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# Rotation of Earth

## Earth rotates on its axis, which creates the day-night cycle.

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Everybody Jump Now!

### Everybody Jump Now!

Credit: Guillaume
Source: http://www.flickr.com/photos/guiguibu91/2889883615/

There are 7 billion people on Earth now; so many more than ever before. We are changing the face of the planet, but could we all get together to change the planet itself?

#### Could We Knock Earth Out of Orbit?

Credit: Robert Simmon, NASA's Earth Observatory
Source: http://neo.sci.gsfc.nasa.gov/view.php?datasetId=SEDAC_POP

Global population density (darker colored areas have more people) [Figure2]

The size of the human population is having a large effect on Earth by changing habitats, altering climate, depleting resources and many other things. Since the human population is so massive we might wonder what we could do if we made a plan. Maybe we could change the length of the day or change the seasons. Maybe we could knock Earth entirely out of its orbit! At least we could start a big earthquake, couldn’t we?

#### Explore More

1. What would happen to the length of a day if everyone on Earth lay down at the same time? Why?
2. What did the massive earthquake in Japan do to day length and why?
3. If 7 billion people stood shoulder-to-shoulder in the same spot and then jumped, what would happen?
4. How many people would need to jump at the same time to recreate the Japanese earthquake?

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