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Things that take your breath away

  1. Aug 12, 2008 #1
    Ok, so the idea is this: List some tidbit of information about physics or math or chemistry or whatever that gives you a feeling of awe / goose bumps / mystery when you look at.

    I'll go first to give an idea of what I am talking about.

    Some initial facts:

    - For your eye to register light, you need about 9 photons within a 100 ms period of time.
    - In dim light, a human pupil has a diameter of about 8 mm.

    The star "Betelgeuse" is somewhere around 400 ly away from us, but we can see it with the naked eye. This means every 50 mm^2 of the surface of a sphere with a radius of 400 light years, receives at least 9 photons every 100ms. The sheer amount of photons generated boggles my mind.

  2. jcsd
  3. Aug 12, 2008 #2
    Actually according to Dr. Daniel Robinson you only need about 5 photons. If the five photons hit one cone you'll see it, but all five need to hit one cone. If one photon hits a rod and another hits a neighboring rod etc until 5 photons hit five neighboring rods you will see it, that's why your peripheral vision is more sensitive than looking straight on when it is dark
  4. Aug 12, 2008 #3
    Ok. My source (from 1986 or so) said "five to nine". I still get dizzy thinking about the end product though :)

  5. Aug 12, 2008 #4
    that's okay I made mine up
  6. Aug 12, 2008 #5
    just kidding, I have it on a books on tape lecture
  7. Aug 12, 2008 #6
    No wonder the ratio of photons to baryons is a billion to one.

    http://zebu.uoregon.edu/1996/ph123/l6b.html" [Broken]
    Last edited by a moderator: May 3, 2017
  8. Aug 12, 2008 #7
    I'm sort of amazed at the amount of the Universe that is made up of stuff that isn't what we're made of. What's the latest percentages? 85%Dark matter/dark energy vs 15% our stuff.
  9. Aug 12, 2008 #8
  10. Aug 12, 2008 #9
    I think it's 95/5, but don't forget, we are dark matter ourselves.
  11. Aug 12, 2008 #10
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