Planets and Stars
The most prominent scientific theory about the origin of the Earth involves a spinning cloud of dust called a solar nebula. This nebula is a product of the Big Bang. Philosophers, religious scholars and scientists have lots of ideas about where the universe came from, but the most widely-held scientific theory is the Big Bang Theory. According to this theory, the universe originated in an enormous explosion.
Before the Big Bang, all of the matter and energy now in the universe was contained in a singularity. A singularity is a point with an extremely high temperature and infinite density. It's also what's found at the center of a black hole. This singularity floated in a complete vacuum until it exploded, flinging gas and energy in all directions. Imagine a bomb going off inside an egg -- matter moved in all directions at high speeds.
As the gas from the explosion cooled, various physical forces caused particles to stick together. As they continued to cool, they slowed down and became more organized, eventually growing into stars. This process took about a billion years.
About five billion years ago, some of this gas and matter became our sun. At first, it was a hot, spinning cloud of gas that also included heavier elements. As the cloud spun, it collected into a disc called a solar nebula. Our planet and others probably formed inside this disc. The center of the cloud continued to condense, eventually igniting and becoming a sun.
There's no concrete evidence for exactly how the Earth formed within this nebula. Scientists have two main theories. Both involve accretion, or the sticking together of molecules and particles. They have the same basic idea -- about 4.6 billion years ago, the Earth formed as particles collected within a giant disc of gas orbiting what would become our sun. Once the sun ignited, it blew all of the extra particles away, leaving the solar system as we know it. Our moon formed in the solar nebula as well -- read "Where Did the Moon Come From?" to learn more.
At first, the Earth was very hot and volcanic. A solid crust formed as the planet cooled, and impacts from asteroids and other debris caused lots of craters. As the planet continued to cool, water filled the basins that had formed in the surface, creating oceans.
Through earthquakes, volcanic eruptions and other factors, the Earth's surface eventually reached the shape that we know today. Its mass provides the gravity that holds everything together and its surface provides a place for us to live. But the whole process would not have started without the sun.
Check out the links below to learn more about the Earth, the sun and related topics.
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More Great Links
- Britt, Robert Roy. "Moon Mechanics: What Really Makes Our World Go 'Round." Space.com, March 18, 2003. http://www.space.com/scienceastronomy/moon_mechanics_0303018.html
- Britt, Robert Roy. "When North Becomes South: New Clues to Earth's Magnetic Flip-Flops." Space.com, April 7, 2004. http://www.space.com/scienceastronomy/earth_poles_040407.html
- "The Carbon Cycle." NASA Earth Observatory. http://earthobservatory.nasa.gov/Library/CarbonCycle/
- Chown, Marcus. "Solar Wind to Shield Earth During Flip." New Scientist, May 15, 2004. http://www.newscientist.com/article.ns?id=dn4985
- "Cracking the Ice Age." NOVA Online. http://www.pbs.org/wgbh/nova/ice/
- "Earth's Atmosphere." NASA. http://liftoff.msfc.nasa.gov/academy/space/atmosphere.html
- "The Earth's Layers." North Dakota University System. http://volcano.und.nodak.edu/vwdocs/vwlessons/lessons/Earths_layers/Earths_layers1.html
- Glasner, Joanna. "Earth Hurtles Toward 6.5 Billion." Wired, February 21, 2006. http://www.wired.com/news/technology/0,70238-0.html?tw=wn_index_1
- "Global Warming and Our Changing Climate." United States EPA, April 2000.
- "Global Weather Patterns." BBC. http://www.bbc.co.uk/schools/gcsebitesize/geography/weather/elementsofweatherrev10.shtml
- Graham, Steve, et al. "The Water Cycle." NASA Earth Observatory. http://earthobservatory.nasa.gov/Library/Water/
- "The Great Ice Age." U.S. Geological Survey. http://pubs.usgs.gov/gip/ice_age/
- Hawkes, Nigel. "Waterworld: How will Life on Earth Look in 1000 Years." Times Online, February 17, 2006. http://www.timesonline.co.uk/article/0,,3-2044465,00.html
- Herring, David. "Ocean and Climate." NASA Earth Observatory. http://earthobservatory.nasa.gov/Library/OceanClimate/
- Illinois State Museum. "Why Are there Ice Ages?" http://www.museum.state.il.us/exhibits/ice_ages/why_4_cool_periods.html
- Larson, Josh. "Understanding Global Climate Patterns." USA Today, August 6, 2004.
- NASA Earth Observatory. http://earthobservatory.nasa.gov
- Seeds, Michael A. "Foundations of Astronomy." Wadsworth Publishing Company. 1994.
- Simkin, Tom, et al. "This Dynamic Planet." USGS. 1994.
- Smith, Lewis and Ben Hoyle. "World Has Only 20 Years to Stop Climate Disaster." Times Online, January 31, 2006. http://www.timesonline.co.uk/article/0,,2-2017322,00.html
- "Steam Explosions, Earthquakes, and Volcanic Eruptions - What's in Yellowstone's Future?" Fact Sheet 2005-3024, U.S. Geological Survey. http://pubs.usgs.gov/fs/2005/3024/
- Vastag, Brian. "North Magnetic Pole is Shifting Rapidly Toward Russia." National Geographic. December 15, 2005. http://news.nationalgeographic.com/news/2005/12/1215_051215_north_pole.html
- "What Is Photosynthesis?" Arizona State University, February 7, 2006. http://photoscience.la.asu.edu/photosyn/education/learn.html
- "Why Isn't the Earth Hot as an Oven?" NASA Earth Observatory. http://earthobservatory.nasa.gov/Library/Oven/