A theory of quantum gravity that describes the universe as beginning in a “Big Bounce” rather than a Big Bang has succeeded in explaining several anomalies in the cosmic microwave background (CMB) radiation.

Loop quantum gravity (LQG) is an alternative to string theory, and describes space itself as being quantized at the smallest scales, known as the Planck length, about 10–35 m. According to LQG, space cannot be crushed down any smaller than this, and the application of LQG to the broader Universe is known as loop quantum cosmology (LQC).

In standard Big Bang cosmology, were we to run the history of the universe backwards so that it collapses rather than expands, the universe would contract into an unknowable singularity. However, in LQC, the collapsing universe would stop collapsing at the Planck length, and then rebound. This suggests that if LQC is correct, there was no Big Bang

Now, new research by a team led by Abhay Ashtekar at Pennsylvania State University, has found that LQC can explain several anomalies in the CMB that have eluded explanation by other theories. The research is described in Physical Review Letters and the team includes Penn State’s Brajesh Gupt and Donghui Jeong, as well as Vijayakumar Sreenath of the National Institute of Technology Karnataka in India.

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