Ptolemy proposes a geocentric universe in which the sun, moon, and other planets revolve around the Earth in a complicated system of circular orbits
Apr 18, 1543
Copemicus introduces a heliocentric system, with the planets in circular orbits
Italien scientist Giordano Bruno claims that neither Earth nor the sun is the center of the universe. Instead he suggests that the sun is simply one of infinitely many stars, and that there might be countless planets like Earth
Tycho Brahe proposes a system that combines the aspects of both the Copernican and Ptolemaic models, with the sun rrevolving around the Earth and the other planets orbiting the sun
Johanes Kepler posits three 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 periods than those farther from th
Galileo Galilei builds his first telescope, which leads to the discovery that ultimately confirm the heliocentric system
Isaac Newton publishes Mathematical Principles of Natural Philosophy. It formulates his law of universal gravitation, which explains Kepler's laws of planetary motion
Friedrich Bessel, a German mathematician and astronomer , 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 thus provides final proof that Earth does, in fact, orbit the
Albert Einstein presents a trailblazing model of gravitation: the general theory of relativity. This becomes the foundation for modern cosmology. Einstein introduces spacetime in three spatial and one temporal dimension
Georges Lamaitre presents an early version of the big bang theory based on the theory of relativity
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
Fretz Zwicky discovers the first indications that the space between galaxies might contain an invisible form of matter (dark matter) that can be deducted from its gravitational effects on its surroundings
George Gamow publishes The origin of Chemical Elements which gives a possible explanation for the distribution of the elements in the universe, the foundations for the modern big-bang theory
English astronomer Fred Hoyle derides Gamow's theory, calling it the big bang, while revising and presenting the steady state theory that posits the constant creation of new atoms in empty space. Hoyle claims the universe has always looked like it does n
American astronomers arno penzias and robert wilson stumble upon cosmic microwave background radiation while testing a highly sensitive antenna. Because scientists see this leftover energy from hot, early universe everywherre they look, it is convincing
American astronomers 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 stars
The COBE satellite shows, as predicted that the cosmic microwave background is the remnant of heat of the early universe -- at a temperature of 2.726 degrees above absolute zero
Research teams from the US and ASustralia endependently show that the universe is expanding at a constantly increasing rate. astronomers theorize that a repulsive force known as dark eneryy must be pushing the universe apart.
The Wilkinson microwave anistropy 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 g
Maps of the universe's macrostructure 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
