[AZ-Observing] Mercury, Sun, and Earth Diameters

The most common question we will get when we show the Mercury transit to the 
public (after "how much did that telescope cost?") will probably be about the 
size of the Sun and Mercury.  I have found that one significant figure is more 
than enough, and don't use km, even though metric has been adopted in all other 
parts of the civilized world.

Diameters:
Sun: 900,000 miles
Mercury: 3000 miles
Earth: 8000 miles


During the transit, Mercury is about two-thirds of the way to the Sun.  Placed 
at the distance of Mercury, the Earth would appear less than three times as 
large as the tiny, black dot.

Tom
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