Skip to comments.An Introduction to Zero-Point Energy
Posted on 02/28/2003 2:59:02 PM PST by sourcery
Quantum physics predicts the existence of an underlying sea of zero-point energy at every point in the universe. This is different from the cosmic microwave background and is also referred to as the electromagnetic quantum vacuum since it is the lowest state of otherwise empty space. This energy is so enormous that most physicists believe that even though zero-point energy seems to be an inescapable consequence of elementary quantum theory, it cannot be physically real, and so is subtracted away in calculations.
A minority of physicists accept it as real energy which we cannot directly sense since it is the same everywhere, even inside our bodies and measuring devices. From this perspective, the ordinary world of matter and energy is like a foam atop the quantum vacuum sea. It does not matter to a ship how deep the ocean is below it. If the zero-point energy is real, there is the possibility that it can be tapped as a source of power or be harnassed to generate a propulsive force for space travel.
The propellor or the jet engine of an aircraft push air backwards to propel the aircraft forward. A ship or boat propellor does the same thing with water. On Earth there is always air or water available to push against. But a rocket in space has nothing to push against, and so it needs to carry propellant to eject in place of air or water. The fundamental problem is that a deep space rocket would have to start out with all the propellant it will ever need. This quickly results in the need to carry more and more propellant just to propel the propellant. The breakthrough one wishes for deep space travel is to overcome the need to carry propellant at all. How can one generate a propulsive force without carrying and ejecting propellant?
There is a force associated with the electromagnetic quantum vacuum: the Casimir force. This force is an attraction between parallel metallic plates that has now been well measured and can be attributed to a minutely tiny imbalance in the zero-point energy in the cavity between versus the region outside the plates. This is not useful for propulsion since it symmetrically pulls on the plates. However if some asymmetric variation of the Casimir force could be identified one could in effect sail through space as if propelled by a kind of quantum fluctuation wind. This is pure speculation.
The other requirement for space travel is energy. A thought experiment published by physicist Robert Forward in 1984 demonstrated how the Casimir force could in principle be used to extract energy from the quantum vacuum (Phys. Rev. B, 30, 1700, 1984). Theoretical studies in the early 1990s (Phys. Rev. E, 48, 1562, 1993) verified that this was not contradictory to the laws of thermodynamics (since the zero-point energy is different from a thermal reservoir of heat). Unfortunately the Forward process cannot be cycled to yield a continuous extraction of energy. A Casimir engine would be one whose cylinders could only fire once, after which the engine become useless.
ORIGIN OF ZERO-POINT ENERGY
The basis of zero-point energy is the Heisenberg uncertainty principle, one of the fundamental laws of quantum physics. According to this principle, the more precisely one measures the position of a moving particle, such as an electron, the less exact the best possible measurement of momentum (mass times velocity) will be, and vice versa. The least possible uncertainty of position times momentum is specified by Planck's constant, h. A parallel uncertainty exists between measurements involving time and energy. This minimum uncertainty is not due to any correctable flaws in measurement, but rather reflects an intrinsic quantum fuzziness in the very nature of energy and matter.
A useful calculational tool in physics is the ideal harmonic oscillator: a hypothetical mass on a perfect spring moving back and forth. The Heisenberg uncertainty principle dictates that such an ideal harmonic oscillator -- one small enough to be subject to quantum laws -- can never come entirely to rest, since that would be a state of exactly zero energy, which is forbidden. In this case the average minimum energy is one-half h times the frequency, hf/2.
Radio waves, light, X-rays, and gamma rays are all forms of electromagnetic radiation. Classically, electromagnetic radiation can be pictured as waves flowing through space at the speed of light. The waves are not waves of anything substantive, but are in fact ripples in a state of a field. These waves do carry energy, and each wave has a specific direction, frequency and polarization state. This is called a "propagating mode of the electromagnetic field."
Each mode is subject to the Heisenberg uncertainty principle. To understand the meaning of this, the theory of electromagnetic radiation is quantized by treating each mode as an equivalent harmonic oscillator. From this analogy, every mode of the field must have hf/2 as its average minimum energy. That is a tiny amount of energy, but the number of modes is enormous, and indeed increases as the square of the frequency. The product of the tiny energy per mode times the huge spatial density of modes yields a very high theoretical energy density per cubic centimeter.
From this line of reasoning, quantum physics predicts that all of space must be filled with electromagnetic zero-point fluctuations (also called the zero-point field) creating a universal sea of zero-point energy. The density of this energy depends critically on where in frequency the zero-point fluctuations cease. Since space itself is thought to break up into a kind of quantum foam at a tiny distance scale called the Planck scale (10-33 cm), it is argued that the zero point fluctuations must cease at a corresponding Planck frequency (1043 Hz). If that is the case, the zero-point energy density would be 110 orders of magnitude greater than the radiant energy at the center of the Sun.
CONNECTION TO INERTIA AND GRAVITATION
When a passenger in an airplane feels pushed against his seat as the airplane accelerates down the runway, or when a driver feels pushed to the left when her car makes a sharp turn to the right, what is doing the pushing? Since the time of Newton, this has been attributed to an innate property of matter called inertia. In 1994 a process was discovered whereby the zero-point fluctuations could be the source of the push one feels when changing speed or direction, both being forms of acceleration. The zero-point fluctuations could be the underlying cause of inertia. If that is the case, then we are actually sensing the zero-point energy with every move we make (see origin of inertia).
The principle of equivalence would require an analogous connection for gravitation. Einstein's general relativity successfully accounts for the motions of freely-falling objects on geodesics (the "shortest" distance between two points in curved spacetime), but does not provide a mechanism for generating a gravitational force for objects when they are forced to deviate from geodesic tracks. It has been found that an object undergoing acceleration or one held fixed in a gravitational field would experience the same kind of asymmetric pattern in the zero-point field giving rise to such a reaction force. The weight you measure on a scale would therefore be due to zero-point energy (see gravitation).
The possibility that electromagnetic zero-point energy may be involved in the production of inertial and gravitational forces opens the possibility that both inertia and gravitation might someday be controlled and manipulated. This could have a profound impact on propulsion and space travel.
No, for several reasons. One is that ZPE does not establish an absolute frame of reference (which was the primay reason for assumming the existence of an ether.) Another is that an "ether" in which "things" exist and move is inherently a dualist model of reality, whereas modern physics is based on fundamental unification of forces, particles and geometry. Finally, ZPE is not a "medium" or "transport substrate" for wave propagation, which was the key characteristic of the hypothetical "ether."
Was this absurd statement really written by someone with a physics background?
How is this statement absurd? It seems perfectly true.
Go check your physics for "On Earth there is always air or water available to push against." This is a common misconception by the masses.
Where did you come up with that outrageous conclusion?
Ok. What's your point?
It seemed to be the best interpretation of the point of your question. If that is not what you meant, perhaps you could clarify?
I could be wrong, but that is what I remember from high school.
Just took a survey out the window, and it appears there is air out there and sometimes water. What is the problem, aside from earth should be lowercase?
Noone with a basic understanding of physics would come to that interpretation.
I said check your "physics" not gaze out the window.
There probably is some partial vacuum, especially when considering propellers and the use of lift to generate forward speed, but the idea in the article is of having a two-component medium on earth. One component is the vehicle, the other is the mobile medium being pushed out the back. Even the mechanism of a chromatograph involves a two-component medium, the stationary and the mobile phases. It takes two components to generate controlled motion.
Sure you do. It's a trivial point. Rockets act a little differently in that they carry stuff to push out the back. Cars act a little differently in that they push against solid ground. The specific mechanisms vary except that they all require two components of a medium.
Ok so they should have said "push with" or "expel" or somesuch. Give 'em a break. Physicists, like engingeers don't always have the best writing skills. I'm a perfect example of that, my writing skills are pretty minimal, although I do better than many engineers, especially the youngsters.
[This ping list is for the evolution -- not creationism -- side of evolution threads, and sometimes for other science topics. To be added (or dropped), let me know via freepmail.]
That's essentially correct. High bypass ratio turbofans, like on most airliners, but even the ones on fighters and bombers (excepting the BUFF perhaps) get much or even most of their thrust by this effect. IOW, they don't so much blow as suck their way through the air. :)
When down at the municipal pool, I get around by pushing on the water. There isn't much vacuum in front pulling me along. That's the low-speed case, extremely low speed in my case.
Push refers to the direction of the force. If the force is derived from an IC engine, the force out of the trans is applied to either the air, water, or some hard surface. The force is accurately described as a push. The surface it acts against also exerts a push in the opposite direction. If it's a jet the walls of the motor do the pushing, by directing the hot gases pushing on it.
Actually, even if it's real, it's everywhere and exactly the same everywhere. It's entropic energy. It's useless unless somebody repeals the Second Law of Thermo.
My understanding is that the propeller compresses the air behind it to a high presure while decompressing the air in front to a lower pressure. The propeller is then pushed forward bu the high pressure air behind it into the lower pressure in front of it. Same way a Wing lifts upward because of lower pressure on the top than the bottom. The way a physics teacher explained it and I've never found the need to investigat it further.
A 'Rocket', OTOH, works by having a high pressure in the chamber pressing on the front of the chamber pushing it forward (rear of chamber is open and has nothing for the combusting gasses to press against). Same way for a Jet since the front of the 'chamber' is closed by the high pressure intake air( easiest to visualize with a ramjet, pulse jets exempted). Either way, the author seems to either be trying to give an innacurate but understandable illustration of their operation to those ignorant of the operating principles or else he is basically ignorant of the principles himself and just inventing what he considers a plausible explanation. The explanation detracts from his credibility when talking about an esoteric subject like zero point.
"they move the air backwards"
The English word push, describes that action perfectly.
Write your congressman.
The propellor or the jet engine of an aircraft push air backwards to propel the aircraft forward. A ship or boat propellor does the same thing with water. On Earth there is always air or water available to push against.
You challenged the accuracy of the statement with respect to the actual physics of propellor-driven locomotion. As I read the statement to which you object, it simply states that propellor-driven locomation requires a medium in which the propellor can operate, and mentions that the principle of operation involves "pushing air backwards." The statment is incomplete, but is not incorrect (a propellor does in fact blow air in the reverse direction of the airplane, as anyone who stands behind the propellor can attest.) Of course, it would be incorrect to imagine that forward thrust derives in any way from blowing air against the air behind the plane (which is apparently how you interpret the statement at issue.)
Forward thrust results partially from conservation of momentum: by throwing air molecules backward, the propellor experiences a motive force in the opposite direction, as a consequence of Newton's Third Law of Motion. To me, "pushing air backward" is an acceptable way to state this, when one trusts that the audience understands the physics of motion. Although the pressure gradient created by the action of the propellor also contributes to the thrust vector, failure to mention this component of the thrust is not a sin in this context.
I'm afraid I don't understand what you're driving at, either. Could you spell it out for us?
That would be my first impression. But I am humble, and am always willing to consider the possibility that I am wrong.
The propellor blades are slanted so that there is high pressure on the back of the blade and low pressure on the front. The difference, or net total force produces a thrust forward on the propellor. The vacuum on the front is limited to zero pressure, which is only 14 psi less than atmospheric. I would guess that the pressure increase on the back is more substantial.