Page 16 - Curriculum Visions Dynamic Book

The Earth lies beyond Mercury and Venus, and is the third- closest planet to the Sun.
When we look at the other planets, we see them as strange; but in fact, the Earth is, seen from any of the other planets, far stranger. That is because the Earth is the only planet where water can exist in all three forms—liquid, solid, and gas—all at the same time. And, above all, it is strange because it has on its surface carbon-based life forms (living things like us and plants) that, as far as we know, are unique.
The Earth in the Solar System
The Earth lies about 149,573,000 km from the Sun. It speeds around its orbit at nearly 30 km a second, taking 365.2 Earth days to make a complete revolution around the Sun. The Earth also spins on its tilted axis, revolving once every 23 hours, 56 minutes, and 4 seconds.
If you were to organize the planets in the solar system, you would find that the Earth is the fifth largest. But it is still a mere speck compared to Jupiter and the other giants of the Solar System. It is one of the small rocky planets that mostly lie close to the Sun.
apollo The program developed in the United States by NASA to get people to the Moon’s surface and back safely.
axis (pl. axes) The line around which a body spins.
orbit The path followed by one object as it tracks around another.
solar system The Sun and the bodies orbiting around it.
 Humans first saw the Earth as a globe through the cameras of the Apollo 8 mission to the Moon in December 1968. This is one of the most famous pictures from that eventful mission.
(For other Apollo pictures see pages 44–57.)
For more on the Apollo missions see Volume 6: Journey into space.
 The Earth is the third rocky planet from the Sun.
Details of the other rocky bodies can be found in Volume 4: Rocky planets.
Venus
Mercury
Earth
Mars
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