I've recently watched a "Through the Wormhole" episode from 2010 named "What Happened Before the Beginning?", where cyclic and ekpyrotic cosmological models are explained. In this episode the creators of the ekpyrotic model, Neil Turok and Paul Steinhardt, say that the results from the Planck satellite about gravitational waves will either support one theory or the other.

After doing a little bit of research about the Planck satellite I've come across some 2013 results on the Wikipedia page. However, this information is far too complex for me to understand.

How does this information affect the cyclic and ekpyrotic models? Are the results leaning towards one of the models?

  • $\begingroup$ I think that there is some misunderstanding here because ekpyrotic models are also cyclic. I have not watched the video to be able to see where the misunderstanding comes. In the wiki the contrast is with an inflationary universe. en.wikipedia.org/wiki/… $\endgroup$
    – anna v
    Dec 8, 2013 at 10:04

2 Answers 2


I, also a layman in physics, after watching one of Steinhardt's lectures, became curious as to the results he mentioned as well. I found this article in my search, which seems to state that the data which he is referring to has not yet been released, and is slated for a 2014/2015 release. In particular he refers to the polarized view of the cosmic microwave background radiation, which should show evidence for or against the residual effects of gravitational waves which are a necessary part of the inflationary big bang theory, but a detrimental observation to the cyclical membrane collision theory proposed by Steinhardt.


From the article:

There are further opportunities to solve the mysteries with two more data sets from Planck to be released, one in 2014 and a final one in early 2015. These will also include polarisation data, caused by the signature of gravitational waves at the very dawn of time.

I believe this is the information you are looking for, but as previously stated I am also a layman in physics.


I had the same question after watching Dr. Paul J. Steinhardt's talk at Vanderbilt http://www.youtube.com/watch?v=IcxptIJS7kQ

This gentleman teaches Big Bang Cosmology in Ireland and says the Planck data's non-Gaussian results put a kink in the ekpyrotic models.


In Dr. Steinhardt's paper on his page at Princeton, he writes:

... At the same time, by constraining the spectral tilt and fN L to a significant degree, the current results imply that a new (falsifiable!) prediction for cyclic models is that the intrinsic trispectrum parameter gN L should be negative in sign and of order 10^3 − 10^4 in magnitude. (As a cautionary note, we point out that the method of generating curvature perturbations in cyclic models is, to a large degree, separate from the scenario overall, as in the case of inflation. Other approaches than the one considered here would produce different predictions for non-gaussianity.) Whereas the non-gaussianity is somewhat model-dependent, a model-independent, falsifiable prediction of cyclic models is that there are no detectable primordial gravitational waves on the scales of cosmological interest. Thus, near-future measurements will provide clear-cut tests of these simple cyclic models of the universe.

(Thanks for the edit - here's his homepage with a link to this and some other related papers: http://wwwphy.princeton.edu/~steinh/cycliccosmology.html )


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