26

Sep

2011

Conversations with John Marburger: Constructing Reality

 

As Science Advisor to President George W. Bush and Director of Brookhaven National Lab, the late John Marburger continually received questions from teachers, journalists, political staffers, technicians, students and many others seeking to understand today’s new frontiers in the field. Before his passing this past July, he wrote a book to answer these questions. In his lively guide Constructing Reality (Cambridge University Press; September 20, 2011), Marburger reveals how key conceptual developments from the last century and have led to the extraordinary findings of today.

In June, John Marburger discussed with Cambridge the future of quantum theory, his favorite physics writers, and the current challenges for President Obama’s science advisors.

Why did you want to write this book?

I began writing this book when I was Director of Brookhaven National Lab in 1998 because so many people were asking me questions about the lab’s work.  The questions were coming from teachers, journalists, political staffers, technicians, students and others who were interested in modern physics, but whose ideas about relativity and quantum mechanics were either out of date or highly speculative and unverified.  They didn’t see how it all tied together.  It seemed disconnected, complicated, too mathematical.  I wanted to give them a straightforward, intellectually serious book they could chew on that was more or less complete, more or less non-mathematical, and accurate from the mainstream view without losing key concepts in oversimplifications.

The ideas of ‘modern physics’ hang together with an astonishing coherence that is almost completely obscured in most lay books by efforts to simplify or ‘popularize’ topics that are indeed deep and complex, but certainly comprehensible.  Quantum mechanics is not just another theory. It is THE conceptual framework in which the entire reductionist chain of physical science evolves. You cannot understand the actual phenomena of the world from the classical point of view – this is the significance of Heisenberg’s Uncertainty principle.  So if the world is not ‘classical’ then what is it?  That is what I try to get at in my book.  Its rhythms are more complex than we expected, and we hope new observations will point the way to a simpler version.  But the mainstream view is that the essentially quantum features of this picture are here to stay.  This is not just about some new particles, nor about the Higgs boson.  This is about a completely new way of viewing our world.

What were the most important discoveries/moments that contributed to our understanding of quantum theory?

The chain of discoveries lasted from 1900 through the early 1970s when theory finally (almost) caught up with experiment.  Planck’s realization that the exchange of energy is ‘quantized’ (1900).  Insights by Einstein and Bohr and colleagues into the implications of ‘quantization’ (Old quantum theory prior to 1925).  Logically consistent formulations of the ‘Old’ patchwork of theories by Heisenberg, Schrodinger, Dirac and others (1925-26).  Applications to the structure of matter, including new ‘elementary particles,’ solids, nuclei, chemistry, etc.  There was not a moment of discovery; there was an extended saga, worthy in its monumental sweep and significance of a Homer or a Milton.  By the mid 70s, we had the framework of the Standard Model in hand, which is narrower than quantum theory, but breathtaking in its explanatory power.  We know there are more things ‘out there’ – dark matter, for example – that have not been swept into the symmetries of which the Standard Model is a glimpse.  But we have heard nature’s tune, singing throughout much of the past century.  There were some ‘aha’ moments, but the almost continuous flow of discovery, theoretical and experimental, throughout three-quarters of a century is amazing.

Who are the physicists in the past century that you most admire?

 

 

Einstein stood head and shoulders above all other twentieth century physicists.  None took nature more seriously nor pursued her in as much depth than Einstein and Bohr.  But the profundity of the topic

attracted many other great minds.  I love to read the papers of Dirac, of Fermi.  The most eloquent and insightful theoretical physicist writing today (in my opinion) is Steven Weinberg, whose wide scope ranges from excellent popularizations to authoritative technical books and papers covering much of modern physics.

As the century wore on, more and more dedicated and brilliant men and women were attracted to physics as one of the most challenging and intellectually rewarding human endeavors.  If those earlier in the century stand out it is because the opportunities for discovery were greater and the community was smaller.  I tried to give credit in my book to the discoverers, but there are so many that deserve mention that I have missed more than a few.

What are some of the biggest unanswered questions in the field?

There is actually very little we don’t know about quantum physics.  The point of my book is that quantum physics is actually a straightforward theory, never contradicted by any experiment.  It is THE current conceptual framework in which we attempt to understand all natural phenomena.  That said, quantum theory is a framework upon which theorists have learned to erect geometrical structures that can accommodate a greater variety of phenomena than our current Standard Model.  The most striking missing piece, in my view, is dark matter.  We can see its gravitational effects in astronomical observations, but it has not yet shown up in earth-based laboratory experiments.  We know the universe is expanding and that its expansion is accelerating, but we do not understand why.  And then there is gravity.  Gravity is awkward because it depends on a picture of space-time distorted by energy.  But ‘space-time’ is a classical concept, and bringing it into consistency with the quantum framework has been technically extremely difficult.  Different ideas exist on how to proceed, including string theory, and some are deep and beautiful, but most are speculative and indirect – topics for this century or the next.

How do you think CERN’s Large Hadron Collider will help point the way forward?

The energy and detectors of CERN’s LHC are designed deliberately to probe the region where the Higgs mechanism is expected to break down. The Higgs mechanism is a mathematical device introduced to achieve logical consistency in the Standard Model with the set of fundamental ‘particles’ we have actually observed in the laboratory.  It was inserted into the theory ‘by hand’ in the 1970s, and is known to be inconsistent itself above a certain energy.  The LHC was designed to see what happens at that energy. We hope to see some evidence of new phenomena – a new ‘line’ in the spectrum of ‘elementary particles,’ or something else.  Despite the number of theoretical ideas on the table, we still do not have enough experimental guidance to know what ‘comes next’ in the sequence of ideas that has so far unfolded during the past century.  The LHC is essential for this.

You served as Science Advisor to the President during the Bush Administration. What do you think is the biggest challenge for the current team of science advisors?

The overwhelming challenge for all U.S. domestic discretionary programs now and for the foreseeable future is the unsustainable growth in the mandatory budget: Medicare, Social Security, and interest on the national debt.  All of science is threatened by the uncontrolled rise in the cost of these ‘mandates.’  How to maintain the strength of science and innovation through the long tail of the Great Recession is an extremely vexing challenge for all the world’s large economies.

Budget problems aside, the world’s most difficult science policy challenge is also the least tractable at this time: the link between energy policy and anthropomorphic climate change has led the world into a grave and I am afraid by now unavoidable crisis in long term global environmental conditions.  This is an existential problem that cannot be solved by science or technology alone.  It is a global problem whose solution depends on a widespread and highly unlikely change in socioeconomic behavior on a vast scale.

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