A tide is a periodic change in ocean level driven mainly by the differential gravitational forces of the Moon and Sun, together with the Earth's rotation. Their tidal forces act across the extended planet; a uniform acceleration shared by the whole Earth does not by itself generate a tide. Ocean-basin resonance and coastal geometry modify the local response.
A spring tide has an enhanced high-to-low tidal range because the Moon and Sun are approximately aligned as seen from the Earth, so their principal tidal contributions reinforce. Such alignments occur twice in a lunar phase cycle.
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Tide can refer to several different things, depending on the context: 1. **Oceanography**: Tide refers to the regular rise and fall of sea levels caused by the gravitational forces exerted by the Moon and the Sun, combined with the Earth's rotation. Tides are typically observed in cycles of approximately 12 hours and can significantly influence coastal ecosystems and activities. 2. **Laundry Detergent**: Tide is a brand of laundry detergent produced by Procter & Gamble.