Can a sound wave destroy the universe?
Radio waves are at the lower end of the electromagnetic spectrum. They are used to transmit information and help scientists learn more about our universe.
The Heinrich Hertz Tower in Hamburg
In 1880, the German physicist Heinrich Hertz generated radio waves for the first time. He thus confirmed the theory of the Scotsman James Clerk Maxwell, according to which electromagnetic forces can propagate in waves and according to which visible light is just such a type of wave. Hertz generated radio waves by causing charges in electrical conductors - such as in a transmitting antenna - to vibrate.
Starting with the so-called electrical waves with only a few tens of oscillations per second, the radio waves extend to medium, short and ultra-short waves with which radio programs are broadcast. These consist of up to 300 million oscillations per second. The wavelengths of radio waves can be greater than one meter.
How does the voice get on the radio?
Radio waves can be used to transmit information such as data or sounds wirelessly. To do this, however, the information must first be packaged. Every radio station has its frequency and this describes the electromagnetic wave over which the latest music hits or traffic news are broadcast. The tones are included as changes in this wave. There are two options for this, which are abbreviated to AM and FM on radio receivers:
- With amplitude modulation (AM), the information is contained in the changing maximum deflection (amplitude) of the shrinkage.
- With frequency modulation (FM), on the other hand, the frequency of the wave fluctuates slightly around the value you set on the radio.
The information contained in the received waves in the form of amplitude or frequency modulation is then converted into sound on the radio.
Why can you listen to the radio everywhere?
Even in the desert or on the ocean you have reception for certain transmitters, although there is no transmitter in sight - the ionosphere makes it possible. The ionosphere is a layer of our atmosphere that begins at a height of 100 kilometers and is around 300 kilometers thick. Radiation from space ensures that electrons are released from atoms. The positively charged atomic residues, together with the electrons, form a mirror for radio waves. A radio program from Deutschlandfunk can thus be tossed back and forth several times between the earth and the ionosphere and finally received by a portable radio in the Sahara.
Which transmitters receive radio telescopes?
All over the world, huge radio telescopes monitor the universe and are on the trail of natural signal sources and messages of extraterrestrial life. Because our atmosphere is permeable to electromagnetic waves with wavelengths of less than 20 meters. Cosmic radio waves can thus reach Earth and be picked up by radio telescopes. Because of the large wavelengths, radio telescopes are quite large. The Arecibo Observatory with a dish diameter of 305 meters is one of the largest radio telescopes.
Huge star explosions can be recognized via radio waves. The sun also emits radio waves, as do extra-galactic nebulae and so-called radio galaxies. From their research results, the radio astronomers gained, among other things, important knowledge about the spiral shape of the Milky Way.
And surely the thought is appealing that extraterrestrial intelligences could send us messages with radio waves that can be received by our telescopes. The data are examined for such signals in appropriate research programs.
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