The Night Sky: Earth Rotation

"I Feel The Earth, Move, Under My Feet"

Hello star gazers,

I’ve always had a fascination with time-lapse photography. Shadows and cloud movements become so pronounced, as well as the Earth’s rotation. Attached is a picture composed of 27 images looking toward the east on a summer night in 2010. Each single image was spaced one minute apart. The images were then stacked together to show the effect the Earth's rotation has on the sky.

The picture is a reminder that although we don't feel it, everyone in the Greenwich area is moving at about 400+ mph toward the east (relative to the center of the earth) due to the earth’s rotation. This in turn causes everything in the sky to appear to be rotating around the earth toward the west. I do mean everything. Not just the sun and the moon, the stars also rise in the east and set in the west as can be seen in the picture.

You may notice that the stars to the upper left rotate much slower, and make shorter arcs, than the stars in the lower right of the picture. The earth’s rotation axis points just off the upper left edge of the picture. That is where you would find Polaris, the North Star. Everything in the sky circles Polaris, and Polaris never moves; it is always ‘True North.’ Stars close to Polaris make small circles around it. Stars far from Polaris make large circles or even straight lines if they are at the celestial equator. You may recall I mentioned this rotation effect in my .

I’ve also attached a short movie produced from the 27 images that shows the rotation effect in video form in case some readers prefer that method.

This post is contributed by a community member. The views expressed in this blog are those of the author and do not necessarily reflect those of Patch Media Corporation. Everyone is welcome to submit a post to Patch. If you'd like to post a blog, go here to get started.

Jon Saunders January 06, 2012 at 03:46 PM
Amazing stuff! We love it. (You're the smartest guy we know) Dianne & Jon Saunders


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