Gravity and Tidal Action. What We Know.

.First- what is gravity?  We all know it’s the force that holds us to earth, or to whatever other moon or planet we might string theorysomeday visit. But what is it really? It’s a warp in space time. We have more detailed ideas. But we really are not yet positive of all of it’s secrets.

Most illustrations of Earth’s  mass creating a gravity well are very wrong. 

We have all seen several attempts at placing a three dimension representation in a two dimensional surface and what is shown often looks like this:

But this image is incorrect. What if you wanted to go south pole over North Pole? The drawing is missing half of the gravity well. It should really look like a ball inside a bubble (the bubble being the space-time bent around the mass). It’s really more like this:

gravity 1

The same visual mistake often occurs when you see illustrations of black holes or stars or any body with mass placed in a matrix of space time.

All massive bodies have the same affect on space time but to varying degrees depending on their mass. The more mass the more warp.

Our moon and sun both create the same basic local effect.  However, the amount of the warp of space time not only varies with the mass of each body but also with the distance of the bodies from each other. 

It is expressed in Newtons inverse square law here:newton equation

Simply stated Force is equal to the gravitational constant x mass1( let’s use the sun)  x mass2 (lets say the moon) divided by the distance between them squared. 

If we, for simplicity, pretend the gravitational constant to be 1 (instead of 6.674 x 10 to the minus 11th) we would have:  mass1 x mass2 divided by (Their distance x their distance).

The effect is that when you double the distance between bodies their force is not half as much, it is one fourth as much. 

It looks like this:


The strength of gravity gets weaker just the same as the brightness of a beam of light. Double the distance and the beam is spread over greater area and is one fourth as bright.

So now we move on to how the moon and sun pull up a small bulge from the ocean and cause tides. Their weakened gravity reaches us but still has an impact. 


Actually all of earth or any planet or body is to some degree mis-shapened by tidal forces. The moon is also affected by the earth. 

Water, being fluid, is simply able to move more readily than something solid, and its movement is thus visibly apparent. 

Our tides are created by a combination of external effects of gravity and earths rotation.  The moon and earth try to pull each other closer.   Earth holds on to all of us, but water is more difficult to hold in place, especially for that patch directly between the earth and the moon.   As earth rotates and the moon moves in its orbit around the earth, to a limited degree so does the heights of the oceans.  There is also a bulge on the opposite side caused from earth being pulled away slightly from the less affected water, also partly created from centripetal force.

Also realize that when the moon is in a new moon phases (between us and the sun) the effects of both masses affect the strength to amplify the pull, and when the moon is full it works the same way. This is termed a spring tide (nothing to do with the season). 

When the moon is at first or last quarter it is pulling in a different direction (sideways) from the sun.  You get a smaller tide referred to as a neap tide.

A more detailed explanation can be found here.

And an excellent moving illustration here about a third of the way down the page:

So imagine if you will, mass created curved lines in space time being impacted by other curved lines in space time from moving objects, constantly dynamic and changing.  

This is the stuff of general relativity, employing an X, Y, and Z axis, as in a clear cube with lines up, down, and sideways in 90 degree directions, and how a moving mass changes its position in T, time, the subject of another article I am still trying to simplify. 

I hope you better understand tides, and we’d love to hear from you with any thoughts, corrections, or ideas.

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