Mechanics

# Tides

Tides are ocean movements that occur thanks to the gravitational pull of the Sun and Moon on the water of the seas.

Tides are oceanic movements that occur periodically, characterized by the rise and fall of the water level. This phenomenon occurs due to the gravitational attraction exerted by the Moon and the Sun on the sea. According to the Law of Universal Gravitation, the gravitational force exerted by a body of mass m 1 on another body of mass m 2, which are separated by a distance d, is given by:

g = G m 1 .m
d 2

Where G is the constant of universal gravitation.

According to this equation, we see that the greater the masses and the smaller the distances, the greater the gravitational force. Although the Sun is much more massive than the Moon, the Moon’s gravitational pull outweighs that of the Sun because the distance between the Moon and Earth is much smaller. Look at the figure below:Tides occur in regions close to the Sun or Moon

The image shows how the gravitational force is acting on the water. High tides occur in regions that are closer to the Sun and Moon, while in other regions low tides occur.

When sea water is closer to the Moon, the former is attracted to it with a greater force than at other points. Meanwhile, on the opposite part of the Earth, water tends to move away. Consequently, at the intermediate points, the sea level drops and low tide occurs.

Each of the tides happens twice at every point on the planet. When the Sun, Earth and Moon align, gravitational forces overlap and tides are much higher.