Today
is the birthday of Christian Doppler. He was a physicist who first
described Doppler effect, now used in many space technologies, such as
the Global Positioning System that helps us navigate on Earth.
Humans have looked to the skies to find their way since ancient
times. Ancient sailors used the constellations in the night sky to
figure out where they were and where they were going.
Today, all we need is a simple hand-held GPS (short for Global
Positioning System) receiver to figure out exactly where we are anywhere
in the world. But we still need objects high in the sky to figure out
where we are and how we get to other places.
Instead of stars, we use satellites. Over 30 navigation satellites
are zipping around high above Earth. These satellites can tell us
exactly where we are.
What is GPS?
GPS is a system. It’s made up of three parts: satellites, ground stations, and receivers.
Satellites act like the stars in constellations—we know where they are supposed to be at any given time.
The ground stations use radar to make sure they are actually where we think they are.
A receiver, like you might find in your phone or in your parents car,
is constantly listening for a signal from these satellites. The
receiver figures out how far away they are from some of them.
Once the receiver calculates its distance from four or more
satellites, it knows exactly where you are. Presto! From miles up in
space your location on the ground can be determined with incredible
precision! They can usually determine where you are within a few yards
of your actual location. More high-tech receivers, though, can figure
out where you are to within a few inches!
The ancient sailors of history would be flabbergasted by the speed and ease of pinpointing your location today.
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