On This Day 25 May

By TheBoldAge. Published 2020-05-25
On this day we discover the Doppler Effect, presented in 1842

1842 - Christian Doppler presents the Doppler Effect in Prague

An Austrian physicist, Christian Doppler, described the phenomenon in 1842 presenting it to the Royal Bohemian Society. The phenomenon he described has since become known as the Doppler Effect.

What is the Doppler Effect? Sheldon (Big Bang Theory) had to explain it as the basis for his fancy dress costume as "The apparent change in the frequency of a wave caused by relative motion between the source of the wave and the observer".


Think of an ambulance or police car with its siren blaring. We know that the frequency of the siren doesn't change, however as it approaches us the sound changes, likewise when it recedes. This received frequency being different during the approach and recession is the Doppler Effect.

The below video is one of the best explanations we've come across and is worth watching.

So what... the application of the Doppler Effect is used in multiple areas for example sonar, robotics (the ability to identify moving objects), radar, echocardiogram, ultrasounds, and satellite communications.

So as you are out and about on this day see if you can spot the Doppler Effect in action.

Other events on this day

  • 1720 - 'Le Grand St Antoine' arrived in Marseille and with it the last major plague outbreak in Europe; killing approximately 100,000
  • 1768 - Captain James Cook departed on his first voyage of discovery - charting the coasts of NZ and Australia
  • 1842 - Christian Doppler presents what is now known as the Doppler Effect to the Royal Bohemian Society in Prague
  • 1895 - Oscar Wilde was convicted of gross indecency and sentenced to 2 years hard labour
  • 1939 - Ian McKellen was born
  • 1977 - the first file in the Star Wars saga premiered
  • 1986 - a 95-year-old scores a hole-in-one in Florida
  • 1994 - HST (Hubble Space Telescope) confirms existence of a black hole
  • 2012 - SpaceX Dragon is the first commercial craft to dock at the International Space Station
  • 2018 - GDPR became enforceable
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