NASA Scientist Says a Mysterious 'Fifth Force' May Be Hiding in Our Solar System

We know of four fundamental forces that govern everything in the universe — gravity, electromagnetism, and the strong and weak nuclear forces. Together, they explain how planets orbit stars, how atoms hold together, and how the Sun shines. But what if there is a fifth one, lurking just beyond the reach of our instruments, hiding in plain sight within our own solar system?

A new study published in Physical Review D by Slava Turyshev, a physicist at NASA's Jet Propulsion Laboratory (JPL), proposes that a mysterious fifth force of nature might indeed exist — and that we may finally have a way to detect it. The research has sent ripples through the physics community and made headlines around the world this week. Here is what you need to know.

The Great Disconnect: Why the Universe Doesn't Add Up

For decades, scientists have struggled with what Turyshev calls "The Great Disconnect." When astronomers observe distant galaxies, they see clear signs that something beyond standard physics is at work. Galaxies rotate faster than they should. The universe is expanding at an accelerating rate. These observations have led researchers to invoke mysterious placeholders like dark energy and dark matter — invisible forces that together are thought to make up roughly 95% of the universe's total energy content.

Yet inside our solar system, everything behaves exactly as Einstein predicted. Planetary orbits align with precise calculations. Spacecraft trajectories match expectations down to astonishing levels of accuracy. Signals traveling near the Sun confirm the curvature of spacetime with no measurable deviation whatsoever. If unknown physics governs the cosmos at large, why does it seem to vanish entirely in our local neighborhood? That is the puzzle Turyshev set out to solve.

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The Chameleon and the Shield: Two Ways a Force Could Hide

Turyshev's paper does not claim to have discovered the fifth force. Instead, it offers something arguably more important: a rigorous theoretical framework for how such a force could exist all around us and yet remain completely undetectable with current technology. The key idea is called "screening."

The study explores two distinct screening mechanisms. The first is known as the Chameleon Model. In this scenario, the fifth force is like a chameleon — it adjusts its strength based on the density of matter around it. In the vast, nearly empty stretches between galaxies, the force becomes powerful enough to drive cosmic acceleration. But in dense environments like our solar system, it weakens so dramatically that even our most sensitive instruments cannot pick it up. The force does not disappear; it simply blends into the background of known physics.

The second mechanism is called Vainshtein Screening, named after Soviet physicist Arkady Vainshtein. Unlike the chameleon approach, this model suggests the fifth force maintains a constant strength everywhere. However, strong gravitational fields — like those produced by the Sun — suppress its observable effects within a certain radius. According to Turyshev's calculations, the Sun's screening radius could extend as far as 400 light-years, a staggering distance that would encompass not just our solar system but a vast region of the surrounding Milky Way.

How Would We Actually Detect It?

This is where the study gets especially exciting. Turyshev does not just describe the problem — he proposes concrete experiments to test it. His analysis suggests that as a spacecraft travels farther from the Sun, it should gradually leave the screened zone and enter a region where the fifth force becomes detectable. The transition would produce a faint but measurable anomaly in the spacecraft's trajectory, a tiny deviation from what Einstein's general relativity alone would predict.

In fact, there is historical precedent for exactly this kind of anomaly. NASA's Pioneer 10 and Pioneer 11 spacecraft, launched in the early 1970s, exhibited a mysterious unexplained acceleration as they traveled toward the outer solar system — a phenomenon known as the Pioneer Anomaly. While that specific case was ultimately attributed to thermal radiation pressure from the spacecraft's own systems, Turyshev argues that future missions designed with this fifth-force hypothesis in mind could use far more precise instruments to search for the real signal.

The idea is to send spacecraft equipped with next-generation accelerometers and atomic clocks deep into the outer solar system — beyond Jupiter and Saturn — and watch for the telltale signatures of a screened force transitioning from hidden to visible. It would be one of the most ambitious experiments in fundamental physics ever attempted.

For a deeper dive into how scientists are mapping the very fabric of the cosmos, check out our recent post on 47 Million Galaxies: Scientists Just Completed the Largest 3D Map of the Universe Ever Made — where the DESI project revealed stunning new insights about dark energy.

What a Fifth Force Would Mean for Physics — and for Us

If confirmed, the discovery of a fifth fundamental force would rank among the most transformative scientific breakthroughs in human history. It would mean that the Standard Model of physics — the framework that has guided particle physics for half a century — is incomplete. It could explain the nature of dark energy, which makes up roughly 68% of the universe and is responsible for the accelerating expansion of space itself. It might even open the door to entirely new technologies we cannot yet imagine, in the same way that our understanding of electromagnetism eventually led to radios, computers, and smartphones.

More immediately, Turyshev's work gives the scientific community a concrete roadmap. Rather than waiting for dark energy to reveal itself through increasingly powerful telescopes aimed at distant galaxies, we might be able to find clues right here in our cosmic backyard. The solar system — a place we have been exploring with robotic spacecraft for over 60 years — could hold the key to unlocking one of the universe's deepest secrets.

Speaking of hidden phenomena in our solar system, Origins Weekly recently explored A Bizarre New State of Matter May Be Hiding Inside Uranus and Neptune — another reminder that our own planetary neighborhood is still full of surprises.

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The universe has always had a way of surprising us. Every time we think we have figured out the rules, nature reveals a deeper layer. If Turyshev is right, then the force that governs the fate of the entire cosmos has been right under our noses all along — invisible, patient, and waiting for us to build the tools precise enough to finally see it. The question is no longer whether we should look. It is whether we are ready for what we might find.