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The Past, the Future, and Baby Universes


Thanks to fellow intern Justin Reeder for sending me an interesting article this morning, Does Time Run Backward in Other Universes?, published in Scientific American by cosmologist Sean M. Carroll.

The article (a formidable 6 pages) tackles those ever-so-elusive problems relating to the origins of our universe, and presents a couple of intriguing explanations. Almost as important are the comments at the bottom of the article, which provide a handful of concise critiques and different perspectives.

The author, a physics researcher at the California Institute of Technology, discusses the main ideas behind his and fellow colleague Jennifer Chen's theory that attempts to reconcile the arrow of time (the irreversible unidirectional time we observe) with certain characteristics of our universe, namely its entropy.

Carroll proposes that universes are created spontaneously by patches of ultra-dense dark energy, which expands rapidly into a vast empty space, before immediately shrinking and "pinching off" to form new, separate "baby universes". Under this idea, the big bang becomes an inadequate explanation for what happened at the beginning of our universe, it is simply another "pinching off" event, and our universe is actually one of these baby universes.

While in our own little baby universe time appears unidirectional, on a multi-universe scale the dark energy from other universes that are expanding, collapsing, and exploding into other baby universes occurs in both directions of time- the past and the future. According to the theory, entropy increases as baby universes continue to be spawned into existence by other universes.

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