A NASA scientist has proposed that a hypothetical “fifth force” of nature could be undetectable in the solar system due to environmental screening, despite its influence on cosmic-scale phenomena like dark energy.
How screening effects could hide a fifth force locally
Slava Turyshev, a physicist at NASA’s Jet Propulsion Laboratory, suggests that the mismatch between local gravitational observations and cosmic-scale anomalies may be resolved if a fifth force exhibits screening behavior. In such models, the force weakens in high-density environments like the solar system, making it invisible to current instruments, while remaining potent in low-density regions of space where dark energy effects are observed.
Why the solar system shows no signs of deviation
Within the solar system, planetary orbits, spacecraft trajectories, and spacetime measurements align precisely with Einstein’s general relativity, showing no detectable anomalies. This consistency contrasts with galactic and intergalactic scales, where the universe’s accelerated expansion implies gravitational influences not fully explained by visible matter and standard physics.
What the chameleon model implies for detection
One leading screening mechanism, the chameleon model, posits that a fifth force adapts its strength based on local matter density: it grows stronger in sparse cosmic voids but becomes exponentially weaker near massive bodies like the Sun or planets. This environment-dependent behavior could allow such a force to drive cosmic acceleration while evading detection in laboratory or solar system experiments.
What is the “Great Disconnect” in physics?
The “Great Disconnect” refers to the observed difference in how gravity behaves across scales — appearing consistent with Einstein’s theory in the solar system but requiring modifications like dark energy or altered gravity to explain cosmic expansion.
Could this fifth force be dark energy?
The force described in the screening model is not identical to dark energy but could produce similar effects on large scales; its true nature remains unknown, and the hypothesis remains theoretical pending experimental tests designed to overcome screening suppression.
