Observing with Street Lights

Observing with Street Lights
Dark sky sites not always necessary to see the Milky Way (This image was taken ouside of a B&B in Julian, CA)

Tuesday, February 14, 2023

Moonbow from Julian?; Rainbow Physics; ChatGPT on Moonbows; What if AI goes rouge and other tangential jokes and source of UFOs?

 Greetings from Palmia Observatory

This week we were reminded of the Moonbow phenomena and will comment and look into the physics and then finish up with fun with some jokes.

Some associates in Julian, CA, post a photo of the Moon and Halo or a Moonbow.

Moonbows? from Julian, CA (Source: Julian Dark Sky Network)
Moonbows? from Julian, CA (Source: Julian Dark Sky Network)


Very neat!  Thanks to Yvonne and Doug for their efforts to look after the dark skies that we all still want and hope to enjoy more often!

Those photos triggered a question about how and why moonbows form?  You probably remember some explanation about reflection ad refraction from water droplets that the moonlight shines through, exactly the same as when sunlight shines through water droplets to form a rainbow.  One sight that surfaced during a google search for the physics of rainbows, from which some of the following slides are extracted, is: https://ektalks.blogspot.com/2016/10/rainbows-all-you-need-to-know-about.html


Viewing angle and illumination angle for rainbow formation (Source: ektalks.blotspot.com)
Viewing angle and illumination angle for rainbow formation (Source: ektalks.blotspot.com)

Here we see the viewing and illuminating conditions necessary to see the complete circular viewing of the moonbow.

Viewing angle and illumination angle for rainbow formation (Source: ektalks.blotspot.com)



Of course we have to look at reflection and refraction of spherical water droplets to finish off the physics.
Reflection and Refraction from spherical water droplets (Source: ektalks.blotspot.com)
Reflection and Refraction from spherical water droplets (Source: ektalks.blotspot.com)



Ok, if you are still interested in more of the details check out the referenced website.  In the meantime, I followed up my interest in conversations with ChatGPT.  As described in previous posts, ChatGPT can be sort of a study buddy to help you find answers to questions, even though, like the rest of us, it too can be spectacularly wrong.  So, let's use this as another example of trying to evaluate how well ChatGPT answers questions about astronomical topics.  Here is my two question conversation with ChatGPT.

Conversation with ChatGPT about Moonbows and angular size of images (Source: Palmia Observatory)
Conversation with ChatGPT about Moonbows and angular size of images (Source: Palmia Observatory)
Conversation with ChatGPT about Moonbows and angular size of images (Source: Palmia Observatory)

What surprised me in the conversation was how ChatGPT was how the angular size of the moonbow could be between 1 and 5 degrees depending on the conditions.  I had misremembered the 42 degree number as the angular diameter, but it seems ChatGPT offered a different number.  Hmm, well lets just use Photoshop and measure the size of the moonbows in the Julian photo.  My rough eyeball measurement showed the Moon with diameter of 9 pixels, the first moonbow of 46 pixels, and the second outer moonbow at 127 pixels.  The moon angular size is about 1/2 degree, so we find the first ring is about 46/18 = 2.5 degrees and the 2nd ring is about 127/18 = 7 degrees in diameter.  Hmm, I guess that is maybe close enough.

At the same time, there can sometimes, maybe more often, be halos around the moon, but these, if I remember correctly, are 22 degrees in radius.  The measured angular size, based on the estimated size of the lunar image, is much smaller than this.  Could the diameter of the moon in the photo actually be much smaller and just appears as large as it does because of over exposure?

Ok, its finally time to finish up and have some fun with some recent jokes found online.  First is this photo of Sam Alton, CEO of OpenAI, where he is depicted as carrying "the nuclear codes football" that in this case will save humanity from the case where GPT goes rogue.

Sam Altman, carrying the "nuclear codes football" (Source: BioBootloader)
Sam Altman, carrying the "nuclear codes football" (Source: BioBootloader)

We also received a note from Dave, OCA and Math Whiz, about this trigonometric sin, cos and tan  functions.  Thanks for the note, Dave!

Don't squeeze too much out of this trigonometry joke (Source: Twitter, as forwarded by OCA Dave)
Don't squeeze too much out of this trigonometry joke (Source: Twitter, as forwarded by OCA Dave)

Finally, after years of jokes about Elon and how he must be some sort of alien because he works so hard and has been so innovative.  Given that starting position and what with all of the news of flying objects being shot down out of the skies,  here he pokes some fun at himself and the recent spate of, shall we say, balloons and other UFOs.


Until next time,


Resident Astronomer George



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