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.
Speaking of mysteries, you might find this post quite interesting. It is a great discussion of various theories, including zero point energy, dark matter, m-theories, supersymmetry, etc. The Cosmological Constant – Carroll, Enrico Fermi Institute (pdf)
Yes, it is the breakthrough science that will unleash the earth and make us a member of the galactic travel club.
Without it, we are stuck here.
It would be nice is we could fiqure it out soon.
But, OTOH, if one of the gasses was also a lot hotter than the other one, you can tell after the fact how much white mixed with the black and vice-versa with Boltzmann's formulas. (It corresponds nicely with the amount of temperature change observed in both compartments.)
What Thorne describes--actually a historical narrative in which key insights were made by Bekenstein, Zel'dovich, and Hawking--not only involves such equivalence as there is between logical and thermodynamic entropy, but an equivalence between black hole dynamics and thermodynamics in general.
Thus it was that Hawking, in 1974, having proved firmly that a black hole radiates as though it had a temperature proportional to its surface gravity, went on to assert, without real proof, that all of the other similarities between the laws of black hole mechanics and the laws of thermodynamics were more than a coincidence. The black-hole laws are the same thing as the thermodynamic laws, but in disguise ...Sounds shaky, but Hawking's postulate is so far holding up. Thorne cites some of his own work as an example.
Throw into a black hole's atmosphere a small amount of material containing some small amount of energy (or, equivalently, mass) angular momentum (spin), and electric charge. From the atmosphere this material will continue on down through the horizon and into the hole. Once the material has entered the hole, it is impossible by examining the hole from outside to learn the nature of the injected material (whether it consisted of matter or of antimatter, of photons and heavy atoms, or of electrons and positrons), and it is impossible to learn just where the material was injected. Because a black hole has no "hair," all one can discover, by examining the hole from outside, are the total amounts of mass, angular momentum, and charge that entered the atmosphere.He goes on a bit later,... [T]he logarithm of the number of ways to inject must be the increase in the atmosphere's entropy, as described by the standard laws of thermodynamics. By a fairly simple calculation, Zurek and I were able to show that this increase in thermodynamic entropy is precisely equal to 1/4 times the increase in the horizon's area, divided by the Planck-Wheeler area; this is, it is precisely the increase in the horizon's area in disguise, the same disguise that Hawking inferred, in 1974, from the mathematical similarity of the laws of black-hole mechanics and the laws of thermodynamics.
The thought experiment also shows the second law of thermodynamics in action. The energy, angular momentum, and charge that one throws into the hole's atmosphere can have any form at all ... When the bag is thrown into the the hole's atmosphere, the entropy of the external universe is reduced by the amount of the entropy (randomness) in the bag. However, the entropy of the hole's atmosphere, and thence of the hole, goes up by more than the bag's entropy, so the total entropy of hole plus external Universe goes up. The second law of thermodynamics is obeyed.Similarly, it turns out, when the black hole evaporates some particles, its own surface area and entropy typically go down; but the particles get distributed randomly in the external Universe, increasing its entropy by more than the hole's entropy loss. Again, the second law is obeyed.
IMHO, this is an accurate description of the operation of a ship's propellor, but overly simplifed in describing the action of an airplane propellor. Both are fluid dynamic systems, but hydrodynamics differs from aerodynamics primarily because air is compressible, and water is not. Depending on you POV, the statement that an aircraft propellor derives it thrust from pushing on the air could still be perfectly valid when you consider that the "forward lift" on the front of the blade was created by the leading edge pushing on the air and compressing it in order to induce that lift - it just isn't pushing it backward.
Then it is not dumbing down but incorrectly stated.
Two questions:
Can you prove this?
If I ask you to prove this, am I part of the conspiracy too?
And you have hundreds of posts in the last few weeks attesting to your pro-drug, gun-control, new world order views.
And only on FR can you have back to back posts with such diversity.
Newton's Third Law must be satisfied. Anything that accelerates forward must necessarily push against something in order to accelerate forward. A rocket pushes against its exhaust. A runner pushes against the ground. A rower pushes against the water. A propellor-driven airplane pushes against...what?
Please show me a reference where it says a propellor pushes against the air.
Any such reference he cites, you could simply criticize as wrong and not sufficiently authoritative--just as you have done in the case of the article that initiates this thread. What is needed here is something more definitive, I expect .
So let's perform a thought experiment: turn on a fan; observe that the fan blows air in one direction, and sucks in air from the opposite direction. Then apply Newton's third law to the fact that the fan is transferring momentum to air molecules, so that those molecules are persuaded to move in a particular direction. The conclusion should be obvious.
The same thing, and in the same manner that the wing pushes against to accellerate it upward.
Incidentally, this leads me to another question: Does the Second Law apply to individual atoms, that is, the motion of electrons in the closed system of an atom? It seems to be using 100% of its initial energy, at all times.
Hawking made the opposite statement, that the Black Hole dynamics would ultimately turn out to be the laws of thermodynamics. People had been noticing some parallels in form, but there was no reason to think a mathematical model of a particular large-scale configuration of mass and space in any way needed to resemble the equations describing heat flow. The similarities had been assumed to be a coincidence.
Incidentally, this leads me to another question: Does the Second Law apply to individual atoms, that is, the motion of electrons in the closed system of an atom? It seems to be using 100% of its initial energy, at all times.
Electrons "use" no energy in their ordinary zipping around inside their orbitals. Sometimes people--creationist and ZPE theorist Barry Setterfield comes to mind--wonder why they don't radiate away their energy and spiral into the nucleus under the pull of the positive charges there, but that's misapplying 19th century classical ideas of based on little charged balls flying around.
In the quantum-mechanical model, you can't spiral in because only certain orbitals are allowed and there are no legal in-between states. It takes energy input to pop up into a higher orbital. Energy is released if the electron drops to a lower fixed orbital. Staying within an orbital takes nothing. This no more violates the second law than a planet orbiting a star violates the second law.
... but that's misapplying 19th century classical ideas [of] based on little charged balls flying around.
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