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  2. Earth radius - Wikipedia

    en.wikipedia.org/wiki/Earth_radius

    Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).

  3. Solar radius - Wikipedia

    en.wikipedia.org/wiki/Solar_radius

    Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun 's photosphere where the optical depth equals 2/3: [ 1 ]

  4. Earth-centered, Earth-fixed coordinate system - Wikipedia

    en.wikipedia.org/wiki/Earth-centered,_Earth...

    The distance from a given point of interest to the center of Earth is called the geocentric distance, R = (X 2 + Y 2 + Z 2) 0.5, which is a generalization of the geocentric radius, R 0, not restricted to points on the reference ellipsoid surface.

  5. Equivalent radius - Wikipedia

    en.wikipedia.org/wiki/Equivalent_radius

    The volume of a sphere of radius R is ... For planet Earth, which can be approximated as an oblate spheroid with radii 6 378.1 km and 6 356.8 km, ...

  6. Gravity of Earth - Wikipedia

    en.wikipedia.org/wiki/Gravity_of_Earth

    The gravity g′ at depth d is given by g′ = g(1 − d/R) where g is acceleration due to gravity on the surface of the Earth, d is depth and R is the radius of the Earth. If the density decreased linearly with increasing radius from a density ρ 0 at the center to ρ 1 at the surface, then ρ(r) = ρ 0 − (ρ 0 − ρ 1) r / R, and the ...

  7. Earth - Wikipedia

    en.wikipedia.org/wiki/Earth

    The Hill sphere, or the sphere of gravitational influence, of Earth is about 1.5 million km (930,000 mi) in radius. [164] [n 11] This is the maximum distance at which Earth's gravitational influence is stronger than that of the more distant Sun and planets.

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    mail.aol.com

    Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!

  9. Horizon - Wikipedia

    en.wikipedia.org/wiki/Horizon

    where h is height above sea level and R is the Earth radius. The expression can be simplified as: , where the constant equals k= 3.57 km/m ½ = 1.22 mi/ft ½. In this equation, Earth's surface is assumed to be perfectly spherical, with R equal to about 6,371 kilometres (3,959 mi).