-
1543
Copernicus proposal
Copernicus proposed a sun centered solar system. -
Planetary Parallax
Tycho Brahe realised that if the Earth was moving about the Sun, then the relative positions of the stars should change as viewed from different parts of the Earth's orbit. -
Johannes Kepler
Kepler used the dark night sky to argue for a finite universe. Kepler discovered the key to building a heliocentric model. -
Isaac Newton
Described the movement of the planets with his laws of motion.
Motion of the planets was explained with his theory of gravity.
Suggested that the Earth’s gravity caused the moons orbit. -
William Herschel
Proposes theory that our Sun is at or near the center of ou Galaxy (Milky Way) -
Pierre-simon Laplace
Demonstrated the stability of our solar system. Confirmed Newton's theory of gravitation by applying it to planetary orbits. -
Theory of Relativity
Einstein claimed space and time are not separate continua, instead they define a 4‐dim. spacetime continuum -
Henrietta Leavitt
Cepheid variable stars period‐luminosity relation
crucial step in measuring distances to other galaxies -
Albert Einstein
General Theory of Relativity:
Einstein field equations
‐ represents an entirely new theory of gravity, in which gravity is the result of the local
curvature of space, hence replacing the action‐at‐a‐distance theory of Newton.
‐ spacetime becomes a flexible dynamic medium, warped by energy density -
William de Sitter
first general relativistic cosmology, de Sitter Universe
‐ empty expanding Universe with cosmological constant -
Shapely - Curtis Debate
debate on the distances to spiral nebulae:
are they individual galaxies like the Milky Way or are they part of the Milky Way -
Edwin Hubble
‐ measures distance to few nearby spiral nebulae (Andromeda Galaxy, Triangulum galaxy, NGC 6822)
‐ distances place them far outside our Milky Way
‐ demonstrates that the spiral nebulae are galaxies outside our own Galaxy, the Milky Way
‐ In other words, the Galaxy loses its central unique position and the Universe turns out to be much,
much larger -
Georges Lemaitre
‐ solutions for Einstein field equations, for a perfectly uniform space, confirming Friedmann
‐ discusses the implications, that of an expanding Universe and the creation of the Universe
‐ predicts distance‐redshift relation (later known as Hubble relation)
‐ may indeed have discovered the expansion of the Universe from existing data (ongoing discusssion) -
Fred Hoyle
coins the term Big Bang, meant in a derisive way -
Arno Penzias and Robert Wilson
‐ Discovery of the 2.7K Microwave Background Radiation (CMB)
‐ ultimate proof of the Hot Big Bang
‐ Nobel prize Physics in 1978