I really can’t grasp the concept of waves. I can imagine it a bit for sound waves: a speaker has a surface that pushes air, and the moving air eventually pushes the membrane in our ears.
But I’m confused about wifi etc. What exactly is the thing that physically travels? Is it air or something else? Does it physically move in a wavy pattern?
Edit: thanks for all the answers! But damn I’m overwhelmed. It’s gonna take me days to read and fully understand the answers. But thanks!
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Good question, and it IS really confusing. Starting with the sound waves you understand, these are pretty simple, they are known as mechanical waves. Exactly like the waves on the top of water, these are caused by the movement of particles causing the particles next to it to move. Without these separate particles to move, the wave cannot continue, which is why, for example, sound does not travel in space.
For WiFi, radio, etc., these are known as [electromagnetic waves](https://science.nasa.gov/ems/02_anatomy). These are actually the same thing as light, radiation, microwaves, etc. They are all caused by electromagnetic energy. This is actually the movement of photons, which are particles that have energy and momentum, but no mass (in the normal sense of mass, we’ll skip details about that since this is ELI5). And, yes, they move in waves – they act like both particles and waves. This is how polarized sunglasses work – because light is traveling in waves, there are a lot of tiny lines on the lenses, so the waves have to be moving the right way to travel between the lines. Think of throwing a frisbee at a picket fence – the frisbee has to be oriented just right to pass through the fence slats.
Photons always travel at the speed of light, so we use that to measure/classify the [different types of energy](https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html). The distance between the crests of the waves is known as the wavelength, which is one way to measure. Another is how many waves happen per second, which is known as frequency, and it is measured by “hertz”, with 1 hertz being a wave with 1 crest as it travels 1 second, 2 hertz being a wave with 2 crests as it travels 1 second, etc. We can also measure these in terms of how much energy they have, which we measure in electron volts. because of the speed of light constant, all of these are related to each other, so if you know one, you know them all. Radio waves, microwaves, infrared/UV/visible light, x-rays, gamma rays, etc., are all the exact same thing – photons moving in waves, but at different wavelengths.
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