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  2. Space travel under constant acceleration - Wikipedia

    en.wikipedia.org/wiki/Space_travel_under...

    This plot shows a ship capable of 1-g (10 m/s 2 or about 1.0 ly/y 2) "felt" or proper acceleration [6] can travel vast distances, although is limited by the mass of any propellant it carries. A spaceship using significant constant acceleration will approach the speed of light over interstellar distances, so special relativity effects including ...

  3. One-way speed of light - Wikipedia

    en.wikipedia.org/wiki/One-way_speed_of_light

    The two-way speed of light is the average speed of light from one point, such as a source, to a mirror and back again. Because the light starts and finishes in the same place, only one clock is needed to measure the total time; thus, this speed can be experimentally determined independently of any clock synchronization scheme.

  4. Photon rocket - Wikipedia

    en.wikipedia.org/wiki/Photon_rocket

    A photon rocket is a rocket that uses thrust from the momentum of emitted photons (radiation pressure by emission) for its propulsion. [1] Photon rockets have been discussed as a propulsion system that could make interstellar flight possible during a human lifetime, which requires the ability to propel spacecraft to speeds at least 10% of the speed of light, v ≈ 0.1c = 30,000 km/s. [2]

  5. Light - Wikipedia

    en.wikipedia.org/wiki/Light

    The speed of light in vacuum is defined to be exactly 299 792 458 m/s (approximately 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light. All forms of electromagnetic radiation move at exactly this same speed in vacuum.

  6. Relativistic rocket - Wikipedia

    en.wikipedia.org/wiki/Relativistic_rocket

    Relativistic rocket means any spacecraft that travels close enough to light speed for relativistic effects to become significant. The meaning of "significant" is a matter of context, but often a threshold velocity of 30% to 50% of the speed of light (0.3c to 0.5c) is used.

  7. Hubble's law - Wikipedia

    en.wikipedia.org/wiki/Hubble's_law

    The Hubble length or Hubble distance is a unit of distance in cosmology, defined as cH −1 — the speed of light multiplied by the Hubble time. It is equivalent to 4,420 million parsecs or 14.4 billion light years. (The numerical value of the Hubble length in light years is, by definition, equal to that of the Hubble time in years.)

  8. Redshift - Wikipedia

    en.wikipedia.org/wiki/Redshift

    where c is the speed of light. In the classical Doppler effect, the frequency of the source is not modified, but the recessional motion causes the illusion of a lower frequency. A more complete treatment of the Doppler redshift requires considering relativistic effects associated with motion of sources close to the speed of light.

  9. Lightning - Wikipedia

    en.wikipedia.org/wiki/Lightning

    The rate at which the return stroke current travels has been found to be around 100,000 km/s (one-third of the speed of light). [67] A typical cloud-to-ground lightning flash culminates in the formation of an electrically conducting plasma channel through the air in excess of 5 km (3.1 mi) tall, from within the cloud to the ground's surface.