How the Moon Affects the Tides

We know that our Earth and the moon are gravitationally tied, but how does the moon affect the tides?

The Earth is much bigger and heavier than the Moon, and the Moon orbits us in a circular path.

Our celestial neighbor takes 27.3 days to complete its orbit but along the way, its effects are felt here on Earth.

Tides on Earth

Tidal Variations – The Influence of Position and Distance (National Ocean Service)

How The Moon Affects the Tides

Tides are the rise and fall of ocean water that happen regularly along coastlines. The main reason for this is the gravitational pull of the moon on Earth.

You can think of the moon as a giant magnet with a strong pulling force, tugging at the water in the oceans. Imagine an invisible hand drawing the water towards it.

This creates a “bulge” of water on the side of the Earth that’s facing the moon.

So, on the side of the Earth where the moon is, there’s a high tide because the water is being pulled toward the moon.

Tidal Bulge

As the Earth rotates around its axis, the tidal force causes two bulges of water to form on opposite sides of the planet. One tidal bulge is facing the Moon, and the other is on the opposite side of the Earth.

On the opposite side of the Earth, there’s another high tide because the Earth and moon both spin around a center point.

This spinning creates a force called centrifugal force, which pushes the water away from that center point.

This results in another bulge of water on the opposite side of the Earth from the moon, creating a high tide on that side, too.

In between the two high tides, there are two low tides. These happen because the water is being pulled away from the high tide areas toward the bulges.

This gravitational pull is how the moon affects the tides. The sun also plays a part in tides, but not as much as the moon.

Video Resource: Why Do We Have Tides? (BBC)

How Does the Full Moon Affect the Tides?

When the sun and the moon are in line with each other (during a full moon or new moon), their combined gravitational pull creates even higher high tides, which we call spring tides.

When the sun and the moon are at right angles to each other (during the first quarter and third quarter moon phases), their gravitational forces partly cancel each other out, resulting in lower high tides, which we call neap tides.

This is how the moon’s gravity mainly affects the tides we see on Earth.

It’s like a tug of war between the moon’s pull and the centrifugal force due to the Earth and moon dancing around each other.


  • The moon’s gravitational pull causes the oceans to bulge on the side facing the moon and on the opposite side, creating two tidal bulges.
  • This pull creates high tides on the side of the Earth facing the moon and also on the opposite side, resulting in two high tides and two low tides each day.
  • The combined influence of the moon’s gravity and the Earth’s rotation leads to the regular pattern of tides.
  • The sun also plays a role in tides, with its gravitational pull contributing to higher spring tides and lower neap tides during specific moon phases.
  • The specific timing and height of tides are influenced by things like coastline shape, ocean depth, and local geography.

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