Vote
8 Total Votes
1

Fermi paradox

If there are, as various arguments suggest, many other sentient species in the Universe, then where are they? Shouldn't their presence be obvious?
2 votes
0 comments
2

Einstein–Podolsky–Rosen paradox

Can far away events influence each other in quantum mechanics?
2 votes
1 comment
3

Schrödinger's cat paradox

According to the Copenhagen interpretation of quantum mechanics, a cat could be simultaneously alive and dead, as long as we don't look.
1 vote
0 comments
4

Mpemba effect

Hot water can, under certain conditions, freeze faster than cold water, even though it must pass the lower temperature on the way to freezing.
1 vote
0 comments
5

Irresistible force paradox

What would happen if an unstoppable force hit an immovable object?
1 vote
0 comments
6

Quantum Zeno effect

Echoing the Zeno paradox, a quantum particle that is continuously observed cannot change its state.
1 vote
1 comment
7

Heat death paradox

If the universe was infinitely old, it would be in thermodynamical equilibrium, which contradicts what we observe.
0 votes
0 comments
8

Bentley's paradox

In a Newtonian universe, gravitation should pull all matter into a single point.
0 votes
0 comments
9

Bell's theorem

Why do measured quantum particles not satisfy mathematical probability theory?
0 votes
0 comments
10

Tea leaf paradox

When a cup of tea is stirred, the leaves assemble in the center, even though centrifugal force pushes them outward.
0 votes
0 comments
11

Feynman sprinkler

Which way does a sprinkler rotate when submerged in a tank and made to suck in the surrounding fluid?
0 votes
0 comments
12

Quantum pseudo-telepathy

Two players who can not communicate accomplish tasks that seemingly require direct contact.
0 votes
0 comments
13

Klein paradox

When the potential of a potential barrier becomes similar to the mass of the impinging particle, it becomes transparent.
0 votes
0 comments
14

Quantum LC circuit paradox

Energies stored on capacitance and inductance are not equal to the ground state energy of the quantum oscillator.
0 votes
0 comments
15

Painlevé paradox

Rigid-body dynamics with contact and friction is inconsistent.
0 votes
0 comments
16

Bell's spaceship paradox

A delicate string or thread hangs between two spaceships. Both spaceships now start accelerating simultaneously and equally as measured in the inertial frame S, thus having the same velocity at all times in S. Therefore they are all subject to the s... ame Lorentz contraction, so the entire assembly seems to be equally contracted in the S frame with respect to the length at the start. Therefore at first sight it might appear that the thread will not break during acceleration   more
0 votes
0 comments
17

Loschmidt's paradox

Why is there an inevitable increase in entropy when the laws of physics are invariant under time reversal? The time reversal symmetry of physical laws appears to contradict the second law of thermodynamics.
0 votes
0 comments
18

Trouton-Noble or Right-angle lever paradox

Does a torque arise in static systems when changing frames?
0 votes
0 comments
19

Maxwell's demon

The second law of thermodynamics seems to be violated by a cleverly operated trapdoor.
0 votes
0 comments
20

Black hole information paradox

Black holes violate a commonly assumed tenet of science — that information cannot be destroyed.
0 votes
0 comments
21

Twin paradox

The theory of relativity predicts that a person making a round trip will return younger than his or her identical twin who stayed at home.
0 votes
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22

Ladder paradox

The ladder paradox is a thought experiment in special relativity. It involves a ladder, parallel to the ground, travelling horizontally and therefore undergoing a Lorentz length contraction. As a result, the ladder fits inside a garage which would n... ormally be too small to contain it. On the other hand, from the point of view of an observer moving with the ladder, it is the garage that is moving, so it is the garage which will be contracted to an even smaller size, thus being unable to contain the ladder. This apparent paradox results from the mistaken assumption of absolute simultaneity. The ladder fits into the garage only if both of its ends are simultaneously inside the garage. In relativity, simultaneity is relative to each observer, and so the question of whether the ladder fits inside the garage is relative to each observer, and the paradox is resolved   more
0 votes
0 comments
23

Gibbs paradox

In an ideal gas, is entropy an extensive variable?
0 votes
0 comments
24

I don't understand.

A paradox of the most extreme.
0 votes
0 comments
25

Algol paradox

In some binaries the partners seem to have different ages, even though they are thought to have formed at the same time.
0 votes
0 comments
26

Faint young Sun paradox

The contradiction between existence of liquid water early in the Earth's history and the expectation that the output of the young Sun would have been insufficient to melt ice on Earth.
0 votes
0 comments
27

GZK paradox

Extreme-energy cosmic rays have been observed that seem to violate the Greisen-Zatsepin-Kuzmin limit, which is a consequence of special relativity.
0 votes
0 comments
28

Paradox of youth

Compared to theory, there is an overabundance of young stars close to the supermassive black hole in the Galactic Center.
0 votes
0 comments
29

Archer's paradox

An archer must, in order to hit his target, not aim directly at it, but slightly to the side.
0 votes
0 comments
30

Hydrostatic paradox

Or Archimedes' paradox, a massive battleship can float in a few liters of water.
0 votes
0 comments
31

Aristotle's wheel paradox

Rolling joined concentric wheels seem to trace the same distance with their circumferences, even though the circumferences are different.
0 votes
0 comments
32

Carroll's paradox

The angular momentum of a stick should be zero, but is not.
0 votes
0 comments
33

D'Alembert's paradox

Flow of an inviscid fluid produces no net force on a solid body.
0 votes
0 comments
34

Denny's paradox

Surface-dwelling arthropods (such as the water strider) should not be able to propel themselves horizontally.
0 votes
0 comments
35

Double-slit experiment

Matter and energy can act as a wave or as a particle depending on the experiment.
0 votes
0 comments
36

Upstream contamination

When a fluid is poured from a higher container onto a lower one, particles can climb up the falling water.
0 votes
0 comments
37

Faraday paradox

An apparent violation of Faraday's law of electromagnetic induction.
0 votes
0 comments
38

Mott problem

Spherically symmetric wave functions, when observed, produce linear particle tracks.
0 votes
0 comments
39

Olbers' paradox

Why is the night sky dark if there is an infinity of stars, covering every part of the celestial sphere?
0 votes
0 comments
40

Ehrenfest paradox

The Ehrenfest paradox concerns the rotation of a "rigid" disc in the theory of relativity.In its original formulation as presented by Paul Ehrenfest 1909 in relation to the concept of Born rigidity within special relativity, it discusses an ideally ... rigid cylinder that is made to rotate about its axis of symmetry. The radius R as seen in the laboratory frame is always perpendicular to its motion and should therefore be equal to its value R₀ when stationary. However, the circumference should appear Lorentz-contracted to a smaller value than at rest, by the usual factor γ. This leads to the contradiction that R=R₀ and R   more
0 votes
0 comments
41

Supplee's paradox

The buoyancy of a relativistic object (such as a bullet) appears to change when the reference frame is changed from one in which the bullet is at rest to one in which the fluid is at rest.
0 votes
0 comments
42

Cool tropics paradox

A contradiction between modelled estimates of tropical temperatures during warm, ice-free periods of the Cretaceous and Eocene, and the lower temperatures that proxies suggest were present.
0 votes
0 comments
43

Elevator paradox

Even though hydrometers are used to measure fluid density, a hydrometer will not indicate changes of fluid density caused by changing atmospheric pressure.
0 votes
0 comments
44

Aharonov–Bohm effect

A charged particle is affected by an electromagnetic field even though it has no local contact with that field
0 votes
0 comments
45

Extinction paradox

In the small wavelength limit, the total scattering cross section of an impenetrable sphere is twice its geometrical cross-sectional area (which is the value obtained in classical mechanics).
0 votes
0 comments
46

Boltzmann brain

If the universe we observe resulted from a random thermodynamic fluctuation, it would be vastly more likely to be a simple one than the complex one we observe. The simplest case would be just a brain floating in vacuum, having the thoughts and sensa... tions you have   more
0 votes
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47

Hardy's paradox

How can we make inferences about past events that we haven't observed while at the same time acknowledge that the act of observing it affects the reality we are inferring to?
0 votes
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48

Uncertainty principle

Attempts to determine position must disturb momentum, and vice versa.
0 votes
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