Ellipsoid paradox: This paradox considers a perfectly reflecting cavity with two black bodies at points A and B. The reflecting surface is composed of two elliptical sections E1 and E2 and a spherical section S, and the bodies at A and B are located at the joint foci of the two ellipses and B is at the center of S. This configuration is such that apparently black body at B heat up relative to A: the radiation originating from the blackbody at A will land on and be absorbed by the blackbody at B.

The law that entropy always increases – the second law of thermodynamics – holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations – then so much the worse for Maxwell's equations.

The seemingly mysterious ability of magnets to influence motion at a distance without any apparent energy source has long appealed to inventors. One of the earliest examples of a magnetic motor was proposed by Wilkins and has been widely copied since: it consists of a ramp with a magnet at the top, which pulled a metal ball up the ramp. Near the magnet was a small hole that was supposed to allow the ball to drop under the ramp and return to the bottom, where a flap allowed it to return to the top again.

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Subsequent analysis (and experiment) have shown there is no way to physically implement such a system that does not result in an overall increase in entropy.

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"Just completed the marble run. I had to make a couple of adjustments & now it works great. The documentation on the other hand - needs improvement. Some of the illustrations aren't clear. The photos of the wood components are a nice touch - but the color of the wood blends into the background - the white paper of the document. Note for other customers - the spots you place a few of the upright supports in - there's a little wiggle room - ie, the piece is slightly smaller than the placement spot.

Combining different measurements such as spectroscopy, direct measurement of the speed of light in the past and similar measurements demonstrates that physics has remained substantially the same, if not identical, for all of observable time spanning billions of years.[25]

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The first law of thermodynamics is the law of conservation of energy, which simply states that energy cannot be created or destroyed, but rather is transferred.

To extract work from heat, thus producing a perpetual motion machine of the second kind, the most common approach (dating back at least to Maxwell's demon) is unidirectionality. Only molecules moving fast enough and in the right direction are allowed through the demon's trap door. In a Brownian ratchet, forces tending to turn the ratchet one way are able to do so while forces in the other direction are not. A diode in a heat bath allows through currents in one direction and not the other.

Vacuum energy and zero-point energy: In order to explain effects such Triunfador imaginario particles and the Casimir effect, many formulations of quantum physics include a background energy which pervades empty space, known Ganador vacuum or zero-point energy. The ability to harness zero-point energy for useful work is considered pseudoscience by the scientific community at large.

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Those of you who have taken a physics course or two know that perpetual motion machines are impossible to make Campeón they violate the first and second laws of thermodynamics.