Knocking on Heaven's Door - Randall (2011)

Lisa Randall is the Frank J. Baird, Jr. Professor of Science at Harvard University.  Randall is a particle physicist and cosmologist.  She has written numerous journal and magazine articles.  She also is the author of "Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions."

Knocking on Heaven's Door highlights the research currently being done in particle physics at the subatomic and cosmological scales.  In fact, the impact of scale serves as the unifying theme of Knocking on Heaven's Door.  Randall begins by highlighting one of the great mysteries facing physicists today, namely the fact that theories and laws that function consistently and predictably when investigated at the scale of the observable world simply do not hold true at the subatomic or quantum level.  Physicists are currently in pursuit of a unifying theory that would serve to explain this inconsistency.

Randall suggests that, while such a unifying theory would be helpful, it is not essential.  The author observes that the laws of physics on the observable scale remain reliable and consistent.  When applied at this level, scientists and non-scientists alike can use them to make predictions and assumptions critical to everyday life.  At the quantum mechanical level, other laws apply and can be used to make predictions and assumptions confidently.  As long as these laws remain reliable at the given scale, their value remains undiminished.

Randall provides a first-hand description of the Large Hadron Collider (LHC), which she visited while it was still under construction.  As an internationally respected physicist, Randall was provided access to the entire structure.  The LHC is the most costly machine ever built.  It lies beneath the French-Swiss border and covers a distance of approximately 27km or 17 miles.  The LHC was built and is operated by CERN, the European Organization for Nuclear Research.

Randall provides an summary of the numerous investigations currently underway at the LHC.  The most notable investigation involves an attempt to identify the Higgs boson, which scientists believe is responsible for the formation of matter following the Big Bang.  Identifying this and other elusive particles requires the collision of subatomic particles, in this case protons, at extremely high energy.  It is hoped that these collisions will result in the formation of other subatomic particles such as the Higgs.

The LHC experiments serve as a bridge between the very small subatomic scale and the vast cosmic scale studied by cosmologists.  The LHC experiments, especially the search for the Higgs Boson may explain much about how the universe was formed.

Moving to the cosmic scale, Randall goes on to discuss the role that dark matter and dark energy play in the expansion of the universe.  While dark matter and dark energy have never been seen, their presence has been determined mathematically through the observation that the universe, rather than slowing down as formally predicted, is actually speeding up.  The expansion is uniform much the same as if one put dots on a balloon and then inflates it.

Randall discusses other developing theories in cosmology including String Theory and the Multiverse Theory.  While not a String Theorist, per se, Randall and her colleague Raman Sundrum have proposed a theory to explain why gravity is such a weak force when compared to the other three forces: the strong nuclear, weak and electromagnetic.  This has been a question that has puzzled scientists.  The Randall-Sundrum theory, based upon a solid mathematical foundation, contends that the gravitational force is actually commensurate to the other forces, but it is concentrated in another dimension (Brane).  Adding this fifth dimension to spacetime, would explain why we feel gravity as such a weak force.

Randall concludes her book with an argument for the importance of basic scientific research.  While the goal of much of the research described in Knocking on Heaven's Door is simply to expand our knowledge of the world and the universe in which we live, Randall contends that it is essential.  She provides numerous examples of how knowledge gained from basic research has led to new technologies, such as the microcomputer chip, even though such applications were inconceivable at the time the research was conducted.