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At time 1, the Sun and a certain distant star are both overhead. At time 2, the planet has rotated 360° and the distant star is overhead again (1→2 = one sidereal day). But it is not until a little later, at time 3, that the Sun is overhead again (1→3 = one solar day).
Earth is the third planet from the Sun and the only astronomical object known to harbor life.This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water.
The Solar System is traveling at an average speed of 230 km/s (828,000 km/h) or 143 mi/s (514,000 mph) within its trajectory around the Galactic Center, [3] a speed at which an object could circumnavigate the Earth's equator in 2 minutes and 54 seconds; that speed corresponds to approximately 1/1300 of the speed of light.
In 1862, the physicist William Thomson, 1st Baron Kelvin published calculations that fixed the age of Earth at between 20 million and 400 million years. [19] [20] He assumed that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface temperature gradient to decrease to its present value.
The Jiffy is the amount of time light takes to travel one fermi (about the size of a nucleon) in a vacuum. The Planck time is the time light takes to travel one Planck length. The TU (for time unit) is a unit of time defined as 1024 μs for use in engineering. The Svedberg is a time unit used for sedimentation rates (usually of
[1] [2] The planet orbits the Sun in 687 days [3] and travels 9.55 AU in doing so, [4] making the average orbital speed 24 km/s. The eccentricity is greater than that of every other planet except Mercury, and this causes a large difference between the aphelion and perihelion distances—they are respectively 1.639 and 1.405 AU. [5]
Cosmic time : 42 is a measure of time by a physical clock with zero peculiar velocity in the absence of matter over-/under-densities (to prevent time dilation due to relativistic effects or confusions caused by expansion of the universe). Unlike other measures of time such as temperature, redshift, particle horizon, or Hubble horizon, the ...
Originally launched as the International Sun-Earth Explorer 3, the spacecraft was renamed, and departed the Sun-Earth L 1 Lagrangian point in 1982 in order to intercept the comets 21P/Giacobini-Zinner and Halley. [146] ICE flew through the tail of Halley's Comet, coming within about 40.2 million km (25.0 million mi) of the nucleus on 28 March 1986.