Steinhardt works to avoid a cosmic beginning |  Evolution News

Steinhardt works to avoid a cosmic beginning | Evolution News

Photo: Paul Steinhardt, by Sleepy Geek, CC BY-SA 4.0 via Wikimedia Commons.

On the Closer to Truth YouTube channel, Robert Lawrence Kuhn recently interviewed physicist Paul Steinhardt about his cyclic cosmological model. The model has proven very appealing to atheists because it avoids the philosophical implications of the universe having a beginning. I have already explained why the model does not avoid a beginning and how it requires high levels of adjustment to generate a universe allowing life (here, here). What struck me with renewed force in the recent interview was the layer upon layer of model assumptions unsupported by any empirical evidence.

Renounce inflationary cosmology

Steinhardt is one of the most interesting and influential figures in cosmology. He was one of the first architects of inflationary cosmology. He later rejected the theory for reasons he detailed in his American Scientist article “Pop goes into the universe”. He argued that all major predictions of the simplest and most tractable versions of inflationary theory have failed. And the current versions are so artificial and flexible that they could fit almost any data, so they have no real explanatory power:

A common misconception is that experiments can be used to falsify a theory. In practice, a faulty theory is made more and more immune to experience by attempts to correct it. The theory becomes more pointed and obscure to adapt to new observations until it reaches a state where its explanatory power diminishes to the point that it is no longer pursued… A theory like the multimess excludes nothing and, therefore, has zero power.

The basic framework

Steinhardt proposes that his cyclical model of cosmology better explains the structure of our universe and avoids many of the pitfalls of inflationary cosmology. The basic framework of his theory includes the following elements:

  • Our universe resides in a multidimensional brane that resides in a higher dimensional space containing other parallel branes hosting other universes.
  • The branes collide periodically due to an interbranic force bringing them together.
  • Collisions result in big bang events in the branes. The universes in the branes then expand due to the energy of the collision, bouncing a contracting universe back to an expanding universe. The branes are reset to their original split.
  • The collision transfers energy into a scalar field. This energy is then transferred from the scalar field to the production of matter and energy uniformly filling the universe.
  • The universe expands as in standard Big Bang cosmology with galaxies, stars and planets forming as the universe cools.
  • The expansion of the universe ends up accelerating.
  • The expansion phase ends and the universe begins to slowly contract. The slow contraction smoothes the universe.
  • The contraction ends with a rebound and the universe expands again starting a new cycle.
  • Expansion, contraction and rebound are driven by the energy of the scalar field whose value corresponds to the distance between the branes.

Multitude of hypotheses

The cyclic cosmological model purportedly explains such features of our universe as the near-uniformity of cosmic background radiation and the lack of curvature of space as well as other models, but it can only do so by relying on many speculative assumptions. The whole framework is grounded in string theory which many physicists are beginning to seriously question (here, here). It also assumes the existence of parallel multidimensional branes containing separate universes – a questionable application of string theory, even if true. Brane collision must happen in the right way to generate universes with just the right amount of inhomogeneity to give rise to galaxies with stars and planets.

Even if all of these assumptions were true, the level of fine-tuning required in the rebounds would still be immense. Cosmologist Andrei Linde said of an earlier version of the model the following:

By evaluating the initial amplitude of the quantum fluctuations on the scale corresponding to the observable part of the universe, we find that the branes must be parallel to each other with a precision better than 10−60 scale 1030 times greater than the distance between the branes.

Moreover, even if the branes existed and collided correctly, justifying the dynamics of such highly orchestrated expansion, contraction, and rebounds requires postulating a very particular scalar field. Its value must depend on the distance between the branes, and its energy must be described by a very precise mathematical form. And the transfer of energy from the field to the production of common matter and energy requires the proper coupling of the scalar field with the underlying matter and energy fields.

The irony is that Steinhardt’s criticisms of inflationary cosmology probably apply with equal force to his own theory. No empirical evidence supports any of the essential components of the theory. The many ad hoc features of his model are probably flexible enough to explain all of the observed data with the right choice of fine-tuned parameters and initial conditions. And the only testable predictions of string theory, which form the foundation of the entire framework, failed. Claims that cyclic cosmology offers a convincing explanation for the structure of our universe are considered by most cosmologists to be dubious at best.

A simpler explanation

The most obvious conclusion about our universe is that it was created by a transcendent mind that designed it for the purpose of sustaining life. This hypothesis is further supported by the design evidence we see in our planetary system and throughout life. Denying the conception’s conclusion has forced scientists to come up with the darkest and most contrived theories filled with multiverses, mysterious fields, and other wild speculations. Such efforts on the part of many scientists are perfectly reasonable given their materialistic framework. But an honest assessment of the evidence should at some point prompt them to question their philosophical assumptions.

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