Why are there high and low tides on earth?

Answer 1

This one had me for years. Start by assigning some simple values to the gravity of the moon on certain places around the earth. Assume that the pull of the moons gravity when directly above say England is at level 10. That causes a lump of water on that side of the ocean. You may remember that the pull of gravity decreases with the square of the distance, so while there is a significantly less force( lets say a 9) pulling at the water 8,000 miles away on the other side of the world, the ocean literally floats a bit higher there. Of course on the sides we see a low tide. There is a whole plethora of physics to explain why the 2 high tides are about equal, but that's basically the reason for the two.

Answer 2

Tidal forces are caused by the differential pull of gravity on a planetary body or moon.

Consider the Earth-moon system. The Earth and moon are orbiting around their common center of mass, which is a point that lies somewhere inside the Earth since the Earth is so much more massive than the moon. So since we are in orbit around this center of gravity, we don't feel the moon's gravitational force, much like how astronauts in orbit don't feel the gravitational force of the Earth, even though it is pulling on them all the same.

However, because the Earth is a large body, the pull of the moon is stronger on the side of the earth facing the moon and weaker on the opposing side. The pull of the moon at the center of the Earth falls in the middle. The effect of this differential pull is that the water on the near side wants to pull away from the Earth, and the Earth wants to pull away from the water on the far side. This net effect is a force that tends to stretch the earth and oceans, creates two tidal bulges, hence two high tides per day and two tides per day. The water of course is much more deformable than the Earth itself, so it is the oceans we see forming the tidal bulges. Low tide occurs at the location on the earth at right angles to the Earth - moon line, and high tide occurs along the Earth-moon line.

For more information on this, please see the link below:

• http://www.badastronomy.com/bad/misc/tides.html
• http://www.jal.cc.il.us/~mikolajsawicki/Tides_new2.pdf

Answer 3

Tidal forces are caused by the differential pull of gravity on a planetary body or moon.

Consider the Earth-moon system. The Earth and moon are orbiting around their common center of mass, which is a point that lies somewhere inside the Earth since the Earth is so much more massive than the moon. So since we are in orbit around this center of gravity, we don't feel the moon's gravitational force, much like how astronauts in orbit don't feel the gravitational force of the Earth, even though it is pulling on them all the same.
However, because the Earth is a large body, the pull of the moon is stronger on the side of the earth facing the moon and weaker on the opposing side. The pull of the moon at the center of the Earth falls in the middle. The effect of this differential pull is that the water on the near side wants to pull away from the Earth, and the Earth wants to pull away from the water on the far side. This net effect is a force that tends to stretch the earth and oceans, creates two tidal bulges, hence two high tides per day and two tides per day. The water of course is much more deformable than the Earth itself, so it is the oceans we see forming the tidal bulges. Low tide occurs at the location on the earth at right angles to the Earth - moon line, and high tide occurs along the Earth-moon line.

For more information on this, please see the link below:

• http:/www.badastronomy.com/bad/misc/tides.html
• http://www.jal.cc.il.us/~mikolajsawicki/Tides_new2.pdf

Answer 4

There are high and low tides on Earth due to changes in the moons tilt on its axis.