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Welcome. to the bedtime scientist.
Tonight we learn how the moon moves the sea.
Pull up your covers.
Take a slow breath in.
Let it out.
Let your body get soft and still.
Let your shoulders sink as we dive in.
We're visiting the edge of the ocean to learn how tides work, why the gentle water comes in and goes out like the sea is breathing.
Our journey's quiet and unhurried.
We're careful scientists, noticing small clues in the sky and the water.
Take another breath in and let it out.
Close your eyes and imagine you're sitting on a warm, smooth, sandy beach.
The air smells like salt.
Waves roll in and roll out. leaving foam on the shoreline.
Far out over the water, the moon is rising, round and pale.
Its light paints a soft path across the sea, a silver road just for you.
Tide is the slow rise and fall of the ocean surface.
When the water's higher along the shore, it's high tide.
And when the water's lower and more beach is showing, it's low tide.
If you watched from the same spot all day, You'd see the line where the waves reach move up, then down, then up again.
It's steady, gentle, and powerful.
People sometimes say the ocean is breathing.
That's a good picture.
But what's making the sea breathe?
Well, the moon's gentle pull.
Every object in the universe has a pull called gravity.
It's what keeps your feet on the ground.
The moon's gravity reaches across space and tugs on Earth.
It tugs on the solid ground a tiny bit.
But rock doesn't move easily.
Water does.
So the ocean responds the most.
Picture the ocean stretching into two gentle domes like soft bumps, one facing the moon and one on the far side of the earth.
The bump that faces the moon is made by the moon's pull.
The bump on the far side happens because the moon is pulling on the solid earth a little more strongly than it's pulling on the water on the far side.
So as the moon pulls the whole planet toward it, that far away water gets left behind just a little, making its own gentle bulge.
You can remember it simply as two high places in the ocean, one under the moon and one on the far side of the Earth.
As Earth turns Different coastlines pass into these bulges and then out again.
That's why most places get two high tides and two low tides each day.
You may think that there's a perfect 12 hours between high tides.
It's about 12 hours and 25 minutes.
Why?
Because while the Earth spins, the moon's also moving along its path around us.
The ocean needs a little extra time to catch up to the moon's new spot in the sky.
That means tomorrow's high tide will be about fifty minutes later than today's.
Take your slow breath in and let it out.
Imagine the sea following the moon patient and steady, always a little behind, like a friend, walking calmly after another along the beach.
While we're talking about gravity, the sun's gravity also pulls on Earth's oceans.
It's much farther away, but it's huge.
So its tug still matters.
When the Sun, Moon and Earth line up during a full moon or a new moon, their gravitational pulls team up.
The tides get extra strong.
Higher high tides and lower low tides.
These are called spring tides not because of the season, but because the water springs higher and lower.
When the sun and moon pull at right angles, which happens during the first quarter and third quarter phases, their tugs partly cancel each other out.
So we have softer tides, lower high tides, and higher low tides.
These are called neap tides.
You don't have to remember the names.
Just remember, when the moon and sun work together, tides stretch bigger.
When they pull in different directions, tides are smaller.
If tides are made by the moon and the sun, shouldn't every beach be the same?
Well, they aren't, and that's part of the fun.
The shape of the coastline, how deep the water is and the shape of the seafloor all change how the tide looks.
Let's take a slow walk along the shoreline at low tide.
Close your eyes and imagine the sea has pulled back. revealing stones and little pools left behind.
These are called tide pools and are like tiny aquariums made by nature.
You kneel down beside one.
You spot a sea anemone.
It looks like a green flower with soft arms.
A hermit crab shuffles by in a borrowed shell, peeking out with curious eyes.
A sea star rests on a rock.
Barnacles make a ring of volcano-shaped tomes and open their feathery fans to eat when the water covers them.
Snails attach themselves to rocks and graze on algae.
In one pool a small fish darts into a shadow, then out again, changing color to match the stones.
When the tide returns, These pools will refill and the creatures will be washed with fresh, cool seawater.
The tide is their clock.
It tells them when it's time to hide, to feed, and to rest.
Imagine the tide pools as tiny cities. that appear and disappear.
They're never rushed, always ready for the sea's return.
Let's follow a single droplet of seawater.
Let's call it blue.
Blue rises and falls with the tide, riding gently up the beach and back.
When the moon's pull is strongest, blue climbs a little higher.
When the pull is softer, blue turns back sooner.
On some days, Blue slips into a dive pool, swirling around an anemone and polishing a bit of a shell.
On other days, Blue rides shallow waves over the sand, smoothing out footprints and drawing lines of foam that look like handwriting.
At night, under a bright moon, blue glows for a moment.
When it brushes against tiny plankton, that can shine bioluminescence like stars sprinkled into the water.
In the morning, blue reflects the pink of sunrise and the white of distant clouds.
Blue never hurries, tide will come, the tide will go.
Glue knows the rhythm by heart.
The same gravity that tugs Earth's oceans is what holds you gently to your bed and keeps the moon quietly circling above you each night.
You're part of the same calm, steady universe.
You might wonder why waves whoosh and splash every few seconds but tides take hours.
That's because waves are usually made by wind pushing on the water.
They are fast ripples traveling across the surface.
Tides are the whole ocean rising and falling together because of gravity.
Waves are the ocean's quick footsteps.
Tides are its slow breathing.
Let's rest and remember what we've learned.
We've learned that tides are the ocean's slow rise and fall.
High tide and low tide.
Made mostly by the moon's gravity.
With a helpful tug from the sun.
The ocean forms two gentle bulges, so most coasts peel two highs and two low tides each day.
Because the moon's moving too, tides arrive about 50 minutes later each day.
When the sun and the moon line up, we call that a new moon or a full moon.
On those days, tides stretch bigger, and they're called spring tides.
And when they pull at right angles the first and third quarter phases of the moon, the tides soften.
We visit a tide pool, a tiny world that appears at low tide and gets covered up when the sea returns, and we followed a droplet named Blue, who showed us how calm and steady the ocean's breathing can be.
You have been a patient scientist tonight, as we return to our twilight beach.
The sky is deepening to a dark blue.
Over the water.
A few stars have appeared in the sky, and the moon's reflection stretches across the water like a glowing ribbon.
The tide is turning now.
You can feel it in the way the waves reach just a little farther up in the sand.
Then pause.
Then reach a little less.
Then reach a little less.
The ocean's taking a slow, deep breath.
Air is soft on your cheeks.
The sand under your toes holds the day's warmth.
Let's take one more breath in and let it out.
Let your hands rest.
Feel your body settle like a smooth stone resting at the water's edge.
If thoughts drift in, let them drift right back out again, like a small wave racing back toward the sea.
While you sleep, the moon will keep walking across the sky.
The ocean will follow, patient as ever, rising, falling, and rising again.
And just before you drift off to dream of a universe that never hurries, with silver moon paths tide, pool lanterns, the quiet hush of waves, I want you to know something about you.
Your mind is a wonderful thing, so full of curiosity, and I like your mind just the way it wonders.
I'll be back again soon to wonder more with you.
