There are many different sensors that can be used to detect motion in a given environment. Passive InfraRed (PIR) sensors are the most used today, as they work by detecting moving heat signatures.

We know the Doppler Effect as the reason why horns and sirens drop in tone as they rush by us. But the Doppler Effect works on objects that are twisting around, too. We’ll tell you how the Doppler ...

Sitting on the beach at Gecko Island one afternoon, A man finds himself beneath the flight path of the airplanes leaving East Blue Airport. a) What frequency will the man hear as a jet, whose engines ...

Forbes contributors publish independent expert analyses and insights. I cover the history of science and exploration. Today's Google Doodle celebrates the 214th birthday of Christian Doppler, whose ...

The Doppler effect, discovered in 1842 by Christian Doppler, is familiar to most of us; stationary observers of waves such as sound waves will see wavelengths that depend on the relative motion ...

Krzysztof Bolejko receives funding from The University of Sydney. He is affiliated with Sydney Institute for Astronomy. There are so many galaxies in the universe that if you point a telescope in any ...