We will discuss here about the high tide and low tide and their occurrence.
Sir Isaac Newton discovered that every object of the Universe attracts other objects. He termed this phenomenon as gravitation. Due to this gravitational attraction of the Moon and to a lesser extent of the Sun, the water of oceans and seas on the Earth alternately rises and falls. This is called tide. The rise of water level is called high tide and its fall is called low tide. In 24 hours two sets of high and low tides occur at the same place.
The Moon is existing close to the Earth. So the Moon and the Earth both exert strong gravitational pull towards each other. In this situation solid objects remain fixed at their position, but the water of oceans and seas rises in the direction of the Moon. This is called primary high tide. The water, just at opposite to the primary high tide zone i.e., at the other side of the Earth, also rises a little. It is called secondary high tide. Due to the direct attraction from the Moon primary high tide rises higher than the secondary high tide. As a result of these two high tides at two opposite sides of the Earth, the water level of the oceans falls sharply at other parts of it. This is called low tide.
What is spring tide?
During full moon or new moon, when the Earth, the Sun and the Moon stay in a straight line, the gravitational attractions of both the Sun and the Moon combine. At that time the high tides rise very high and low tides fall very low. This phenomenon is called spring tide.
What is neap tide?
During quarter moon phases, the position of the Sun and the Moon form a right angle with the Earth. So the force of attraction of the Sun reduces the effect of the Moon’s gravity. As a result the difference between high tide and low tide becomes very little. This tide is called neap tide.