You probably send a bunch of texts everyday.
But when you hit send, what happens? How does your message make its way across the room
or to the other side of the world, to someone else’s phone? I’m Greg, and What The Physics?! To send a message out of your phone, electricity
from your battery jiggles electrons in the antenna of your phone, giving off a kind of
light. Not visible light like the filament of a lightbulb gives off, but longer wavelengths,
radio waves, which can be thought of as invisible light. So, how does that invisible light encoded
your message? Well, How would you do it with a flashlight? Maybe you’d shine it on and
off with some sort of code, like Morse code. Dots and dashes. Or ones and zeros, binary.
When your phone and sends the letter U it turns it into a 01010101. Or the message “Why
don’t we text in binary?” is this. Then the antenna in your phone sends out the ones
and zeros in short jiggle stop jiggle stop jiggle stop jiggle stop. Where does the light encoding your message
go? Straight to your friends phone? To a satellite? Nope, the antenna in your phone is too tiny,
and can only send the message a few miles, so to where? You may have never noticed them before, but
if you keep your eyes open you might spot some of these strange fake trees. Have you
ever wondered why it’s called a cell phone? Well antenna towers at like these are every
few miles, or closer, even in what appears to be the middle of nowhere. Every antenna
tower presides over an area of land around it called a cell. These cells divide our land.
And when you send a text from inside a cell, A sphere of invisible light emanates outward
from your phone to an antenna tower jiggling its electrons and transferring the message. But you aren’t the only one sending out invisible
light. How does the tower know that your message didn’t come from somebody else? Like all light,
visible and invisible, for radio waves come in different frequencies, for visible light
that’s different colors. Imagine you have a bunch of people shining
a flashlight Morse code at you, But you can’t tell them apart. If you tell one person, “only
shine in the red,” and another person, “only shine in green,” then you can distinguish
them. That’s kind of what happens with phones. The tower tells my phone, “only text in
these particular frequencies,” and tell your phone, “text in these different frequencies.”
It’s like I am texting in green, and you’re texting in red. And all across cities and towns, spheres of
different frequencies are emanating outward from phones. Now your cell tower knows your message came
from you and it needs to send it to your friend. But how does it know where your friend is?
Well, you might as well call it a brain cell, because it’s connected to all the other cells
through a network of computers that knows all. It watches an tracks your friend, you
and everyone you know. When ever your phone’s on, wherever you go, the big computer brain
of your cellular network knows… your friend is in this cell. And to relay the message to them, the big
computer brain sends the message through cables to their cell ,where now, everything happens
in reverse. That cell tower send out a particular frequency to your friend’s phone, those
radio waves jiggle their antenna, that becomes zeros and ones, which are translated into
the message. And that’s what happens when you send a text.