# Thread: What is the smallest object our instruments can detect with a gravitational field?

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## What is the smallest object our instruments can detect with a gravitational field?

For example, can we detect the gravitational field of an apple?

Gravity is directly proportional to mass, the more mass the more gravity. The moon is remarkably small and less dense compared to the earth yet it has a detectable (and feelable) gravitational field. My question is how small of an object can our instruments detect such a field? For example, can our instruments detect "gravity" from a 10 meter wide solid iron ball?

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Originally Posted by Exposed
For example, can we detect the gravitational field of an apple?

Gravity is directly proportional to mass, the more mass the more gravity. The moon is remarkably small and less dense compared to the earth yet it has a detectable (and feelable) gravitational field. My question is how small of an object can our instruments detect such a field? For example, can our instruments detect "gravity" from a 10 meter wide solid iron ball?
Cavendish, back in 18th century, successfully detected gravity from a 30 cm wide solid lead ball weighing 158 kg (a pair of such).

What is the smallest item so far used in successful repeats of Cavendish experiment?

3. I detected the gravitational action of lead balls on the order of a few kilograms each with a miniature Cavendish apparatus in my college physics lab.

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Interesting info thanks. I was not aware of the cavendish experiments before this.

At what point does gravity become detectable outside of sensitive instruments? For example, the point at which we can "feel", however slightly, its effect...even by watching other objects interacting at a much greater degree than the cavendish apparatus. Does such an object exist on earth? Or would it take some ultra dense object we discover in space, like a piece of a neutron star floating around (if that's even possible), which i read a teaspoonful would weigh several tons here on earth.

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IIRC, using a plumb line next to a large mountain doesn't work all that well, the mountain pulls it off towards the mountain, Come to think of it, gravitometers do exactly what you are asking.

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