Earth is the third planet from the Sun and the only object in the Universe known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.
Earth's axis of rotation is tilted with respect to its orbital plane, producing seasons on the Earth. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earth's orientation on its axis, and gradually slows its rotation. Earth is the densest planet in the Solar System and the largest of the four terrestrial planets.
Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earth's surface is covered with water, mostly by oceans. The remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates the Earth's magnetic field, and a convecting mantle that drives plate tectonics.
Within the first billion years of Earth's history, life appeared in the oceans and began to affect the Earth's atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms. Some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earth's distance from the Sun, physical properties, and geological history have allowed life to evolve and thrive. In the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that ever lived on Earth are extinct. Estimates of the number of species on Earth today vary widely; most species have not been described. Over 7.6 billion humans live on Earth and depend on its biosphere and natural resources for their survival. Humans have developed diverse societies and cultures; politically, the world has about 200 sovereign states.

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  1. CantTouchThis

    Where art thou .kml BLM and public lands for Google Earth?

    I do not understand where OnX gets those nice overlays on their maps for Oregon and other states for that matter. I've been looking all over. All I could find was Hunting Access Map Which is very useful, but we can't mark spots on this without comparing it to google maps and marking it...
  2. U

    How on earth does one manage the inbox for private messages? This is so frustrating.

    So we have this inbox for receiving private messages, but I was recently contacted by 3 people responding to a classified ad for some scopes that I posted, saying on the thread for the ad itself that they could not PM me, because my inbox was full. The problem is that I never received any kind...
  3. cigars

    Child builds Lego gun, Proggies freak out.

    Just another example of who we are dealing with on the left. I'm surprised that this didn't occur out here. Oh well, same Progressive collective mind set. Connecticut school calls police after student makes, points Lego gun at classmates
  4. CoastRange57

    I will follow this GPS to the end of the earth....

    Now first off, I am glad the young man is safe and back with his family. This has turned out badly for a lot of other people. Now with those disclaimers in place, I will simply say...WTF were you thinking ?? Lets look at the factors in play here... 22 years old, not much over the road...
  5. ATCclears

    Stuff in Space

    All the stuff in orbit around the Earth. Stuff in Space
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