What causes tides?
Tides are caused by the effects of gravity in the earth-moon-sun system, and the movement of those three bodies within the system. If you imagine that the earth is completely covered in water, there are two bulges of water – one towards the moon and another on the opposite side (see question 4). The rise and fall in sea-level is caused by the earth rotating on its axis underneath these bulges of water. There are two tides a day because it passes under two bulges for each rotation (24 hours) (see question 7). This is called the lunar tide. Two bulges of water are also caused by the sun, called the solar tide – and these can either reinforce or partially cancel out the lunar tide to give spring and neap tides (see question 8).
Tides are periodic fluctuations (rising and falling) of sea water. Tides are caused from the gravitational attractions between the Earth, sun, and moon. Both the moon and sun have gravity, but because the moon is closer to Earth its gravity has a greater effect on the water (which is moveable) on whatever side of the Earth the moon is on. When the Earth, moon, and sun are positioned in a straight line the gravitational pull on the Earth is greater. But when the moon and the sun are at right angles to the Earth their gravitational pull is decreased. This gravitational pull on the water is what creates the tides.
Tides are created because the Earth and the moon are attracted to each other, just like magnets are attracted to each other. The moon tries to pull at anything on the Earth to bring it closer. But, the Earth is able to hold onto everything except the water. Since the water is always moving, the Earth cannot hold onto it, and the moon is able to pull at it. Each day, there are two high tides and two low tides. The ocean is constantly moving from high tide to low tide, and then back to high tide. There is about 12 hours and 25 minutes between the two high tides. Tides are the periodic rise and falling of large bodies of water. Winds and currents move the surface water causing waves. The gravitational attraction of the moon causes the oceans to bulge out in the direction of the moon. Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side). Ocean levels fluctuate daily as the sun, moon and earth interact. As
Tides are caused by the effects of gravity in the earth-moon-sun system, and the movement of those three bodies within the system. If you imagine that the earth is completely covered in water, there are two bulges of water – one towards the moon and another on the opposite side (see question 4). The rise and fall in sea-level is caused by the earth rotating on its axis underneath these bulges of water. There are two tides a day because it passes under two bulges for each rotation (24 hours) (see question 7). This is called the lunar tide. Two bulges of water are also caused by the sun, called the solar tide – and these can either reinforce or partially cancel out the lunar tide to give spring and neap tides (see question 8). 4. If gravity is always pulling towards the moon, what causes the bulge on the opposite side of the earth? Most people think the moon rotates round the earth. In reality, the earth and the moon rotate about a common centre just inside the earth’s surface (indicated
