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Are there any analogies that are actually meaninful?

  1. Nov 15, 2013 #1
    Obviously most humans understand that the universe is incredibly large, so large that we can't even find an analogy that we can relate to. The problem is no two things we can visualize and comprehend can describe the relation of the size of Earth to the universe.

    The closest one I found and I don't know if it's accurate but it was that 'The size of Earth compared to the size of the universe is the same as 1/180th the width of a hydroden atom compared to Earth

    This still isn't meaninful as I don't think it's possible to visualize that.

    Does anyone know any accurate analogies for things like the speed of light, the size of the universe, or even the milkyway, relative distances ect?
  2. jcsd
  3. Nov 15, 2013 #2


    Staff: Mentor

    Last edited by a moderator: Sep 25, 2014
  4. Nov 15, 2013 #3
  5. Nov 15, 2013 #4


    Staff: Mentor

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    Code (Text):

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    Last edited: Nov 15, 2013
  6. Nov 15, 2013 #5
    Really? I've used the site many times before and it's been fine. That is strange... use this site then http://htwins.net/scale2/
  7. Nov 15, 2013 #6


    Staff: Mentor

    Thanks, I had posted that one in my earlier post but at least now I know you saw it.

    I don't think you'll find an analogy of the universe's size to something on earth since we don't know how big it is.

    Hey maybe you could develop your own analogies and post them here. I think people respond well to analogies that limit the scale to within 100, 1000, or maybe 10,000. Any higher and it can't be easily imagined so you could use that range of 10,000 or less as a baseline.
    Last edited: Nov 15, 2013
  8. Nov 15, 2013 #7


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    The problem with finding an analogy suitable for visualization is fundamentally a problem of extremes of magnitude. The diameter of the Earth is around 13,000 km. The diameter of the observable universe is on the order of 10^24 km. So you've got some 20 orders of magnitude difference between these two things. Humankind's sense of scale is informed by experience, which is limited by the human sensory system. What's the biggest thing you can reliably visualize, and what's the smallest? I think you'll find these things are at most a handful of orders of magnitude different, not 20.
  9. Nov 20, 2013 #8
    OP that's a great question.

    In geology we often use analogy and it usually has little value. In fact it often provides a false understandings of time, size, quantity, etc.

    'There are as many stars as there are grains of sand in the ocean'. No there isn't. Add or subtract a couple of zeros to the numbers of grains of sand and it would mean zilch to any of us. Nobody has a clue as to the number. We can't even fathom the amount of grains in bucket. We use mathematics. Usually the math is logical and expresses a number that is rational in describing some phenomenon. Being logical doesn't mean we relate to it.

    I went to a lecture a couple decades a go and a prof purposely left a zero off of a large number. He mentioned it at the end of the lecture stating that the Universe has been reduced to a tenth of its size but nobody noticed. A tenth or a billionth it's size mean nothing to our limited physical senses and experience in the real world around us.
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