# Re: Earth's Magnitude

From: Björn Gimle (b_gimle@algonet.se)
Date: Sun Jun 29 2003 - 03:21:26 EDT

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```...
> based upon the Earth being 10 time higher albedo than the moon, 13.5
times
> greater cross section area and 8 times closer, I calculate that the
Earth would
> be 9400 times as bright.  10,000 times would mean exactly 10 magnitudes
> (2.511886...etc raised to the 10th power) I would guess that, depending
on the
> phase of the earth beneath you, it would be 10 mag.s brighter than the
moon.
> If it were full (you standing between the sun and the Earth), it would
be mag.
> -22 or -23 (bright - take fast film!)

In the last comment, you are neglecting that Earth is not a point source
of light. What if I take a landscape at 1 km range - not another 22
magnitudes
brighter! The surface brightness is still just 10 times that of the full
moon,
because we receive the same solar illumination.
Jupiter is 25 times fainter, not accounting for the albedo.

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