Science Question for the Hive Mind


Tod Kelly

Tod is a writer from the Pacific Northwest. He is also serves as Executive Producer and host of both the 7 Deadly Sins Show at Portland's historic Mission Theatre and 7DS: Pants On Fire! at the White Eagle Hotel & Saloon. He is  a regular inactive for Marie Claire International and the Daily Beast, and is currently writing a book on the sudden rise of exorcisms in the United States. Follow him on Twitter.

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13 Responses

  1. Avatar Steve C. says:

    Warm air holds considerably more water vapor than cold air. Small aerosol particles absorb some of the moisture, forming haze.Report

  2. Avatar zic says:

    What Steve C. said, and to add: that moisture in the air makes reflects the light. For example, in space (I’ve read this, of course I’ve never actually been in outer space, despite what some of you might think of my mental facilities,) yes, in space, the stars don’t twinkle. That they do here on Earth is because of the atmosphere bouncing of bits of the star’s light hither and yon. The more stuff there is in the atmosphere — moisture and dust — the more they twinkle until their light is so blocked that it doesn’t pierce through the atmosphere at all.

    Since the amount of moisture air holds is temperature dependent — cold air holds less, warm it up and it holds more, really warm it up, and you get a hot steamy humid day, and the air just about shimmers with heat, distorting the views of even that beautiful belle across the room.Report

    • Avatar veronica d says:

      Funny thing, though, stars often twinkle more in cold air than not. This is actually the contrast to the fact above, that warm air hold more moisture. Cold air holds less moisture, but can be less stable therefore. With the dense, warm air, there is a constant scattering of light, but the heaviness of the air causes less small motions as light passes through the layers. Cold air is lighter and thus gives more “twinkle.”

      I’m probably not explaining this perfectly, but the end result is this: for pure visual astronomy a cold night can be better, as more light gets through to your eyes and you can just keep looking and catch good moments. However, if you are doing photographic astronomy, a bit of humidity helps, as long exposure makes up for the lack of light and the stable air allows longer exposure with good resolution.

      This stability goes by the moniker “seeing,” as in “tonight we have good seeing.”

      Obligatory wiki link.Report

      • Avatar zic says:

        I think part of that is that in very cold air, you simply see more stars; thus enhancing the ‘twinkle’ effect; some are whole galaxies, appearing as a single point of light that appears and disappears as the air either enlarges the light (like a lens) or obscures it (like a filter).Report

      • Avatar zic says:

        Also, @veronica-d these effects of light in the atmosphere, (atmospherics) are mostly what I chase after with my camera. I’m constantly searching for the places where I can explore how light moves, particle or wave, as captured by the sensor in it. I can put together a album of some examples if you like.Report

  3. Avatar Kolohe says:

    In addition to what every one else said, winter in North America generally brings down less (particulate) polluted Arctic air, while summer patterns bring air from the mid- to lower- lattitudes where people live. (not as big of a difference in the Pacnorwest or Cali compared with Megalopolis due to the Pacific vs Continental land mass, but China et al gives y’all a good sprinkling of Gobi dust every so often)Report

  4. Avatar Doctor Jay says:

    Might I remark: That was one hell of a view!

    I’ve only seen it from an airplane, though that’s happened more than once.Report