from sea level, the biosphere goes up about 9 km and down about 19 km. what is the thickness of the biosphere in meters?

Answer 1

1 km = 1,000 meters
28 km = ?? meters

Answer 2

if I put a banna in the fridge will it turn black tommorow?

Answer 3

Try it and find out.

Answer 4

An interesting thing to try is does putting other ripe fruit with the banana speed up the 'going black' process? Alternatively does putting a ripe banana with other fruit speed up their ripening?