Como funciona a influência da Lua nas marés

You may have heard that the moon is what causes the tides. But do you know how that happens? The phenomenon of tides is caused by the movement of the moon and the Earth around a common center of mass.

Tthe water from the oceans is maintained on the surface of the planet by the force of gravity. The gravitational force of the moon, which is about 15% that of the Earth affects the surface of the Earth, attracting objects to its gravitational center. The oceans are a fluid body which is deformed by the lunar gravity.

But each point on the Earth is affected by gravity with different forces. The points which are closer to the moon are displaced towards it forming bulbs in the oceans. And the movement of the Earth around the center of mass of the Earth/Moon system generates a centripetal force around this point, resulting in bulbs on the opposite side .

The bulbs are the result of the accumulation of water attracted towards the lunar center of gravity. These are the high tides, which occur on both sides of the planet. As the earth rotates, the tides vary, generating two low tides and two high tides per day.

But the sun also participates in the phenomenon. Despite being much more massive than the moon, its influence is almost half that of the lunar influence, because of the great distance. When the sun and the moon are aligned, their gravitational forces add up.

The phenomenon is called spring tide, and is more intense than the usual one. High tides become higher, and low tides become lower. But when a right angle is formed between the moon and the sun, the effect is the opposite.

And the difference between the tide and low tide becomes smaller.