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 Astronomy: Earth


Earth has been a strange discovery. For years mankind thought the Earth was flat. And we only recently discovered that our planet isn't the center of the Universe.
It wasn't until the twentieth century that we finally got to see our planet; we went into space and looked down at our blue planet.

  • The Greek Plato (427-347 BC) presumed that Earth wasn't the center of the universe.
  • Aristarchos from Samos (310-230 BC) thought that Earth orbits the sun.
  • Astronomer Nicolaus Copernicus supported these ideas and put them in a book which he published in 1543.
  • Tycho Brahe (1546-1601) calculated the orbital paths of the planets.
  • Galileo Galilei (1564-1642) defended Copernicus' theories and convinced other astronomers.
  • Johannes Kepler discovered in 1606 that these paths were elliptical shaped and not perfect circles. Kepler found that stars and planets attract each other.
  • Isaac Newton confirmed these theories and explained the tide of the seas and calculated the orbital time of the planets.

    Facts about our planet

    Now we know much more about our planet than a few centuries ago.

  • Distance from the sun: 150.000.000 km
  • Density 5.52 (water has a density of 1)
  • Orbits the sun in 365,25 days
  • Turns in 23 hours and 56 minutes
  • Earth has one Moon which always faces the same side. Because of its tilding orbit it's possible to see 59% of the Moon from Earth
  • Inclination: 23 1/2o, which causes the seasons on the planet. This inclination also has a cycle. Once every 25.800 years it turns around. As a result Deneb will be our new polestar in 8000 years from now.
  • Our atmosphere protects us from solar radiation and small meteors and contains 46% oxigine.

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    Stunning picture from Earth
    < JPG image 590 X 767 pixels >



    Earth seen in 1969. Photo taken by the Apollo 11 astronauts.

    Earth's aurorae

    Aurorae are caused by charged particles ejected from the Sun, which become trapped in the polar regions of the planet's magnetic field. The charged particles energize in the upper atmosphere causing them to glow.

    This effect can be observed in ultraviolet light, but sometimes also is observed with the naked eye.

    Click here to see the aurorae in ultraviolet of Jupiter or Saturn. Or see more aurorae on Earth.

    Related subjects

    >> Spacemap: from Earth until the Local Group of Galaxies
    >> Extinction of the Dinosaurs
    >> The Moon
    >> Meteors
    >> Aurorae on Earth

    Aurorae on Earth (in true colors).


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    Richard Hubers  © 2002-2008