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Wednesday, March 17, 2010

Sunrise...Sunset, Sunrise...Sunset

Here are some cool geeky sun charts I just found at:

The chart below shows sunrise, sunset, dawn and dusk times for the whole year for Providence, RI. Start of dawn and end of dusk times are based on the definition of "civil twilight".

The next chart is a sun path diagram, which is a visualization of the sun's path through the sky. This path is formed by plotting azimuth (left-right) and elevation (up-down) angles of the sun in a given day to a diagram.

To find out the position azimuth = 60, elevation = 30, for example, imagine standing at the center of the diagram heading to the true north. To find the azimuth angle 60, you must turn 60 degrees to the right. Now the altitude angle 30 can be located by raising your head 30 degrees from the horizon.

It can be seen from the orange line on the diagram (Sun's path today, 3/18/10) that the sun rises from the East (azimuth = 90) in Providence at 06:52. Sunset happens at 18:56 when the sun is in the West (azimuth = 270). The elevation angle is approximately 48 degrees at noon.

Saturday, 3/20 is the Vernal Equinox...better known as the first day of Spring. So what is an equinox? Funny you should ask.

Far from being an arbitrary indicator of the changing seasons, March 20 is significant for astronomical reasons. On March 20, 2010, at precisely 1:32 P.M. EDT , the Sun will cross directly over the Earth's equator. This moment is known as the vernal equinox in the Northern Hemisphere. Translated literally, equinox means "equal night." Because the sun is positioned above the equator, day and night are about equal in length all over the world during the equinoxes.

And that is your moment of GEEK, brought to you by TOTW!

1 comment:

Loving the Bike said...

Whoa....that's some very deep stuff you have there, but very interesting. Thanks for sharing it.