[Stu Pidasso]

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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