Science feed
Low contrast
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.
0.01°C
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.
15 cm
The Eiffel Tower expands when its iron warms and contracts when it cools, but a fixed 15-centimeter summer height gain is not a reliable universal measurement. The tower operator also describes roughly 15-centimeter daily movement of the summit from uneven solar heating, which is a different quantity.