Posted on 02/28/2003 2:59:02 PM PST by sourcery
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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