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Edge of the Universe

Explore the cutting edge of cosmological sciences

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Edge of the Universe

Cover to Edge of the Universe: A Voyage to the Cosmic Horizon and Beyond by Paul Halpern

John Wiley & Sons, Inc.
Paul Halpern tackles an ambitious subject: taking readers on a tour of the most complex questions scientists face about how to explain time, space, and the development of our very universe. In doing this, he covers not only the known and well-understood aspects of cosmology and astrophysics, but into realms that are extremely speculative. He navigates both areas adeptly, though if there's one flaw it's that the book is not always quite so clear on which ideas are well accepted by the physics community and which ideas are considered more fringe.

The Book's Science

Cosmology and astrophysics are fields which currently contain many of the most profound mysteries facing modern science. Much of the field is very well understood, but there are several open questions that, due to the limitations of our ability to observe the universe, we have yet to resolve. Halpern does an excellent job of explaining what is known, but then also discussion the various unknown possibilities and laying them out in a way that is accessible to a broad range of readers.

The book covers the standard range of concepts in modern cosmology, starting with The Big Bang theory and the expansion of the universe, including the recent findings about dark matter and dark energy. He discusses the way that the anthropic principle could be used to explain the physical properties that we observe.

These are all the standard things that you'll find in pretty much any cosmology book over the last decade. But what makes this book stand out is how broadly he looks at some of the more speculative approaches related to these open questions, to show the diversity of thinking that goes into them, without taking a firm stance on them. His goal seems to be to demonstrate the range of thinking, rather than to push his own pet theory, which is a refreshing change of pace.

Consider just a few of the speculative theories that he presents:
  • Might it be possible to explain the universe's expansion without relying on dark energy. Specifically, he calls into question whether the it is possible that the Copernican principle doesn't apply to our universe in the way we think it does? A 2008 research paper, "Living in a Void: Testing the Copernican Principle with Distant Supernovae," "suggested that our part of the universe might not be typical as [sic] all, but instead constitute an unusually empty region called a void. The authors [...] argued that setting aside the Copernican principle, as applied to the cosmological scale, could offer a natural solution to the acceleration issue without applying dark energy."
  • Halpern discusses the speculative models of a cyclic universe, such as the ekpyrotic universe described by Paul Steinhardt and Neil Turok on their book Endless Universe: Beyond the Big Bang, as well as another idea by Steinhardt that there might be another substance, called quintessence, that could fill result in the expansion observed in our universe.
  • Discussion of the holographic principle, including how it relates to black holes, and how it might be possible to detect a sort of "holographic noise" using gravity wave detectors.
  • A mysterious region of space that is moving in unexpected ways, dubbed dark flow by the researcher leading the investigation into it.
  • If a multiverse exists, might it be possible to experimentally detect different bubble universes colliding with each other? In recent years, physicists have proposed a way to search for signs of exactly these sorts of collisions with in the cosmic microwave background radiation data. The theory has not been refuted, although more data needs to be analyzed before scientists can tell if the predictions match observations.
  • And if the multiverse does exist, would there potentially be a way to travel to a parallel universe, perhaps through a wormhole?
It's an exciting trip through some cutting edge physics. If Halpern's book has one shortcoming, it's that the reader might be left with the idea that physicists view the majority of the theories presented in the book equally, but it's definitely a mixed bag. Some of what he discusses is well established and there's little doubt of it, but still other ideas are highly speculative and have no solid experimental or observational evidence. No doubt in a decade, physicists will look back on many of these more speculative ideas and find that they didn't pan out very well, with little evidence to support them, but for those who are wanting to better understand some of the most extreme theories in physics, this is a good place to start.

Book Specifics

Published: October 2, 2012
Publisher: John Wiley & Sons, Inc.
Hardcover edition comes in at 236 pages, with 15 chapters, Acknowledgements, Notes (6 pages), Further Reading (3 pages), and an Index (8 pages)

Notable Quotes

The recombination era is the age, some 380,000 years after the Big Bang, when atoms formed and light began to travel freely through space. Light from that era is the earliest we can detect. Before then, the universe was opaque, meaning that light was unable to travel far.

As Princeton astrophysicist J. Richard Gott and his collaborators calculated, the observable universe--the part we can potentially detect--is currently about 93 billion light-years in diameter.

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