Physics is all about scales : Earth Water and Air
Ask a person “how much water there is on earth?” and chances are you will hear 67% or 70% as the answer.
And ask them “how much air is on the earth?” and chances are you will get a blank stares.
This picture illustrates the scales remarkably well.
The water sphere measures 1390 kilometers across and has a volume of 1.4 billion cubic kilometers. This includes all the water in the oceans, seas, ice caps, lakes and rivers as well as ground water and that in the atmosphere.
The air sphere measures 1999 kilometers across and weighs 5140 trillion tones. As the atmosphere extends from Earth it becomes less dense. Half of the air lies within the first 5 kilometers of the atmosphere.
So the answer to the questions are:
1.1% water
2.7% air
Source:
ADAM NIEMAN / SCIENCE PHOTO LIBRARY
March 13th, 2008 at 4:56 pm
This is beautiful
March 14th, 2008 at 7:04 pm
Very pretty illustrations, but I don’t know why you imply that “70%” is somehow the wrong answer. It’s right if one speaks about surface area, which you happen not to be.
March 14th, 2008 at 10:50 pm
(a) the volume of air is meaningless without specifying a pressure.
(b) Besides: by mass, 1.4 billion km^3 of water is about 1.4E21 kg. Thus, there is ~270 times more water than air (by mass).
(c) Assuming the molecular weight of air is about 29 g/mol, this still leaves more atoms of water than air by a factor of 170.