Do we need a new cosmology? Maybe so
Do we need a new cosmology? Scientists have spent 60 years developing the Standard Model of cosmology. It is the idea that our universe began with the Big Bang. It explains the expansion of the universe, the large-scale distribution of galaxies, the cosmic microwave background, and much more. But some observations do not fit the Standard Model. And in early 2023, NASA’s new James Webb Space Telescope casts more doubts about the Standard Model. So, do we need a new model of the universe… a new cosmology? Hear from a scientist — below — who thinks we do.
Rajendra Gupta, University of Ottawa/University of Ottawa.
Do we need a new cosmology?
How old is the universe exactly? A new theory suggests that it has been around for twice as long as previously thought.
Early observations of the universe by the James Webb Space Telescope (JWST) cannot be explained by current cosmological models. These models estimate the age of the universe to be 13.8 billion years, based on the Big Bang concept of the expanding universe.
My research proposes a model that puts the age of the universe at 26.7 billion years, which explains the impossibly early observations of galaxies by the James Webb Space Telescope.
The impossibly early galaxies point to the fact that some galaxies dating back to the cosmic dawn — 500 to 800 million years after the big bang — have disks and bulges similar to those that went through a long period of evolution. Smaller galaxies appear to be more massive than larger galaxies, which is exactly the opposite of expectations.
frequency and distance
This age estimate is derived from the expansion rate of the universe by measuring the redshift of the spectral lines in the light emitted by distant galaxies. The previous explanation for the redshift was based on the hypothesis that light loses energy as it travels cosmic distances. This tired light explanation was rejected because it could not explain many of the observations.
The redshift of light is similar to the Doppler effect on sound: noise appears to have a higher frequency (pitch) as it approaches, and lower as it recedes. The redshift, which is a lower optical frequency, indicates when the object has receded from us; The greater the distance of the galaxy, the faster the regression and redshift.
An alternative explanation for the redshift was due to the Doppler effect: distant galaxies are moving away from us at speeds proportional to their distance, indicating that the universe is expanding. The expanding universe model became a favorite of most astronomers after two Bell Labs astronomers, Arno Penzias and Robert Wilson, accidentally discovered the cosmic microwave background (CMB) radiation in 1964, which the steady-state model could not satisfactorily explain.
The rate of expansion essentially determines the age of the universe. Until the launch of the Hubble Space Telescope in the 1990s, uncertainty in the expansion rate estimated the age of the universe to be between seven and 20 billion years. Further observations have led to the currently accepted value of 13.8 billion years, which places the Big Bang model on the pedestal of cosmology.
limitations of previous models
Research published last year proposed solving the impossible early galaxy problem using the tired light model. However, tired light cannot satisfactorily explain other cosmological observations such as the redshifts of supernovae and the uniformity of the cosmic microwave background.
I tried to combine the standard big bang model with the tired light model to see how well it fit with the supernova and JWST data, but it didn’t fit the latter well. However, the age of the universe has increased to 19.3 billion years.
Next, I tried to create a hybrid model that included tired light and a cosmological model that I developed based on the evolving coupling invariants proposed by British physicist Paul Dirac in 1937. This matched the data well, but nearly doubled the age of the universe.
The new model extends the galaxy formation time by 10 to 20 times that of the standard model, providing enough time for the observed “impossible” early, evolved galaxies to form.
And as with any model, it would need to provide a satisfactory explanation for all those observations that the standard cosmological model satisfies.
The approach of mixing two models to explain new observations is not new. Isaac Newton considered light to propagate as particles in his theory of light, which prevailed until it was replaced by the wave theory of light in the 19th century to explain the diffraction patterns observed in monochromatic light.
Albert Einstein revived the particle-like nature of light to explain the photoelectric effect, in that light has dual properties: particle-like in some observations and wave-like in others. Since then it has been established that all particles have such dual properties.
Another way to measure the age of the universe is to estimate the age of the stars in globular clusters in our galaxy, the Milky Way. Globular clusters contain up to a million stars, all of which appear to have formed at the same time in the early universe.
Assuming that all galaxies and groups began forming simultaneously, the age of the oldest star in the group should provide the age of the universe (less than the time when the galaxies began forming). For some stars like Methuselah, which is believed to be the oldest in the galaxy, astrophysical modeling gives an age greater than the age of the universe determined using the Standard Model, which is impossible.
Einstein believed that the universe is the same that can be observed from any point at any time: homogeneous, isotropic and timeless. To explain the observed redshift of distant galaxies in such a steady state of the universe, which appears to increase in proportion to their distance (Hubble’s law), the Swiss astronomer Fritz Zwicky proposed the tired light theory in 1929.
While some Hubble Space Telescope observations did point to an impossible early galaxy problem, this problem wasn’t fixed until the launch of the James Webb Space Telescope in December 2021, and data it provided since mid-2022.
To defend the standard Big Bang model, astronomers have tried to solve the problem by compressing the formation timeline of massive stars and primordial black holes that accumulate mass at unphysically high rates.
However, a consensus is developing towards new physics to explain the James Webb Space Telescope observations.
Rajendra Gupta is Assistant Professor of Physics, University of Ottawa/University of Ottawa.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Bottom line: do we need a new cosmology? The Standard Model, which is based on the Big Bang theory, explains many things quite well. But it doesn’t explain everything. New data from the James Webb Space Telescope raises more questions about whether the Standard Model needs a revamp.
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