In 1988, I read Stephen Hawking’s “A Brief History of Time.” At the time, I don’t remember coming away from the book with any deeper understanding of time. But I do remember coming away from it with a deeper understanding of why I should care about the science.
“If we do discover a complete theory of the universe, it should in time be understandable in broad principle by everyone, not just a few scientists. Then we shall all, philosophers, scientists and just ordinary people, be able to take part in the discussion of why it is that we and the universe exist.”
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As should be expected from one of our generation’s great physicists, Hawking’s ideas strained the minds of both the millions of “ordinary people” who followed his work as well as his peers in the scientific community. He made us all think a little harder about what physics has to tell us about the universe. He laid out the promise of a unified theory of physics – the “one theory to rule them all.” And – most importantly in my book – he prompted a range of public discussions about black holes and singularities and space and time and what it might mean if we – everyone – understand the nature of the universe.
Hawking attacked physics at its most vulnerable point: the intersection between relativity and quantum theory. This exposed science’s dirty little secret that there are actually two branches of physics, each describing beautifully the way the universe works, but at different scales. Relativity does a great job describing how space, time and objects work at large scales, defining time and gravity and their interactions with things like planets, moons and baseballs. Quantum theory does equally well describing how nature works at the sub-atomic level of photons and protons and quarks. But the two theories don’t play well with one another. To have two different sets of equations and theories describing one universe is unsatisfactory, and leads physicists to admit that we simply haven’t quite figured it all out, just yet.
Any complete theory of the universe should reconcile this break between the physics of the big and small. And that’s where Hawking’s work came in. Black holes are defined by their gravitational effect; they have enough mass to gravitationally bend space so much that light itself is trapped, and time itself stops. That puts black holes in the realm of Einstein’s relativistic physics of the big. But black holes are also small. If they are not singularities – objects with no dimensions of length, width or height – then they are not much bigger than that. And that certainly puts them in the realm of quantum physics.
By considering black holes from both relativistic and quantum perspectives, Hawking came to some conclusions that challenged both branches of physics. But he did go on to develop new understandings of what happens at the intersection of the physics of the big and the small. And he gave rise to a generation of physicists who now understand the intersections of their respective disciplines in a new way.
No, he didn’t find a complete theory of the universe. But perhaps he put us on a path that will lead to one, and a future in which we shall all be able to take part in the discussion of why it is that we and the universe exist. Only time will tell.
We explore many of these ideas at the South Florida Museum during our monthly Stelliferous Live discussions and during our daily live Planetarium shows. And, of course, we follow Hawking's example by keeping our discussions on a level understandable by all.
Jeff Rodgers, South Florida Museum Provost & COO, can be emailed at JRodgers@SouthFloridaMuseum.org.