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I'm learning a bit of how WiFi works under the hood, and have a basic grasp of the general process.

First, you make an internet request. Your computer then sends out a WiFi signal which your router picks up.

The router converts this WiFi signal into a long-range signal. This signal can traverse the length of the Earth.

The router's signal is picked up by the server you made the request to. The server repeats the process to respond back to you.

But I have a question with this procedure (assuming I'm correct with this basic explanation): Because light waves follow the inverse square law, wouldn't the router's initial signal need to be incredibly strong? Otherwise how can it be detectable at incredibly far distances (like the opposite side of the Earth)?

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    $\begingroup$ Your home router doesn't blast the signal all the way to the other side of the earth. It uses a routing protocol to find a nearby router along a path from your router to the other side of the earth. This journey will generally take many hops along many different routers (that are usually connected by wires, not wireless). To see all the hops use the "traceroute" utility. $\endgroup$
    – hft
    Commented Jul 27, 2023 at 21:21
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    $\begingroup$ ("traceroute" on linux, or "tracert" on windows) $\endgroup$
    – hft
    Commented Jul 27, 2023 at 21:23
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    $\begingroup$ Also between the routers there are other devices which transform and/or amplify the signal: switches, bridges, repeaters, transceivers, media converters, amplifiers... $\endgroup$
    – pabouk - Ukraine stay strong
    Commented Jul 28, 2023 at 9:28

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The router converts this WiFi signal into a long-range signal. This signal can traverse the length of the Earth.

No, the route usually goes via more than one router, and the signal only has to reach the next router in the chain.

Because light waves follow the inverse square law,

They follow the inverse square law when there's nothing to guide them. But most long range data links guide the electromagnetic energy with a cable or optical fiber. The inverse square law doesn't apply.

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    $\begingroup$ In other words, the internet beyond your router is made up of long "pipelines" that guide the signals. Or, if you will, a series of tubes. $\endgroup$
    – Michael Seifert
    Commented Jul 28, 2023 at 21:02
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First, you make an internet request. Your computer then sends out a WiFi signal which your router picks up.

Yes.

The router converts this WiFi signal into a long-range signal. This signal can traverse the length of the Earth.

No. By far the most typical internet connection is a wired or fiber optic connection. It is not a radio signal and it is certainly not transmitting to the other side of the planet.

Because light waves follow the inverse square law, wouldn't the router's initial signal need to be incredibly strong? Otherwise how can it be detectable at incredibly far distances (like the opposite side of the Earth)?

Correct. It helps that radio receivers are quite sensitive. But transmitting to the other side of the planet is tricky. You also get to trade between bandwidth and signal strength.

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    $\begingroup$ Thanks for your answer. I’m don’t really understand how the light waves can follow the inverse square law in a wired scenario (which you described in your second response). $\endgroup$
    – Loic Stoic
    Commented Jul 27, 2023 at 21:23
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    $\begingroup$ @LoicStoic, The inverse square law is simple geometry. It describes the behavior of energy that radiates outward in all directions from a central point. Energy that is guided by a transmission line (e.g., coaxial cable, Cat5 twisted pair, or optical fiber) cannot radiate outward. It is confined to the wire, and it can only go from one end to the other. $\endgroup$
    – Solomon Slow
    Commented Jul 27, 2023 at 23:31
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    $\begingroup$ @LoicStoic water spraying from a fountain behaves differently than water pumped through a pipe, does it not? Same thing for light, it can travel tremendous distances once you confine it in a fibre. $\endgroup$
    – Stian
    Commented Jul 28, 2023 at 6:50
  • $\begingroup$ To get a sense of scale for how far a lightwave in a fibre-optical cable can go, see Submarine communications cable: they use powered repeaters at regular intervals around 100 km apart. $\endgroup$
    – ojdo
    Commented Jul 28, 2023 at 9:12
  • $\begingroup$ And the light in fiber is LASER light, which has much less dispersion. $\endgroup$
    – Barmar
    Commented Jul 28, 2023 at 14:21
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The missing piece here is that a given signal only reach the next device in the chain. Then this device emit a new signal -which can be optical, electrical, or radio- to communicate with the next device.

Think about the alarm tower in the Lord of the Rings: a fire is lit at Minas Tirith, which is seen by a watcher on a mountain peak. The watcher lit a second fire, which is seen by a second watcher, and so on on. At the end of the chain this is a human that emit a vocal signal that reach the other peoples.

Only the first watcher can see the original signal, and there's different transmission method used (light from the fire and voice).

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  • $\begingroup$ Nice analogy. Also, the time it takes from the guys seeing the fire, to lighting their own one, makes it clear why each hop introduces extra latency on top of the lightspeed one. $\endgroup$
    – Bart van Heukelom
    Commented Aug 2, 2023 at 22:33

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