaucrat]

I heard about laser cooling a few years ago, it's nothing new, as I understand it, the photons get absorbed and then released with higher energy taking the heat with them. As to macroscopic observations, I feel it will be nothing interesting, just dry academic journal articles.

 

Oh, and regarding the battery application, a few months ago I heard that somebody IS doing it. Some kind of helical thin gold foil or carbon something, and something else using electrical charges.

Edited June 3, 2007 by Order of the Hammer Bureaucrat

[demagogue]

As to macroscopic observations, I feel it will be nothing interesting, just dry academic journal articles.

 

 

May be just a matter of opinion about what ideas are interesting. I'm sure the articles that describe it will be dense and technical ... but you could say the same thing about two massive black holes colliding and it doesn't make the very idea any less cooler. Observable quantum entanglement is something I would put right at the top of a list of things that just sound inherently cool in the very concept ... anything but "dry".

Edited June 3, 2007 by demagogue

[Order of the Hammer Bureaucrat]

Actually for me colliding black holes are about as interesting as tabloids about celebrities. I have no interests in science, but go nuts over technology - maybe that's why I chose to become an engineer. Actually, the only scientific topic which interests me greatly, and has done so since I was 7, is gravity's connection to electromagnetism, etc, and propellant-less propulsion.