Earth-3

Ancient Cosmology: Ancient China held concepts like 'the sky is round and the earth is square,' while ancient Greek scholars inferred Earth's spherical shape through phenomena like lunar eclipses and ships disappearing over the horizon. Earth Measurement: In the 3rd century BC, Greek scholar Eratosthenes cleverly estimated Earth's circumference by utilizing the difference in shadows at various locations. Geocentric vs. Heliocentric Models: The geocentric model was long prevalent; after Copernicus proposed the heliocentric model, human understanding of Earth and planets gradually shifted through the research of figures like Galileo and Kepler. II. Astronomical Aspects Space Observation: In 1957, Sputnik 1 became the first artificial satellite. Since then, humanity has continuously observed Earth from space. Earth Imagery: The iconic 'Earthrise' photo taken during the Apollo 8 mission in 1968, showing Earth rising above the lunar horizon, became a classic image in space exploration history. Satellite Applications: Weather satellites observe cloud systems and typhoons, while remote sensing satellites monitor changes in forests, oceans, ice caps, and land. Earth Observation: Scientists use satellites and ground measurements to track global warming, sea-level rise, and glacier melt, and also study Earth's gravitational and magnetic fields.