What Makes Rain? (1946)

[Music] now for my Mayo what's [Music] this A letter from Billy Johnston I wonder why he's written me Dear Mr weatherman can't you do something about the weather today I was getting ready to go on a picnic with Mother and Dad bad but it rained and we couldn't go so I decided I would write you I know that the rain comes from the sky but how does all that water get up there and what makes it come down yours Billy Johnston PS please promise me good weather for our next picnic guess I'd better answer Billy's letter right away too bad the rain spoiled his picnic dear Billy you know that neither I nor anyone else can make the rain stop or start but maybe I can tell you where it comes from where it goes and how it gets back up in the sky do you remember how you've looked up and seen the clouds shutting off the Blue Sky the clouds got bigger and darker as you watched and soon it was raining rain does a lot of good work Billy it fills the streams and Brooks and rivers it gives water to the trees and bushes and flowers so they can grow some of it makes puddles on the ground maybe by the walk in your yard but when the rain stops and The Sun Shines again the water in the puddles gradually disappears though you can't see it some of the water is going right back into the air air when you've watched mother get your supper have you ever noticed the tea kettle boiling on the stove as the water boils the steam rises from the spout and goes into the air if the water boiled long enough it would all turn into steam and go into the air and that Billy is what happens to the water in the puddles the sun warms the water and turns some of it into water vapor which goes into the air but so slowly that you can't see it this invisible water is called water vapor and here's another way to answer your question Billy you may have helped mother hang wet clothes out on the line if water didn't turn into vapor and go into the air those clothes would never dry no matter how long they hung they'd stay wet full of water but because water does turn into vapor in the warm air the clothes will dry as they hang out on the line for a few hours whenever water goes back into the air we say that it evaporates evaporates see the word vapor in there evaporates means to turn into vapor later when you came back to take the clothes down they were nice and dry because all the water in them had evaporated into the air all the rain that fall sooner or later goes back into the air that's how the rain gets up in the sky water evaporates from the puddles it also evaporates from the Brooks and the lakes and the rivers and from the oceans everywhere it is evaporating turning into water vapor and going back into the air you've played with a mirror haven't you flashing the sun's reflection on the side of the house if you blow on the mirror you'll see that your breath gives off water vapor too see how it dulls the mirror you can rub it off plants too return water to the air but again you can't see it because water vapor is invisible yes plants of all kinds give off water vapor the flowers the bushes and the trees they all use water from the earth and send it back into the air some of it goes high in the sky where it gathers into pretty white clouds but now Billy what makes this Vapor return to Earth is water watch sometime when mother pours hot water into the sink when the hot steam touches the cool glass it forms drops of water which are almost like raindrops see how wet the window gets heating water makes it evaporate cooling Vapor changes it back to water we say it condenses look at the glass next time you drink your milk does it seem to sweat or the Glass isn't really sweating of course but it is wet it's just the water vapor in the nearby air being condensed or turned back to Water by the cool glass the same thing happens Outdoors invisible water vapor is turned back to Water by the cool air some vapor condenses on flowers and bushes where it forms tiny drops of water called Dew sometimes the cool air condenses the water vapor into a heavy gray Mist that looks like steam this we call fog but much of the vapor Rises into the sky there it condenses into tiny water droplets which gather into clouds as more Vapor Rises and cools the larger and darker the clouds become when they are heavy with water the rain falls on very cold winter mornings you may have seen an icy white pattern on the window pane that's Frost which comes from water vapor in the room and freezes on the cold glass when water vapor freezes in the sky it falls to Earth as snow snow stays on the ground for a while but slowly melts under the sun's warming rays and goes back into the air as Vapor just remember water always evaporates into the air from the oceans and rivers and Brooks it evaporates also from Plants but while water is always evaporating into water vapor from some places on Earth in other places it is constantly returning as Dew or fog or Frost or snow or rain it's important to understand that the Earth and everything on it use the same water over and over again I know what else I can do I can send Billy this book it tells what makes rain when you open this book look carefully at the drawings they show how when the clouds are heavy with water the rain comes down forms puddles travels on top of or through the ground to the Brooks and rivers even to the ocean how some of it goes into the ground to feed the trees and plants this water evaporates and goes back into the air as water vapor some of it rises into the sky where it forms clouds to fall again to the Earth to be used over and over again you see Billy water is never lost it condenses and evaporates into water vapor to condense again that's the story of rain where it comes from where it goes and how the Earth has been using the same water over and over again ever since the World began P.S now you know too why I can't promise you good weather for your next picnic