Doppler effect

The pitch of a flashing sound put into a law

Christian Johann Doppler (Salzburg, November 29, 1803 – Venice, March 17, 1853)

One fine day in 1845, a Dutch scientist had a brilliant idea to find out if the Doppler effect really existed. He drove a locomotive with a bugler on board on the railway between Utrecht and Maarssen.

On the platform, a music expert and a number of experts listened to the tone of the passing horn player.

They found that the tone of the approaching blower rose, that it was at its highest as it passed the platform and that it became increasingly lower after passing the locomotive. Although the horn player always blew the same note. The experiment was repeated several times.

The difference in tone also appeared to decrease or increase as the locomotive drove slower or faster. With this, the young meteorologist Christophorus Buys Ballot (1817890) had proven the theory of Doppler in practice.

The Doppler effect says that the frequency of a wave emitted by a source of light or sound changes when the source or the observer move relative to each other. Doppler is everywhere today.

You can use the effect to measure how far the stars are from us, and whether they are flying away from us or approaching us. The Doppler effect is used for everything that has to do with navigation of ships, planes and cars. With this famous effect, the police catch speeders.

All radar technology relies on Doppler. Doctors use Doppler to make an ultrasound of babies in the belly of pregnant mothers; with Doppler, the doctor can see if the blood flow in any part of the body is normal.

Christian Johann Doppler was born in Salzburg in 1803. His father was the most important exponent of an ancient dynasty of stonemasons who built altars and works of art in the region of Augsburg, Munich, Passau and Salzburg.

Father Doppler worked for the Bavarian king Ludwig I, among others, he had an academy education and was later distinguished by the Vienna art academy. Christian's older brother continued that tradition.

Christian himself was the baby of the family. His health was weak and he was not strong enough to work the hard marble. So he continued learning. Mathematics was his passion, but he didn't really excel at it.

He fumbled around as an assistant, took countless exams for a job at university or college, but failed. For a year and a half he earned his living as a bookkeeper in a cotton mill.

He sold his scarce possessions and had already applied for emigration to the American consul in Munich when he got a job at a secondary technical school in Prague. Little by little he conquered a full teaching position at the local technical college.

As a hobby, the ailing math teacher wrote articles about all kinds of physical phenomena.

His treatise Über das farbige Licht der Doppelsterne und einiger anderser Gestirne des Himmels dates from 1842, extensive and very detailed; the evidence still had to be provided.

However, he was no match for the cadaver discipline at his school. He once had to examine 256 students in writing and orally for mathematics and algebra in 17 days. On one occasion he had to deal with 145 men in eight days for the subject of land surveying.

He collapsed, was bedridden for two years and showed the first signs of tuberculosis.
On January 17, 1850, because of his wonderful scientific publications, he was well known enough to be appointed director of a new physics institute in Vienna. Two years later he was given a holiday to use his weak lungs to seek out the better climate of Venice.

No one expected him back. A successor was appointed shortly after his departure. He died in March 1853, aged less than 50.

Together with the composer Igor Stravinsky, the dance master Diaghilev, the poets Ezra Pound and Joseph Brodsky, Doppler is buried on the island of the dead San Michele, not far from the Venetian St. Mark's Square.

His beautifully restored tombstone stands very prominently under an arcade, near the entrance.

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