CUTTING EDGE

Tide lines show Moon’s move

Marks left by tides 3.2 billion years ago suggest the Moon was once much closer

The gravitational pull of the Moon hauls up Earth’s oceans into two bulges on opposite sides of the planet. As Earth rotates beneath these twin bulges, sea levels along the coastlines rise and fall, creating the tides. Much of the world’s shores, including around the UK, experience two cycles of high and low tides roughly equal in magnitude every day.

The Sun’s gravity also has an effect on the ocean’s tides, and roughly twice a month (one lunar orbit), when both the Moon and Sun are in line with Earth, their gravitational effects combine to create a much larger range