Physics Photo of the Week May 10, 2024

 Broken Contrail Shadow - Photo by Nasuna Stuart-Ulin



Betsy Warren - a PPOW reader - recently sent me a link to a NY Times article (April 15, 2024) that featured a jet's contrail shadowed on the thin clouds below the contrail.  The photo was taken on eclipse day (April 8, 2024) during the partial phase (the Sun was about 90 % blocked by the Moon).

The photo has a number of interesting features:

The contrail appears to lie below the thin cirrus clouds.  That is just an illusion.  The clouds are thin, and we see the contrail through the thin clouds.  The camera is looking up at the sky; the over-exposed Sun is very far away far above the sky and clouds.  In order for the contrail to cast a shadow the contrail must be above the clouds, between the clouds and theSun.

 Notice also that the contrail's shadow appears broken and even doubled in the region where the two shadows overlap.  That is caused by two distinct thin layers of clouds.  The brighter clouds at the leading part of the contrail are higher in altitude and closer to the contrail.  The fainter thin clouds further aft of the brighter clouds (in the center of the photo) are lower than the brighter clouds at the top of the photo.  Thus the shadow cast onto the lower clouds is further displaced to the left from the contrail.  Two parallel shadows of the contrail are also visible.  That double shadow is caused by the overlapping region of the two separate cloud layers.

Another feature in the photo is an image of the partially eclipsed Sun in the upper part of the photo, but below the over-exposed image of the Sun at the top edge (zoomed-in image at right).  This is an artifact due to lens flare in the camera that shows a faint "ghost" image of the Sun in the upper middle of the photo about 2/3 of the way from the leading part of the contrail to the Sun's position.  The "ghost" image shows the "smile" of the partially-eclipsed Sun.   When photographing bright objects such as the Sun, Moon, or powerful lights, ghost images show up due to internal partial reflections between the elements of the camera's lens displaced from the bright object itself.


Finally, the lower part of the top photo shows a curved band of color (reproduced as a thumbnail at left).  The color is part of a Sun halo caused by the refraction of sunlight by ice crystals in the cirrus clouds.   For more on the solar halo see PPOW for Sept 22, 2023.

This the final Physics Photo of the Week for the 2023-2024 academic year as the Physics Photo goes on vacation.  Everyone have a good summer!  Congratulations to new Warren Wilson College graduates!

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Physics Photo of the Week is published periodically during the academic year on Fridays by Donald F. Collins, professor emeritus of Warren Wilson College. These photos feature interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to dcollins@warren-wilson.edu.

All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion.  These photos and discussions may be used for private individual use or educational use.  Any commercial use without written permission of the photoprovider is forbidden.

To join the mailing list, please request to Donald Collins at the e-mail address below.  You will receive no more than one message every two weeks, or when a very interesting physics/astronomy event is happening.



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