Phases of Moon and Ocean Tides in Vishnu Puran

'How the phases of Moon affect the Ocean Tides' is described in Vishnu Puran.

Tides are all about gravity. Moon tries to pull everything present on the Earth, but Earth is able to hold everything except water, as water is moving. Everyday there are two high tides and two low tides and ocean is constantly moving from high tide to low tide and then back to high tide. There is time gap of about 12 hours and 25 minutes between two high tides. But the phases of the Moon also affect tides.

When Moon is full or new, high tides are at their highest and low tides are lower than usual. These are called spring tides. These tides occur when the Sun, Moon and Earth all line up.

During the Moon's quarter phases, Sun and Moon are at right angles and thus the bulges cancel each other. As a result, there is smaller difference between high and low tides. These are called neap tide and they occur when the gravtitational forces of Moon and Sun are perpendicular to one other w.r.t the Earth.

The whole description of Spring and Neap tides is given in Vishnu Puran(Book 2, Chapter 4, Verses 90-92).

स्थालीस्थमग्निसंयोगादुद्रेकि सलिलं यथा I

तथेन्दुवृद्धौ सलिलमम्भोघौ मुनिसत्तम II90II

अन्यूनानतिरिक्ताश्च वर्घन्त्यापो ह्वसन्ति च I

उदयास्तमनेष्विन्दोः पक्षयोः शुल्ककृष्णयोः II91II

दशोत्तराणि पञ्चैव ह्याङ्गुलानां शतानि वै I

अपां वृद्धिक्षयौ दृष्टो सामुद्रीणां महामुने II92II

Like water in a caldron, which in consequence of its combination with heat, expands, so the waters of the ocean swell with the increase of the moon. The waters, although really neither more or less, dilate or contract as the moon increase or wanes in the light and dark fortnights. The rise and fall of the waters of the different seas is five hundred and ten inches.