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~42°
A primary rainbow is centered on the point opposite the Sun.
A primary rainbow is centered on the antisolar point, directly opposite the Sun from your viewpoint. Its outer red edge lies about 42 degrees from that direction.
A primary rainbow is centered on the point opposite the Sun.
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0.01°C
Water can boil and freeze at the same time.
Water can coexist as ice, liquid and vapor near its triple point, about 0.01 °C and 611 pascals. In a vacuum demonstration, evaporative cooling can make liquid water freeze while it is still boiling.
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Low contrast
The Great Wall is difficult to distinguish from orbit with the naked eye.
The Great Wall is generally not discernible with the unaided eye from low Earth orbit, and it is not visible from the Moon. Saying it can never be seen from any altitude called space is too absolute: viewing conditions, equipment and identification all matter.
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