The effect of gravity of earths moon?

Question

I went fishing the other day got bored and started musing.In certain cycles the moon causes the sea to rise due to the pull of it's gravity. I suppose that all things on earth would be pulled by this same force therefore weighing less during this same cycle.. Here's my plan---buy several tons of gold at high tide and sell at low tide when it would be heavier. Any of you potential investors see fault with this? I think I might start going to the meat market at high tide also.

Answer 1

Beware of misinformed answerers.
The tides are not related to the moon's elliptical orbit (which is only very slightly elliptical; it's practically a circle). And things do NOT weigh much less on Mount Everest; they weight SLIGHTLY less (roughly a third of a percent less). But not much gold trading is done on Mt. Everest, so that doesn'thelp your get-rich-quick scheme.

The tides are not affected by how hard the moon is pulling on the water directly under it. (Clearly, it isn't pulling hard enough to overcome the earth's gravity and lift the water straight up.) Instead, the tides are caused by the DIFFERENCE in the moon's gravitational pull on water at different locations on the earth's surface. Specifically, these differences cause the water that is halfway between the nearest and farthest points on earth (from the moon's perspective) to flow ACROSS the earth's surface, either toward the near side or toward the far side, resulting in "bulges" in these two diametrically opposite locations, both of which experience high tide simultaneously.

And how great would the moon's gravitational force be on the gold that you are buying and selling? Well, the moon's mass is about 1/100th of the earth's mass. And the distance from the gold being weighted to the moon is about 60 times the distance to the earth's center (240,000 miles vs. 4,000)

Since the force of gravity is proportional to the body's mass, and inversely proportional to the SQUARE of the body's distance from the object, the moon's gravity would generate (1/100) / (60^2) times as much force as earth's gravity on the gold. Thus it is approximately 1/360,000th as strong as earth's gravity.

If you bought $360,000 worth of gold, waited till the moon moved to where it would have the most favorable effect, and then sold the gold, you should gain about 1/360,000th of the amount bought and sold. In other words, you'd make one dollar. That would hardly justify your time, effort, and expense

Answer 2

The moon revolves around the Earth once every 28 days (number rounded off slightly), AND, it also rotates around it's axis in 28 days. Which is why the same side always faces the Earth.

A common misconception among people is "gravity free" space. There is no such thing. Gravity is in EVERY square inch of the universe. We sometimes hear the astronauts talk about "Zero-G", but that is just a term we use in the profession. There is no such thing as Zero Gravity. Its microgravity. Folks don't actually "float", as they are actually being "pulled" around the Earth by ot's Gravity, or by the Moon's gravity.

Apollo 8 was the first manned craft to leave the Earth's gravity, and when it did, it was then being "pulled upon" by the Moons Gravity. That's also why in Apollo 13 (watch the movie), the NASA folks decide to keep the craft going, to be pulled in by the Moons gravity, which then would "slingshot" it around the Moon and back to earth.

Answer 3

Lunar phases do not affect how high the tides are, or how heavy the gold is. What does is how near or far the Moon is. Since the Moon is on an elliptical orbit (not a circular one), it is nearer at some point (again, not depending on phase). The effect would be so small, that I think the balances/scales that gold-market people probably do not have balances precise enough to get anything different.

Also, if you sell gold on Mount Everest, it'll weigh MUCH less than at sea level. So buy high, sell low :)

Answer 4

the moon turns so that the same side always faces the earth, so the rock would always be pulled in the same direction. However, even though the earth's moon isn't affected much by gravity, that doesn't mean that moons in general aren't. One of Jupiter's moons is made molten at the core because of the heat created by the various pulls from the planet and other moons that all pull in different direction.

Answer 5

I'm not to sure if your theory on the weight differences in the weight of Au will pan out, but I'd try it if I were you. If after a couple of trades it does provide you with equity, I would go with a big order On Margin. You could get rich! As far as rare metals go, ingots are stamped with their official weight at the furnace, and it is unlikely you could get an Officially re-weighing of the ingot unless you were purchasing a really big lot! Also, would not the gravitational push and pull of the Moon on your pallet of Au have the same effect on the scale causing a neutral change ! In answer to your 1st question Astronomers feel over eons the Moon and Earth are getting closer. But because of the moon and the Earth's wobble, calculating said distance using mathematics would take a very long time!

Answer 6

The overall effect of tidal pull is lateral and not perpendicular to earth's own gravity axis. Hence, gold would not weigh more or less during high or low tide. But it would "tend" to shift eastwards or westwards.

Answer 7

Yea and tell your wife not to check her weight on low tide. Moon's gravity is not strong enough to make that kind of difference. Ocean do feel the moon's gravity but it is also huge in size.