Sunrise, Sunset

In Astronomy by Brian Koberlein0 Comments

Yesterday on Reddit, a user named SipTime posted two images.  One of sunrise in Florida, and another of sunset in Japan.  The two photos were taken within minutes of each other. Sunrise and sunset at the same time.

Since we live on a small rocky sphere, this happens all the time. While the sun rises on one end of the planet, it sets on the other.  Between these two points it is either noon or midnight.  As the Earth turns, we move in and out of the shadow of our world. The Sun appears to rise and set as the Earth rotates upon its axis.

Of course we know that both are the same Sun.  Since the Sun is about 150 million kilometers away, the light must travel for more than 8 minutes to reach us.  All that distance and time, just to reach Earth.  If it had traveled in a slightly different direction, it would have missed the Earth entirely. The Earth is only 12,700 kilometers wide, so the light of sunrise and sunset left the Sun in almost the same direction. A difference in direction of only 0.4% of a degree (18 seconds of arc) is enough to separated morning sunlight from evening.

So not only are these the same Sun, they are almost the same light.

We live on a small rock racing through space.  And our days are marked by the rising and setting of a star.

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