Lucien LaCoste

Who was Lucien LaCoste?

Lucien LaCoste was a prominent physicist and meteorologist. He was coinventor of the modern gravimeter, invented the zero-length spring, and vehicle-mounted gravimeters. He was also co-founder of a prominent company selling gravimetric instruments.

LaCoste discovered the zero-length spring in 1932 while performing an assignment in Arnold Romberg's undergraduate physics course. A zero-length spring is a spring supported in such a way that its exerted force is proportional to its length, rather than the distance it is compressed. That is, over at least part of its travel, it does not conform to Hooke's Law of spring compression.

The zero-length spring is extremely important to seismometers and gravimeters because it permits the design of vertical pendulums with infinite periods. In practice, periods of a thousand seconds are possible, a hundredfold increase from other forms of pendulum.

Over a short period starting in 1932, the design of these instruments was revolutionized, obsoleting all previous designs.

During this period, LaCoste and his physics teacher Arnold Romberg invented the first modern seismographs and gravimeters, using steel and quartz zero-length springs.