Aristarchus’s Contribution: Aristarchus of Samos, an ancient Greek philosopher, used simple geometry to estimate the relative distances and sizes of the Earth, Sun, and Moon. • Methodology: Aristarchus’s method involved observing the phases of the Moon, particularly the first quarter phase, to determine the relative positions of the Earth, Sun, and Moon in space. • Time Period: Aristarchus lived from approximately 310 BC to 230 BC, over 2200 years ago. • Aristarchus’ Method: Aristarchus used the 90-degree angle between the Sun, Earth, and Moon during the first quarter moon phase to calculate the relative distances between the Earth and the Sun. • Angle Measurement: Aristarchus measured the angle between the Sun and the Moon in the sky to be approximately 87 degrees, which is slightly less than the actual angle of 89 degrees and 51 minutes. • Distance Calculation: By measuring the angle and using trigonometry, Aristarchus was able to determine the relative distances between the Earth and the Sun. • Sun’s Size and Distance: Aristarchus discovered that the Sun is much larger than the Moon and about 19 times further away from Earth. • Angular Size and Actual Size: The apparent size of celestial objects in the sky doesn’t directly correlate with their actual size, as demonstrated by the Sun and Moon appearing similar in size despite their vast difference in distance. • Moon’s Size Estimation: Aristarchus estimated the Moon’s size to be about half of Earth’s size based on the duration of lunar eclipses and the assumption of a linear Earth’s shadow. • Aristarchus’s Discoveries: Aristarchus determined the relative sizes of the Earth, Moon, and Sun using rudimentary measurements and observations. • Earth-Sun Distance Estimation: Aristarchus estimated the Earth-Sun distance to be about 20 times the Earth-Moon distance, which is off by a factor of 20 but still remarkable for the time. • Lunar Eclipse Observations: Aristarchus used the time it took for the Moon to pass through the Earth’s shadow during a lunar eclipse to estimate the size of the Sun. • Sun’s Size and Position: The Sun is much larger than the Earth and the Moon, leading to the question of whether it should be the center of the cosmos. • Earth’s Movement: The Earth’s movement in the sky is not directly perceivable, raising the question of how we know it moves. • Scientific Inquiry: The question of the Earth’s movement led to the development of calculus and modern science.