On Earth, how can you tell up from down?

Well if your talking ABOUT the earth then they use satellite imagery and scan the earth, and I’m pretty sure they would know the bottom from the top because of the contents and such. But when i think about it there really isn’t a up and down on the earth cause it’s a sphere, or maybe the moon is the bottom and the sun is the top.

The answer is d) by requesting advice on science internet sites

B) raising the temperature and reducing the volume of the gas.|-/