Tidal Force
Definition
The stretching force from gravity being stronger on one side of a body than the other — what raises ocean tides and can shred moons apart.
Technical definition
Tidal acceleration ≈ 2GMr/d³ across a body of radius r at distance d. It falls as 1/d³, faster than gravity's 1/d², so it dominates at close range.
Example
The Moon raises ~0.5 m ocean tides on Earth, while Jupiter's tides squeeze Io so violently it is the most volcanic body in the solar system.
Common confusion
Tides are not caused by the Moon simply 'pulling the water up' — they come from the DIFFERENCE in pull across Earth's diameter, which is why there are two high tides a day, not one.