Science feed
Zero resistance
A superconductor can carry direct current with zero electrical resistance while it remains within its superconducting operating limits. Those limits involve temperature, magnetic field, and current, not temperature alone.
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.
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.