How to yell across a solar system

First two-way telephone conversation in 1876.

Learn how spacecraft communicate with Earth across the solar system.

How to yell across a solar system

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The transceiver in the movie sends the data through space using electromagnetic energy. One kind of electromagnetic energy is the light we see with our eyes. But there are many other forms of electromagnetic energy. One form is radio waves. We can't see radio waves, but we know how to make them and we know how to detect them. We also know how to make them carry messages. It is radio waves that bring you radio and TV!

Electromagnetic spectrum 'Energy meter.'

Changing the shape of the radio waves to make them carry information is called "modulating" the wave. A radio wave that has been modulated to carry information is called a "signal." Now the wave is more than electromagnetic energy. It is a message!

Radio signal may be amplitude or frequency modulated.

An FM signal has its frequency, or wavelength, modulated. An AM signal has its amplitude, or height, modulated. Spacecraft modulate the waveform in yet a different way, but we will save that explanation for another time! If you are curious, see our classroom activity article on the subject.

It is the transceiver's job to convert an ordinary radio wave into one that carries a message.

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