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Space-time curvature is caused by huge objects in space like black holes, merging black holes, or planets. This curvature is what causes gravity. Can molecules cause at least a really tiny curve ?

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    $\begingroup$ Planets consist of atoms. The total effect of all the molecules in a planet is also partially due to the binding energy (gravitational and non gravitational) which makes a negative contribution. So, the fact that a planet has a gravitational field proves that the atoms the planet consists of have a gravitational field. $\endgroup$ – Count Iblis Jul 3 '16 at 0:25
  • $\begingroup$ ok but no curve can be caused by a molecule on it's own ? $\endgroup$ – Sandy Danial Jul 3 '16 at 0:28
  • $\begingroup$ We don't assume otherwise, although measurements stop at roughly 0.1mm these days, so we can't say, for sure, if gravitation behaves the same below that scale. If it doesn't, it would have grave implications above the TeV scale, so the next two or three generations of accelerator experiments will be able to tell. $\endgroup$ – CuriousOne Jul 3 '16 at 0:31
  • $\begingroup$ I can't find the question/answer right now, but I read on this site that the effect of Earth's gravity on elementary particles has been experimentally seen. Of course, this is not the same thing as testing the gravity between two particles. $\endgroup$ – Javier Jul 3 '16 at 23:40
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In a nutshell, yes.

Think about Newton's gravity. Even you and I have some gravitational pull, even though it is tiny. The same is true for General Relativity. Even the tiniest of particles makes an indentation in the fabric of spacetime.

Here's another analogy: think about a rubber sheet. This is spacetime. Now, imagine you put a bowling ball on that rubber sheet. It'd definitely make a dip, right? Now, let's say you put a baseball on the rubber sheet. It'd still make a dip, though not as big. Now, let's bring it down to a marble. The dip would be small, but it would still be there, right? Now, imagine an atom. It would an insanely small dip, but it would still be there, just like in General Relativity.

Here's yet another analogy. Imagine you are the size of a planet, and there are other planets and a star near you (relatively speaking, of course). Look down at the fabric of spacetime beneath you. Wouldn't you make a dip? Now, imagine you are the size of a molecule of salt, say. Now, imagine other molecules of salt, and electrons, and other atoms around you. Now, imagine the fabric of spacetime beneath you. Wouldn't you still make a dip?

As this website says,

Large objects such as the Sun and planets aren't the only masses that warp the fabric of space-time. Anything with mass—including your body—bends this four-dimensional cosmic grid. The warp, in turn, creates the effect of gravity, redirecting the path of objects that travel into it. The strength of gravity depends on the size of the space-time warp. A large object with little mass creates a smaller distortion than a tiny object with a huge mass.

If our bodies warp spacetime, why wouldn't particles?

Hope this helps!

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  • $\begingroup$ You have measured the gravitational attraction between molecules? $\endgroup$ – CuriousOne Jul 3 '16 at 0:38
  • $\begingroup$ No; however, this is known. As Wikipedia says, " In Einstein's theory, energy and momentum distort spacetime..." and as E=mc^2 says, mass and energy are two forms of the same thing. A particle has mass, therefore it has energy, therefore it distorts spacetime (though by a very small amount). $\endgroup$ – heather Jul 3 '16 at 0:44
  • $\begingroup$ This is not known. The most precise Newtonian gravity measurements can reach just below the 1mm scale. How gravity behaves below that scale is neither known, nor do theorists expect it to necessarily keep behaving according to Newtonian theory or general relativity. It would, indeed, be very valuable if it didn't behave like naive high school physics expects because that would move interesting physics well below the Planck scale. If you want to know what we really think might be happening, then look up "compact extra dimensions". $\endgroup$ – CuriousOne Jul 3 '16 at 0:47

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