Center For Integrating Research and Learning

Arrow1910 - 1929

Timelines

The year 1911 saw two great discoveries. The first cracked open the door to a new type of electricity holding great promise as a power source for future generations. The second marked an important step in scientists’ understanding of the atom.

1911 also marked the farewell of English physicist J.J. Thomson’s “plum pudding” model of the atom, which had theorized an atom across which positive and negative charges were distributed regularly. The flaw in this model was exposed by the famous gold foil experiment devised by Ernest Rutherford of New Zealand. In the experiment, conducted by physicists Hans Geiger and Ernest Marsden, a sheet of gold foil was bombarded with alpha particles (helium nuclei). Based on Thomson’s model, the scientists expected all the particles to pass through the foil unfazed. Instead, a small percentage scattered, indicating they had hit something very small and very dense. This led Rutherford to the idea of a nucleus with a positive charge around which electrons orbited, like planets around a sun, an idea he published in 1911.

Iconoscope

Though more accurate than Thomson’s, Rutherford’s atom had its flaws, too. This was apparent to Danish physicist Niels Bohr, a colleague of Rutherford. Two years after news of the solar-system model was published, Bohr came out with his own, inspired by the recent theories about energy quanta. Bohr posited that electrons must inhabit very specific orbits, and that these orbits can accommodate a certain number of electrons and no more. Electrons, Bohr explained, can jump from one orbit to the next, depending on an atom’s stability and other circumstances.

More important insights into the atom followed in this time period. In the 1920s George Uhlenbeck and Samuel Goudsmit, students studying physics in the Netherlands, suggested that electrons don’t just orbit nuclei, but also spin about their axes, as does the Earth. In 1928, British physicist Paul Dirac predicted the existence of an antiparticle to the electron with the same mass but opposite electric charge and spin. The predictions came true four years later with the discovery of the positron by American physicist Carl Anderson.

While all this work went on in the minds and labs of the world’s great physicists, average citizens watched as electricity and the innovations inspired by it transformed their lives. For one, they were communicating differently. In 1915, thanks to Lee De Forest’s audion, the first transcontinental phone call took place, between San Francisco and New York. By 1920, a third of all American households had a phone. Service would be improved with the broadband coaxial cable, for which a patent was filed in 1929.

Advances in radio brought the new medium to more people. In 1920, the world’s first radio broadcasting station opened for business in Pittsburgh, Pennsylvania. A few years later, Americans heard the first major courtroom coverage, the famous Scopes “Monkey” Trial. American electrical engineer Edwin Armstrong invented the regenerative circuit, the superheterodyne receiver and the super-regenerative circuit during this period, making significant refinements to radio.

Lighting advanced to the point at which it was no longer just utilitarian, but also decorative. Neon tube lighting became commercially available in the early 1920s, and was soon seized on by advertisers.

Electricity, along with the growing array of appliances it inspired, made its way into more and more homes. In 1913, the first home dishwasher and refrigerator hit the market, followed by the first pop-up toaster in 1919 and, in 1927, the first garbage disposal. Russian inventor Vladimir Zworykin filed a patent in 1923 for the iconoscope, the first completely electronic means of scanning a picture for television; two decades later this technology would hit American homes full-force, and Zworykin would go down in history as “the father of television.”

1910 - 1929

1911

German physicist Heike Kamerlingh Onnes discovers that some materials exhibit almost no electrical resistance when they are cooled to extremely low temperatures, a phenomenon referred to as superconductivity.

1911

Under the direction of Ernest Rutherford, Hans Geiger and Ernest Marsden carry out numerous experiments on the scattering of alpha rays, leading Rutherford to posit a new model of the atom.

1912

High-pressure mercury lamps are invented, but do not become commercially available until more than 20 years later.

1912

While still a student at Columbia University, Edwin Armstrong invents the regenerative circuit, which enables amplification of a signal many times by the same vacuum tube.

1912

German physicist Max von Laue proves that x-rays are electromagnetic in nature.

1915

Thanks to American inventor Lee De Forest’s audion, telephone signals are able to be carried across country, making possible the first transcontinental phone call between San Francisco and New York.

1919

German physicist Heinrich Barkhausen discovers that a ferromagnetic material to which an increasing magnetic field is gradually applied is magnetized in small steps rather than on a continuous basis. Known as the Barkhausen effect, this phenomenon provided clear support for the theory of ferromagnetic domains.

1919

American inventor Edwin Armstrong invents the superheterodyne circuit, providing the broadcasting industry a greatly improved way to receive, convert and amplify weak, high-frequency electromagnetic waves.

1919

Quench-hardened steel magnets are introduced commercially.

1919

English electrophysiologist Edgar Adrian demonstrates that nerve cells generate voltages that trigger muscle contractions.

1920

The first radio broadcasting station in the world, station KDKA in Pittsburgh, Pennsylvania, is launched by the Westinghouse Electric and Manufacturing Company.

1922

Neon tube lighting becomes available commercially and is especially popular for advertising purposes.

1922

German physicists Otto Stern and Walther Gerlach demonstrate through the use of a molecular beam that the spatial orientation of atomic particles in a magnetic field is restricted (a concept termed space quantization).

1923

Russian inventor Vladimir Zworykin files a patent for the iconoscope, the first completely electronic means of scanning a picture for television.

1924

As part of his doctoral dissertation, German physicist Ernst Ising introduces a model, now known as the Ising model, to explain the behavior of ferromagnetic materials.

1925

While graduate students in the Netherlands, George Uhlenbeck and Samuel Goudsmit postulate that in addition to their orbital motions, electrons spin about their axes.

1928

British physicist Paul Dirac accurately predicts that there exists an antiparticle to the electron that has the same mass as the electron but the opposite electric charge and magnetic moment.

1929

American engineers Herman Affel and Lloyd Espenschied apply for a patent for coaxial cable, a transmission line for high-frequency signals that is characterized by low radiation loss and interference.

1929

Japanese geophysicist Motonori Matuyama studies the reversal of magnetic fields in rock strata and reasons that the Earth must occasionally undergo reversals of its polarity.



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