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2. On the Sizes and Distances (Aristarchus) - Wikipedia

   en.wikipedia.org/wiki/On_the_Sizes_and_Distances...

   Aristarchus's 3rd century BCE calculations on the relative sizes of, from left, the Sun, Earth and Moon, from a 10th-century CE Greek copy. On the Sizes and Distances (of the Sun and Moon) (Ancient Greek: Περὶ μεγεθῶν καὶ ἀποστημάτων [ἡλίου καὶ σελήνης], romanized: Perì megethôn kaì apostēmátōn [hēlíou kaì selḗnēs]) is widely accepted ...

3. Empirical evidence for the spherical shape of Earth - Wikipedia

   en.wikipedia.org/wiki/Empirical_evidence_for_the...

   Such a conjecture would also leave open for explanation the tides seen in Earth's oceans, which are conventionally explained by the gravity exerted by the Sun and Moon. The Earth would also quickly approach light-speed in this scenario because the pull of gravity would increase by -9.8m/s, each second (as the formula for gravitational ...

4. Aristarchus of Samos - Wikipedia

   en.wikipedia.org/wiki/Aristarchus_of_Samos

   Aristarchus of Samos (/ ˌ æ r ə ˈ s t ɑːr k ə s /; Ancient Greek: Ἀρίσταρχος ὁ Σάμιος, Aristarkhos ho Samios; c. 310 – c. 230 BC) was an ancient Greek astronomer and mathematician who presented the first known heliocentric model that placed the Sun at the center of the universe, with the Earth revolving around the Sun once a year and rotating about its axis once a day.

5. Perturbation (astronomy) - Wikipedia

   en.wikipedia.org/wiki/Perturbation_(astronomy)

   In astronomy, perturbation is the complex motion of a massive body subjected to forces other than the gravitational attraction of a single other massive body. [1] The other forces can include a third (fourth, fifth, etc.) body, resistance, as from an atmosphere, and the off-center attraction of an oblate or otherwise misshapen body.

6. Lunar theory - Wikipedia

   en.wikipedia.org/wiki/Lunar_theory

   The perturbations on the Moon when it is nearly in line along the Earth-Sun axis, i.e. near new or full moon, point outwards, away from the Earth. When the Moon-Earth line is 90° from the Earth-Sun axis they point inwards, towards the Earth, with a size that is only half the maximum size of the axial (outwards) perturbations.

7. Astronomical unit - Wikipedia

   en.wikipedia.org/wiki/Astronomical_unit

   This is because the distance between Earth and the Sun is not fixed (it varies between 0.983 289 8912 and 1.016 710 3335 au) and, when Earth is closer to the Sun , the Sun's gravitational field is stronger and Earth is moving faster along its orbital path. As the metre is defined in terms of the second and the speed of light is constant for all ...