How could it be possible to exert gravity without mass?

Some of what I read in How could a 4D organism influence events in our world made me think in a different direction about a question I asked before.

I'm trying to create a large sphere shaped field of gravity, without a physical mass at it's center, that floats in space. Inside the field would exist a habitat that humans could live in. Basically a massive ball of air held together by this force in what I imagine would be a microgravity situation. I already assume this couldn't be found in nature. I guess it would have to be some kind of super science.

How could the physical mass be "elsewhere" but it's gravity be felt "here"? Could something exist in another dimension or reality but exert its effects in our reality?

EDIT:

From https://www.nationalgeographic.com/science/space/dark-matter/

"One leading hypothesis is that dark matter consists of exotic particles that don't interact with normal (baryonic) matter or light but that still exert a gravitational pull." Does that help with ideas?

Adding onto edit 1:

https://www.space.com/33850-weird-galaxy-is-mostly-dark-matter.html

From the article: "Motions of the stars tell you how much matter there is," van Dokkum said in a statement. "They don't care what form the matter is, they just tell you that it's there. In the Dragonfly galaxy stars move very fast. So there was a huge discrepancy: using Keck Observatory, we found many times more mass indicated by the motions of the stars, than there is mass in the stars themselves." In other words, van Dokkum and his team found evidence of way more mass than they could actually see.

OR EDIT 2: Could the use of massless particles lead to an answer?

https://en.wikipedia.org/wiki/Massless_particle

EDIT 3: A version of String Theory known as M Theory suggests that separate "branes" interact through gravity (The central idea is that the visible, three-dimensional universe is restricted to a brane inside a higher-dimensional space, called the "bulk"). Could something along these lines be an answer?

posted about 6 years ago

Len‭

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