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  2. Spacetime diagram - Wikipedia

    en.wikipedia.org/wiki/Spacetime_diagram

    A spacetime diagram is a graphical illustration of locations in space at various times, especially in the special theory of relativity.Spacetime diagrams can show the geometry underlying phenomena like time dilation and length contraction without mathematical equations.

  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. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    The astronomical unit (symbol: au [1] [2] [3] [4] or AU) is a unit of length defined to be exactly equal to 149 597 870 700 m. [5] Historically, the astronomical unit ...

  5. Earth's orbit - Wikipedia

    en.wikipedia.org/wiki/Earth's_orbit

    Earth at seasonal points in its orbit (not to scale) Earth orbit (yellow) compared to a circle (gray) Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi), or 8.317 light-minutes, [1] in a counterclockwise direction as viewed from above the Northern Hemisphere.

  6. Low Earth orbit - Wikipedia

    en.wikipedia.org/wiki/Low_Earth_orbit

    A wide variety of sources [5] [6] [7] define LEO in terms of altitude.The altitude of an object in an elliptic orbit can vary significantly along the orbit. Even for circular orbits, the altitude above ground can vary by as much as 30 km (19 mi) (especially for polar orbits) due to the oblateness of Earth's spheroid figure and local topography.

  7. Galactic year - Wikipedia

    en.wikipedia.org/wiki/Galactic_year

    The galactic year, also known as a cosmic year, is the duration of time required for the Sun to orbit once around the center of the Milky Way Galaxy. [1] One galactic year is approximately 225 million Earth years. [2]

  8. Kármán line - Wikipedia

    en.wikipedia.org/wiki/Kármán_line

    Earth's atmosphere photographed from the International Space Station.The orange and green line of airglow is at roughly the altitude of the Kármán line. [1]The Kármán line (or von Kármán line / v ɒ n ˈ k ɑːr m ɑː n /) [2] is a conventional definition of the edge of space, though it is not universally accepted.

  9. Kepler's laws of planetary motion - Wikipedia

    en.wikipedia.org/wiki/Kepler's_laws_of_planetary...

    Voltaire's Eléments de la philosophie de Newton (Elements of Newton's Philosophy) of 1738 was the first publication to use the terminology of "laws". [ 6 ] [ 7 ] The Biographical Encyclopedia of Astronomers in its article on Kepler (p. 620) states that the terminology of scientific laws for these discoveries was current at least from the time ...