This long-exposure photo taken on December 23, 2017 shows the Andromeda galaxy – where researchers believe they have witnessed the collapse of a dying star into a black hole. — © AFP John MACDOUGALL
Astronomers are facing a cosmic mystery: Why does the Universe behave differently on a massive scale compared to our solar system?
While distant galaxies reveal clear signs of something bending the rules of gravity—often attributed to dark energy or a hidden “fifth force”—everything nearby seems to follow suit. Einstein’s Playbook perfectly.
A force REFER to an action that can cause an object to change its speed or shape, or resist other forces or cause pressure changes.
Dark energy and dark matter are among the most difficult concepts to test. Observations across vast regions of space strongly suggest that something is affecting gravity in ways that Einstein’s theory does not fully explain. However, inside our solar system, everything seems to behave exactly as expected.
Dark matter and dark energy are invisible components of the universe: dark matter pulls matter together through gravity, while dark energy drives the accelerating expansion of the universe.
A new study by Slava Turyshev, a physicist at NASA’s Jet Propulsion Laboratory, explores how researchers can address this discrepancy. His work suggests that the key may lie in being extremely precise and selective in the way experiments are designed to look for signs of dark energy and dark matter closer to home.
The Great Schism
At the heart of the problem is what scientists call “Big breakup.The laws of physics seem to operate differently depending on the scale being observed. In regions with very little matter (ie, no gravitational force), the effects associated with dark energy or modified gravity become much more apparent. In contrast, in dense environments filled with matter and strong gravity, the same effects appear to disappear, at least based on current instrumentation.
Inside the solar system, everything conforms to traditional physics. The planets follow their expected orbits. Space-time measurements around the Sun, including data from spacecraft signals, match predictions exactly. Any probe sent through the solar system behaves as if only standard gravity were at work. There are no obvious signs of anything unusual.
New perspectives
The situation changes when we look beyond our “local neighborhood.” On the scale of galaxies and beyond, The universe appears to be expanding. While scientists continue to debate the exact rate of this expansion, there is strong evidence that something is affecting gravity or spacetime in ways that are not fully captured by current theories.
Currently, dark energy is the best explanation for this behavior, although its true nature remains unknown.
of the universe is expanding due to dark energya mysterious force driving this acceleration, accounting for about 68% of the universe.
One possible explanation involves a phenomenon known as “screening.” In this idea, whatever causes the discrepancy changes the way it behaves depending on the surrounding environment. As the density increases, its effects become weaker or harder to detect.
Screening models
There are two main types of screening models. The first is called the “chameleon” model. In this scenario, a hypothetical fifth force of nature (in addition to gravity, electromagnetism, and the two nuclear forces) regulates its strength based on the amount of matter nearby.
In regions of low density, it becomes strong and produces effects associated with dark energy. In dense areas, it weakens so much that current instruments cannot detect it, even though it is still there. Around objects like the Sun, it can only appear in a thin outer layer, but in principle it can still be measured there.
The Weinstein Show
Another explanation is the Vainstein model of emergence. Arkady Vainshtein (born February 24, 1942) is a Russian-American theoretical physicist known for his contributions to particle physics.
Here, the force itself does not change. Instead, the surrounding gravity effectively suppresses its impact, making it appear weak. The model introduces the concept of a Vainshtein Radius, which marks the distance where the force regains its normal strength.
The model of the Vainstein display it is a mechanism that suppresses additional gravitational forces near massive objects via derivative self-interactions in modified gravity theories. It operates on scalar-tensor systems where the action involves nonlinearities with the highest derivative of the scalar field.
For the Sun, this radius is estimated to extend about 400 light years. That region includes many stars, meaning the force will remain suppressed beyond the solar system and even across large parts of the galaxy.
Why might new solar system missions be needed?
Both screening patterns can leave subtle imprints on large-scale observations collected by missions such as Euclid and The Dark Energy Spectroscopic Instrument (DESI). However, these surveys focus on distant galaxies and cannot directly reveal how such forces behave within the solar system.
To test these ideas locally, scientists would need a dedicated mission designed specifically for this purpose. More importantly, researchers would need a falsifiable theory that predicts what such a mission should reveal.
Next steps
It may take time to develop instruments sensitive enough to detect these subtle effects. Meanwhile, incremental progress will be important, with missions focused on improving measurement capabilities step by step.
If a well-defined and testable prediction emerges from the current data, and if an experiment can actually be constructed to test it, pursuing this possibility could lead to a major breakthrough. Such a discovery has the potential to reshape our understanding of gravity, dark energy and the fundamental workings of the Universe.
Research paper
of findings appear in Diary Physical examination D. The research paper is titled “Solar System Experiments in the Search for Dark Energy and Dark Matter.”
