Astronomy Picture of the Day

Circum-axial Leaf Trails

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#100649 by @ 20.05.2007 00:00 - nach oben -
Circum-axial Leaf Trails


Are photographs of star trails really evidence of the
Earth's rotation
about its axis?

Yes they are, and
science journalist Trudy E. Bell discovered that there is a
simple way to demonstrate this, if you have the stomach for it.

First, find a playground equipped with a standard
Merry-Go-Round (MGR)
located under or near a large, leafy tree.

Seat yourself near the middle of the MGR platform.

Ask a local playground expert (KID) to get you
spinning very, very fast.

As the scenery flashes by at a dizzying rate, point your camera
skyward and take a picture with a slow shutter speed setting.

The result will be similar to this excellent image of concentric,
arcing leaf trails centered at a point corresponding to the MGR's
axis of rotation - a convincing imitation of
circumpolar star trails recorded in
hours-long exposures
of planet Earth's night sky.

Then, just stand up and walk away ...
if you still can.

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