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Removed for Rule 2:

• All comments must be a single character (including number and emoji, they too have to be single letter), except:

1: When the post title begin with [Meta]; 2. Comments reminding people that they violate the rules.

Following is the original reply:

If you’re asking why it doesn’t fall off into space, it’s for the same reason you don’t. Gravity pulls on everything on Earth, including water.

I know dude. I just asked the question for fun.