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Q & A: zero-point energy?

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Q:
Can you tell me about Zero Point Energy? Apparently, extremely high vacuum fluctuations are occuring around us, and some feel it can be used as a power source if we can find a method of receiving the energy. Prigogines Nobel Prize for a system of self-organization is cited, but Im not entirely convinced. What do you think? Thanks
- Matt (age 20)
C.S.U
A:
You're skeptical- a good thing in general and especially in this case.

Zero-point energy is a natural consequence of quantum mechanics. Take a little mass on a spring. Its potential energy is lowest when the spring is exactly unstretched. But that means that the mass is at a particular place, and the uncertainty principle would then require that its momentum have an infinite spread, giving it infinite kinetic energy. The real lowest energy state has the mass spread out over a little region, with the potential and kinetic energies each a little above their lowest possible values, but with the total as low as possible. That minimum is called the zero-point energy. Many quantum systems are mathematically analogous to a mass on a spring and have similar zero-point energies.

It's misleading to say that large fluctuations 'are occurring' in that lowest state, although scientists often use sloppy phrases like that. The system is just sitting in a state, which happens not to have definite values of position and momentum. It's not true, however, to say that its position and momentum are changing in any way. That language comes from inconsistent attempts to force quantum facts into classical descriptions.

No valid theory predicts any way to extract such energy, which would require leaving things in a state with less energy than the state with least energy, by definition of 'zero-point.'

What Prigogine's 'self-organization' ideas have to do with this is beyond me, since they weren't even concerned with quantum mechanics. (His main ideas on quantum mechanics concerned the role of density matrices in time irreversibility- and these ideas are rarely mentioned by any serious students of that issue.) The only connection that comes to mind is that Prigogine wasn't above shoveling a bit of BS on occasion.

Mike W.


Actually, this isn't the whole story here. Zero-point fluctuations in the fields of known particles, particularly the photon, have measurable effects. And even a very tiny amount of energy can be extracted from this when done properly, but you can also think of it as extracting energy from reducing the potential energy associated with the configuration of actual pieces of matter. Here's how this works:

In 1948, Hendrik Casimir found that the zero-point fluctuations in the photon field of the vacuum are affected by nearby conducting bodies, which create a boundary condition on the electromagnetic field, forcing some components to be zero on the surfaces of the conductors. Classically, this means that standing waves in cavities can have wavelengths no more than twice the length of a cavity. The quantum fluctuations are in the standing-wave modes for a piece of vacuum bounded by conducting walls, and so long-wavelength quantum fluctuations (ones with lower energy) are not allowed, while high-frequency, short-wavelength fluctuations are still present. If you make the cavity small enough, or put two conducting plates close enough together, you can shut out an ever-increasing portion of the fluctuation spectrum, starting at the low end. The low-frequency oscillations still take place outside of the cavity, and so the energy density of the zero-point fluctuations inside the cavity is less than that outside. The sides of the cavity therefore feel an inward force (typically this is done with two parallel conducting plates) and the force per unit area is

F/A = pi^2*(hbar)*c/(240d^4)

where hbar is Planck's constant divided by 2pi, c is the speed of light, and d is the distance between the two plates. The force is very very very feeble except at very short distances (microns or nanometers). There are important corrections to this for real materials -- the calculation above assumes that the conducting plates are shiny at all frequencies. Real materials start becoming transparent to very high-frequency electromagnetic radiation, and for real materials the force is less. The apparently large value of 1/d^4 for small d gets cut off by the fact that the short frequencies aren't reflected well.

The force is so feeble it has taken a large amount of effort and technology even to measure it. Here's an article in Reports on Progress in Physics at this link describing recent measurements of the force.

This is kinda cool, but it really isn't a very good source of energy. In particular, once you've brought your conducting plates together, that's it -- no more energy can be extracted from these plates until you pull them apart again. The force acts a like an weak attractive spring between two conducting plates; it can be overshadowed by other forces, like the electrostatic force if the plates aren't at exactly the same voltage, or perhaps even gravitational forces.

So there's a potential energy associated with the Casimir force between two conducting plates at a particular separation. You can add energy to the system by pulling the plates apart or get energy out by allowing them to pull together. But you cannot get free energy this way, for the same reason that you couldn't if the plates were held together with rubber bands.

Tom

(republished on 07/21/06)

Follow-Up #1: unsound ideas

Q:
Even though the focus of Puthoff and his lab in texas doesnt always sound like "sound" science based on your interpretation of so little potential extraction from this field, do you not think that the exploration and persuit of what this might do for humanity, still not worthwhile?
- sean (age 23)
colo. spgs. colo
A:
Not really. There are an infinite number of crazy ideas people can come up with. Meanwhile there are a lot of difficult but plausible ideas to pursue-  from near-term improved solar electrical generation to potential long-term nuclear fusion, and so forth. Focusing on the real possibilities seems to make more sense.

Mike W.

(published on 09/18/07)

Follow-Up #2: ZPG?

Q:
Am I correct in saying you do not think that this is a practicle solution to the energy problem? If so then what do you think of the fact that there is a prototype production ZPG.
- Dylan Shroll (age 14)
Watertown, SD, USA
A:
I don't believe it.

Mike W.

Neither do I.

LeeH

(published on 05/06/08)

Follow-Up #3: entropy and zero-point energy

Q:
Wouldent Zero point energy increase the entropy?
- Anonymous
A:
Nice question. If you consider the zero-point energy of a mass on a spring, it has zero entropy. That's because there's a unique lowest-energy state, even though it has some energy.

Mike W.

(published on 05/23/08)

Follow-Up #4: ZPE hopes

Q:
The question is not if there is an alternate energy source, but where. No matter if we call this ZPE or quiggles doesn't mean much. It is scientific, but short-sighted to assign physical laws to this source but perhaps this energy does not even reside in this dimension. Maybe there is a way to access this energy but we need a conduit to gain access. There is substantial proof that Tesla did this in several applications. If you check NASA has a patent for a ZPE collector. Common sense would dictate that no long term space flight can occur without another form of fuel. Rocket fuel is not the answer. However if there is energy in the vacuum of space, this opens up myriad opportunities and outcomes. Can you think of anything better to focus on?
- Rod Czlonka (age 47)
IL
A:
If there were some real new energy source described by a patent, someone would be able to build one. No one has.
Hope is not scientific evidence.

Mike W.

(published on 01/28/09)

Follow-Up #5: old guys

Q:
Mike; I realize that you are young and still at an age where you believe that the government is here to help us, but that is simply not accurate. The former government, did not want new energy sources, cures for cancer, or an end to world hunger. There has always been some private interest which has controlled our politians and nation to their own self-serving end. I am referring to this as formerly because we do not know what the current administration will do. As for Zero point look up Moray, Tesla, T Townsend Brown, even Einstein made note of its existence. The either which at one time was thought to be an empty vacumm is now seen for what it truly is; an untapped sea of energy.
- Rod Czlonka (age 47)
IL
A:
Hi Rod- I'm sorry to say I'm older and even more cynical than you. Cynical enough, in fact, to believe that there are shysters who have figured out how to get rich by fooling people into investing in bogus energy schemes.

Mike W.

p.s.  Lee H will also weigh in, and he's older and more cynical than me.

I'm just a tad older and a tad more skeptical than Mike.  What I am not skeptical about, however, is the First Law of Thermodynamics which is "There's no such thing as a free lunch".  People who believe in free untapped energy sources are self-delusional. 
LeeH

(published on 02/13/09)

Follow-Up #6: conspiracies

Q:
I'm older and more cynical than everyone else so far, for whatever that's worth. I have no doubt that NASA or the CIA or somebody could be persuaded (i.e. paid) to squelch a great idea that would solve all our energy problems forever (the phrase "electricity too cheap to meter" comes back to mind). No tactic would be considered out of bounds; no play would be thought too foul. So I notice with interest that there are few reports of zero-point energy enthusiasts mysteriously disappearing without a trace, or highly promising garage experiments unaccountably going wrong with lethal results (sort of like meth labs, which actually do make money some times, at least for a while). I notice that the miscreants who discovered bench-top cold fusion don't seem to have been "disappeared" and all their lab equipment stashed away like Indy's Ark; rather they were simply refuted in perfectly ordinary scientific fashion. In any case, if it's possible to believe that "the government" would ruthlessly suppress genuine knowledge to benefit a favored few, isn't at least equally possible to believe that the same government would figure out how to promote, license, and tax such knowledge to benefit some other favored few? What I really want to know is, where do I have to go to find a web site without any conspiracy theories?
- Jonathan Ramlow (age 59)
Midland, MI
A:
Jon- I strongly dispute your first claim. I'm also 59 years old, so I admit you could be a few months older. But Lee H is really really old and really really cynical. (Just kidding, Lee)

If I may speak for our zero-point-energy friends, have you ever wondered why you haven't seen those reports of disappearing cold-fusion researchers? Huh?

We could point you to the conspiracy-theory-free version of this website, but then they would find out about it.

Mike W.

I'll stay out of this discussion.
LeeH

(published on 03/19/09)

Follow-Up #7: Casimir in cosmology

Q:
I stumbled upon this site when reading about the Casimir effect. Ignoring all the conspiracy theory responses (government workers are generally too lazy and disorganised to be effective conspirators). I have a feeling that gravity may be able to be explained through the mechanisms of the Casimir effect (wish I had more time and the Math skills to work on it). Are there any established theories that expand the Casimir effect to a general theory of gravity (cosmological theories)?
- Nick (age 33)
Adelaide, Australia
A:
Yes. In General Relativity, any energy associated with empty space actually drives an accelerating expansion. We currently are seeing an accelerating expansion, so there seems to be some such background energy.
Is it associated with the Casimir effect? That effect acts as if there were a vacuum electromagnetic field energy, just as expected from quantum field energy. If one were to add up the energy from all modes at all wavelengths, the answer would be an infinite background energy density, contrary to observation. Fortunately, we believe that all our current theories break down on a tiny distance scale, the Planck scale, at which quantum gravity becomes important. So when we're adding up modes, we really should stop before including modes with shorter than Planck wavelengths. Then the electromagnetic background energy of the vacuum would only be 10125 (yes, that's one followed by 125 zeros) as big as the density inferred from the accelerating expansion.
So obviously there's something needed to complete the story and make things consistent.
There are lots of ideas. You're young. Stay tuned.

Mike W.

Grumble, grumble.  In my opinion the Casimir effect has nothing to do with gravity, and never will .  LeeH

(published on 04/29/09)

Follow-Up #8: Zero-point energy: the purest Baloney

Q:
I would like to hear your opinion to this explanation on Zero Point Energy http://www.wandtheworld.com/amegacall/?go=seest With best regards Jesper
- Jesper Seest Mogensen (age 42)
Berlin, Germany
A:
Jesper- I think you can guess what we think. A magic stainless steel wand that sweetens lemons, mellows wine, removes facial wrinkles....? It's supposed to be driven by some deep physical force? Absolutely pure baloney. Even if there were some such zero-point energy source, how would it magically know to change each particular physical thing (e.g. a pH) in just the way that happens to appeal to our tastes? They do throw in a little broccoli extract, which has absolutely nothing to do with fundamental physics but might be good for you. I suggest comparing the price of their offer (somewhere in the $49-$900 range) with the price of:
1. a pen that doesn't write
plus
2. a little broccoli.

Mike W.

Lee- should we post this website? I hate to give them any traffic.

(published on 02/02/11)

Follow-Up #9: zero-point history

Q:
As part of my general activities on the internet, I frequently run across all sorts of people that have obviously crazy beliefs. Recently, someone directed me to a book titled "The Hunt for Zero Point: Inside the Classified World of Antigravity Technology", a book by an apparently respectable individual. Amongst other claims, it says that the classic flying saucer shape is ideal for what is referred to as "electrogravic reaction", that the Zero Point Energy extracted from something the size of a coffee cup can boil the world's oceans six times over, and that Nazi scientists tapped this power in the closing days of the second world war. A previous question addressed on your site was about somebody trying to pedal some sort of new age cure-all device he claims runs on Zero Point Energy, so I thought I'd ask the following - what is it about zero point energy that attracts this sort of idea? Was there some kind of early speculation, or some alternate explanation for ZPE that caused people to believe that it is essentially a free energy source of such magnitude?
- Adam C. (age 20)
Hobart, Tasmania, Australia
A:
I don't know of any obvious scientific excuse for the ZPE craze. It sort of sounds like the type of thing that would attract con men, but that's not really an explanation.

Just to be complete, I should mention one possibility for how ZPE could be released. The background energy density of space may plausibly be associated with some particular string state, one of a huge number of suspected solutions to the hypothetical string equations. (We're obviously not on solid ground here.) If so, there could be a phase transition to a new, lower-energy, background state. The process would thoroughly wipe out anything that was around beforehand. It's not  altogether clear that the number of spatial dimensions to emerge would be unchanged. And no, even if those speculations turn out to be correct, I'm not worried about some marketing department triggering the event with their broccoli extract or toy pens.

Mike W.

(published on 05/24/11)

Follow-Up #10: entropy minima and maxima

Q:
I have a question about one of your answers (Follow up #3), in which you said: " If you consider the zero-point energy of a mass on a spring, it has zero entropy. That's because there's a unique lowest-energy state, even though it has some energy. " My understanding of entropy, limited as it is, is that it really is a measure of the DISTRIBUION of energy in a system, with lower entropy being associated with an uneven distribution, and maximum entropy with an even distribution. The energy available to do work is the result of entropy being less than the maximum. Therefore, if we talk about the entropy of an unstressed spring, we could create a sphere around the spring and compute its energy distribution as being at a maximum, having no potential energy available for doing work. Its entropy must therefore be at a maximum, not a minimum. When we talk of an evacuated chamber having low entropy, I believe we are implicitly referring to the fact that if the chamber and its exterior are considered part of a "system", then it is not at maximum entropy because useful work can be done by allowing it to refill from the outside. If the chamber interior is taken as the system, its interior entropy would again have to be considered at a maximum. Comment?
- Bill Chestnut (age 67)
Calgary, Alberta Canada
A:
We've said that the entropy of a mass-on-spring in its ground state is zero, because there's only one state and ln(1)=0. You argue that since no work can be extracted from that system, its entropy must be maximized. That's true, but maximized within what range of possibilities? The assumed range is that of all states with that value of the energy. There's only one of them. So, given that particular E, the maximum entropy is zero, which is also of course the minimum entropy.

An empty chamber will indeed maximize its entropy, given some constraint on its energy. For a given energy, the occupation of different photon modes will follow a Boltzmann distribution, with some temperature proportional to the fourth root of the energy density.

Mike W.

(published on 06/30/11)

Follow-Up #11: entropy and free energy of spring

Q:
From your answer - the following statements: 1. ln(1) = 0. Agreed. 2. Entropy of an unstressed spring is at maximum. Agreed. (Thank-you for acknowledging that.) 3. Entropy of a system with only one state is zero. Agreed. ==================== HOWEVER,your statements: "...maximized within what range of possibilities? The assumed range is that of all states with that value of the energy." make no sense to me. Does not appear to be a reasonable assumption. An unstressed spring can (by being stressed) have a large number of different energy values. Therefore the spring is not a "single state" system. Therefore computing it's entropy as zero on the assumption it has only one energy state cannot be correct. If the entropy of the spring unstressed is zero, its entropy when stressed, would then, unavoidably be less than that, resulting in its having negative entropy values. I hope you're OK with that. Also, the attempt to treat the spring system as being constrained to discrete levels, does not seem to be an appropriate approach either. The spring system is macroscopic, and for all intents and purposes has an infinite set of possible energies. (Yes, the energy levels are still quantized, but the differences are vaanishingly small.) Therefore it does noto appear that Boltzmann's statistics would be suitable here in any case. I have searched elsewhere for comutational examples of the entropy of potenial and stored energy systems, separate from temperature considerations. I have not been able to find many satisfactory treatments of this for Hookes law. Even J.D Fast's book Entropy, does not treat this example in detail, although he does treat other potential energy systems such as those involving magnetism and the losses due to hysteresis. However, another physics forum treats the subject of Hookes Law and thermodynamics with the following calculation: "The elongation of the spring would add another term to your energy equation: U=TS−PV+Fx=TS−PV+k(T)x2 F=U−TS=−PV+k(T)x2 S=−(∂F∂T)V=−∂k(T)∂Tx2" For this development see web page: http://www.physicsforums.com/showthread.php?t=221196 This appears to offer a more satisfactory treatment.
- Bill Chestnut (age 67)
Calgary AB Canada
A:
I was too brief before.  Let's do some background. When we say that the amount of work extractable from a system is given by how much its free energy (let's use F here) is above the minimum value, that only even has meaning in the context of an environment with a well-defined temperature. The T in U-TS is not the system temperature, which in general does not exist, but the temperature of its environment, although U and S  are the energy and entropy of the system. When we say that equilibrium is reached when F is minimized, that's equivalent to saying that equilibrium is reached when the total entropy of the {system+environment} is maximized.

Now let's look at the spring in its unique ground state. If it's in equilibrium with an environment, the environment is obviously at T=0. Now we're back at the start of the argument I made last time. S=0 even though the system is in equilibrium and thus the net system+environment entropy is maximized, within its extremely limited range of possibilities.

When you say the entropy of the stressed spring would be less than of the unstressed spring, you're mixing up the system with the {system+environment}. Assuming net energy is conserved, if the environment is near T=0 then net entropy will increase as the spring dumps its energy into the environment. However, the spring entropy goes down in the process.

To get perspective, let's look at the case where the ground-state spring (call it U=0) is in an environment at some T > 0. Let's assume, as you like, that T is big enough so that in equilibrium equipartition is obeyed and the average U of the spring is just kT. This spring then is not in equilibrium when it's in the ground state. Work can be extracted from it. (The amount of work is TS-U, roughly kT*ln(kT/hf)-kT in this classical regime, where hf is one energy quantum for the spring.)

You're puzzled. How can the lower energy spring be one that can do more work? Actually, that's a very general feature. Yes, you can power a heat engine with some hot water. You can also power a heat engine off some cold liquid nitrogen. All that's required is that things be out of equilibrium, e.g. a system at different temperature than the environment. Which direction the heat flows only affects details of the calculation.


Your last point is on a somewhat different topic. Sometimes it's convenient to forget about the discrete states, e.g. in order to convert a sum over states to an integral. You always run into problems if you push that approach too far, since it can never give any absolute measure of entropy. If there were only measures of volume in phase space, rather than of actual counts, there would be no reason to reject negative entropies.

Mike W.

(published on 07/06/11)

Follow-Up #12: Free energy? No way

Q:
I've been to Methernitha, a community in Switzerland. They have free energy machines - Testatica. Also Eugene Mallove was murdered - probably due to his promotion of cold fusion. Also read the testimony of Dennis Lee to see how far the "authorities" will go to suppress free energy. Free energy is real. Stanley Meyer also demonstrated that a car can run on impure water as a fuel. Do the research yourself. Attend one of the many annual conferences on free energy where scientists and inventors meet to discuss their ideas and how to take the technology from proven workability to commercial usage. Many free energy inventors have published their inventions for free, i.e. they weren't motivated by profit. Methernitha have no desire to profit from this technology. But there are dark forces who want to keep this knowledge hidden and this pervades all our lives. For example, Project Censored produce a book every year detailing incredibly important stories which never make it into the mainstream media. These are articles/stories that only the alternative press prints. So ask yourself why these stories aren't picked up by the mainstream media. I have a special interest in the Haut de la Garenne child abuse case in Jersey some years ago. Read Lenny Harper's testimony about the case. He was the senior investigating officer on the case until he was retired early and discredited. So you think that these same people wouldn't suppress free energy when they can cover up a serious child abuse case involving child murder. Do the research folks. That's the only way. Do your own research.
- Louis Shawcross (age 34)
Kuala Lumpur
A:
I'm sorry, but this device has to be a scam of some sort.  Since I haven't seen it myself I can't point my finger at any particular fault but the premise goes against one of the most fundamental laws of physics, the first law of thermodynamics.  This law can be paraphrased as 'There is no such thing as a free lunch' and has been verified time and time again.  The patent offices of all nations are inundated with schemes of this sort.  They never work.

LeeH 

(published on 08/15/12)

Follow-Up #13: Free-ish energy

Q:
"Free Energy" doesn't have to violate the laws of thermodynamics to exist. Solar cells give us "free" energy in the economical sense. I think that a lot of people wonder about these conspiracy theories due to the fact that we are still paying for electricity when things like heat engines, geothermal, solar, and wind should be integrating into our society at a much faster rate. The science necessary to remove my electric bill isn't that complicated. My personal opinion is that capitalistic tendencies are suppressing our success in this facet of our society. Why give away for free what we can put a meter on. Zero point isn't necessary, mother earth gives us plenty of ways. I guess my question is, do you really believe that we aren't being repressed/suppressed?
- Doug G (age 29)
Xenia, OH, USA
A:
You raise a number of important points.

Solar cells don't give us economically free energy, because they are costly to manufacture and install, and they don't last forever. Fortunately the cost is going down following the standard sort of pattern for mass-produced electrical devices. They're becoming very economically feasible, and will become more so. That's far from saying they are "free". They won't remove your electric bill but they will do far less damage to the environment in which our kids will live. Wind energy has similar benefits. With regard to the previous discussions on this thread, solar cells use standard physics, not mysterious fantasy effects.

As the fraction of our energy from solar and wind goes up, there will be problems maintaining a steady supply. Major technical progress (e.g. on storage techniques) is needed to address that.

You might want to have a look at David McKay's free online book  (http://www.withouthotair.com/ ) giving a good analysis of this whole issue.

Probably I should stay away from commenting on the social/economic/political issues you raise, but it's too tempting.

Most scientists involved in energy issues believe that we should have a much bigger push toward greater energy efficiency in housing and transportation, using easily available technologies. Much more aggressive work on current clean energy generation technologies and new ones could also be pursued. In my opinion, all these efforts would be long-term (and sometimes short-term) very cost-efficient for society as a whole.

Why aren't we doing better in these efforts? Of course you're right that powerful economic interests are not perfectly aligned with the general interests of most citizens, and they don't hesitate to use their power to swing things their way. Such effects have been found in non-capitalist systems as well. One current problem is the funding from huge fossil-fuel corporations for widespread propaganda to the effect that global warming isn't happening, and besides it's caused by nature rather than fossil fuels, and anyway it's good for us, and besides it too late to stop it. That campaign, not exactly a hidden conspiracy, does make it hard to persuade people of the costs of staying on our current path. In addition, even without the flack from the bad guys, it's hard to persuade people to make even small sacrifices for the long-term good.

Mike W.

(published on 04/10/13)

Follow-Up #14: various energy questions

Q:
You mentioned energy storage, that is the only real issue left to be solved in my opinion. I have been investing into my own backyard solar project for a couple years and Lead-Acid batteries just don't cut the mustard. 600 amp-hours worth of batteries in and I'm finally getting close to powering half the house. The solar cell prices are so low now though, I can make more power than I can ever store. Do you have any good resources on that subject? My google results are so downtrodden with junk that sifting through has been difficult to say the least. "Free-ish energy" is the right way to put it. The investment factor is, in my humble opinion, bologna. 600 dollars and I received four powerful solar panels from a company called uni-solar. That is hardly a lot of money compared to my electric bill for the next 20 years, per the warranty. Inverters...well I am still studying how to bypass that issue, but again 1000 dollars or so is little compared to what we get back. Then the lead-acid, if you buy retail, 1000 dollars. 3000 dollars could easily be re-paid in less than 3 years. I guess my point is in alignment with your comment, people need to start doing this on their own. Uncle Sam and his cousin Capitalism are not going to help us anytime soon. We could easily reduce the costs of these investments with some more open-source efforts. I have seen charge controller designs all over the Internet, home brewers working on inverters, and I myself studying the basic concepts of lead-acid and nickel-metal hydride design. I ramble.... Dark-Matter...I have read a little...seems like bollocks...are these hadron colliders really trying to make something from nothing, or am I mis-interpreting entirely?
- Doug G (age 29)
Xenia, OH, USA
A:
Thanks for the account of your adventures with home solar installation. It does sound like a good deal for someone in the right climate, willing to put in the labor. All aspects of this should improve quickly as the device manufacture and installation gets more routine. I don't know of any special resources on electrical storage. Major resources are going into battery development, although I believe that's slowed down since the fiscal stimulus ended.

Have you converted your hot water heating system to use an electrical heat pump? That's highly efficient (you get about 5 J of heat pumped in for 1 J of electrical input) and does give a way of storing some energy made while the sun shines. Perhaps in your situation (intermittent very cheap and clean electrical energy) it would be worth investing in a really big hot water tank to go with the system.

On your totally separate topic:  I'm surprised that dark matter sounds like "bullocks" to you. The gravitational evidence for some other stuff clumping with the galaxies is very strong. It fits with other lines of evidence. The leading candidates to explain it are weakly interacting massive particles. When you think about it, it would be a bit odd for nature to arrange that all of its many particles happen to interact strongly with our kind of stuff. Neutrinos, for example, don't. So if there happens to be some heavier type of weakly interacting stuff, you would have cold dark matter. In a way, it would be surprising if there isn't any.

Mike W.

(published on 04/12/13)

Follow-Up #15: Scams and more scams

Q:
I would like to ask. What are your thoughts about the Elf Generator? Does it really work? i found this website while i am reading about scalar energy www.zephyrtechnology.com does this website tell facts?
- Charles Xavier (age 20)
Manila, Philippines
A:
Dear Charles,
Save your money and don't believe in these claims and advertisements.   The well established laws of thermodynamics, verified by many careful experiments, counter the claim that you can get something for nothing.   "There's no such thing as a free lunch"

LeeH

(published on 04/17/13)

Follow-Up #16: Casimir Energy in Cosmology

Q:
Is it possible that the casimir effect is responsible for the accelerating expansion of the universe? What I mean is, If one knew the size of the universe as a whole, and multiplied the area of the bubble of the universe by 1/2 the casimir effect (one half because it would only be pushing on one "plate"), would that be enough energy to be responsible for the expansion rate of the universe? The idea is attractive to me because the more the universe expands, the more area there would be for force to act on, thereby speeding up the expansion as time goes forward. Perhaps it could be calculated backwards, i.e. take the known energy acting on the universe, divide by the casimir effect, then see if this is any where near the ballpark of the estimated size of the universe? My math is horrific and I don't know any of these constants which is why I'm asking someone who might. Thanks
- Dan Kelly (age 46)
Pittsburgh, PA, USA
A:

That's a great idea! It turns out it won't work, not because the Casimir effect is too small but rather because it's too big.

Having some sort of fixed background energy density filling space does drive an accelerating expansion, according to general relativity. That's why a common way of describing a likely source of the acceleration is to call it "dark energy." The argument is something similar to what you wrote.

 If you were to just take the basic Casimir effect, and calculate the energy density associated with it, you get infinity. Whoops. This infinity comes from adding effects at smaller and smaller distance scales. It can be removed from the experimental predictions, which only involve finite effects on large distance scales. You can get rid of that infinity by noting that we don't know what becomes of the laws of physics on scales where quantum gravity becomes important, the Planck length. That gets the Casimir effect down to giving something like 10125 times the amount needed to drive the acceleration. Whoops again. People say that there may be other effects on small distance scales that reduce this background density to maybe 1055 (if I remember right) times too much energy density. So it just doesn't work.

What sort of physics will get rid of this problem? We don't know. One possibility, discussed by Lenny Susskind in The Cosmic Landscape, is that there are universes with all sorts of different background densities, suggested by string theory. Too much density leads to a universe that quickly blows apart. Negative density leads to collapse. There's only a little range where you'd get an inhabitable universe. Not coincidentally, we're in that range.

Mike W.


(published on 06/12/13)

Follow-Up #17: Negative temperatures?

Q:
After having started research at Zero-point energy, moving onto the Casimir effect, and reading into the laws of thermodynamics, I've found an article that seems to be an elegant solution to the problems involved in the first law of thermodynamics.. A "quantum gas" created (or discovered, I'm not quite sure which) by Ulrich Schneider and Immanuel Bloch's team by achieving an inverted Boltzmann distribution, as the gas is at negative kelvin temperatures. "Also supposedly impossible heat engines can be realized with the help of negative absolute temperatures, such as an engine with a thermodynamic efficiency above 100%" Http://m.phys.org/news/2013-01-atoms-negative-absolute-temperature-hottest.html#jCp Thoughts?
- Jesse (age 25)
A:

True negative temperatures can't be achieved, The reason is that, as you point out, the Boltzmann factors for states would go up with energy. When you deal with a collection of states with an upper limit on their energy, say for a batch of spins, that's possible. All real-world systems also include electromagnetic modes and modes of various particle-antiparticle pairs. These extend up to arbitrarily high energy, so there's no way to make the probabilities add up to one for negative temperature. You can only get subsystems, like those spins, to have negative quasi-temperatures on time scales short compared with the time it takes them to exchange energy with electromagnetic fields.

Mike W.


(published on 09/19/13)

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