Zenith, the point in the heavens that is directly above the head of the observer. The opposite point, that directly below the observer's feet, is the nadir. Zenith also applies to the highest point a heavenly body appears to reach above the horizon. The sun reaches its zenith at noon.
Did bunnies just attack that sailboat, or was it a narwhal playing with a school of fish? Are you going crazy, or are you just watching the clouds?
If you have a theory that potato chips are making you fat (with the proof being your expanding waistline), you've just used two scientific terms in a very unscientific way.