Last month, coastlines saw extreme high and low tides known as king tides, which are caused by a chance alignment of the moon, Earth, and the sun. Now the tides are back.

Depending on geography and weather, king tides can lead to coastal flooding. For example, the northeast coast of Australia is now bracing for a cyclone that's expected to make landfall on Friday. The fact that the storm coincides with a king tide is anticipated to cause sea levels to rise by more than 13 feet.

But what causes king tides in the first place?

All tides happen due to the gravitational pull of the moon and, to a lesser extent, the sun. Because gravity is stronger at shorter distances, the