How do the moon’s phases influence the tide on Earth?
In: Physics
The moon’s phases don’t influence the tide. They just tell us where the moon is relative to the sun. Since the tides are based on the location of the moon, the phase of the moon tells us where the tides will be relative to the sun.
During the time of a full moon or a new moon, the tides will be the highest high and the lowest low of the month. This is called a “spring tide” (it has nothing to do with the season of spring). During the time of a quarter moon, the high tide will be the least high and the low tide will be the least low. These are called “neap tides”.
The reason for this is: the moon pulls water towards it due to gravity. The sun also does this but the effect is much smaller. But during a full moon, the sun and moon are on the same side, both using gravity to pull the earth in the same direction. When it’s a quarter moon, the sun and moon are pulling in contrasting directions and so the gravitational effect is muted.
That makes a lot of sense now that it’s been explained! Thank you for taking the time to do so, everyone. The visual aid also helped quite a bit.
Most of the tides are due to the moon, but about a third of the tides are due to the sun. At full moon and new moon the tides from both the sun and the moon are working together and so they’re more extreme. These are called “spring” tides (no relation to the season of the same name). When the tides from the sun and the moon are not working together, as at first and last quarter, the tides are less extreme. These are called “neap” tides.
The phases of the moon are linked to the way the sun and moon are aligned in the sky. If the sun and moon are in the opposite parts of the sky then we see the side of the moon that’s fully lit by the sun: full moon. If the sun and the moon are close together in the sky then we see the side of the moon that’s unlit by the sun: new moon. In both of these two cases, the sun, earth and moon are roughly in a line and the tidal forces add.
Very roughly, there’s a high tide on the part of the earth that’s nearest the moon as well as on the part of the earth that’s farthest from the moon. That’s why most places have two tides on most days, and why the sun and moon are working together when they’re on opposite sides of the sky.
Tides happen because the moon is pulling the water closest to it more than it’s pulling the earth, and it’s pulling the earth more than it’s pulling the water furthest from it.
The phases of the moon are just a neat way the moon’s location relative to the sun and the earth affects how much light hits it.
The two don’t interact at all, but the phases tell you where the moon is, which *does* affect the tides.
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