Lucien LaCoste (1908 – 1995) was a

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...

and

metrologist Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in Fran ...

. He coinvented the modern

gravimeter Gravimetry is the measurement of the strength of a gravitational field. Gravimetry may be used when either the magnitude of a gravitational field or the properties of matter responsible for its creation are of interest. Units of measurement Gr ...

and invented the

zero-length spring A spring is an elastic object that stores mechanical energy. In everyday use the term often refers to coil springs, but there are many different spring designs. Modern springs are typically manufactured from spring steel, although some non- ...

and vehicle-mounted gravimeters. He was also co-founder of

LaCoste Romberg Lacoste S.A. is a French company, founded in 1933 by tennis player René Lacoste, and entrepreneur Mangkha. It sells clothing, footwear, sportswear, eyewear, leather goods, perfume, towels and watches. The company can be recognised by its gr ...

, a prominent company selling gravimetric instruments.

Life

LaCoste_suspension_seismometer_principle

LaCoste discovered the

in 1932 while performing an assignment in

Arnold Romberg Arnold may refer to: People * Arnold (given name), a masculine given name * Arnold (surname), a German and English surname Places Australia * Arnold, Victoria, a small town in the Australian state of Victoria Canada * Arnold, Nova Scotia ...

'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 In physics, Hooke's law is an empirical law which states that the force () needed to extend or compress a spring (device), spring by some distance () Proportionality (mathematics)#Direct_proportionality, scales linearly with respect to that ...

of spring compression. The zero-length spring is extremely important to

seismometer A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The outpu ...

s and

s because it permits the design of vertical pendulums with (theoretically) infinite periods. In practice, periods of a thousand seconds are possible, a hundredfold increase from other forms of

pendulum A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the ...

. 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

invented the first modern seismographs and gravimeters, using steel and quartz (respectively) zero-length springs. While a graduate student, LaCoste decided to go into business together with Romberg, selling advanced gravimeters to oil-exploration companies. LaCoste's most famous invention is the ship, and aircraft-mounted gravimeter. These revolutionized exploration for minerals by allowing wide-ranging geological surveys. The chief problem that Lacoste defeated was to distinguish the accelerations of the vehicles from the accelerations due to gravity, and measure the minute changes in gravity. Since the accelerations from the vehicle typically are hundreds to thousands of times more forceful than the measured changes, this invention was considered impossible until LaCoste demonstrated it.

References

*December 1984 issue of The Leading Edge. *Eos, December 12, 1995, p. 516.

External links

* {{DEFAULTSORT:Lacoste, Lucien 1908 births 1995 deaths 20th-century American physicists Gravimetry