Question

The gravitational attraction of both the moon and the sun have an effect on tides. Which body imposes the largest gravitational force on the earth, the moon or the sun? Which body has the largest effect on tides? Explain, briefly.

Answer 1

Tides are the rise and fall in the sea levels caused by the gravitation of moon and sun (combined)

The sun is larger in mass and more distant in comparison to the moon. If we use the inverse square law, we can realize easily that the the attractive force due to the Sun is far more greater than that caused by the moon.

But the moon actually is a more significant contributor for tides in comparison to sun.

This is mainly because of the fact that the close object has a greater tidal influence because the inverse square law drop in gravitational force gives a larger ratio of the force on near side of the object to that on the farther side.

Tidal ratio is the ratio between force on near side to the farther side.

So tides are manly caused by the difference in the gravity field across the earth. the earth's diameter is a very or insignificant fraction of the sun-earth distance which makes the gravity field change by a very small factor. Sun's tidal influence is nearly half of what is created by moon.