The discovery of gravitation by Isaac Newton in the 17th century is often referred to as the beginning of physics as we know it. More than two centuries later, the value of the gravitational constant, “the big G,” serves as the fundamental basis for understanding large-scale cosmic structures, while providing the essential theoretical foundation for general relativity. Yet, despite centuries of experimentation, the global dataset for G remains frustratingly inconsistent. Compared to the strength of the electromagnetic interaction, known to a relative uncertainty of 0.2 parts-per-billion, G is only known to 22 parts-per-million. This staggering five-order-of-magnitude gap highlights the unique stubbornness of gravity. Two primary factors contribute to this: (1) unlike its dimensionless electromagnetic counterpart, G is a dimensioned quantity tied to our macroscopic units, and (2) the gravitational force is extremely weak compared to other fundamental forces and impossible to shield. In this talk, I will discuss the recent NIST measurement that we undertook to better understand the global dataset. I will attempt to answer three central questions: Why is G so difficult to pin down? How did we measure it? And what now for the future of the gravitational constant?

No colloquium; Fall Break.

Global celebration greeted the 2012 discovery at CERN’s Large Hadron Collider of a particle that matches the textbook description of the Higgs boson. That achievement validated a remarkable chain of theoretical reasoning that combined the notion that symmetries dictate interactions with lessons from superconductivity. It was enabled by triumphs of accelerator art and experimental technique, and by human resourcefulness and collaboration on a global scale.

Some imagine that, once the keystone of the standard model of particle physics has been set, our subject is over. Others worry that we may be at an impasse, without sharp clues to a more complete understanding. I prefer to savor the challenge that our description of nature is incomplete, that we have so much more to learn.

This colloquium surveys themes that explore the breadth and depth of opportunities to enhance our understanding of the physical world, illustrated by examples from my research.