EarthTides
Science
The Earth's tides are caused by the moon's gravitational force, pulling on the earth and its oceans, with different strengths.
Tides are caused by the moon's gravitational force, pulling on the earth and its oceans, with different strengths. The pull on the near side ocean is the strongest because it's the closest. So it moves most towards the moon. The earth also moves towards the moon, but not so much as its further away. Finally, the far side ocean moves towards the moon least because its farthest from the moon. These movements due to gravity create two high tides and two low tides as the earth rotates through 24 hours. But there's a big object that's missing from our diagram.
If we back up, we can also see the sun and how it lights up both the earth and the moon into the day and night sides. We'll turn off the stars to make it clearer. When the moon is right in front of the sun, it's invisible to us because we can only see its dark night side. This is the new moon position. You can see that each day corresponds to one earth rotation. In just over 7 days, that is 7 earth rotations. The moon orbits around the earth to its first quarter position, where we can see half its day and half its night side. After another 7 days or so, the moon orbits to the opposite side of the earth to the sun, and we can see its full day side. This is the full moon. Then it continues onto the third quarter.
Before returning to the new moon position to start all over again. Does the sun also pull on the oceans and make them bulge like the moon does. Yes, everything causes gravity, and the more mass of the object, the stronger it is. But this diagram isn't a scale and the sun's much further away than the moon, reducing its tidal effect to about half that of the moons. But this is important when the sun and moon line up so that gravitational attractions combine to make super tides. This happens at the new moon making the high tides higher and the low tides lower. This extreme tide is called a spring tide. But when the moon goes into the first quarter, the gravity is pull in different directions. And the sun actually takes away from the moon's tidal effect.
The high tides are not so high and the low tides are not so low this more moderate tide is called a neap tide. At the full moon, the moon and sun's gravity's line up again, so we get another spring tide. At the third quarter, the gravity are out of whack again, so we get another neck tide. Thin back at the new moon position, the moon's gravity combines with the suns to start over again with another spring tide. Each month the earth spins almost 30 times, so we get nearly 60 high tides and 60 low tides of these two spring tides and two and neap tides.