Evrim Yazgin
Cosmos science journalist
The controversial physicist who last year suggested the universe is twice as old as we thought has come out with a new contentious hypothesis: the cosmos doesn’t have any dark matter in it.
Observations of the gravitational effects within and around galaxies have led to what’s known as ‘the Standard Model of Cosmology.’ This generally accepted theory suggests that the visible matter that we see and interact with makes up only about 5% of the “stuff” in the universe.
So-called “dark matter” is theorised to be more than 5 times as plentiful as “normal matter” while the rest consists of the mysterious “dark energy” which is believed to drive the accelerating expansion of the universe.
While dark matter doesn’t interact with ordinary matter, light or the electromagnetic field, it’s existence would help scientists understand the behaviour of galaxies, stars and planets. And there are some major efforts being made to detecting it, such as the SABRE South experiment based in regional Victoria.
But Rajendra Gupta, a physics professor at the University of Ottawa in Canada, believes this isn’t the only answer to the unsolved questions of the cosmos.
Gupta’s latest research is published in the Astrophysical Journal.
His model uses a combination of two theories called ‘covarying coupling constants’ (CCC) and “tired light” (TL).
The essence of Gupta’s model is that the forces of nature decrease over cosmic time and light loses energy when it travels long distances.
“In standard cosmology, the accelerated expansion of the universe is said to be caused by dark energy but is in fact due to the weakening forces of nature as it expands, not due to dark energy,” according to Gupta.
Gupta compared his model with observations of the “redshift” – reddening of the light from distant galaxies as they move further away – from recent galaxies. Simulations of this theory match up with observations including how galaxies spread apart and the evolution of light from the early universe.
Gupta’s research made international headlines last year when he suggested that the universe is not 13.8 billion years old , but nearly twice that age. He believes the latest research provides further evidence for this reassessment of the age of the cosmos.
“The study’s findings confirm that our previous work about the age of the universe being 26.7 billion years has allowed us to discover that the universe does not require dark matter to exist,” explains Gupta.
“There are several papers that question the existence of dark matter, but mine is the first one, to my knowledge, that eliminates its cosmological existence while being consistent with key cosmological observations that we have had time to confirm,” Gupta says.
Cosmologists aren’t all on board, though. When discussing Gupta’s earlier research which claims the universe is twice as old as we thought, Professor Tamara Davis from the University of Queensland told Cosmos: “Extraordinary claims require extraordinary evidence. You have to go and test it, and test it in different ways.”
For now, Gupta’s model remains a theory competing against the conventional understanding of the universe. But it does provide a new framework into exploring the fundamental properties of the universe.
