A CD has a radius of 12 cm for a playtime of 74 minutes because it is the playtime of Beethoven’s 9th symphony.
Know more
It’s usually said that the great wall of china is “the only human building that can be seen from space”...actually it’s false.
From the moon’s or other high orbits, no human construction can be seen. From low orbits, the great wall can be seen such as many other building. It may be long, but it’s thiner than any other motorway.
Share this DYK with your friends (*)(*) If you are friendless, this my be the right thing to start gather some!