-
150
Ptolemy proposes a geocentric universe
the sun, moon, and other planets revolve around the Earth in a complicated system of circular orbits -
Apr 13, 1543
Copernicus
Introduces a heliocentric system with the planets in circular orbits -
Giordano Bruno's Claim
Says that neither Earth nor the sun is the center of the universe. Suggests that the sun is simply one of infinitly many stars, and that there might be countless planets -
Tycho Brahe proposes new system
Proposes system that combines aspects of both the Copernican and Ptolemaic models, with the sun revolving around the Earth and the other planets orbiting the sun. -
Johannes Kepler posits 3 laws of Planetary motion
The planets move in elliptical orbits around the sun; they travel faster when they are closer to the sun in their orbit; those closer to the sun have shorter orbital persiods than those farther from the sun. -
Galileo builds telescope
Galileo Galilei builds his first telescope which leads to discoveries that ultimately confirm the heliocentric system. -
Isaac Newton publishes philosophy
Isaac Newton pulblishes Mathematical Principles of Natural Philosophy. It formulates his law of universal gravitation, which explains Kepler's laws of planetary motion. -
Friedrich Bessel measures parallax
Friedrich Bessel is the first to measure stellar parallax, the shift in a star's position when it is viewed from different points in earth's orbit. He provides the final proff that earth does in fact orbit the sun. -
Albert Einstein presents modell of gravitaion
Albert Einstein presents a model of gravitation: the general theory of relativity. This becomes the foundation for modern cosmology. Introduces spacetime in three spatial and one temporal dimension. -
Georges Lemaitre
Georges Lemaitre presents an early version of the big-bang theory based on the theory of relativity -
Edwin Hubble
Edwin Hubble discovers that the speed at which galaxies are moving away from us is proportional to their distance from Earth. This is now called the Hubble law -
Fritz Zwicky
Fritz Zwicky discovers the first indications that the space between galaxies might contain an invisible form of matter that can be deduced from its gravitational effects on its surroundings. -
George Gamow publishes The Origin of Ghemical Elements
The Origin of Chemical Elements gives a possible explanation for the distribution of the elements in the universe, the foundations for the modern big-bang theory -
Fred Hoyle dirides Gamow's theory
Calls his theory the big bang, while revising and resenting the steady-state theory that posits the constant creation of new atoms in empty space. -
Arno Penzias and Robert Wilson
Stumble upon cosmic microwave background radiation while testing a highly sensitive antenna. Because scientists see this leftover energy from the hot, early universe everywhere they look, it is convincing evidence of the big bang. -
Vera Rubin and Kent Ford
Show that stars on the outskirts of a spiral galaxy move much faster than expected. Their finding is a strong indication that dark matter exerts a gravitational pull on the stars. -
The COBE satellite
Satellite shows that the cosmic microwave backgroungd is the remnant heat of the early universe- at a temperature of 2.726 degrees above absolute zero. -
Research teams from U.S. and Australia
Research teams independently show that the universe is expanding at a constantly increasing rate. Astronomers thorize that a repulsive force known as dark energy must be pushing the universe apart. -
The Wilkinson Microwave Anisotropy Probe
The probe precisely measures the very small temperature differences in the afterglow of the big bang, which suggest that matter was not evenly distributed in the early universe but instead had "lumps" that became the seeds of galaxies and stars. -
Maps of universe's macrosturcture
reveal that galaxies are not distributed uniformly throughout the universe. Instead, the universe has a foamlike structure in which galaxies and galaxy clusters lie on the surface of bubbles containing enormous voids.
