Radical new Big Bang theory says gravitational waves created galaxies, stars and planets

A radical new theory regarding the origin of the universe suggests that gravitational waves, tiny ripples in spacetime first predicted by Albert Einstein back in 1915, could have given rise to cosmic matter, eventually spawning galaxies, stars and planets.

The theory aims to do away with a range of speculative and adjustable parameters within the standard Big Bang theory. The fact that these parameters can be so freely modified is challenging, as it means that scientists can't tell if a model of the beginning of the universe truly predicts observations of the modern cosmos, or if it has simply been adapted to fit this picture.

"For decades, cosmologists have been working on a model, the 'inflationary paradigm,' that suggests the universe expanded at an incredible rate, explaining everything we observe today," team leader Raúl Jiménez of the University of Barcelona told Space.com. "The new model suggests that natural quantum oscillations of spacetime itself, gravitational waves, were sufficient to trigger the tiny density differences that ultimately gave rise to galaxies, stars, and planets."

"The inflationary paradigm can explain why our universe is so homogeneous and isotropic [possessing the same amount of matter at the same density in all directions] and that the fluctuations of a quantum origin of the primordial density arise from the amplification of vacuum fluctuations of a scalar field. This is crucial because these primordial quantum fluctuations are precisely the seeds that explain the entire structure of the universe we see today," team member Daniele Bertacca of the University of Padua told Space.com. "But there's a problem: this theory includes too many 'free' or 'tunable' parameters, which can be adjusted at will.

"Too much flexibility in science can be problematic because it makes it difficult to determine whether a model is truly predicting something or simply adapting, a posteriori [after the fact], to observed data."

Inflation not 'inflaton'

The team's model begins with initial cosmic inflation described by an expanding cosmic state called "De Sitter space," which they explain can be considered as a condensation of "gravitons," the hypothetical particles that convey the force of gravity in a similar way that photons are the "messenger particles" (or gauge bosons) of the electromagnetic force.

This de Sitter spacetime would have decayed completely when its near-equilibrium state, when quantum effects became so strong that they caused the universe to become a chaotic quantum system.

This all represents their model, depending on a single energy scale that goes on to account for all predictions of cosmic evolution.

This does away with the need for a range of hypothetical fields and particles, such as the "inflaton" field, a hypothetical field with a high potential energy that generated a repulsive force in the early universe, which caused rapid and exponential inflation in some Big Bang models. Instead, gravitational waves, as natural quantum oscillations of space-time itself, are enough in this model to create the density fluctuations that lead to matter developing structures like galaxies, stars, and planets.

"This was almost 'magical,' since the only free parameter of the de Sitter scale is its energy scale, and due to its complexity and nonlinearity, this turns out to be linked to the observed level of fluctuations," Bertacca said. "It is precisely the elegance and simplicity of the proposed model, and the absence of free parameters, that are key.

"Furthermore, we expect it to be able to elegantly and naturally explain the energy scale and the time course of inflation. Both determine all observable predictions and are necessary to solve the cosmological horizon and flatness problems."

Of course, this is science, not magic, and when it comes to any scientific theory, verification with observational evidence is key. The team thinks that their model could provide fingerprints that can be detected in astronomical data.

"Like all theoretical models, ours must be confirmed by measurements and observations that researchers can analyze, evaluate, and compare with data from ground-based and space-based experiments today and in the near future," Bertacca said. "These gravitational ripples interact and build complexity over time, leading to testable predictions that researchers can now compare with real data."

Data that could confirm or refute this new model includes measurements of a cosmic fossil called the cosmic microwave background (CMB), a field of radiation left over from an event just after the Big Bang. Observations of the large-scale structure of the universe and measurements of primordial gravitational waves could also make or break this new model.

"Our work provides a minimalist yet powerful, elegant, and potentially falsifiable framework. This is science at its best: clear predictions that future observations can confirm or disprove," Jiménez concluded. "Finally, these new results demonstrate that we may not need speculative ingredients to explain the cosmos, but only a deep understanding of gravity and quantum physics. If the model holds true, it could mark a new chapter in the way we think about the birth of the universe."

The team's research was published in July in the journal Physical Review Research.