center of the earth

Not necessary. We understand the physics of S-waves. They pass into solids (reflecting some) and don't pass into liquids. When S-waves are blocked, whatever blocked them is liquid.

Cold rock ain't liquid.Liquid iron ain't cold.

Absolutely. And it tells us how the mass is distributed.A satellite's orbit is affected very slightly by weensy little variations in the amount and distribution of material in the body it's orbiting. Sophisticated instrumentation can detect those effects and translate them into a map of density and mass distribution. Previous measurements ahve been made on the orbits of satellites put up for other purposes. Recently, satellites dedicated to this kind of measurement have been put in orbit, and more are coming.. Mapping with GRACE: Twin Satellites Chart Changes in Earth's Gravitational Field, Combined Gravity Field Model EIGEN-CG01C, GOCE — Surfer of the gravitational field.{Added in edit: Everyone should look at the second link, especially the very bottom of the page. Cool images}This message has been edited by JonF, 01-24-2005 17:27 AM

Yup.

Yup. Literally tens of thousands, maybe hundreds of thousands, of times. With all kinds of different materials, metal and non-metal, magnetic and non-magnetic, in all sorts of different places, with increasing precision over time, and with different types of apparatus. Cavendish's version is a standard experiment in many college courses. People have done it with different materials hoping to find some exception to Newton's laws. Nobody has yet. Instructions for doing the experiment at the University of Chicago as part of Physical Sciences PS 11900: Stellar Astronomy and Astrophysics. Google turns up lots of similar things at other universities.One of many papers including work on different materials is A new precise determination of Newton's gravitational constant. Se also Experimental Gravity Program, Department of Physics and Astronomy, University of California, Irvine.Have you noticed that every possiblity you raise that might be a problem with the theory has been anticipated by many scientists, often hundreds of years ago, and has been tested far more thoroughly than you could have imagined? Reflect on that and your state of knowledge.

I don't think so. In what message did you ask that? Seems to me that you did no such thing. You have made a lot of assertions, but you haven't yet supported any of your claims or demonstrated anything. I haven't seen any disagreements. Specifically what disagreements do you see? We might, but we don't. We have literally millions of observations and tests of the rest of the Universe, none of which indicate anything different about the Earth's makeup or gravitational field. The burden of proof is on you.

Nope. Your ignorance is leading you astray ... yet again. It's certain.Gravity exists and is observed, and acts in one certain way on Earth, on other planets in the Solar System, throughout the Solar System, in our Galaxy, in the local cluster of galaxies, and so on up at all scales. Gravity is caused solely by mass¹. Gravity acts in one and only one way, which is described by Newton's law of universal gravitation². These facts are certain and rock-solid.We are far from certain as to why gravity acts the way it does. We are far from certain what the fundamental source of gravity is (knowing that only mass causes gravity doesn't tell us why only mass causes gravity). We don't know why inertial mass and gravitational mass are exactly the same. And we don't know why our equations don't give us the right answers when we try to apply them to the incredibly tiny subatomic world in which quantum mechanics is king.But, since the Earth (or any portion thereof that we are considering in this thread) is unimaginably too big to be subject to noticable quantum effects, and we don't have to know why our equations work in order to know that they do work in almost all situations and in order to know the very few and irrelevant (to this thread) situations in which they do not work, all our lack of understanding is irrelevant to this thread.--------------
¹General Relativity shows that in the absence of any other information measurements of the forces caused by acceleration are indistingushable from gravitational forces, and this is a profound equivalence; but in the real world we have lots of other information that we can use to distinguish the two.²In extreme circumstances Newton's law is a little bit off, and we need to use General Relativity instead, but such extreme cases never arise on or in the vicinity of Earth.

Er, yes it has, just not in this thread.First, those "dips and bulges" are not physical dips and bulges. The height of a bulge above the surface on the maps indicates the gravitational force that is measured and is in excess of the gravitational force expected if the Earth were uniformly dense, and the dips are the same except there's a deficit rather than an excess.Second, it should be intuitively obvious to the most casual oberver that such asymmetric patterns could not be caused by symmetric rotation.Third, the efects of rotation are well understood, and are subtracted out before those maps are made. The increase in gravitation force at the Equator due to the Equatorial bulge caused by the Earth's rotation is much larger than the effects shown in those maps. They didn't bother to explicitly say that's waht they did (although I bet they do somewhere deep inside the real scientific papers) because it's so obvious to the scientists who are their main audience.

Not by faith, by evidence.Learning about all the evidence and all the details is a subject for a lifetime, not for one thread on this board. Nonetheless, a very little bit of the evidence has been presented already.If you think that any claims we have made are based solely on faith, ask for details and supporting evidence. Supplying such evidence on request is part of the forum rules, and the one that is most often ignored by your ilk.

No, it's saying that if all we can measure is a force that we can't tell the difference between a force caused by gravity and a force caused by acceleration. However, in the real world there's always lots of other things we can measure. It could ... if and only if we were riding on the center of the Earth and the center of the Earth were accelerating relative to our measurement frame.{looks out the window}Nope, the Earth is still one solid object. The center of the Earth is not accelerating relative to us. Any force we feel from the Earth is gravity, not acceleration.By the way, it's not possible that different physical laws apply down there, although I bet you don't have the several years of college math required to really understand why. Briefly, we have observed that momentum is always conserved. Through some pretty impressive and complex math we can show that conservation of momentum implies that the laws of physics don't change as you move around left-right, up-down, or forward-backward; and vice-versa. See Symmetry and CP Violation. Your reasons are based solely on your ignorance and unwillingness to follow the evidence where it leads. Being Bible-based, they are inappropriate in this forum, and are just meaningless noise in the scientific study of the Earth.Now, if you had some actual evidence, or even an interesting reason why we should look for some particular as-yet-undiscovered evidence, then you'd have something. But you appear to be incpable of that, too.

Your exact words were "But we do have assurances of how wonderful we can all be sure it is all figured out, just by faith so far, mind you!", which deos maen overall that yuo think there's no evidence. Now you say "some measure of faith" instead of "just by faith". Which is it?

The results at the link I posted have nothing to do with seismic waves. The are derived from measurements of the position of two satellites relative to each other. No other data is involved.Of course the results do agree with the much-less-precise seismic wave results. They do. It tells us that the Earth's gravitational field is not perfectly uniform. Since only mass causes gravity (in this situation), this means that the Earth's distribution of mass is not exactly uniform, and tells us quite a bit about how big those nonuniformities are and how they are distributed. Specifically, the results tell us that the Earth is denser at the center than at the surface, and the nonuniformities are very very small.

Nope. It is admitted that we haven't seen the center of the Earth. We know a lot about the center of the Earth. Since what is known in science about a spirit world is absoluley nothing, that's a fruitless exercise.

Wrong. It's liquid. The only way that we know that could be is by being hot. You should have said "no indication that it could be cold or tepid". No proof other than "that's how gravity works, and here's the evidence". Sorry, the burden of proof is on you. The current interpretation is the only one known that fits the evidence. What's your alternative interpretation that fits all the evidence? Sorry, the burden of proof is on you. The current interpretation is the only one known that fits the evidence. What's your alternative interpretation that fits all the evidence? Nope, the law of gravity is not at all uncertain. Why the law of gravity is as it is ... that's uncertain. Where did you get that crazy idea from? The only connection between the satellite data and seismic waves is that they produce consistent results. Neither one depends on the other. There's no mention of siesmic waves at any of the satellite sites to which I linked, and they make it clear where the data came from.

Becasue momentum is conserved, the laws of physiocs are the same here on the surface as a the Earth's core.No such forces exist here on the surface of the Earth.Therefore, no such forces exist at the Earth's core.QED. As has been pointed out many times in this thread:1. Density does not cause gravity.2. Mass is the only cause of gravity. Hey, he is wrong. Links to other loons don't prove much.