Berni Alder’s early work lets scientists simulate nature

Alder pioneered using computers for science back in the 1950s. “There’s no higher high that you can get than working in science and achieving a goal that’s been waiting there for a long time,” says Alder, reflecting on his early triumph in using computers to simulate physical phenomena.

Molecular dynamics is a type of computer simulation used to study nature at the scale of atoms and molecules. EarthSky spoke with physicist Berni Alder, who pioneered using computers for science back in the 1950s.

Berni Alder: Computers originally were really computers! They were only used for what we used to call “experimental arithmetic.” All they could do was add and subtract and multiply and divide, and do that much faster than humanly possible.

Those early mechanical computers back in 1948 and ‘49 weighed about as much as a couple of SUVs and were available almost exclusively to scientists. But the scientific goals were much the same then as now – to understand nature. Dr. Alder was one of the first to use computers to simulate something real. He gave the example of a wave crashing on a beach.

Berni Alder: If you take it from the atomistic point of view, a crashing wave has so many particles in it that no computer will ever simulate it by the particle methods.

In other words, from a scientific perspective – when viewed at the scale of atoms – no computer built or imaginable can simulate the entire reality of a wave hitting the beach. Alder’s triumph was using computers to simulate precisely a tiny piece of that reality.

Berni Alder: One of the great discoveries we made is that hydrodynamics applies on a very small scale.

He said that – for a few hundred atoms, running less than a billionth of a second, these scientists could quantitatively reproduce the precise movement of water in an ocean wave. For this early work using computers on these sorts of simulations, Dr. Alder received a 2009 U.S. National Medal of Science, the highest honor given by the U.S. government to scientists.

Dr. Alder talked about the big problems in physics of the 1950s.

Berni Alder: The big problem at the early days when we were working is whether hard spheres could form a solid phase. In other words, could you form a solid without any cohesive forces between the particles, which make up the material. So the solid-fluid phase transition, does it exist or not, was a crucial question in the area of material science. And we didn’t resolve that problem. In fact, you can use hard spheres to make a solid, just elastic billiard balls without any attractive forces, will form at sufficiently high density a crystalline solid phase.

He had some encouraging words for the younger scientists of today.

Berni Alder: Keep going. I think science is an extremely exciting field. When you really make a discovery, when you for the first time know something which nobody else knows, which is important to medicine or whatever field you’re working on, I mean there’s no higher reward in this world and no higher high that you can get than working in science and achieving a goal that’s been waiting there for a long time.

Jorge Salazar