Clouds emerge and descend as these giant obstacles play their games with them. Rising and cooling air can contain much less water, so molecular water droplets condense around tiny dust particles - we see this phenomenom as clouds.
If these droplets become big enough, gravity pulls them down: it starts to rain. As these clouds descend into valleys and air warms up, the water is reabsorbed, and the sky clears.
This happens every day. Air is filled with water, mainly drawn from the oceans and land foliage. When air cools, rain starts to fall back on the ground, where water is running into streams and rivers, and finally reaches the ocean.
This delicate system is what we call Water Circulation.
WHAT CAN WE LEARN HERE?
There's a few things to consider here. Water circulation as a whole is truly a substantial element to Earth's healthy life. Earth sciences describe the planet as subsystems of the so-called geosphere, hydrosphere, atmosphere and biosphere. These subsystems can be observed individually but it's more accurate if treated as a combined whole, delicate system.
Water is a fundamental element in all of these subsystems: earth's soil and crust; all the lakes, rivers, oceans and ice; the air; and all living things contain and circulate water - in fact water is circulating across these systems. You see, it is crucial to understand that the overall quality of water in these subsystems influence one another: if soil is polluted, water in the hydrosphere and biosphere will be too. Let poisonous gases into the atmosphere and acid rain will damage all the biosphere, hydrosphere and geosphere.
Industrial agriculture helped mankind get rid of hunger and destitution. Petrochemicals advenced mankind technologically in an unprecedented scale.
But fertilizers and artificial chemicals used in farming as well as carbon-monoxide and carbon-dioxide as byproducts of burning fuel spoil water and air and stay there for long decades.
Are we capable to face these negative effects of these technological leaps?
Are we reasonable enough to notice how we pollute Earth's delicate systems?
Can we moderate our speed and be more responsible with the world we once need to hand over to our children?