Fission splits a heavy nucleus into lighter ones that are more tightly bound per particle, so some mass becomes energy, mostly as motion of the fragments, which turns into heat.
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Ole Roemer made the first measurement in the 1670s from timing eclipses of Jupiter's moon Io. Armand Fizeau made the first Earth-based measurement in 1849 using a toothed wheel.
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Entropy counts possible arrangements of a system and is tied to missing information. Its tendency to rise is the usual basis for time's direction, though the details remain actively studied.
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The square-cube law says volume grows faster than surface area as things get bigger. Kleiber's law says metabolic rate scales roughly with mass to the 3/4 power, though that exponent is debated.
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Bell's theorem rules out local theories matching quantum predictions; the measurement problem shows quantum theory alone does not say why single outcomes occur. Neither is settled in interpretation.
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A returning boomerang is a spinning wing. Its blades make uneven lift, and gyroscopic precession turns that uneven lift into a curved path back to the thrower.
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Bananas are slightly radioactive because of potassium-40. One banana gives roughly 0.1 microsieverts, an informal unit called the banana equivalent dose, which poses no meaningful risk.
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Some experiments report hot water freezing first, but results are hard to repeat and researchers disagree over whether the Mpemba effect is real or an artifact of measurement.
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We feel changes in motion, not steady motion. Earth's spin is smooth, we and the air move with it, and gravity far outweighs the tiny outward effect of rotation.
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A rolling bicycle stays up because its steering turns into any lean. A rider usually supplies this, but several bike features can do it alone.
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A twin who travels at high speed and returns is younger than the twin who stayed home. The apparent paradox disappears because the twins' paths through spacetime are not symmetrical.
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Schrödinger devised the cat in 1935 as a reductio ad absurdum, to show that applying quantum superposition to large objects gives absurd results, not to claim cats can be both alive and dead.
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Maxwell's demon is a 1867 thought experiment in which a tiny sorting being seems to defy the second law of thermodynamics. Information theory and the cost of erasing memory resolved it.
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Landauer's principle says erasing one bit of information must dissipate at least k_B T ln 2 of energy as heat. At room temperature that is about 2.9×10^-21 joules.
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Special relativity says light's speed is a fixed limit: massive objects would need infinite energy to reach it, and faster signals would break cause and effect. Why nature works this way is unexplained.
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It says that position and momentum cannot both be sharply defined at once; their uncertainties have a minimum product of ħ/2. This is not just a limit of instruments.
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Machines that run forever without an energy source would break the laws of thermodynamics, and real systems also lose energy to friction and drag.
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If Earth were scaled up to represent an atomic nucleus, an atom's electron cloud would extend roughly 1.3 billion km out, far beyond the Moon and into the outer solar system. Electrons have no single fixed distance because their positions are described by probability clouds rather than orbits.
Not factually verified
