Gravity Illusion: Questions on Space-Time Curvature Granularity

[gaaah]

I wonder if someone would field a beginner's muse I had: If gravity is just an illusion of the curvature of space caused by mass, does not the matter within that space follow the curve? and what is the granularity of that curvature? Does the curvature exist in the space between the nucleus and the electrons? Is the nucleus itself curved? Are the electrons curved?

 

[Ibix]

I'm not sure it's correct to say that gravity is an illusion. Rather, for a long time we interpreted it as a force, but now we regard it as curved spacetime. Matter does, indeed, follow curved paths as a result.

However, exactly how gravity works on the quantum scale is an open question. We don't have a complete answer, largely because we haven't done experiments precise enough to detect gravity at that scale.

 

[Dale]

If gravity is just an illusion

It isn’t an illusion. And I am pretty sure that no professional source characterized it that way.

 

[PeterDonis]

the curvature of space caused by mass

Mass (more generally, stress-energy) doesn't curve space, it curves spacetime.

 

[pervect]

I wonder if someone would field a beginner's muse I had: If gravity is just an illusion of the curvature of space caused by mass, does not the matter within that space follow the curve? and what is the granularity of that curvature? Does the curvature exist in the space between the nucleus and the electrons? Is the nucleus itself curved? Are the electrons curved?

I wouldn't say that gravity is an illusion, but I would say it's a consequence of the curvature of space-time. I'm not sure what you mean by "matter within that space follows the curve", though there is a well known remark by Wheeler.

Spacetime tells matter how to move; matter tells spacetime how to curve.

Note that for technical reasons Wheeler says "matter" and not "mass". That is because there are other properties of matter other than "mass" that contribute to space-time curvature.

The curvature, in the form of the Riemann curvature tensor, does exist in the empty space where there is no matter. For example, the sun is a lump of matter, and it causes space-time curvature here on the Earth, which we can see and measure directly in terms of the tidal forces that are present on the Earth. An instrument known as the "gravity gradiometer", and also as the "Forward mass detector" can use these local tidal force measurements to detect the presence and distribution of distant masses. The underlying theory has practical usage for the purposes of oil exploration.

The Gravity of Oil and Gas Exploration
By Trent Jacobs 21 Jan 2015

A Cold War technology invented to stealthily guide the United States Navy’s nuclear submarine fleet is now serving a much more peaceful purpose: aiding in the search for oil and gas deposits. Far removed from the ocean depths, gravity gradiometry has evolved to become an increasingly sophisticated aerial technology that has been used to rapidly analyze the subsurface of every continent in the world.

Since its introduction to the oil and gas industry in the 1990s, airborne gravity gradiometer (AGG) technology has become an increasingly popular greenfield exploration tool because of its ability to analyze wide areas onboard airplanes for a fraction of the cost of 3D and 3D seismic surveys.