2.4: Effect Of Sun And Moon On Tides
1. Gravitational pull of Sun is greater than Moon’s.
2. However, the Sun is much further away than Moon.
3. Where tides are concerned, the difference of the gravitational pull at the centre of the Earth and the point directly under the Sun is what matters.
4. Thus, solar tides are less powerful as compared to lunar ones.
At new or full moon, the Sun and the Moon will be pulling in the same direction, or in exactly opposite directions, and will produce strong tides known as spring tides. The much lower neap tides occur when the Moon is at first or last Quarter, as its gravitational pull works against that of the sun.
Fig 18: Spring and Neap Tides I
Figure 19: Spring and Neap Tides II
On top of these, the centrifugal force produced as the Earth revolves around the Sun tends to project force in the opposite direction as that of the Moon’s gravitational pull. (The centrifugal force resulting from the Earth’s rotation on its own axis plays no part in the tides). This will strengthen the second high tide, which occurs on the side away from the Moon
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