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Astronomy Index

Absorption Spectra
Archaeoastronomy
Aristarchus of Samos
Astronomical Timeline
Bayer, Johann
Brahe, Tycho
Cassini, Giovanni
Copernicus, Nicolaus
Doppler, Christian
Draper, Henry
Einstein, Albert
Eratosthenes
Fabricius, David
Galilei, Galileo
Galle, Johann
Great Red Spot (Jupiter)
Hall, Asaph
Halley, Edmond
Herschel, William
Hipparchus
Huggins, William
Huygens, Christiaan
Janssen, Pierre-Jules-Cesar
Kepler, Johannes
Lippershey, Hans
Lockyer, Joseph Norman
Messier, Charles
Montanari, Geminiano
Mount Wilson Observatory
Murray, Margaret Lindsay
Newton, Isaac
Piazzi, Giuseppe
Ptolemy, Claudius
Roemer, Ole
Schiaparelli, Giovanni
Schwabe, Samuel

 

HISTORY OF SCIENCE AND TECHNOLOGY

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The Big Bang

The Big Bang theory developed in the late 1920's. A Belgian priest and mathematician, Georges Lemaître, who received a doctorate from MIT, presented the theory in 1927. Two years later Edwin Hubble produced evidence that supported Lemaître.

According to the Big Bang theory, 12 to 14 billion years ago the universe was very small, probably much smaller than a pinhead. The temperatures and pressures inside this microscopic bubble were enormous. This means that it was extremely hot and extremely dense. The birth of the universe happened when this bubble exploded.

Less than a second after the Big Bang the universe was already the size of a galaxy. As it expanded, it cooled. Energy became matter and protons and neutrons, the particles that are found in atoms, were formed. After three minutes the temperature had dropped to around 1 billion °C and after 3000 000 years it had dropped to around 3000 °C. Small atoms, such as hydrogen and helium, now formed as the protons and neutrons clumped together under the pull of gravity.

 

  NASA/ESA-ACS Science Team

© NASA/ESA-ACS Science Team
NASA/ESA Hubble Space Telescope
Cone Nebula (in NGC 2264)

 

As the universe continued to expand and cool down, over millions of years, gas clouds formed. These clouds became galaxies and started to give birth to stars. There is much evidence to prove that the universe is still expanding. Hubble made measurements to show that distant galaxies are moving away from the Earth. The speed at which they are moving is directly proportional to their distance from Earth (Galaxies that are twice as far from the Earth move twice as fast). More recently, physicists have detected microwaves from outer space that can be measured all over the sky. These microwaves have come from the farthest points of the universe; they are left over from the Big Bang.

 

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