Q1. What are solid Earth tides and ocean tides?
A： The Earth can be regarded as a solid body that deforms periodically under the gravitational pull of the Sun and Moon. Although the Sun is more massive, the Moon is much closer, so its tidal force is about 2.25 times stronger than the Sun's. As the relative positions of the Sun and Moon change, the shape of the Earth changes accordingly—this is the solid Earth tide. The familiar daily rise and fall of the sea is also driven by the Sun and Moon, hence ocean tides vary with their positions.
