Do we yet have equipment sensitive enough to perform useful high-rez scans of the ground by measuring gravity?

Question

To specify further, I mean a scan the likes of which could render a realistic image of what's there in various densities. All you would need it a weighted chain or balanced platform connected to circuitry sensitive enough to measure the minute changes that would occur over spots of divergent densities. Something that could discern the outline of, say, a wedding ring to a resolution useful enough to tell what shape the object is.

Cellophane - the lagrange point isn't meaningful on the scale I'm talking about. It would have no impact on microcosmic low-level gravity scans.

Answer 1

If we want to scan Earth's surface:
Remember that the inside of the Earth is not uniform, that means you could have many different layers with many different densities, and if you don't know the depth of every layer(meaning that you also have to know before hand that the layers are there), then the experiment fails.

If you perform the experiment for a small object, the problem is that a gravity sensor cannot tell how far away ALL the mass that is exerting a gravity pull is. Remember that
F = Gm1m2/r^2
So distance does matter - in other words, the sensor cannot tell both if an object is hollow, or not, and how much mass there is. To get an accurate scan of the object, you would need to know the density before hand.

Answer 2

Let me get this straight. The center of gravity for the Earth is not at it's core, but at a point located between the core and the moon. The gravitational forces of the moon is enough to change the tides of the oceans. The sun also has an effect, but not as great as the moon. You would like to have a device that is portable enough to move out in the field that can ignore the everchanging center of gravity of the earth as it rotates to detect a wedding ring from how far? And the instrument can not be effected by the gravitational force generated by the instrument, and the observers that are using the instrument.

You are better off with a metal detector.

Answer 3

Yes, there are gravity maps of earth, see the references. The GRACE satellites are doing just that. But not nearly enough resolution to find a wedding ring. A metal detector or ground-penetrating radar would do much better. So would a rake and shovel. Gravity is an extremely weak force. Dirt is nearly as dense as gold, but not nearly as conductive.

Answer 4

Yes, in fact recent scans have shown that greenland has significantly less gravity now than it did a few years ago, due to melting ice.

Re. cellophane, the point you speak of is called a lagrange point, but since the moon is not part of the earth, it is not included in center of mass calculations.

Answer 5

Gravity can be used to map the density of the earth's crust, but not nearly so accurately as you suggest.

Answer 6

It's routinely being done to look for mineral deposits.

Answer 7

Well....yes and no. We do have instruments that sensitive but they cannot be moved.