Do the constants of nature—the numbers that determine how things behave, such as the speed of light—change over time as the universe expands? Does light get a little tired of traveling the vast distances of space? Dark matter and dark energy were believed to explain these cosmological phenomena, but recent research suggests that our universe is expanding without dark matter or dark energy.
Removing dark matter and dark energy solves the “impossible early galaxy problem” that arises when trying to explain galaxies that do not meet expectations for size and age. It is possible to find an alternative to dark matter and energy that fits existing cosmological observations, including the distribution of galaxies.
Read more: Exactly how old is the universe? A new theory suggests it has been around twice as long as previously believed
Dark matter
Dark matter is a hypothetical form of matter that does not interact with ordinary matter in any way other than gravity. It was proposed as a theoretical way to explain our astrophysical and cosmological observations. Ordinary matter can travel through dark matter without any resistance and vice versa.
In space, the force of gravity determines the speed at which an object orbits. The higher velocity than expected from nearby orbiting objects is attributed to the existence and gravitational pull of dark matter.
The gravitational force of dark matter can also bend light rays, causing a gravitational lensing effect just like normal matter. This makes it possible to measure the dark matter in a bending object, such as galaxies and galaxy clusters.
The most reliable support for the existence of dark matter comes from the small variations observed in the cosmic microwave background radiation (leftover radiation from the Big Bang), measured with ever-increasing precision.
Another argument for the existence of dark matter is that the large-scale structures of the universe, such as galaxies, could not have formed without dark matter in the finite age of the universe.
(NASA Goddard Space Flight Center/Stephen Walker)
An alternative theory
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 Newton’s inverse square law of gravitational attraction is a simplified version of the full force, which only becomes perceptible at very large distances when the Newtonian force becomes negligible.
Another alternative is a version of the MoND that incorporates Einstein’s relativistic effects and explains observations where the MoND is limited, such as the cosmic microwave background. Then there is the proposed theory of retarded gravity, which also claims to be consistent with these observations.
Astronomers are surprised to find that many observations show the complete absence of dark matter or dark matter-deficient structures. This leads to doubts about its existence.
One then has to find an explanation for what might have caused the problem, such as the tidal forces generated by the flyby of nearby galaxies that remove the 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 any dark matter.
Dark energy theory negates the gravitational pull of matter, causing the universe to expand faster over time than observed. Interrelated variations of natural constants, called covarying coupling constants (CCCs), achieve the same effect by weakening gravitational pull and other natural forces over 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 a dark energy-like constant that is 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 from the historical rate of expansion of the universe and can vary depending on the model used for the expansion. The expansion rate can determine the redshift measurements of the exploding stars, called type 1a supernovae, and their observed brightness.
Redshift is the reduction of spectral line frequencies as a function of the recession velocity of the emitting object, similar to the frequency of a receding ambulance siren. By allowing the redshift due to the tired light effect to coexist with the expansion redshift, the expansion rate of the universe decreases and the age of the universe increases.
(NASA, ESA, CSA, STScI, B. Robertson (UC Santa Cruz), B. Johnson (CfA), S. Tacchella (Cambridge), P. Cargile (CfA))
This new model predicts that the universe is older than we think—26.7 billion years in the CCC cosmology compared to 13.8 in the standard cosmology—and allows galaxies and their clusters to form without dark matter. The increase in the age of the universe in the early times when structures began to form was up to 100 times greater in the new model.
The absence of dark matter, which reduces the gravitational force and increases the time for matter to collapse to form structures, is greatly overcompensated by the older age in the CCC model.
Slowing down time
The expansion of the universe makes time seem to slow down when observing distant galaxies. The CCC+TL model is consistent with observations showing a time dilation effect that appears to slow down clocks in distant objects.
Emerging criticisms of the CCC+TL model are based on faulty hypotheses, such as the flaws presented by the tired light concept or incorrect analyses, including the analysis of the redshift of the cosmic microwave background temperatures. The single free parameter in CCC cosmology determines the variation of all constants that asymptotically approach their respective constant values. As in the standard cosmology, the CCC cosmology has only two free parameters. Adding a tired light to CCC does not require any additional free parameter.
The Standard Cosmological 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 galactic rotation curves, galaxy clusters, or gravitational lensing. Using CCC+TL cosmology means that we have to seriously consider alternative physical processes to account for astrophysical observations previously attributed to dark matter.