ELI5. why do scientists always search for radio sygnals in space? Why do they think aliens use that to communicate?
In: Technology
Ultimately, there only are four ways that matter and energy can influence each other. We call these the *fundamental forces*.
**1. The Strong Force**
This is, as the name implies, the strongest of the four forces. It binds quarks together to form protons & neutrons, and in turn binds those together to form atomic nuclei. It’s responsible for the existence of the very elements. However, its range is ludicrously short. It can only reach across the width of an atomic nucleus before it vanishes, and so cannot be used for communication across any distance.
**2. The Weak Force**
This is the weaker of the two nuclear forces. It’s responsible for nuclear decay. Its range is also ludicrously short, rendering it useless for communication.
**3. Gravity**
This is by far the weakest of all four forces, although it does have a long range. It’s created by mass, but it’s so weak that you need planet-sized clumps of mass to get a noticeable amount of gravity. Generating signals for communication is nigh-impossible; gravitational waves are so weak that we only managed to prove that they exist a few years ago, and it took the collision of two supermassive black holes to create a signal big enough to detect.
**4. Electromagnetism**
This is the other long-range force, and it’s responsible for almost everything we experience in our everyday lives. It creates atoms and molecules, and dictates the behavior of solids, liquids, and gases. *Light itself* is a wave passing through the electromagnetic field, as are microwaves, x-rays, radio waves, and others. Electromagnetic waves are so easy to generate & so common that we have two organs embedded in our faces that are evolved to detect them. You can generate a radio signal simply by moving an electric charge back and forth rapidly, and detect it by watching the radio wave move an electric signal in a wire somewhere else.
TL;DR: Radio is a type of light, one of the most basic components of our universe, and the only such component that’s suited for long-distance communication.
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