Is Outer Space a Viscous Fluid? A New Theory Challenges Everything We Know About the Universe
A new theoretical paper proposes that outer space behaves like a viscous fluid rather than empty nothingness—an idea that could reshape how scientists understand dark energy, cosmic expansion, and the fate of the universe.
1/26/20263 min read
For decades, scientists have described outer space as a vast, mostly empty vacuum—an immense stage where galaxies, stars, and planets drift apart under the influence of dark energy. But what if space itself isn’t empty at all? What if it behaves more like a thick, slow-moving fluid?
A new theoretical paper by Muhammad Ghulam Khuwajah Khan, a researcher at the Indian Institute of Technology (IIT) Jodhpur, proposes exactly that. According to Khan’s model, space may possess fluid-like properties, capable of stretching, flowing, and subtly resisting the universe’s expansion. While the idea has not yet undergone peer review, it has sparked fresh discussion among cosmologists searching for answers to growing inconsistencies in our understanding of the cosmos.
The Standard Model of the Universe—and Its Cracks
Modern cosmology relies heavily on the Lambda Cold Dark Matter (ΛCDM) model, which explains how the universe formed after the Big Bang, why galaxies hold together, and why cosmic expansion is accelerating. In this model, dark energy is represented by a constant value—Lambda (Λ)—that uniformly pushes space apart everywhere and at all times.
However, recent observational data is raising uncomfortable questions. Measurements from large-scale sky-mapping projects such as the Dark Energy Spectroscopic Instrument (DESI) in Arizona and the Dark Energy Survey (DES) in Chile suggest that dark energy may not be as constant as once believed .
These surveys indicate that the rate of cosmic expansion might be changing over time—implying that dark energy could be weakening as the universe ages. This directly conflicts with the assumptions of the ΛCDM model and has left scientists searching for explanations.
A Radical Idea: Space as a Stretchy, Viscous Medium
Khan’s proposal attempts to bridge this growing gap between theory and observation by rethinking the nature of space itself. Instead of treating space as an abstract geometric backdrop, he models it as a viscous, elastic fluid—similar in behavior to thick honey slowly flowing under pressure.
In this framework, space is not passive. It responds to forces, stretches unevenly, and generates internal resistance to expansion. This resistance arises from what Khan calls “spatial phonons”—vibrational disturbances in space caused by the movement of matter at the atomic level.
In solid-state physics, phonons describe how vibrations move through materials like crystals. Khan’s theory extends this idea to the fabric of space, suggesting that atomic activity generates tension waves that ripple across the universe.
Why This Could Explain Dark Energy’s Strange Behavior
According to the theory, dark energy still drives the expansion of the universe, just as the ΛCDM model predicts. But as space stretches, spatial phonons create a subtle opposing force—like internal friction in a fluid.
This interaction could explain why expansion appears uneven or slower in certain epochs of cosmic history. When Khan’s fluid-space equations are applied to recent DESI observations, the discrepancies that trouble the ΛCDM model begin to smooth out.
In simpler terms:
Dark energy pushes space outward
Space itself pushes back
The result is a non-uniform expansion that evolves over time
This preserves the usefulness of dark energy while introducing a new mechanism that better matches observational data.
How Serious Is This Theory?
It’s important to note that Khan’s work is theoretical and not yet peer-reviewed. Many such ideas never survive rigorous testing. Still, history shows that bold reimaginings—such as Einstein’s view of gravity as curved spacetime—often begin as radical departures from accepted thinking.
Upcoming data releases from DESI and other observatories will provide more precise measurements of cosmic expansion. If these observations continue to challenge the ΛCDM model, alternative frameworks like viscous-space cosmology may receive greater attention.
Why This Matters Beyond Astrophysics
Understanding what space truly is affects far more than cosmology. It shapes theories about:
The ultimate fate of the universe
The behavior of gravity at extreme scales
Potential unification of quantum physics and relativity
If space has physical properties like viscosity and elasticity, it could open entirely new directions in theoretical physics—and even future space technologies.
For now, the idea remains speculative. But as astronomical instruments become more precise, long-held assumptions about the universe may need revision. Whether Khan’s theory stands or falls, it represents a growing willingness among scientists to question the most fundamental concepts of reality.
References
Khan, Muhammad Ghulam Khuwajah. A Viscous Fluid Model of Cosmic Expansion. Preprint, 2025.
DESI Collaboration. “Early Dark Energy Results from the Dark Energy Spectroscopic Instrument.” The Astrophysical Journal, 2024.
Abbott, T. M. C., et al. “Dark Energy Survey Year 3 Results.” Physical Review D, vol. 105, no. 2, 2022.
Riess, Adam G., et al. “Observational Evidence from Supernovae for an Accelerating Universe.” The Astronomical Journal, vol. 116, no. 3, 1998.
Peebles, P. J. E., and Bharat Ratra. “The Cosmological Constant and Dark Energy.” Reviews of Modern Physics, vol. 75, no. 2, 2003.