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  2. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    Another quantum effect that predicts the occurrence of faster-than-light speeds is called the Hartman effect: under certain conditions the time needed for a virtual particle to tunnel through a barrier is constant, regardless of the thickness of the barrier. [50] [51] This could result in a virtual particle crossing a large gap faster than ...

  3. Faster-than-light - Wikipedia

    en.wikipedia.org/wiki/Faster-than-light

    Faster-than-light (superluminal or supercausal) travel and communication are the conjectural propagation of matter or information faster than the speed of light in vacuum (c). The special theory of relativity implies that only particles with zero rest mass (i.e., photons ) may travel at the speed of light, and that nothing may travel faster.

  4. Lighthouse paradox - Wikipedia

    en.wikipedia.org/wiki/Lighthouse_paradox

    The theory of relativity says information cannot be transmitted faster than light. This experiment does not actually transmit a signal from object 1 to object 2. The time when the light beam strikes object 2 is controlled by the person at the lighthouse, not anyone on object 1, so no one on object 1 can transmit a message to object 2 by this ...

  5. Foucault's measurements of the speed of light - Wikipedia

    en.wikipedia.org/wiki/Foucault's_measurements_of...

    The light path from m to M is entirely through air, while the light path from m to M' is mostly through a water-filled tube T. Lens L' compensates for the effects of the water on the focus. The light reflected back from the spherical mirrors is diverted by beam splitter g towards an eyepiece O.

  6. Accelerating expansion of the universe - Wikipedia

    en.wikipedia.org/wiki/Accelerating_expansion_of...

    Spectral lines of their light can be used to determine their redshift. For supernovae at redshift less than around 0.1, or light travel time less than 10 percent of the age of the universe, this gives a nearly linear distance–redshift relation due to Hubble's law. At larger distances, since the expansion rate of the universe has changed over ...

  7. Tachyon - Wikipedia

    en.wikipedia.org/wiki/Tachyon

    Spacetime diagram showing that moving faster than light implies time travel in the context of special relativity. A spaceship departs from Earth from A to C slower than light. At B, Earth emits a tachyon, which travels faster than light but forward in time in Earth's reference frame. It reaches the spaceship at C.

  8. Speed of gravity - Wikipedia

    en.wikipedia.org/wiki/Speed_of_gravity

    Formally, c is a conversion factor for changing the unit of time to the unit of space. [4] This makes it the only speed which does not depend either on the motion of an observer or a source of light and / or gravity. Thus, the speed of "light" is also the speed of gravitational waves, and further the speed of any massless particle.

  9. Fizeau experiment - Wikipedia

    en.wikipedia.org/wiki/Fizeau_experiment

    According to the Stokes' hypothesis, the speed of light should be increased or decreased when "dragged" along by the water through the aether frame, dependent upon the direction. [S 5]: 33 The overall speed of a beam of light should be a simple additive sum of its speed through the water plus the speed of the water.