Yes, Eratosthenes estimated the Earth's diameter using the angle of the sun's rays at two different locations on the same day. By measuring the difference in the angles, he was able to calculate the Earth's circumference and thus its diameter.
Eratosthenes
Mercury's diameter (at the equator) = 4880km or 0.3825 x Earths diameter Venus' diameter = 12104km or 0.9488 x Earths Earth's diameter = 12756km Mars' diameter = 6794km or 0.5323 x Earths The inner planets are all much smaller than the outer gas planets; Jupiter's diameter = 142,984km or 11.21 x Earths Saturn's diameter = 120,534km or 9.45 x Earths Uranus' diameter = 51,114km or 4.01 x Earths Neptune's diameter = 49,532km or 3.88 x Earths
Approximately 4 Earths would equal the diameter of Uranus
From largest (1) to smallest (8) 1 Jupiter. Diameter = 142,984km or 11.21 x Earths diameter 2 Saturn. Diameter = 120,534km or 9.45 x Earths 3 Uranus. Diameter = 51,114km or 4.01 x Earths 4 Neptune. Diameter = 49,532km or 3.88 x Earths 5 Earth. Diameter = 12756km 6 Venus. Diameter = 12104km or 0.9488 x Earths 7 Mars. Diameter = 6794km or 0.5323 x Earths 8 Mercury. Diameter (at the equator) = 4880km or 0.3825 x Earths
Uranus is third largest. Diameter = 51115km, about 8 times that of Earths diameter.
Eratosthenes
False
He postulated the circumference of the earth.
Mercury's diameter (at the equator) = 4880km or 0.3825 x Earths diameter Venus' diameter = 12,104km or 0.9488 x Earths Earth's diameter = 12,756km Mars' diameter = 6794km or 0.5323 x Earths Jupiter's diameter = 142,984km or 11.21 x Earths Saturn's diameter = 120,534km or 9.45 x Earths Uranus' diameter = 51,114km or 4.01 x Earths Neptune's diameter = 49,532km or 3.88 x Earths (Pluto's diameter = 2306km or 0.18 x Earths) I included Pluto on the end there, its not classed as a planet any more though, but a dwarf planet.
Eratosthenes
90/
From smallest (1) to largest (8) 1 Mercury. Diameter (at the equator) = 4880km or 0.3825 x Earths diameter 2 Mars. Diameter = 6794km or 0.5323 x Earths 3 Venus. Diameter = 12104km or 0.9488 x Earths 4 Earth. Diameter = 12756km 5 Neptune. Diameter = 49,532km or 3.88 x Earths 6 Uranus. Diameter = 51,114km or 4.01 x Earths 7 Saturn. Diameter = 120,534km or 9.45 x Earths 8 Jupiter. Diameter = 142,984km or 11.21 x Earths
One.
Mercury's diameter (at the equator) = 4880km or 0.3825 x Earths diameter Venus' diameter = 12104km or 0.9488 x Earths Earth's diameter = 12756km Mars' diameter = 6794km or 0.5323 x Earths The inner planets are all much smaller than the outer gas planets; Jupiter's diameter = 142,984km or 11.21 x Earths Saturn's diameter = 120,534km or 9.45 x Earths Uranus' diameter = 51,114km or 4.01 x Earths Neptune's diameter = 49,532km or 3.88 x Earths
because the chord can be determine by the diameter and the diameter can be determine by the chord.
Planets, by definition are all approximately spherical in shape, though their axial rotation often means that they are oblate spheroids (look like `squashed spheres`, longer across the equator than from pole to pole). The size of the planets varies; Mercury's diameter (at the equator) = 4880km or 0.3825 x Earths diameter Venus' diameter = 12104km or 0.9488 x Earths Earth's diameter = 12756km Mars' diameter = 6794km or 0.5323 x Earths Jupiter's diameter = 142,984km or 11.21 x Earths Saturn's diameter = 120,534km or 9.45 x Earths Uranus' diameter = 51,114km or 4.01 x Earths Neptune's diameter = 49,532km or 3.88 x Earths
110 times greater..