Do the constants of nature — the numbers that govern how things behave, like the speed of light — change over time as the universe expands? Does light get a little tired of traveling vast cosmic distances? Dark matter and dark energy were once thought to explain these cosmological phenomena, but recent research suggests that our universe is expanding without dark matter or dark energy.
Eliminating dark matter and dark energy solves the “impossible early galaxy problem” that arises when trying to explain galaxies that do not conform to expectations for size and age. It is possible to find an alternative to dark matter and energy that satisfies existing cosmological observations, including the distribution of galaxies.
Read more: Just How Old Is the Universe? A New Theory Suggests It’s Been Around Twice As Long As Thought
Dark matter
Dark matter is a hypothetical form of matter that does not interact with ordinary matter in any way other than through gravity. It was proposed as a theoretical way to explain our astrophysical and cosmological observations. Ordinary matter can pass through dark matter without any resistance and vice versa.
In space, gravity determines the speed at which an object rotates. A higher speed than expected from surrounding objects is attributed to the existence and gravity of dark matter.
The gravity of dark matter can also bend light rays, creating a gravitational lensing effect, just like normal matter. This makes it possible to measure dark matter in the object that is causing the bending, such as galaxies and clusters of galaxies.
The most robust evidence for the existence of dark matter comes from the tiny variations observed in the cosmic microwave background (leftover radiation from the Big Bang), which are measured with ever-increasing precision.
Another argument for the existence of dark matter is that large-scale structures of the universe, such as galaxies, could not form without the dark matter within the limited age of the universe.
(NASA Goddard Space Flight Center/Stephen Walker)
Alternative theories
There are alternatives to dark matter that account for many astrophysical observations. The oldest and most popular theory is modified Newtonian dynamics (MoND), which suggests that the Newtonian inverse square law of gravity is a simplified version of a full force that only becomes observable at very large distances when the Newtonian force becomes negligible.
Another alternative is a version of MoND that includes Einstein’s relativistic effects and explains observations where MoND is limited, such as the cosmic microwave background radiation. Then there is the proposed theory of retarded gravity that also claims to satisfy such observations.
Astronomers are surprised to find that many observations show a complete absence of dark matter or dark matter-deficient structures, casting doubt on its existence.
Then you have to find an explanation for what might have caused the problem, such as tidal forces exerted by the passage of nearby galaxies that strip away dark matter. Even the mass of the Milky Way has recently been determined to be much smaller than expected from cosmology.
Does dark matter exist?
Recent discoveries cast doubt on the existence of dark matter. Despite extensive research and billions of dollars in investment, there has been no direct detection of dark matter.
The theory of dark energy negates the gravitational pull of matter, causing the universe to expand more rapidly with time, as observed. The interrelated variation of constants of nature, called covarying coupling constants (CCC), achieve the same effect by weakening gravity and other forces of nature with time, thus eliminating the need for dark energy.
Combined with the tired light (TL) effect, which assumes that light slows down due to energy loss, such a cosmological model has no room for dark matter. The CCC approach could also replace the dark energy-like constant thought to be responsible for the extremely rapid expansion of the universe after the Big Bang, called inflation.
The age of the universe is determined by the historical expansion rate of the universe and can vary depending on the model used for the expansion. By measuring the redshift of exploding stars, called type 1a supernovae, and their observed brightness, the expansion rate can be determined.
Redshift is the reduction of the frequencies of the spectral line as a function of the recession velocity of the emitting object, similar to the frequency of a retreating ambulance siren. By combining the redshift due to the tired light effect with the expansion redshift, the expansion velocity of the universe is reduced and the age of the universe is increased.
(NASA, ESA, CSA, STScI, B. Robertson (UC Santa Cruz), B. Johnson (CfA), S. Tacchella (Cambridge), P. Cargile (CfA))
This new model predicts the universe is older than we think — 26.7 billion years in CCC cosmology compared to 13.8 in standard cosmology — and allows galaxies and their clusters to form without dark matter. The increase in the universe’s age at early times, when structures began to form, was up to 100 times larger in the new model.
The absence of dark matter, which reduces gravity and increases the time it takes for matter to collapse into structures, is largely overcompensated by the increased age in the CCC model.
Slowing down time
The expansion of the universe causes time to appear slowed down when observing distant galaxies. The CCC+TL model is consistent with observations showing a time dilation effect that appears to slow down the clock in distant objects.
Emerging criticism of the CCC+TL model rests on flawed hypotheses, such as the shortcomings of the tired light concept, or on incorrect analyses, including redshift analysis of cosmic microwave background temperatures. A single free parameter in CCC cosmology determines the variation of all constants that asymptotically approach their respective constant values. As in standard cosmology, CCC cosmology has only two free parameters. Adding tired light to CCC does not require an additional free parameter.
The standard cosmology model requires dark matter to fit observations, such as accounting for redshift when measuring the brightness of supernovae. Dark matter is also used to explain physical processes, such as rotation curves of galaxies, clusters of galaxies, or gravitational lensing. Using CCC+TL cosmology means that we must seriously consider alternative physical processes to explain astrophysical observations previously attributed to dark matter.