(upbeat music)
- My name is Tess Winlock.
I'm a software engineer at Google.
Here's a question.
How does a picture, text message, or email
get sent from one device to another?
It isn't magic.
It's the Internet, a tangible, physical system
that was made to move information.
The Internet is a lot like the postal service,
but the physical stuff that gets sent
is a little bit different.
Instead of boxes and envelopes,
the Internet ships binary information.
Information is made of bits.
A bit can be described as any pair of opposites,
on or off, yes or no.
We typically use a one, meaning on,
or a zero, meaning off.
Because a bit has two possible states,
we call it binary code.
Eight bits strung together makes one byte.
One thousand bytes all together is a kilobyte.
One thousand kilobytes is a megabyte.
A song is typically encoded using about
three to four megabytes.
It doesn't matter if it's a picture, a video, or a song.
Everything on the Internet is represented
and sent around as bits.
These are the atoms of information,
but it's not like we're physically sending
ones and zeroes from one place to another
one person to another.
So, what is the physical stuff that actually gets sent
over the wires and the airwaves?
Well, let's look at a small example here of how humans
can physically communicate to send a single bit
of information from one place to another.
So say that we could turn on a light for a one
or off for zero or use beeps
or similar sort of things of like Morse code.
These methods work, but they're really slow, error prone,
and totally dependent upon humans.
What we really need is a machine.
Throughout history, we've built many systems that can
actually send this binary information
through different types of physical mediums.
Today, we physically send bits
by electricity, light, and radio waves.
(electricity humming)
To send a bit via electricity,
imagine that you have two light bulbs
connected by a copper wire.
If one device operator turns on the electricity,
then the light bulb lights up.
No electricity, no light.
If the operators on both ends agree that light on means one
and light off means zero,
then we have a system for sending bits of information
from one person to another using electricity.
They have kind of a small problem.
If you need to send a zero five times in a row,
well, how can you do that in such a way
that either person can actually count the number of zeroes?
Well, the solution is to introduce a clock or a timer.
The operators can agree that the sender will send one bit
per second, and the receiver will sit down and record
every single second and see what's on the line.
To send five zeros in a row,
you just turn off the light, wait five seconds.
The person on the other end of the line will write down
all five seconds, fives ones in a row.
Switch it on.
Five seconds, write down every second.
Obviously, we'd like to send things a little bit faster than
one bit per second, so we need to increase our bandwidth,
the maximum transmission capacity of a device.
Bandwidth is measured by bitrate,
which is the number of bits that we can actually send
over a given period of time, usually measured in seconds.
A different measure of speed is the latency,
or the amount of time it takes for one bit to travel
from one place to another,
from the source to the requesting device.
In our human analogy, one bit per second was pretty fast,
but kind of hard for a human to keep up with.
So let's say that you wanna actually download
a three megabyte song in three seconds.
At 8,000,0000 bits per megabyte,
that means a bitrate of about 8,000,000 bits per second.
Obviously, humans can't send or receive
8,000,000 bits per second,
but a machine can do that just fine,
but now there's also a question of what sort of cable
to send these messages over
and how far the signals can go.
With an Ethernet wire,
the kind that you find in your home or office or school,
you see measurable signal loss or interference
over just a few hundred feet.
For the Internet to work all around the world,
we need to have an alternative method to send bits
really long distances.
We're talking across oceans.
So what else can we use?
Well, what do we know that moves a lot faster
than just electricity through a wire?
Light.
We can actually send bits as light beams
from one place to another using a fiber optic cable.
A fiber optic cable is a thread of glass
engineered to reflect light.
When you send a beam of light down the cable,
light bounces up and down the length of the cable
until it is received on the other end.
Depending on the bounce angle,
we can actually send multiple bits simultaneously,
all of them traveling at the speed of light,
so fiber is really, really fast, but, more importantly,
the signal doesn't really degrade over long distances.
This is how you can go hundreds of miles
without signal loss.
This is why we use fiber optic cables
across the ocean floors to connect one continent to another.
In 2008, there was a cable that was actually cut near
Alexandria, Egypt, which really interrupted the Internet
for most of the Middle East and India.
So we take this Internet thing for granted,
but it's really a pretty fragile physical system,
and fiber is awesome, but it's also really expensive
and hard to work with.
Form most purposes, you're gonna find copper cable.
But how do we move things without wires?
How do we send things wirelessly?
Wireless bit sending machines typically use radio signal
to send bits from one place to another.
The machines have to actually translate the ones and zeroes
into radio waves of different frequencies.
The receiving machines reverse the process
and convert back into binary on your computer.
So wireless has made our Internet mobile,
but a radio signal doesn't travel all that far
before it completely gets garbled.
This is why you can't really pick up a Los Angeles
radio station in Chicago.
As great as wireless is,
today it still relies on the wired Internet.
If you're in a coffee shop using Wi-Fi,
then the bits get sent through this wireless router
and then are transferred to the physical wire
to travel the really long distances of the Internet.
The physical method for sending bits may change
in the future, whether it's laser sent between satellites
or radio waves from balloons or drones,
but the underlying binary representation of information
and the protocols for sending that information
and receiving that information have pretty much
stayed the same.
Everything on the Internet, whether its words, emails,
images, cat videos, puppy videos,
all come down to these ones and zeroes being delivered
by electronic pulses, light beams, radio waves,
and lots and lots of love.
(upbeat music)