How messages get sent, and the mystery of how quickly they can be received regardless of how far they have to travel, is explained in this short video.  If you have 10 minutes, I highly recommend it.  

In describing how the networking standard has evolved to enable greater traffic - so more data can move more quickly - the video also provides a plain language view on the infrastructure behind the internet.

Without getting overly technical, the video explains the fundamentals of telecommunications.  That a message is converted into pulses. The pulses travel along a network of physical cables or wires to be received and interpreted at the other end.  An early generation of this can be found in Morse Code. We've come a long way since then and that's largely thanks to glass.  For more, follow the link!

https://www.theverge.com/22393952/glass-fiber-internet-cable-wifi-speed-5g-explainer-video

P.S. Glass is made from sand, but not your Sahara Desert sand but specific sand that contains silica (which is comprised of small grains of quartz crystals made up of molecules of silicon dioxide). It's not surprising the famous technology-hub in California is called Silicon Valley.