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### Course: NASA>Unit 2

Lesson 4: Spectroscopy

Created by NASA.

## Want to join the conversation?

• How was radio waves discovered?
• They were predicted by James Clerk Maxwell. His theory of electromagnetism was published in 1865. His namesake equations were proposed that there was a wave connecting magnetic and electrical fields that has the property of traveling at the speed of light. In 1887, Heinrich Hertz was the first to incontrovertibly prove the existence of radio waves. He did this by building an instrument that could detect VHF (Very High Frequency) and UHF (Ultra High Frequency) radio waves. Today, a hertz is known as a SI unit of frequency; one cycle per second.
• Are there any light waves beyond radio waves?
• Yes, radio waves are lower in the Electromagnetic Spectrum than visible Light.
If your asking is there any visible light "below" or lower in the Electromagnetic Spectrum than radio waves, the answer would be no. Since the Electromagnetic Spectrum starts at 1 Hz or 1 cycle per second.
A good visualization of the Electromagnetic Spectrum can be seen here:
https://en.wikipedia.org/wiki/Electromagnetic_spectrum
Hope that helps.
• How do radiowaves actually work? All of the videos just say it does but someone has to know if we use it.
• They are energy waves. When chemical reactions happen inside stars, for instance, the reactions produce energy as well as changing matter. This energy can be light, heat, or even kinetic energy. Radio waves are a form of radiation energy, which is one way that energy can transfer between matter. (The other two are conduction and convection.) This is specifically a form of electromagnetic radiation, meaning that energy is carried through electromagnetism. Radios work by encoding sound on one end into electricity that can be sent to another radio. Then, the other radio converts it to sound again.
• At how can a baseball on the moon fill the entire field of view of an array of radio antenneas
• I'm not too educated on this field (yet), but I believe they are referring to the power of its zoom ability. Like zooming in on a photo taken from the outside of some library, but being able to zoom in through the front yard, through a window, down a hall, and into the pages of an open book on the floor - and reading the words on it.
• what are quasars?
(1 vote)
• They are luminous black holes that emit radio waves.
(1 vote)
• How did Karl Jansky discover that objects in space radiated radio waves?
• At :14 to :39, it talks about radio waves getting sent out. Wouldn't the radio waves run out of energy and stop going eventually? Would it bump into something? How did the radio wave survive this many years?
• Well, if you look at a light spectrum, you can see that radio waves are just another kind of light. We can see stars many billions of light-years away, and so if those were actually radio wave sources, then we would be able to detect the waves. The waves we would be able to detect are bumping into the earth.

So no, the waves wouldn't run out of energy, and yes, they would eventually bump in to enough things that there wouldn't be any wave left; however, the universes' materiel is so long and far in between that it wouldn't hit very many objects.