The Water Cycle
Did you know that the Earth does not make any new water? The exact same water that rained down on the mighty T-Rex millions of years ago is the very same water coming out of your kitchen tap today! Join Bill Nye the Science Guy to discover the spectacular invisible engine that keeps Earth's water moving.
You Are Drinking Dinosaur Water!
Earth is a giant closed system! Gravity traps our atmosphere in place, acting like a giant lid on a jar. The water simply changes form from solid ice to liquid water to invisible gas, constantly recycling itself over and over again without ever leaving the planet.
The water is spread incredibly thin! A cloud is not a solid object or a floating pool of liquid. It is made of billions of microscopic liquid droplets that are so tiny and lightweight that they can easily ride on the upward currents of warm air.
Put Your Instincts to the Test
Think about how water behaves when it is heated up or cooled down. Pick an answer for each question, then see if your instincts were right.
It turns into an invisible gas and floats into the air! The heat energy from the sun causes the liquid water to evaporate, turning it into invisible water vapour that travels up into the atmosphere.
Less than 3 percent of it! The vast majority of water on Earth is salty ocean water or frozen solid in giant glaciers. That is why it is so incredibly important to protect our fresh water supplies from pollution.
Understanding the Science
Tap each card to uncover the specific scientific vocabulary that describes Earth's ultimate recycling system.
Key Concepts
Evaporation
Tap to learn moreThe crucial process where heat energy from the sun turns liquid water into an invisible gas called water vapour, sending it high into the sky.
Condensation
Tap to learn moreWhen invisible water vapour cools down and turns back into tiny liquid droplets, clumping together to form visible clouds in the atmosphere.
Precipitation
Tap to learn moreWhen the liquid droplets in clouds get too heavy for the air to hold and fall back down to Earth as rain, snow, or hail.
Collection
Tap to learn moreThe final stage where falling water gathers together in vast oceans, winding rivers, deep lakes, and hidden underground aquifers.
Water Vapour
Tap to learn moreThe completely invisible gaseous form of water that is constantly floating all around us in the Earth's atmosphere.
Transpiration
Tap to learn moreThe special biological process where living plants and trees absorb liquid water from the soil and release invisible water vapour from their leaves.
Closed System
Tap to learn moreA sealed physical system where no new material is added and none is lost. Earth's water cycle is a closed system that recycles the exact same water continuously.
Solar Energy
Tap to learn moreThe massive, incredibly powerful heat energy from the sun that physically drives the entire water cycle by forcing liquid water to evaporate.
Try It: The Global Water Engine Lab
Take control of the planet's climate!
Instructions: Earth is a closed system. Use the Solar Heat slider to evaporate the ocean water into invisible gas. Then, use the Atmospheric Cooling slider to condense that gas into clouds. You must balance both to keep the cycle flowing continuously!
CYCLE STATUS: PAUSED
Apply Your Knowledge
Let us see if you can successfully map the journey of a single water droplet.
Match the Cycle
Click a scientific term to select it, then click the matching description to place it.
turns a liquid ocean into invisible floating gas.
atmosphere and clumps together to form white clouds.
and fall rapidly back to the ground as rain or snow.
water up and release it as invisible gas from their leaves.
Real World Challenge
If the entire Earth is a completely closed system and water just keeps continuously cycling perfectly round and round, why do some countries experience terrible, dry droughts where their rivers completely dry up?
What Has Changed Since This Episode Aired
This episode originally aired in 1995. While the physics of water remain identical, our modern space technology and our understanding of the changing global climate have completely advanced!
Updated: In the 1990s, measuring this hidden underground water was incredibly difficult. Today, scientists use brilliant twin satellites called GRACE (Gravity Recovery and Climate Experiment). These satellites actively orbit the Earth and measure tiny changes in gravity to track exactly how much water is hidden deep beneath our feet!
Updated: Yes! Today, modern scientists know that global climate change is actively supercharging the water cycle! Because our atmosphere is getting warmer, it can hold much more water vapour. This causes much faster evaporation (leading to severe droughts in some areas) and massive, sudden dumps of precipitation (leading to extreme flooding in others).
Test Your Understanding
Answer these 10 questions and get instant feedback. How many can you get right?
Results
Your score:
Reflection
If the global water cycle connects every single drop of water on Earth, why is it so incredibly important to make sure we do not pollute our local rivers and small streams? Think about where that water eventually ends up!
Episode Discussion
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