Hypothetically, one could imagine a universe without gravity, although it would look radically different from anything we experience or could easily conceive of.
For one thing, without gravity there would be no gravitational clumping of matter. We could therefore forget about planets, stars, stellar clusters, galaxies, galactic clusters, and the vast cosmic structures that emerge from gravity drawing matter together.
That said, not everything would necessarily disappear. Atoms could still exist because atomic nuclei are held together primarily by the strong nuclear force, while the electromagnetic force binds electrons to those nuclei. The weak nuclear force would still play its usual role in certain particle interactions and radioactive processes.
Beyond that, things become highly speculative. Without gravity, there would be no familiar mechanism for assembling matter into the large-scale structures we see throughout our universe. Instead, one might imagine something more akin to an enormous, diffuse particle soup, governed by the remaining fundamental forces.
The question of how such a universe would expand is considerably more complicated. Removing gravity would not automatically mean that the universe would expand without resistance or inevitably end in a Big Rip. Cosmic expansion depends on the underlying laws governing spacetime and on the universe’s energy content, including dark energy. If gravity as described by general relativity simply did not exist, we would need an alternative theory to tell us how spacetime itself behaves.
So, yes, a gravity-free universe can be imagined—but once gravity is removed, virtually every feature of the cosmos that we take for granted becomes radically different. The resulting universe might still contain particles, atoms, and electromagnetic interactions, but it would lack the gravitational architecture that transforms matter into the stars, galaxies, and cosmic structures we know.
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