# Sun and tides

1. Dec 13, 2004

Why isn't there a more pronounced effect from the Sun on tides? The distance from the Earth to the Sun seems negligible considering the mass of the Sun.

While typing this out and thinking about it, the most reasonable explanation I can come up with is that the Sun has so much mass that the effects from the gravity are somehow equalized on all parts of the Earth.

Am I close?

RR

2. Dec 13, 2004

### matt.o

the tidal effect is caused by the difference in the gravitational potential on different sides of the planet. this difference is caused by the diameter of the earth and the fact that gravity is a r^-2 law ie the side farthest from the sun feels less gravitational pull compared to the side closest to the sun. now since the diameter of the earth is negligible when compared to the distance to the sun, i assume the tidal effect is also negligible.

3. Dec 13, 2004

### Janus

Staff Emeritus
Tidal forces vary directly with the mass and inversely to the cube of the distance. The fact that the Sun is about 27,000,000 times the mass of the moon is counterbalanced by the fact that it is about 400 times as far. 400 cubed is 64,000,000,000, which shows why the Sun's tidal effect is a little less than 1/2 that of the Moon's

4. Dec 13, 2004