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The minimum distance between Earth and Mars has been declining over the years, and in 2003 the minimum distance was 55.76 million km, nearer than any such encounter in almost 60,000 years (57,617 BC). The record minimum distance between Earth and Mars in 2729 will stand at 55.65 million km.
Radar is used to measure the distance between the orbits of the Earth and of a second body. From that measurement and the ratio of the two orbit sizes, the size of Earth's orbit is calculated. The Earth's orbit is known with an absolute precision of a few meters and a relative precision of a few parts in 100 billion (1 × 10 −11).
the vector r is the position of one body relative to the other; r, v, and in the case of an elliptic orbit, the semi-major axis a, are defined accordingly (hence r is the distance) μ = Gm 1 + Gm 2 = μ 1 + μ 2, where m 1 and m 2 are the masses of the two bodies. Then: for circular orbits, rv 2 = r 3 ω 2 = 4π 2 r 3 /T 2 = μ
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Minimum orbit intersection distance (MOID) is a measure used in astronomy to assess potential close approaches and collision risks between astronomical objects. [1] [2] It is defined as the distance between the closest points of the osculating orbits of two bodies. Of greatest interest is the risk of a collision with Earth.
The siriometer is an obsolete astronomical measure equal to one million astronomical units, i.e., one million times the average distance between the Sun and Earth. [13] This distance is equal to about 15.8 light-years, 149.6 Pm, or 4.8 parsecs, and is about twice the distance from Earth to the star Sirius. [14]
At the present time the proper distance equals the comoving distance since the cosmological scale factor has value one: () =. The proper distance represents the distance obtained as if one were able to freeze the flow of time (set d t = 0 {\displaystyle dt=0} in the FLRW metric) and walk all the way to a galaxy while using a meter stick. [ 2 ]
Musk does have a plan for making Mars an attractive destination for long-term living: Terraforming, a hypothetical scenario in which humans make Mars more Earth-like by pumping gases into the ...