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Earth Numbers - perihelion, aphelion? At what month is the Earth closest to the Sun? circumference? How fast is the Earth moving? - Windows to the Universe

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# What is the distance from the Earth to the Sun when the Earth is at perihelion and when it is at aphelion? At what month is the Earth closest to the Sun? What is the circumference of the Earth? How fast is the Earth moving about its axis; how about around the Sun?

#### Scientists use fancy words to describe things sometimes. The Earth doesn't orbit the Sun in a perfect circle. So, there is a point when the Earth is closest to the Sun and farthest from the Sun. Scientists call the closest point perihelion and the farthest point aphelion. In 2000, perihelion for the Earth was on January 3, 2000, and aphelion was on July 4, 2000. The Earth was 91,405,436 miles from Sun at perihelion and 94,511,989 miles from Sun at aphelion. The actual date for perihelion and aphelion will differ from year to year. You can see that the Earth is closest to the Sun in January and farthest from the Sun in July! This may not seem right. I mean it's winter in the northern hemisphere in January when we are closest to the Sun. Shouldn't it be warmest then because we are closer? Actually, our seasons are determined by the tilt of the Earth and not by how close the Earth is to the Sun.A few more numbers for you...the circumference of the Earth is 24,901.55 miles (40,075.16 km) at the equator. The Earth travels around, or "orbits" the Sun at a speed of 29.8 km/sec (67,000 mph). At the same time, the Earth also spins on its axis at a speed of .47 km/sec or a 1000 mph. Whew! Almost makes you dizzy, doesn't it?

Submitted by Leslie (Missouri, USA), Wayne (New York, USA), Terry (Michigan, USA), Kristi (Toronto, Canada), Wykeenie (Louisiana, USA), Tommy (Pennsylvania, USA)
(November 7, 2000)

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