[bunny]

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I dont even see what the coincidence is. My hand "exactly covers the sun" if I hold it up in front of my face. Anything, of any size (bigger than your pupil) will if it's close enough - and the moon isnt at some exact distance to make this happen - could be more, could be less, it would still cover the sun. What's the stellar coincidence?

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The coincidence is the disc of the sun is the same relative size as the disc of the moon from the perspective of an earthbound observer. Its why during a total solar eclipse the surface of the sun is completely covered but features emanating from the surface(corona, prominences, etc) are not.

You can of course make your thumb appear to be the same relative size as the disc of the sun. You would have to make the decision to place your thumb at the specific distance away from your eye so that your thumb exactly covers the surface of the sun, but does not cover features emanating from that surface. If you left the distance up to chance you would likely go blind before achieving success.

Astronomers attribute this feature of a total solar eclispe as the occurence of improbable happenstance.

Stu

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But I dont think this is true. If it were, the shadow on the Earth's surface in that photo would be an exact point. It isnt it's a region of darkness, the reason being that the distance isnt exact at all. The moon could move further away and the area of the shadow would shrink, the moon could move closer and it would grow bigger. There's nothing special about where it is - optical effects not withstanding. [img]/images/graemlins/confused.gif[/img]

There's nothing particularly special about the size of the shadow. If it exactly covered the Earth's surface (so the earth was in total darkness) or exactly met at a point (so only one specific point experienced a total eclipse) then it might be unusual. As it is, it's nothing remarkable - it's just somewhere within the range which causes total solar eclipses.

EDIT: Do you have an astronomy link or citation where this is explained? I'm just not getting it...