For decades, physicists have wondered whether there might be a fifth fundamental force at work in nature. Right now, four forces are known to govern the universe: electromagnetism, gravity, the strong nuclear force, and the weak nuclear force. But the big question remains: Could a fifth force exist that explains various anomalies in our observations?

Since the 1980s, researchers have proposed different ideas, ranging from concepts like antigravity to “quintessence” — a hypothetical force that might help explain dark energy. In 2015, a team from the Hungarian Academy of Sciences (which you can read about here) announced the discovery of a particle 30 times heavier than the electron, which could hint at a fifth force. Yet, many physicists remain skeptical, arguing that this elusive fifth force may simply not exist.

How Asteroids Are Helping in the Hunt

Asteroids — especially those whose paths are tracked with high precision, like Bennu — provide a unique natural laboratory for pushing the limits of physics. The idea is simple: If there’s an unknown force at play, it could cause tiny deviations in an asteroid’s orbit. If those deviations can’t be explained by the known four forces, scientists might have clues pointing toward new physics, according to a recent study published in Nature Communications Physics.

Although this study didn’t detect signs of a fifth force influencing Bennu’s motion, scientists are optimistic. The successor to the OSIRIS-REx mission, called OSIRIS-APEX, is set to deliver even more detailed data as it heads toward the asteroid Apophis.