APOD: Equinox Earth (2013 Sep 28)

[barakn]

The Sun illuminated both poles on the date the APOD was taken, but the view doesn’t extend clear to both poles because the satellite isn’t high enough. Since the Earth’s radius is 6,378 and the satellite (and all others in geostationary orbits) is 42,164 km from the Earth’s center the maximum latitude visible would be ~ 90 - arctan (6378/42164) = 81.4 deg.

Extra point question: How high would the satellite need to be to actually see both poles?

If we're going to analyze this thoroughly, we must recognize that since the Sun is larger in diameter than the Earth, at autumnal equinox it illuminates beyond the pole by a factor of arcsin((695,500-6357)/(1.0034*149,597,871)) = 0.263 degrees (discounting atmospheric refraction). Note that I have used the polar radius of Earth, and the Earth is 1.0034 AU from the Sun at autumnal equinox. There's also a correction due to gravitational lensing, though I suspect it's extraordinarily small and tends to get lumped in with atmospheric refraction.

[Dieselfixer]

Are you guys serious? This is the fakest picture of earth I’ve ever seen! I mean they’re all fake but this is terrible! There’s clearly duplicated clouds! How anybody would honestly believe this is real it’s either seven years old or lying to themselves because they want to believe! Ridiculous!