• Member Since 28th Oct, 2012
  • offline last seen 10 hours ago

Pineta


Particle Physics and Pony Fiction Experimentalist

More Blog Posts441

  • 5 weeks
    Eclipse 2024

    Best of luck to everyone chasing the solar eclipse tomorrow. I hope the weather behaves. If you are close to the line of totality, it is definitely worth making the effort to get there. I blogged about how awesome it was back in 2017 (see: Pre-Eclipse Post, Post-Eclipse

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    10 comments · 167 views
  • 13 weeks
    End of the Universe

    I am working to finish Infinite Imponability Drive as soon as I can. Unfortunately the last two weeks have been so crazy that it’s been hard to set aside more than a few hours to do any writing…

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    6 comments · 177 views
  • 16 weeks
    Imponable Update

    Work on Infinite Imponability Drive continues. I aim to get another chapter up by next weekend. Thank you to everyone who left comments. Sorry I have not been very responsive. I got sidetracked for the last two weeks preparing a talk for the ATOM society on Particle Detectors for the LHC and Beyond, which took rather more of my time than I

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    1 comments · 165 views
  • 17 weeks
    Imponable Interlude

    Everything is beautiful now that we have our first rainbow of the season.

    What is life? Is it nothing more than the endless search for a cutie mark? And what is a cutie mark but a constant reminder that we're all only one bugbear attack away from oblivion?

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    3 comments · 229 views
  • 19 weeks
    Quantum Decoherence

    Happy end-of-2023 everyone.

    I just posted a new story.

    EInfinite Imponability Drive
    In an infinitely improbable set of events, Twilight Sparkle, Sunny Starscout, and other ponies of all generations meet at the Restaurant at the end of the Universe.
    Pineta · 12k words  ·  51  0 · 890 views

    This is one of the craziest things that I have ever tried to write and is a consequence of me having rather more unstructured free time than usual for the last week.

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    2 comments · 164 views
Aug
2nd
2018

Blue Moons and Lunar Eclipses · 7:56pm Aug 2nd, 2018

New story out today—yes I can still write stories! Please take a look at Once in a Rainbow Moon, written following last week’s lunar eclipse. Here are the notes on the science in this one.

EOnce in a Rainbow Moon
One night in the crystal empire, Twilight Sparkle and Rainbow Dash decide to engineer a blue moon.
Pineta · 2.1k words  ·  59  3 · 1.1k views

“What is a Blue Moon?” is a science question with a long history. I once meet an astronomy professor who told a story of how after he first gave a talk to a primary school class, the first question he got from a young child was “what is a blue moon?” and he had to admit that he hadn’t a clue.

That was many years ago. I think there were quite a few astronomers at that time who would have also struggled to answer to that question. The trouble is that telling people that it’s just an expression meaning something very rare, and doesn’t really mean anything, is not the answer they want to hear. A Blue Moon really should be something cool and astronomical.

However, once internet searches became possible, the situation changed. Once one blogger found a satisfactory answer, everyone else could copy it. So we now have a widely accepted response that a blue moon is the second full moon in a calendar month. This is particularly useful to anyone running an astronomy news feed as it provides a regular opportunity to release There’s Going To Be A Blue Moon! posts. And then we have rival groups of amateur folklorists who can post an alternative calendar using the Maine Farmers' Almanac definition, and have hours of fun arguing with each other in the blog comments.

If you want to read more about this bit of modern folklore, see Once in a Blue Moon (Sky and Telescope)


The more interesting question for an atmospheric physicist is whether there are any weather phenomena which can make the moon appear blue. The answer is yes, but it doesn’t happen very often, and it’s hard to predict when it will.

A quick bit of revision of atmospheric scattering:

  • Clouds are white as they are made of large water droplets which scatter all the colours in the white light from the sun equally.
  • The sky is blue as air molecules scatter more blue light than other colours
  • Sunsets are red as we are looking at the unscattered light after the blue light has been scattered during its passage through the low sky.

To get a blue moon (or sun for that matter) you would need to look at it through something that scatters or absorbs an excess of red and thus turn white moonbeams blue. That’s a bit more difficult to arrange as most colour-dependent scattering process work the other way round scattering more of the shorter blue wavelengths. But if you have airborne particles of the right size it can happen, perhaps from forest fires, volcano eruptions (or a snoring dragon), or something else. There have been reports of blue moons seen in snowy conditions.

This article gives a detailed explanation of these processes: Twice in a Blue Moon (Weatherwise)


Lunar eclipses are a much more clearly defined thing. When the Earth comes directly between the sun and moon, the moon falls in its shadow, but it is still illuminated by the light scattered in the Earth’s atmosphere, as red as the sunset. And thanks to the millimetre-thick ozone layer, other bands of colours are also visible, as explained here: Colorful Lunar Eclipse (NASA).

Comments ( 2 )

¡:yay:! ¡I shall read!

Can Luna pull the moon closer and make a rainbow moon?

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