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Feb 9, 1543
Heliocentric Model
Nickolaus Copernicus developed the first Heliocentric Model, the geometric proof that supported the idea of Aristarchus' (Heliocentric Theory) that the Earth revolved around the Sun, and not the other way around. -
Law of Ellipses (1st Kepler Law)
Johannes Kepler's first law explains that planets, including Earth, orbits the Sun in a path that resembles an ellipse. An ellipse is close to a circular shape, but also ovular. -
Law of Equal Areas (2nd Kepler Law)
Johannes Kepler's second law describes the speed of which any given planet will move while orbiting the sun. He also discovered that if the planet is closer to the sun, it will move faster than a planet farther from the sun. However, the length of time will be equal, although time may seem faster/slower on one side than another, hence the term "equal areas". -
Law of Harmonies (3rd Kepler Law)
Johannes Kepler's third law is described as: the square of the total time period of the orbit is proportional to the cube of the average distance of the planet to the Sun. Simply, it compares the orbital time period and radius of an orbit of any planet to those of other planets; it also implies that the bigger the radius of a planet's orbit, the longer it takes for it to orbit the sun. -
Theory of Universal Gravitation
Isaac Newton's Law of Universal Gravitation states that any two bodies in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. More simply put, it explains that gravitational force decreases with distance. In addition, the theory notes that the greater an object's mass, the greater its gravitational force. -
Herschel's Map
William Herschel, with extremely large telescopes, made two major discoveries that had an important impact on our understanding of the cosmos. The first discovery was the fact that we live in a huge collection of stars called the Milky Way, and second is the existence of nebulae, some of which consisted of stars, and others of luminous clouds. -
Concept of Black Holes
Simon Pierre LaPlace predicted the existence of black holes during years of research, studying the subject of escape velocity. Laplace discovered a connection between the size of an object and its mass; if you made an object smaller, but kept its mass the same, the escape velocity increased. He concluded that if you kept squeezing the Earth smaller and smaller, eventually the escape velocity would equal the speed of light, thus the idea of black holes. -
General Theory of Relativity
Albert Einstein created the Theory of Relativity, explaining how gravity works and how gravity could bend light rays. The central idea of general relativity is space and time are two components of "spacetime". Spacetime was discovered to be curved in the presence of gravity, matter, energy, and momentum. -
Hubble's Discovery of Other Galaxies
Edwin Hubble found dozens of stars in Andromeda, and determined their distance. He calculated that Andromeda must be at least 10 times farther away than the farthest stars in the Milky Way; this discovery came to the conclusion that implied that other, even fainter, spirals were probably also galaxies even farther away. Astronomers no longer thought our galaxy was the entire universe and knew that the universe was composed of many, many galaxies other than the Milky Way. -
Hubble's Discovery of the Expanding Universe
Edwin Hubble measured the redshifts of a number of distant galaxies and their relative distances by measuring the brightness of stars (Cepheids) in each galaxy. Hubble's brilliant observation was that the red shift of galaxies was proportional to the distance of the galaxy from earth. That meant that things farther away from Earth were moving away faster. This discovery led to the conclusion that the universe must be expanding.
