To my understanding, the tides and waves on Earth's oceans are caused by various factors such as the moon's gravity, the water cycle (rains, storms, evaporation), Earth's rotation, etc. Although the moon's impact on tides isn't as big as I thought it was, it still affects Earth's oceans. What I want to know is which factors are the ones that influence tides and waves the most. And how exactly is each factor's influence, individually. To do this, I'll ask 3 different questions:

  1. How would tides and waves on earth be different if we didn't have a sun (no evaporation/rain) but we would still have the moon and earth's rotation?
  2. How would tides and waves on earth be different if we didn't have a moon but we would still have the sun and earth's rotation?
  3. How would tides and waves on earth be different if the earth wouldn't rotate but we would still have the moon and the sun?

1 Answer 1


You miss the main factor: Moon/Sun are the triggers, but tidal wave is at first the mechanical response of the water body constrained by the topography of the floor and coasts. That's why some regions in the world can have huge tides, and some others have 1 or 3 high tide a day instead of 2. Sort of vibrating modes.

I don't see how evaporation and rain could have any influence. Meteorology is just an additional factor to the sea level (low pressure, or wind blowing towards the coast).

Earth rotation would only induce a small deviation in the direction of the tide via the Coriolis effect. But beside, earth rotation is the first factor (making the moon appareantly rotate daily around the earth, while it's period is 28 days).

Moon rotation is unimportant (but by the slow change of tide hour) since 30 times slower than earth.

Sun effect is just another tidial trigger superimposed, half weaker, so sufficient for that there is some difference between acting in the same or opposite direction than the Moon tide.

So, no earth rotation would be the maximal effect. (30 time slower tides, probably little coastal amplification factor). The no moon, since it would let only sun: very similar tides, just weaker. No sun would just let the average tides with no modulations.

Beside, I guess you know that the trigger effect is not only at Earth point closest to Moon, but also at the opposite ? (Since tidial effect is squeezing Earth as an ellipse. It's the spatial derivative of attraction, not the attraction).


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