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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Unfortunately the real answer to your question is a bit long, because electromagnetic waves are different than any other kind of wave you are used to, in that there is no medium that the wave is traveling through, like water or air. They can even travel through empty space. But I will do my best.
Electricity and magnetism are related in an interesting way. If you run electric current through a wire near a compass, you’ll cause the compass to change direction. If you spin a magnet near a coiled wire, you will cause an electric current in the wire. They are related to each other, but in a strange, physically perpendicular way you’d never really guess on your own.
Hold your right hand out like you were making a finger gun. Pew pew. But now, also half-extend your middle finger to point to the left. Your thumb, index finger, and middle finger form a 3-way x/y/z axis. This is how electricity, magnetism, and physical force are related: a magnetic field in the direction of your index finger causes an electric charge in the direction of your middle finger, and both together cause a force in the direction of your thumb.
Now imagine you could sort of “grab” a little bit of empty space, and “pull” a bit of electric charge in one direction from nothing, with no physical object there. Almost like you were stretching a virtual rubber band. This would create a magnetic charge rubber band stretching the same amount, in a perpendicular direction. Now let go.
What’s interesting is that these two stretched rubbed bands kind of “tug” on each other, wanting to get back to neutral. So the perpendicular electric and magnetic forces pull each other back towards zero, but there’s nothing to stop them when they get there, so they keep going right past each other and end up stretching back out the same distance, but in the opposite direction, as from where they started.
Now they pull on each other again, back to zero, and again right past each other. Back and forth, back and forth. There is no “friction” to slow them down, so they are a permanently oscillating little bit of electricity and magnetism. How fast do they oscillate? Well, depends how far you stretched the little rubber bands to begin with. The more you stretched them, e.g. the more energy you put into creating your little packet to start with, the faster they snap back and forth.
But remember your little finger gun: the result of this oscillation between your index finger (magnetic) and ring finger (electric) directions results in a force in the direction of your thumb.
Meaning, your oscillating little “packet” of electric and magnetic rubber bands experiences a force, and it *moves.* How fast does it move? Well, it has no mass, remember. It has no inertia, ‘cuz it’s not made of “stuff.” So it moves as fast as anything in this universe can: the speed of light.
So it is a distinct little packet of energy that is moving through space like a bullet. But that packet is made up of oscillating electric and magnetic fields. The rate of the oscillation depends on how much energy created it to begin with. How much the rubber bands were stretched before you let go. But no matter how fast they oscillate, they still travel through space at the same speed of light. High energy packets will travel less distance before they return to their initial configuration. Lower will travel further. This is the “wavelength” that differentiates wifi, from visible light, from radio, or gamma rays.
[Here’s an attempt at showing this animated.](https://commons.wikimedia.org/wiki/File:EM-Wave.gif)
It’s very hard to actually draw this, as it’s a 3D thing with stuff wiggling along 2 axes while traveling in a third. So most depictions of electromagnetic waves simplify it significantly, as a static 2D squiggle on paper. And because the actual explanation is a whole lot longer and requires knowing about the relationship between electricity and magnetism (see length of above), most grade school science books just say “eh, close enough” and move on. Unfortunately, that simplification tends to cause the same confusion you have.
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