Astronomical Discoveries

John Michael C. Pacis

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Astronomical Discoveries

1. The Planets Move (2000 B.C. – 500 B.C.)

A thousand years of observations reveal that there are stars that move in the sky and follow patterns, showing that the Earth is part of a solar system of planets separate from the fixed stars.

2. The Earth Moves (1543)

Nicolaus Copernicus places the sun, not the Earth, at the center of the solar system.

3. Planetary Orbits Are Elliptical (1605 – 1609)

Johannes Kepler devises mathematical laws that successfully and accurately predict the motions of the planets in elliptical orbits.

4. Jupiter Has Moons (1609 – 1612)

Galileo Galilei discovers that Jupiter has moons like the Earth, proving that Copernicus, not Ptolemy, is right. Copernicus believes that Earth is not unique, but instead resembles the other planets, all of which orbit the sun.

5. Halley's Comet Has a Predictable Orbit (1705 – 1758)

Edmund Halley proves that comets orbit the sun like the planets and successfully predicts the return of Halley's Comet. He determines that comets seen in 1531 and 1607 are the same object following a 76-year orbit. Halley's prediction is proven in 1758 when the comet returns. Unfortunately, Halley had died in 1742, missing the momentous event.

6. The Milky Way Is a Gigantic Disk of Stars (1780 – 1834)

Telescope-maker William Herschel and his sister Carolyn map the entire sky and prove that our solar system resides in a gigantic disk of stars that bulges in the center called the Milky Way. Herschel's technique involves taking a sample count of stars in the field of view of his telescope. His final count shows more than 90,000 stars in 2,400 sample areas. Later studies confirm that our galaxy is disk-shaped, but find that the sun is not near the center and that the system is considerably larger than Herschel's estimation.

7. General Relativity (1915 – 1919)

Albert Einstein unveils his theory of general relativity in which he proposes that mass warps both time...