Wednesday, January 4, 2012

Earth-Sun Distance at its Closest Tonight

Happy Perihelion!

Tonight at roughly 7pm local time, the earth was at its closest point to the sun in its annual orbit. This point in the earth's orbit is called its "perihelion." That's right, January 4th (give or take a day or two, depending on the year) is when the earth is closest to the sun! One may not think so, given that this is the winter season. But the distance between perihelion and aphelion (when the sun is furthest away in early July) is only about 1.5 million miles. That's just 1.5 percent of the earth's average distance from the sun -- roughly 93 million miles.

The earth's 23.5 degree tilt on its axis is far more influential in determining seasons than its distance from the sun. At this time of year, the northern hemisphere is tilted away from the sun at about 23 degrees and we get colder temperatures as a result. In the summer, the northern hemisphere is tilted 23 degrees toward the sun and our temperatures are warmer.

The image above shows the inner planets' elliptical orbits with perihelion and aphelion points.

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