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Darkness (or not) of space

  1. Dec 19, 2015 #1
    OK. I'm slightly confused. A good number of years ago now I read somewhere a comment from one of the early astronauts (I think back in the 60s) that when he saw space for the first time, he was surprised at how much brighter it seemed when compared to being viewed from earth, such that it didn't really look black.

    This week, Tim Peake (the first official British astronaut) has commented on his first impressions of looking out into deep space and said "It is just the blackest black and that was a real surprise to me."

    So I'm obviously getting something wrong (likely my understanding of the first astronaut's comment). Can anyone shed any light (pun intended) on why their two accounts seem to differ so much?
     
  2. jcsd
  3. Dec 19, 2015 #2

    Student100

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    Most likely just two different subjective experiences. If anything, it should be darker as there isn't as much "stuff" in the way to scatter light like here on Earth. Maybe astronauts 1 saw more stars due to better viewing, while Tim Peake focused on the stuff between the point light sources.

    Maybe you'd be interested in reading about Olbers' Paradox?
     
  4. Dec 19, 2015 #3

    marcus

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    Not sure I understand astronaut #1's finding it "brighter" but you might say the sky was brighter if you saw many more stars (per "square degree" or in your field of view) and these more densely packed stars were brighter than you were used to.

    Most of us live in cities and seldom really see the stars---getting up into the mountains away from civilization on a night when the air is perfectly clear can leave a memorable impression. A really starry sky is dazzling. He could have been talking about an analogous version of that experience.
     
  5. Dec 20, 2015 #4
    Re Olber's Paradox, as I understand it that was conceived well before anyone had been to space, and even well before any of the recent discoveries about the state of the universe (not least Hubble's work on redshift and the expanding universe). I suppose it can be used to provide a background as a lead in to why space is dark not light in the context of actual in-space observations of deep space, but I don't think it particularly gives any insight as to the two different experiences of astronauts.

    The comment re city vs country observations could be part of the answer. As I understand it, the atmosphere blocks out a lot of the starlight from the rest of the universe from reaching earth's surface, even when it's a clear, moonless night, and even up at high altitudes. That was one reason why the Hubble Space Telescope was built (another being to reduce the distortions caused by the atmosphere). So, compared to a view from earth, I'd anticipate that there would be far more faint stars visible when viewed from space. That could explain the earlier astronaut's feeling that space was brighter (maybe even slightly a very very dark grey). Peake's view was also coloured by expectation, which appears to be because he had been anticipating something different (as evidenced by the end of his quote "...that was a real surprise to me.")

    I'd be interested to know other astronauts opinions and initial impressions, but don't know where I'd find that kind of specific information.
     
  6. Dec 20, 2015 #5
    The early astronaut (I believe it's the same quote you read) was describing daytime orbit, with a brilliant white sun shining. Our atmosphere scatters much of the sunlight, but in space there is no such scattering, so the sun seems extraordinarily bright when looking toward it. Tim Peak was possibly describing his 'night time' orbit experience from ISS, but, even during 'daytime', space is exceptionally black since the sun out shines light from distant stars.
    http://www.universetoday.com/18689/color-of-the-sun/
    Lastly, space isn't 'black' or 'dark', it's transparent. The perception of darkness is from the edge of the visible universe, since light from objects beyond haven't had enough time to reach us. They are cloaked in the universal 'dark ages', because when we 'look' that far away, we are also 'seeing' far back in time, when space was opaque.
    https://en.wikipedia.org/wiki/Reionization
     
  7. Dec 21, 2015 #6
    I don't remember anything in the quote I read about looking near the sun. I seem to remember it was about looking out into space, in much the same way as Tim Peake did, and being surprised at how it wasn't the deep black he'd expected but was bright with stars (and I'm paraphrasing all of that). It was so long ago now (over 17 years) since I read or heard it, and I don't have the reference or even remember who said it, that I can't provide the evidence to support even my recollection of the observation :frown:
     
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