S.Y. Tan

History and Background

It is human nature to want to find out about our surroundings, to explore our neighborhood, our planet Earth, and beyond. Until the twentieth century, viewing Earth from a space-based perspective could only be accomplished by imagination. From ancient times, astronomers have looked up at the sky, recorded their observations, and made up stories about how the universe was created and what it was like. Ancient Greeks were more aware of the truth of their surroundings than other cultures in that time period. They helped to discover that Earth was a sphere and developed observational and mathematical techniques to measure the circumference of the planet. With increasingly powerful ground-based telescopes came the discovery of the Milky Way and other galaxies and our understanding that the universe is expanding.