Physics To Go is an online monthly mini-magazine and a collection of more than 1000 websites with physics images, activites, and info. You can view an archived version of our March 16, 2009 issue, Observing the sun below, or click to see our September 1, 2013 issue, Two views of Earth.

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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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

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