A sunrise from the edge of space. Credit: Project Soar

Why Does the Sun Rise in the East (and Set in the West)?

13 Mar , 2012 by

Each morning, the sun rises in the east, makes its slow journey across the sky, and then sets in the west. Then it continues a journey around the other side of the Earth, and rises again the next morning. This is how it looks from here on Earth, and that’s what ancient people thought was happening, but that view is totally wrong.

The truth is that the Earth is orbiting the Sun. It’s the Sun that’s motionless, and the Earth that’s moving around it. From our vantage point, it looks like the Sun is going around the Earth, because it’s actually the Earth that’s turning. The Earth rotates on its axis once every 24 hours, so that the Sun returns to the same position in the sky every day.

If you could look down on the Solar System and see all the planets, they would all be rotating in the same direction: counter clockwise, from west to east. Actually, there are two exceptions. Venus rotates backwards compared to the other planets. Astronomers think that it was stuck by a large asteroid millions of years ago that disturbed its original direction of rotation. Uranus has been knocked over so it looks like it rotates on its side, probably from a similar asteroid impact millions of years ago.

If you could fly out of the Earth and stare down at our planet’s north pole, you would see the world spinning beneath you in a counterclockwise direction. This means that if you’re standing on the Earth and looking at the Sun, it appears to be moving west in the sky. Of course, this is actually just your feet moving east as the planet rotates. As the day goes on, parts of the Earth which are to the west will get their chance to be in the sunlight, one after the other. This is why sunrise on the east coast of the United States happens 3 hours before regions on the west coast.

Why does the Earth rotate? That’s a different article. And here’s why the Earth has seasons.

Here’s an article from Cornell’s Ask an Astronomer about this question. And this article from How Stuff Works explains the whole Solar System.

We have recorded an episode of Astronomy Cast just about the Sun called The Sun, Spots and All.

NASA StarChild

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