A recent paper has proposed a new idea for what is causing the observed accelerated expansion of the universe, and dark matter, suggesting both of them may be a "cosmic illusion" caused by the changing constants of the universe. 

By observing the universe from the cosmic microwave background to our nearest galaxies, we know that our universe is expanding. Weirder (and subject to further observations and analysis) the expansion appears to have sped up, beginning around 5-6 billion years ago. We call the mysterious influence driving the accelerated expansion dark energy. 

Dark matter, meanwhile, is invisible matter that doesn't emit its own light and only interacts with normal matter through gravity, which we can see evidence for in galaxies and galaxy clusters. As well as finding evidence for it in the rotation rate of galaxies, and in the bullet cluster, there is evidence for its existence in the gravitational lensing of galaxies.

While there are many dark matter candidates, and plenty of experiments looking into it, detection has not yet happened, and we are no closer to figuring out what dark energy is. There's even evidence to suggest it could be evolving.

There's a lot to explain, and any new big idea would have to explain a vast amount of observations with it. In a new idea from Rajendra Gupta, adjunct professor in the Department of Physics at the University of Ottawa, the observations can be explained by changes to the strength of the fundamental forces of the universe over time.

"The universe's forces actually get weaker on the average as it expands," Gupta said in a statement. "This weakening makes it look like there's a mysterious push making the universe expand faster (which is identified as dark energy). However, at galactic and galaxy-cluster scale, the variation of these forces over their gravitationally bound space results in extra gravity (which is considered due to dark matter). But those things might just be illusions, emergent from the evolving constants defining the strength of the forces."

The paper suggests that galaxy rotation curves, gravitational lensing, and dark energy could all be explained with covarying coupling constants (CCC), or the idea that the universe's "constants" like the strength of gravity and electromagnetism change over time, related to each other. In this model, the coupling constants (noted 𝛼) are fixed on cosmological scales, but are allowed to vary locally depending on the distribution of normal baryonic matter.