Many people get it wrong about the reason for gravity of moon and sun responsible for tides. Now, let me ask you something, why don’t we see tides in a lake? And why don’t we see sand and rocks levitate, Due to the Gravity of moon and sun?

Let’s see what actually cause tides. When you are in an accelerating bus( technically in an accelerating frame or non-inertial frame), what ever may be the mass of the object, they  experience force while bus turns, in a direction opposite to the turn. This force is similar to the Tidal force experienced by earth.

Here, what ever may be the mass of the object on earth, they should move out of the surface of earth. But that’s not happening here, all the objects aren’t moving out. The tidal force isn’t acting only on the moon-earth line, because if that was the case ( tidal force acting along the moon earth line), we should see the lakes, ponds, rocks, you and me raising, but we aren’t. And the tidal acceleration due to the gravity of moon along the earth moon line is 1/10,000,000th gravity of earth, so it is not possible for this tiny force to lift something on earth. But that tides are real here!!!!

Then, what is really causing tides???

Until now, we only have considered forces on the earth-moon line. Now consider the forces acting on some other points on earth, the resultant of the forces at that point, i.e., the TIDAL force at that point is observed to be radially downward. By mapping the direction of tidal force at various points on earth, it looks something like the image down below. With the image below, it is clear that, this force is not lifting or stretching but getting SQUEEZED.

2000px-Field_tidal.svg

From an unknown source on the internet, I have read that this phenomenon is similar to that of squeezing a pimple;);) So true.. This makes it easy to answer my above question “Why do lakes don’t have tides?”. Well… You got it, they are like small pimples, hard to blast:);). They have a smaller surface area and have tiny microscopic tides, which can’t be seen. By the way, the similar is the case with sun. The Sun is very far from earth yet with a huge mass. So,according to the position of the sun, earth and moon the bigger and smaller tides are formed!

Let me know, what you think!

Published by Abhijit

13 thoughts on “Misconceptions about tides! What really causes tides?”

  11. This is a very important post. Most people think the gravity of the moon is the sole reason….but it depends on numerous factors.

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  12. I have argued this point for decades…especially in college. My instructor actually (after class) agreed with me. It can’t be possible for the Moon to be causing the tides. Now, there may be a correlation of data with where the moon is when the tides occur, but that just happens to be a correlation. Not a CAUSE. Many things have been theorized to occur over the course of history – the earth is FLAT – for example. But to be proven false in later eons. The same will, of course, be with the tides. It is not the gravitational presence of the moon that CAUSES the tides… it’s simply that the moon phases (shadow of the sun and position of its orbit) are in direct correlation with the fluid state of the oceans.

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