# Things that take your breath away

1. Aug 12, 2008

### kenewbie

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.

k

2. Aug 12, 2008

### tribdog

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

3. Aug 12, 2008

### kenewbie

Ok. My source (from 1986 or so) said "five to nine". I still get dizzy thinking about the end product though :)

k

4. Aug 12, 2008

### tribdog

that's okay I made mine up

5. Aug 12, 2008

### tribdog

just kidding, I have it on a books on tape lecture

6. Aug 12, 2008

### Jimmy Snyder

7. Aug 12, 2008

### tribdog

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.

8. Aug 12, 2008

### throng

9. Aug 12, 2008

### Jimmy Snyder

I think it's 95/5, but don't forget, we are dark matter ourselves.

10. Aug 12, 2008