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  2. Cosmological horizon - Wikipedia

    en.wikipedia.org/wiki/Cosmological_horizon

    The particle horizon differs from the cosmic event horizon, in that the particle horizon represents the largest comoving distance from which light could have reached the observer by a specific time, while the cosmic event horizon is the largest comoving distance from which light emitted now can ever reach the observer in the future. [3]

  3. Event horizon - Wikipedia

    en.wikipedia.org/wiki/Event_horizon

    In cosmology, the event horizon of the observable universe is the largest comoving distance from which light emitted now can ever reach the observer in the future. This differs from the concept of the particle horizon , which represents the largest comoving distance from which light emitted in the past could reach the observer at a given time.

  4. Horizon - Wikipedia

    en.wikipedia.org/wiki/Horizon

    For an observer standing on the ground with h = 1.70 metres (5 ft 7 in), the horizon is at a distance of 4.7 kilometres (2.9 mi). For an observer standing on the ground with h = 2 metres (6 ft 7 in), the horizon is at a distance of 5 kilometres (3.1 mi).

  5. Particle horizon - Wikipedia

    en.wikipedia.org/wiki/Particle_horizon

    The particle horizon (also called the cosmological horizon, the comoving horizon (in Scott Dodelson's text), or the cosmic light horizon) is the maximum distance from which light from particles could have traveled to the observer in the age of the universe.

  6. Maps show which states could see northern lights this weekend

    www.aol.com/maps-show-states-could-see-184107321...

    800-290-4726 more ways to reach us. Sign in. Mail. 24/7 ... intensity of the aurora borealis over North America with a line showing how far south the lights could be seen on the northern horizon.

  7. Observable universe - Wikipedia

    en.wikipedia.org/wiki/Observable_universe

    For example, the current distance to this horizon is about 16 billion light-years, meaning that a signal from an event happening at present can eventually reach the Earth if the event is less than 16 billion light-years away, but the signal will never reach the Earth if the event is further away. [9]

  8. ‘Like going to the moon’: Why this is the world’s most ...

    www.aol.com/going-moon-why-world-most-120326810.html

    800-290-4726 more ways to reach us. Sign in. ... “That’s a bit too far for me.” ... Newer boats often have more spacious rooms and bigger windows so that you can watch the horizon, which ...

  9. Line-of-sight propagation - Wikipedia

    en.wikipedia.org/wiki/Line-of-sight_propagation

    Assuming a perfect sphere with no terrain irregularity, the distance to the horizon from a high altitude transmitter (i.e., line of sight) can readily be calculated. Let R be the radius of the Earth and h be the altitude of a telecommunication station. The line of sight distance d of this station is given by the Pythagorean theorem;