March 16, 2009 Issue

Physics To Go 69 - Observing the sun

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Physics in Your World

Ancient Observatories: Chaco Canyon image
image credit: M. B. Schwenn, (image not available elsewhere on web), larger image

Ancient Observatories: Chaco Canyon

This photograph shows the famous Sun Dagger at the Chaco Canyon National Monument in New Mexico, USA, a product of the Pueblo culture around the end of the first millennium A.D.
-- The dagger passed through the center of the spiral at the summer solstice, the longest day of the year.
-- Sadly, in 1989 one of the huge rock slabs that formed these shadows changed its position, possibly due to the effects of visitor activity at the site, so the Sun Dagger is a thing of the past.
-- To find out more, visit Ancient Observatories: Chaco Canyon and The Solstice Project.

[This feature was updated on August 14, 2013.]

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Physics at Home

Making a Sun Clock

Visit the Exploratorium's Making a Sun Clock to find out how to build a sun clock, and how it works.


From Physics Research

Spotless Sun: Blankest Year of the Space Age image
image credit: SOHO (NASA/ESA); image source; sun at solar max

Spotless Sun: Blankest Year of the Space Age

The image above shows the sun on March 11, 2009--nary a sunspot to be seen. But click on the image to see the sun at the last solar maximum, in March of 2001. To learn more, visit Spotless Sun: Blankest Year of the Space Age and the Exploratorium's Sunspots.

Worth a Look

Sun-Earth Day

In 2009, Sun-Earth Day is March 20 (the spring equinox). To learn more about this annual special event, see this NASA online flyer .

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