In Defense of Nuclear Physics

From Quantum Diaries: In Defense of Nuclear Physics
By Byron Jennings

This song always reminds me of nuclear physics. The scales (i.e. sizes) involved in nuclear physics are too large to be of interest to the reductionists, also known as particle physicists. They say it is just chemistry. The chemists, on the other hand, are not interested because the scales are too small. Nuclear physics, the archetypal in-between science, has scales too short to apply directly to everyday life and too long to be at the cutting edge of short-distance physics. In-between science includes atomic physics, low energy nuclear physics, QCD and, if the LHC is successful, electro-weak physics. At the other end of the scale, we have the solar system and galactic science which have too a short a scale to be of interest to the cosmologists who are doing science at scales the size of the visible universe.

So, why do in-between science? Let’s take low-energy nuclear physics, the physics done at rare isotope facilities like TRIUMF’s ISAC facility, as an example. The nucleus is an intriguing object. It is built of neutrons and protons which are themselves emergent objects, that is, objects that are not present explicitly in the underlying QCD model. They emerge from solving that model. It is somewhat like building on sand, but as in the case of sand castles, that can be productive and interesting. Actually, things are not so bad. We now have a very good understanding of the relation between low-energy nuclear physics and QCD.

The nucleus is self-bound: the forces between the components hold it together. This allows all kinds of behaviour: it rotates, vibrates, has single-particle excitations, and pairing. It slices, it dices… well let’s not get carried away, this isn’t a TV commercial. Disentangling the various types of excitation can be fun—just get any of my experimental colleagues going on the topic. There are real intellectual challenges in sorting it all out. Great progress has been made but we are not at the end of the trail yet.

We also know a lot about nuclear power (no not in reactors, but in the stars). Stars are powered by gravitationally confined nuclear fusion. No need to build tokomaks—the universe has been powered by nuclear fusion from the beginning. To understand how the universe evolves through time, it is necessary to understand this energy source. And it’s not just ordinary stars, but novae and super novae are powered by nuclear energy as well. We are composed of the remnants of stars, remnants blown into space by novae and super novae explosions. We are star dust. Billion year old carbon.[2] To understand all this, is to understand nuclear physics. Explosive, short lived, and dynamic processes in the heavens depend on the properties of short-lived nuclear isotopes. Coming back down to our planet, the need for studying these isotopes and their associated reactions is fulfilled by facilities like ISAC which make and study short lived isotopes.

Even more down to earth, is nuclear medicine. Medical imaging, using short lived nuclear isotopes, explores questions such as, ‘What causes Parkinsonism?’ and ‘Can we catch Alzheimer’s disease at an early stage and cure it?’ Radiation has been used to cure cancer for a long time now and more progress is being made. In diagnosis and treatment, nuclear medicine is now mainstream. Cyclotrons, once the hallmark of elite physics departments, are now almost a necessity at research hospitals. The pure research in nuclear physics had led to benefits beyond our wildest dreams

And finally nuclear bombs; destruction beyond our wildest dreams. I would guess that in the USA, the right to keep and bear nuclear arms is covered by the second amendment. In any event, as with any science, nuclear physics can cure or kill. Fire keeps us warm, yet wood smoke is carcinogenic. What we need, always and everywhere, is reality-based thinking and responsible people.

To conclude, in-between science is driven by the same impulse that drives all science: a longing to know and a hope to help. Science at any scale is cool (or is that fundamental?).

I work like a dog with no recreation and they call me Mr In-between

Mr In-between, Mr In-between, makes a fellow mean, Mr In-between[1]

[1] From a song written by Harlan Howard and made popular by Burl Ives.

[2] From Woodstock by Joni Mitchell