Earth & Space
Why do tides rise and fall?
Two pictures of the same coast show different amounts of water.
The short answer
The Moon's pull differs across Earth, and the Sun contributes too. This creates tides. As Earth rotates, many coasts experience rising and falling water. Coast shape affects the pattern.
An imagined Wusel scene
Puschel and Flauschi investigate
From the protected promenade they look at the distant coast. Flauschi puts down a picture. Flauschi“The water level was higher here.”
Puschel compares the picture and view. Puschel“Has the sea taken a break?”
Flauschi“It has not gone away. At many coasts the water rises and falls with tides. The Moon and Sun help cause them.”
Puschel stays behind the rail. Puschel“Then we will not look for the water out on the mudflats.” Flauschi“Exactly. That can become dangerous quickly.”
They keep comparing the views. What looks calm from far away is not necessarily a safe walking route. Their coast question fits at the table too.
Little Wusel quiz
What is the ebb tide?
Choose one answer: a), b).
- a)The water level falling.
- b)The local water level rises.
Show answer
Correct answer: a): The water level falling. The ebb tide is the falling water level.
Are high-tide times the same at every coast?
Choose one answer: a), b).
- a)Yes.
- b)No, they differ between places.
Show answer
Correct answer: b): No, they differ between places. No. Coast shape and sea depth affect tides.
Word help
- tides
- The regular rise and fall of seawater caused by the interplay of gravity and motion.
Explore in more detail
Here you will find longer explanations and further details. You can explore them together.
Understand step by step
How it works – simply explained
Lunar attraction varies
The Moon pulls more strongly on nearer parts of Earth than more distant parts. These differences matter for tides.
Water levels change
Earth and oceans respond to those differences; the Sun contributes too. Rising water is flood tide, falling water ebb tide. Water is not switched off.
Coasts make a difference
Basin shape, depth and other influences change local times and heights. A simple diagram explains the idea but cannot predict a safe tidal-flat walk.
Why there is an effect on the far side too
The Moon pulls the near side more strongly than Earth’s centre and the far side less strongly. Relative to the centre these differences stretch both sides outwards. A simplified model has two water bulges as Earth rotates beneath them. Continents interrupt real oceans, so local water does not follow this model everywhere. Coastal visits require local safety guidance and adults knowing tide times.
The key points again
Discovery 1
Sea level rises and falls regularly at many coasts. Rising water is the flood tide; falling water is the ebb tide. High and low tide are the highest and lowest water levels.
Source: [3]
Discovery 2
Differences in the Moon’s pull on different parts of Earth are an important cause. The Sun also contributes. This attraction is called gravity.
Source: [1]
Discovery 3
Coast shape and sea depth affect local tides. Times and heights are not the same everywhere; the water does not simply disappear.
Source: [2]