It's Only a Sliver Moon (Daily Astronomy Log with Mike Brown)


19 Responses to “It's Only a Sliver Moon (Daily Astronomy Log with Mike Brown)”

  1. RadioSilence says:

    ooh, that was great. i just wish you’d posted it a few hours earlier so we could have taken advantage here in europe. by the time i read it the sun and moon were long gone from my sky.

    i’ll have another look tomorrow to see if it’s still visible.

  2. DanielZKlein says:

    “The dark side glows with earthshine” should be the name of a short story.

  3. Anonymous says:

    Wow! That is a breathtaking picture! The moon is always a wonder to look at, and I love watching the sky.

  4. coop says:

    My grandfather referred to this as “the new moon in the old moon’s arms”.


    • pidg says:

      My grandfather referred to this as “the new moon in the old moon’s arms”.

      Always thought this was a lovely phrase. Only place I have heard it used is in the traditional Scottish ballad “Sir Patrick Spens”: Fairport Convention’s version

      “Last night I saw the new moon, with the old moon in her arms / A sign, a sign, since we were born, that means there’ll be a deadly storm..”

  5. Ugly Canuck says:

    That old devil moon reminds me of an old piece of machine music:

    (Machine = player piano in this case)

    That is, it does, when that old devil moon doesn’t remind me of that old devil moon:

    How many songs are there, songs inspired by the moon?

    Without the moon, who’s to say that we’d have any poetry at all?

  6. Xeni Jardin says:

    Great post, Mike!

  7. Robert says:

    And remember, to keep looking up! :D

  8. Rob Beschizza says:


  9. pidg says:

    The fact that we see sliver moons, quarter moons, and full moons is not so much because the moon is changing, as that our vantage point is changing.

    Wait… what?

    Only kidding. Loved this post. :)

  10. Heisenberg says:

    What a great post. These words were just dripping with joy. Thanks!

  11. Aant says:

    Wonderful post – looking forward to the following weeks’ ones. One minor point, though: in the following sentence:

    A few days after new moon, though, when the sun is at, say, the 5 o’clock position, we should see just the tiniest sliver of the sunlit side against a mostly dark moon.

    shouldn’t we be talking about the /moon/ being at 5 o’clock?

  12. SamSam says:

    That was wonderful. And I actually stopped reading after the second paragraph, put on a coat, and stepped out of the office to look at the new moon (actually, first I look at it through the window, then I cursed myself for looking at the new moon through glass, and then I remembered that I’m no longer superstitious. Hmmm…)

    I never had any trouble visualizing why the crescent looks the way it does once I started imaging us and the moon as different planets next to each other. For some reason, this sci-fi-like mental model made it much easier to think of the moon as a sphere — or as us, really — and think about why the shadow was where it was. (I had always been told by adults that the crescent moon was due to the Earth’s shadow on the moon, so this notion took a little while to disabuse itself.)

    Once I saw where you were going with earthshine, though, I was very happy.

    • wrecked_em says:

      “Keep watching the skis! I mean skies.”

      The Earth and moon *are* planets next to each other. It’s not sci-fi.

      If you stretch your arms out fully, the Earth would be a 2-inch ball in your left hand, and the moon a half-inch marble in your right (or about 60 inches at this scale.)

      • SamSam says:

        Hmmm, you must have missed the post where everyone decided that Mike was a devil-scientist whose sole purpose in life was to wickedly tell them that they weren’t allowed to call their most favorite planet in the whole wide world a “planet” anymore.

        Let’s not get him angry by calling the moon a planet too!

  13. Anonymous says:

    That’s no moon…

  14. mdh says:

    I happened to see the moon before I saw this post.


  15. Anonymous says:

    An excellent post, I thoroughly enjoyed the easy to follow explanation. It’s exciting to engage in these kinds of mental exercises, trying to wrap my mind around moon phases has always been challenging for me.

    I’d noticed the ghostly glow when I was a kid and my parents told me that I was just imagining it because I knew the moon was round and my brain was ‘filling in’ the missing part with an illusory glow. Earthshine is a long overdue explanation, I’m really happy to have found out about it here.

    It’s probably because I’m simple, but I have a question which I cannot solve at the moment – is there such a thing as a ‘full earthshine moon’?

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