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Is The Inflationary Universe A Scientific Theory? Not Anymore by Sabine Hossenfelder.
Sabine is a theoretical physicist sp

We are made from stretched quantum fluctuations. At least that’s cosmologists’ currently most popular explanation. According to their theory, the history of our existence began billions of years ago with a – now absent – field that propelled the universe into a phase of rapid expansion called “inflation.” When inflation ended, the field decayed and its energy was converted into radiation and particles which are still around today.

Inflation was proposed more than 35 years ago, among others, by Paul Steinhardt. But Steinhardt has become one of the theory’s most fervent critics. In a recent article in Scientific American, Steinhardt together with Anna Ijjas and Avi Loeb, don’t hold back. Most cosmologists, they claim, are uncritical believers:

“[T]he cosmology community has not taken a cold, honest look at the big bang inflationary theory or paid significant attention to critics who question whether inflation happened. Rather cosmologists appear to accept at face value the proponents’ assertion that we must believe the inflationary theory because it offers the only simple explanation of the observed features of the universe.”

The quantum fluctuations inherent to space, stretched across the Universe during cosmic inflation, gave rise to the density fluctuations imprinted in the cosmic microwave background, which in turn gave rise to the stars, galaxies, and other large-scale structure in the Universe today.

And it’s even worse, they argue, inflation is not even a scientific theory:

“[I]nflationary cosmology, as we currently understand it, cannot be evaluated using the scientific method.”

As alternative to inflation, Steinhardt et al. promote a “big bounce.” In this scenario, the universe’s current expansion was preceded by a phase of contraction, yielding similar benefits to inflation.


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