Center For Integrating Research and Learning

Arrow1930 - 1939

Timelines

Though the roaring twenties ended with the onset of the Great Depression, the progress of electricity and the tools it made possible seemed unstoppable in the 1930s. “Electricity is a modern necessity of life,” proclaimed U.S. President Franklin Roosevelt in 1938.

This decade saw the advent of FM radio, invented by Edwin Armstrong as an alternative to static-plagued AM. Most of the United States and much of Europe was connected via the radio; by the late 1930s four out of five American households had one.

Cyclotron

Average citizens in developed countries were also increasingly enlightened. In 1930, the photoflash lamp made its debut, replacing flash powder for photographers. Not long afterwards sodium vapor lamps began illuminating the country’s highways; an increase in automobile ownership fueled demand. The more economical mercury vapor lamp came on the market during this time, as did fluorescent lamps. In 1934, the coiled-coil filament was invented. Along with two other incandescent light bulb improvements made earlier in the century – the tungsten filament and the argon-nitrogen filled bulb – it brought brighter, more efficient bulbs to homes and businesses.

In 1931, two landmark scientific instruments were born. In California, Ernest Lawrence built the first cyclotron, a circular particle accelerator that used electric and magnetic fields to increase the energy of charged particles. These particles could then be shot toward another substance under study in order to examine its atomic structure. Lawrence’s original 4-inch wide “proton merry-go-round,” as he called it, was a great improvement over the existing linear accelerators. Before long he was making much larger, more powerful versions which became workhorses of atomic level research.

Meanwhile, half a world away in Berlin, a university student conceived of a tool that would create images that would put ordinary microscopes to shame. Knowing that the waves of electrons are 100,000 shorter than light waves, Ernst Ruska predicted they could be used in special microscopes to provide more detailed pictures. He made his first electron lens in 1931, using an electromagnet to focus a beam of electrons. Within two years he assembled a series of these lenses to create the first electron microscope, allowing scientists to see things at 10 times the magnification of light microscopes. Today’s electron microscopes can enlarge objects to more than 1,000,000 times their original size.

Fluorescent Lamp

A variety of events related to magnetism occurred during this period. Man-made magnets, first developed in the 1920s with steel, progressed rapidly in the 1930s with the fabrication of different alloys, notably alnico (aluminum, nickel and cobalt). Far superior to its steel counterparts, alnico magnets led to more sophisticated applications, including better radio and television technologies. Concurrently, a number of inventors were developing magnetic tape recording devices. These were used for broadcasting for the first time in the mid 1930s and would play an important role in World War II.

In the arena of theory, Walther Meissner and Robert Oschenfeld of Germany made a major stride in the still mysterious field of superconductivity with the discovery that superconducting materials exclude magnetic fields. This property, which became known as the Meissner-Oschenfeld effect (or sometimes just the Meissner effect), would go on to charm countless students watching demonstrations of levitating magnets. Around the same time, the Earth’s magnetic field was the subject of attention for another German, physicist Walter Elsasser. He proposed that the Earth’s magnetic field was the result of currents of liquid iron at the core of the planet.

1930 - 1939

1930

The first permanent alloy magnets of aluminum, nickel and cobalt (alnico magnets) are produced.

1931

British physicist Alan Wilson applies the band-gap theory of energy to account for the behavior of superconductors and insulators.

1931

The first cyclotron, a circular particle accelerator in which subatomic particles are accelerated by an alternating high-frequency electric field in a fixed magnetic field, is built.

1931

German physicist Ernst Ruska, while still a student in Berlin, constructs the first electron lens, using an electromagnet to focus a beam of electrons just as a lens focuses a beam of light. By 1933, he uses several electron lenses in a series to make the first electron microscope with better definition than a light microscope.

1932

James Chadwick of England discovers the neutron, a particle with mass similar to a proton, but that does not have an electrical charge.

1932

American physicist Carl Anderson discovers the positron, a particle with mass similar to an electron, but with a positive rather than negative charge.

1933

Walther Meissner and Robert Oschenfeld of Germany discover that as a material loses its resistance to electricity when its temperature is dropped below a certain temperature, the magnetic field inside the material is completely or partly expelled. Characteristic of all superconductors, this phenomenon came to be commonly known as the Meissner effect or the Meissner-Oschenfeld effect.

1933

Sodium vapor lamps come into use to light highways.

1934

German inventor Semi Joseph Begun constructs the first magnetic tape recorder used for broadcasting.

1934

The fluorescent lamp is introduced in Europe.

1934

In the United States, the coiled-coil filament is invented, resulting in brighter and more energy-efficient electric light bulbs.

1935

Magnetic tape for audio recording becomes available commercially in Germany following its introduction at the Berlin Radio Exhibition.

1936

French physicist Louis Néel develops the concept of antiferromagnetism, a temperature-dependent form of magnetism in which adjacent ions arrange themselves in antiparallel formations so that nearly no overall external magnetism can be detected.

1939

Walter Elsasser, a German-born American physicist, proposes that the Earth’s observable magnetic field is the result of rotation-related eddy currents in the liquid core of the planet.



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