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For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200 000 km/s (124 000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.
Surface gravity is measured in units of acceleration, which, in the SI system, are meters per second squared. It may also be expressed as a multiple of the Earth 's standard surface gravity, which is equal to [1] g = 9.806 65 m/s2. In astrophysics, the surface gravity may be expressed as log g, which is obtained by first expressing the gravity ...
using SI units of meters for , hertz (s −1) for , and meters per second (m⋅s −1) for , (where c=299 792 458 m/s in vacuum, ≈ 300 000 km/s) For typical radio applications, it is common to find d {\displaystyle d} measured in kilometers and f {\displaystyle f} in gigahertz , in which case the FSPL equation becomes
The Hubble constant is most frequently quoted in (km/s)/Mpc, thus giving the speed in km/s of a galaxy 1 megaparsec (3.09 × 10 19 km) away, and its value is about 70 (km/s)/Mpc. However, crossing out units reveals that H 0 is a unit of frequency (SI unit: s −1) and the reciprocal of H 0 is known as the Hubble time. The Hubble constant can ...
Isometric graph paper or 3D graph paper is a triangular graph paper which uses a series of three guidelines forming a 60° grid of small triangles. The triangles are arranged in groups of six to make hexagons. The name suggests the use for isometric views or pseudo-three-dimensional views. Among other functions, they can be used in the design ...
In most situations it is impractical to achieve escape velocity almost instantly, because of the acceleration implied, and also because if there is an atmosphere, the hypersonic speeds involved (on Earth a speed of 11.2 km/s, or 40,320 km/h) would cause most objects to burn up due to aerodynamic heating or be torn apart by atmospheric drag. For ...
At a fixed point on the surface, the magnitude of Earth's gravity results from combined effect of gravitation and the centrifugal force from Earth's rotation. [ 2 ] [ 3 ] At different points on Earth's surface, the free fall acceleration ranges from 9.764 to 9.834 m/s 2 (32.03 to 32.26 ft/s 2 ), [ 4 ] depending on altitude , latitude , and ...
Recessional velocity. Recessional velocity is the rate at which an extragalactic astronomical object recedes (becomes more distant) from an observer as a result of the expansion of the universe. [1] It can be measured by observing the wavelength shifts of spectral lines emitted by the object, known as the object's cosmological redshift.