The Moon’s gravity produces the strongest tide-generating force, the Sun modifies it, and Earth’s rotating ocean basins determine when and how high local tides arrive. Tides are not simply water being pulled straight toward the Moon.
Three things to know
- Primary driver
- The Moon
- Its differential gravity is stronger for tides than the more distant Sun’s.
- Spring tides
- Aligned
- New and full moons reinforce lunar and solar tide-generating forces.
- Local pattern
- Basin-shaped
- Coasts, depth and resonance determine one, two or mixed cycles per day.
A planet-scale wave
Tides arise from differences in gravitational pull across Earth and from the motion of the Earth–Moon system. The resulting disturbances travel through real ocean basins. Continents interrupt them, friction slows them and shallow water amplifies or redirects them.
Why there are often two highs
A simplified equilibrium model produces bulges on the side facing the Moon and the opposite side. Real high tides do not sit obediently beneath those bulges. They rotate around amphidromic systems and arrive according to the response of each basin, estuary and coast.
Spring and neap
When the Sun, Moon and Earth line up, their tide-generating effects combine and the tidal range tends to increase: a spring tide. Near the first and third quarter moon, the effects partially oppose and the range tends to shrink: a neap tide. Weather can still raise or lower the observed water level.
What people usually ask
Does the Moon pull on lakes too?
Yes, but the response is usually much smaller and can be overwhelmed by wind and atmospheric-pressure changes.
Are spring tides related to the season spring?
No. The name refers to the water ‘springing’ higher and lower; they occur throughout the year.
Here’s where the answer came from
Open the original government science or research-institution source behind this page.