Wednesday 9 March 2016

117) “Newton also theorized and it is now commonly taught that the Earth’s ocean tides are caused by gravitational lunar attraction. If the Moon is only 2,160 miles in diameter and the Earth 8,000 miles, however, using their own math and “law,” it follows that the Earth is 87 times more massive and therefore the larger object should attract the smaller to it, and not the other way around.”

Let’s pause there, Mr Dubay, because there’s a big misunderstanding. 

Both the earth and the moon attract each another, but because the moon only has about 1.2% as much mass as the Earth, it has correspondingly much less gravitational effect. But like all bodies, the moon does attract the Earth, too, in proportion to its mass.

And of course, gravity declines in proportion to the square of the distance between the objects. Since the oceans are much closer to the Earth than to the moon, that exaggerates the difference further.

You go on :“If the Earth’s greater gravity is what keeps the Moon in orbit, it is impossible for the Moon’s lesser gravity to supersede the Earth’s gravity, especially at Earth’s sea-level, where its gravitational attraction would even further out-trump the Moon’s. And if the Moon’s gravity truly did supersede the Earth’s causing the tides to be drawn towards it, there should be nothing to stop them from continuing onwards and upwards towards their great attractor".
And indeed it does not “supersede” the Earth’s gravity. The much greater gravity of the earth does indeed stop the seas from being drawn up into the sky. Not surpsising, since the mass of the Earth is more than 83 times that of the moon, and th moon ios much further from th oceans than the Ewarth is. But that doesn’t mean that the moon’s gravity can’t have any effect at all. It isn’t and all-or-nothing, winner-takes-all game.

For any one given cube of sea water, there is a lot of earth gravity pulling it downwards, and a little Moon gravity pulling it upwards. How do we work out what will happen? Subtract the moon gravity from the Earth gravity. Notice that this doesn’t mean that the Moon’s gravity has no effect on the water, just that it is a small effect – enough to raise the water a few feet, but not nearly enough to pull it up into the air, against the much greater attraction of the Earth.

You may not want to admit that this is what happens, but you have to agree that it is at least consistent in its own terms. And expecting the seas to leap in the air would be completely inconsistent with our knowledge of gravity.

Incomprehension of the model

If you want to disprove Newton, you first have to cite him correctly. He doesn't say that "the larger object should attract the smaller to it and not the other way around ". His third law of motion clearly states:

"When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body."'s_laws_of_motion

Therefore, the earth pulls the moon and the moon pulls the earth. And inertia is the key factor why the moon can be held in an orbit around the earth, while the earth doesn't experience much more of a wobble than the changing tides of the oceans.

 Passing mathematics isn't mandatory.

Apparently, because this guy sure did not. Gravity depends on distance and on masses. And, surprisingly, mass doesn't include only volume. To illustrate that point, there's the old question; what's more massive, a kg of feathers or a kg of lead? Well, both  are a kg, so they are equally massive. Which one's got more volume? The feathers, of course. 

The difference in distance between the two opposing sites of the earth is two times the earth's radius. The force of gravity is inversely proportional to the distance squared; there is thus a difference between the force acting on water on the far side and water on the near side of the moon. As a result, water flows.

The theory of tides is slightly more complicated than that, where this looks like a neat explanation. Read it if you wish.

The question you must ask yourself is this. Place a marble and a football so that their equators lie in a plane. What is the distance from the equator of the marble to the centre of the football? Is the distance from the top of the marble larger than that from the equator? The distance between the centres shall be called 
L. If the marble has size x, then the distance between equators is simply Lx. However, the distance from the top is a horizontal L and a vertical x, so Pythagoras' theorem tells us that this distance is L2+x2−−−−−−√. As you might imagine, these distances differ. 
Which mean the forces differ.

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