meta_title: "What Causes Tides on Earth: A Fun Guide for Young Explorers"
meta_description: "Discover what causes tides on Earth with playful experiments, simple explanations and story-based activities. Perfect for curious kids, parents and teachers."
Have you ever built a brilliant sandcastle, only to have the sneaky ocean creep up and gobble it all up? That’s the tide at work!
So, what makes the ocean move like that? The simplest answer is gravity. Our cosmic neighbour, the Moon, is constantly giving Earth a gentle, invisible tug. That pull is strong enough to make the water in our oceans bulge out—and that’s what makes ocean tides.
The Secret of the Moving Ocean
Picture the ocean as a massive, wobbly swimming pool. As our planet spins, the Moon is always nearby, pulling on it. This pull is the force of gravity, and it’s the biggest clue to solving the mystery of the ocean tides.
The Moon isn’t strong enough to yank the water into space, but its pull does create a slight bulge on the side of Earth facing it. Imagine a giant, invisible hand giving the water a gentle squeeze. That bulge is what we call a high tide!
As our planet spins once every 24 hours, different bits of coastline sail through this bulge. When your bit of coast is in the bulge, the water level rises—hello, high tide! Move out of it, and the water level drops—goodbye, low tide.
The Moon’s gravity is the main cause of Earth's tides. It’s like a cosmic game of tug-of-war, where the Moon always has a gentle but firm grip on our oceans!
To get a better grip on this amazing force, you can find out more about how gravity works in our simple guide. Gravity is the same invisible power that keeps our feet on the ground and the planets orbiting the Sun.
Learning about ocean tides is a brilliant first step to becoming a real cosmic explorer, just like Space Ranger Fred! It shows how everything in space is connected in a huge, wonderful dance.
The Moon: Our Planet's Tide Master
Right, let’s zoom in on the main character in our tide story: the Moon! Even though it’s much smaller than Earth, its gravitational pull is the biggest reason our oceans seem to dance up and down the shore.
Think of the Moon giving Earth a gentle, gravitational hug. This hug tugs most strongly on the side of our planet facing the Moon, and it gently pulls ocean water towards it. This creates a big mound of water, which scientists call a tidal bulge. When your beach happens to be in this bulge, you get a high tide!
The Surprising Second Bulge
Here’s a brilliant puzzle: if the Moon is pulling the water on one side, why do most places get two high tides each day? The answer is super clever!
There isn’t just one bulge; there are two. As the Moon pulls on Earth, it tugs on both water and land. The water on the side closest to the Moon gets pulled most, creating the first bulge.
On the opposite side, the solid Earth itself is pulled slightly towards the Moon, leaving the water “behind.” This forms a second bulge over there. It’s a bit like standing on a spinning roundabout—you feel like you’re being pushed outwards!
As Earth spins on its axis, we pass through both of these watery bulges every day.
Tides in the Real World
If Space Ranger Fred were flying over the UK, he’d see this effect happening all the time. The UK has 42 special tide gauges in its National Tide Gauge Network just to measure these ocean tides. The difference between high and low tide can be huge; in Immingham, the spring tidal range reaches 6.20 metres—that’s taller than a double-decker bus!
You can learn more about the UK’s amazing tides from the scientists who study them.
Try This at Home: Imagine you and a friend playing tug-of-war. You are the Moon, and your friend is Earth. As you pull, your friend moves towards you—that’s the first tidal bulge. Now imagine their jumper is loose, so as you pull, the back of the jumper is left behind, creating a second bulge. That’s exactly like our two daily high tides!
For more lunar learning, you might enjoy Moon phases for kids.
How the Sun Creates Super Tides
The Moon might be the main character in our ocean tides story, but it doesn’t work alone. The Sun, our giant star, also joins the action with its own mighty gravity. Even though it’s much further away, the Sun is so enormous that its pull still gives our oceans a big tug.
When the Sun and Moon team up, they can create extra-special tides that are even bigger or smaller than usual. It all depends on where they are in relation to Earth.
Spring Tides: When the Gravity Gang Teams Up
Twice a month, something special happens during the new moon and full moon. Earth, Moon and Sun fall into a nearly straight line. Think of it as a cosmic tug-of-war where the Sun and Moon stand side by side, pulling together.
Their combined gravity gives Earth’s oceans a massive pull, creating much higher high tides and much lower low tides than normal. These are called spring tides. Don’t be fooled by the name—they happen all year round, not just in springtime!
A spring tide is like getting a huge push on a swing from two friends at once. That extra gravitational boost from the Sun and Moon working together makes ocean tides swing much higher and lower.
In the UK, the average tidal range is about 3.40 metres, but spring tides at Immingham can surge to 6.20 metres—taller than three Space Rangers stacked up! You can find out more about how UK tides are measured.
Neap Tides: When the Sun and Moon Pull Apart
About a week after a spring tide, during the first and third quarter moon phases, the Sun and Moon form a right angle with Earth. They pull the ocean water in different directions, almost cancelling each other out. This cosmic arm-wrestle creates neap tides, when the difference between high and low tide is at its smallest.
This pattern of spring and neap tides makes ocean tides predictable—a wonderful, slow dance you can watch from any beach on Earth. You can even spot the same right-angle pattern in our guide on what causes solar eclipses.
Why Tides Behave Differently Around the World
Have you ever wondered why the tide at one beach seems gentle, while at another the water rushes in like a river? While the Moon and Sun are the grand masters of ocean tides, it’s actually the shape of our coastlines and the depth of the sea floor that decide how tides behave in different places.
It’s a bit like sloshing water in different bathtubs. Gently rock a wide, open one and the water moves slowly. Do the same in a long, narrow one, and the water builds up to make a much bigger splash!
How Land Shapes the Tides
When a tidal bulge travels across the open ocean, it’s barely noticeable. But when it hits land, the coastline can squeeze, funnel and channel the water, changing the tide’s height dramatically.
- Narrow Bays and Channels: Water forced into a V-shaped bay or tight channel has nowhere to go but up, piling the tide much higher.
- Shallow Seas: In shallow areas, tidal waves slow down and build up, making the difference between high and low tide more dramatic.
The world’s most extreme tides happen because of this funnelling effect. The Bay of Fundy in Canada and the Bristol Channel here in the UK see water levels rise by more than 12 metres—as tall as a four-storey building!
Next time you visit the seaside, be a coastline detective. Is the beach in a wide bay or tucked into a narrow inlet? Spotting the shape of the land helps you guess whether the tides will be big or small. You can discover more playful investigations on our free activities page.
Become a Tide Explorer with Fun Activities
Reading about what causes tides on Earth is a great start—but to really get it, you’ve got to get hands-on! A family trip to the beach or a simple kitchen experiment can become an unforgettable STEM adventure.
Try the Human Tide Experiment
This playful game lets you act out tidal bulges without getting wet. It’s perfect for a group, but you can do it with just two people.
- Choose Roles: One person is the Earth (standing in the middle), another is the Moon (slowly circling the Earth). Everyone else holds hands in a big circle as the ocean.
- The Moon’s Pull: As the Moon circles, they gently “pull” the nearest ocean person—that’s the first bulge.
- The Second Bulge: On the opposite side, that ocean person steps outwards, showing the second high tide.
- Watch the Dance: As the Moon continues to orbit, different ocean people move outwards—just like real tides.
Be a Beach Detective
Turn a day at the seaside into a tide-tracking mission.
- Mark the Spot: Draw a line in the sand at the water’s edge when you arrive.
- Check Again: After an hour, see if the tide has crept in (incoming tide) or retreated (outgoing tide).
- Create a Map: Make a new line each hour to map the tide’s movement in real time.
Chat about tide times and beach safety, or try an RYA Competent Crew course for more seaside skills. And don’t forget our Space Ranger Fred free activities page for even more playful STEM ideas.
Your Top Questions About Tides Answered
Even the most brilliant space explorers have questions! Here are answers to some of the most common queries about ocean tides.
Why Are There Two High Tides a Day?
Great question! The Moon’s gravity pulls on the water creating one bulge on the near side of Earth. But it also pulls on the solid Earth itself, leaving water on the far side “behind”—that’s the second bulge. As Earth spins once every 24 hours, most coasts pass through both bulges, giving two high tides and two low tides each day.
Top Tip: Imagine holding a big water balloon. Pull one side towards you and a bulge appears. At the same time, the opposite side stretches out into a second bulge—just like Earth's tidal bulges.
Do Lakes Have Tides?
The Moon’s gravity pulls on all water, even lakes and ponds. But lakes are too small compared with the vast ocean. The tidal effect on them is only a few centimetres, so we can’t see it. You need a massive body of water—like an ocean—for tides you can notice.
How Do Tides Affect Animals?
The area between high and low tide marks is called the intertidal zone—a tough place to live! Animals here have incredible survival tricks:
- Limpets and Barnacles clamp onto rocks to avoid drying out.
- Crabs and Starfish hide in rock pools or under seaweed.
- Wading Birds feast on worms and shellfish uncovered at low tide.
Tides bring fresh food and wash away waste, making the intertidal zone a bustling world full of life.
Why Is It Important to Know About Tides?
Knowing tide times is essential for anyone who works or plays near the sea. Sailors, fishermen and beach visitors all rely on tide predictions for safety. Scientists study ocean tides to understand our seas and predict how coastlines might change over time.
Ready for your next mission? The universe of Space Ranger Fred is packed with more stories, STEM adventures and playful challenges. Grab your copy of the latest Space Ranger Fred book and explore the wider world of cosmic learning!