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HISTORY OF SCIENCE AND TECHNOLOGY
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
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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