Energy into Mass

In Paris last year the Curie-Joliots bombarded a piece of lithium with alpha particles, produced neutrons and boron atoms. The scientific world at that time was engrossed with neutrons whose existence Cambridge University atomic physicists had just discovered (TIME, March 7, 1932). The significance of the boron atoms in the Curie-Joliot experiment attracted less attention until last week Dr. Kenneth T. Bainbridge, who weighs atoms at Bartol Research Foundation laboratories in Swarthmore, Pa., presented an interpretation.

The fact that boron atoms and neutrons resulted when alpha particles struck lithium atoms confirms the Einstein Formula, Dr. Bainbridge declared. The Einstein Formula which Dr. Albert Einstein reached through recondite logic, looks simple: Mc^2 equals E.* It simply demonstrates that mass and energy are interchangeable, that heat can bundle itself into a lump of coal as well as a lump of coal can dissipate into heat.

A lithium atom has an atomic weight of almost seven (reasoned Dr. Bainbridge in effect). An alpha particle has an atomic weight which may be called four. If they merged during the Curie-Joliot bombardment, their combined weight was almost eleven. If the alpha particle and lithium atom did merge, they at once split into a boron atom and a neutron, whose combined weights totaled infinitesimally more than the combined weights of the lithium atom and alpha particle.

The important question was: whence the additional weight?

From the kinetic energy of the alpha particle which hit the lithium atom, argued Dr. Bainbridge. Where others only surmised, the Curie-Joliots actually saw energy turning into matter, saw E equalling c^2M.

* Mass (in grams) times the square of the velocity of light (in centimeters per second) equals energy (in ergs).

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