# Eli5: how does the moon affect low and hightide of the ocean which is pretty heavy but does not cause other things which are lighter to start floating?

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Eli5: how does the moon affect low and hightide of the ocean which is pretty heavy but does not cause other things which are lighter to start floating?

In: Physics

Small object are attracted by moon but the affect is too small so the movement isn’t visible, there isn’t gravitational force between them. However due to the combined mass of water in ocean enough gravitational force is created that can be visible.

That’s why small water bodies like rivers, lakes don’t have tides.

Gravity pulls on all mass the same. A kilogram will experience the same force if it’s the same distance away no matter what it is a part of. A quadrillion kilograms of ocean will therefore feel a quadrillion times the force that a kilogram dumbbell will feel.

The moon pulls ever so slightly harder on one side of Earth than the other. It’s a difference in force of (by my math) something like 0.1%. This tiny difference causes a little bit of tidal force on every atom of Earth. This is slowly causing us to spin less. Since water is free to move, that small amount of force adds up and can move huge amounts of water.

I suppose if you had a few day old party balloon that was nearly neutral you might have some luck getting it to float at the time of a high tide. The effect the moon has is very very small, much less than one percent on measured weight. The reason the tide is observable is there is so stinking much ocean that a tiny fraction of it is still a lot of water.