Just one more. does the sun and moons gravity shift the earths center of gravity?

Question

seems like it would.

other words the earths center of gravity wouldn't be at the center of the earths mass due to the gravity of the sun and moon.

Answer 1

No the center of gravity is not defined by any outside forces acting on the object. The center of gravity is just a point from which the mass of the object is uniform from all sides.

Answer 2

What the heck, I'm gonna go against the majority of responses you've gotten so far.

From the standpoint of gravitational energy on the surface of Earth -- meaning the amount of acceleration due to gravity an object on Earth's surface would experience -- the gravity of the moon and sun and for that matter all the other planets as well DOES influence Earth's surface gravity. For example, the center of gravity for the Earth-sun system is NOT at the geographical center of Earth but at some point displaced away from it. Therefore it follows that the NET gravitational energy experienced by an object on Earth's surface is derived from that center of gravity. True, Earth's surface gravity is influenced infinitesimally, like the difference in gravitational attraction experienced by your head as compared to your feet, but influenced none the less.

Answer 3

NO.

The Sun and the Moon have no part in changes in the Earth's center of gravity. The Earth's crust is a hard, broken crust of silica rock and dirt. Underneath is a vast bed of molten rock and metal material called magma. The crust is moving over its liquid base ever so slowly, but moving just the same. That is the cause of earthquakes and mountain ranges, enormous cracks (fissures) in the earth, and some undersea landslides.

As the crust moves about over the molten magma below, minor changes in the center of the Earth's mass can, and do occur. That is why the North and South poles wanter about somewhat and are not fixed points on the Earth. Scientists and geologists report the Poles wandering anywhere from one to ten miles over the course of several years. As I recall one report, it said something to the effect that previous positions seemed to roughly be in a circle, so a drastic shift to the East or West is not forecast.

"Seems like" and "Might" are not the same as "Does" and "Is."

Answer 4

No, but the earth does wobble because of the sun and moon's gravity (the moon's mostly). When the moon is up in china, we still get a high tide because the entire earth is being pulled towards the moon, while the water is left behind, making the water rise a few feet.

Answer 5

In an ideal world, in which astronomical bodies were SPHERICALLY SYMMETRIC, Newton showed that they would ALL attract one another as though their total mass were CONCENTRATED at their geometrical centres. So in such an idealised situation, their "centre of gravity" would IMMUTABLY be at their GEOMETRICAL CENTRE. What's more, their mutual laws of attraction would be PRECISELY an inverse square law.

In REALITY, bodies are NOT completely spherically symmetrical, if only because they all rotate and that introduces a non-sphericity. (There are many other departures too, for the Earth and Moon, for example, because there ARE mass departures from sphericity.)

Under those circumstances, THERE IS NO SUCH THING AS AN IMMUTABLE CENTRE OF GRAVITY, nor is there a mathematically PRECISE inverse square law of attraction between them.

Thus a problem with your question is that the term "centre of gravity" doesn't really apply to such more general situations. In contrast, the centroids (or centres of mass) of individual objects or of any collection of them are well-defined for any given set of relative orientations. However, although those points are themselves well-defined, they have NO direct connection with the mutual gravitational forces (direct attractions and/or torques) being experienced by or exerted on those bodies.

Thus, if stars or planets had the shape of tetrahedra or cubes, their attraction on one another from arbitrary directions would have to be worked out from scratch for each specific orientation, and would not necessarily be along the line joining their CENTROIDS (which themselves ARE immutably defined points). The point is that the local value of the acceleration due to gravity (or "gravitational force per unit mass"), ' g,' is derived from a POTENTIAL. If a body is non-spherical, its potential field and in particular its constant potential surfaces will also be non-spherical. Therefore the local ' g,' everywhere perpendicular or "normal' to the local level surface, will not point to any given central point. The full possible sets of such normals will be rather like ill-focused light rays defining a region near the centroid rather than a point that one could call the "centre of gravity."

In a sense this is a positive answer to a modified form of your question : It says that the gravitational effects of the Sun and Moon on the Earth differ in detail from idealised "centre-to-centre" attraction, and it will also depend on their relative orientations.

Because such effects are small, their consequences must be sought in subtle, long-term difference from those of centre-to-centre attraction. The slow expansion of the Moon's orbit is one of those subtle consequences.

This more precise formulation is necessary because the term "centre of gravity" is no longer appropriate under these circumstances. If that disappoints you, too bad. It's how it is.

Live long and prosper.

P.S. Don't let 'braxton_...' mislead you. What he calls the "center of gravity" is an incorrect term for the CENTROID or CENTRE OF MASS of the two masses. (This confusion of terms is a common mistake.) As such, it says NOTHING directly about what 'braxton_...' describes as "the NET gravitational energy experienced by an object on Earth's surface ... derived from that center of gravity." That's just a lot of meaningless psuedo-scientific mumbo-jumbo, with no hard mathematical basis.

Answer 6

not the center of gravity but the wobble at the axis.