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The Internet | Wires, Cables, and Wi-Fi

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My name is Tess Winlock, I'm a software engineer

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at Google. Here's a question: How does a picture,[br]text message, or email get sent from one device

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to another? It isn't magic, it's the Internet.[br]A tangible, physical system made to move information.

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The Internet is a lot like the postal service,[br]but the physical stuff that gets sent is a

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little bit different. Instead of boxes and[br]envelopes, the Internet ships binary information.

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Information is made of bits. A bit can be[br]described as any pair of opposites: on or

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off, yes or no. We typically use a 1 meaning[br]on, or a 0 meaning off. Because a bit has two

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possible states we call it binary code. 8[br]bits strung together makes 1 byte. 1000 bytes

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all together is a kilobyte. 1000 kilobytes[br]is a megabyte. A song is typically encoded

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using about 3-4MB. It doesn't matter if it's[br]a picture, a video, or a song, everything

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on the Internet is represented and sent around[br]as bits. These are the atoms of information.

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But it's not like we're physically sending[br]1s and 0s from one place to another or one

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person to another. So what is the physical[br]stuff that actually gets sent over the wires

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and the airways? Well, let's look at a small[br]example here of how humans can physically

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communicate to send a single bit of information[br]from one place to another. Let's say that

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we can turn on a light for a 1 or off for[br]0. Or use beeps or similar sorts of things

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to Morse code. These methods work but they're[br]really slow, error prone, and totally dependent

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upon humans. What we really need is a machine.[br]Throughout history, we've built many systems

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that can actually send this binary information[br]through different types of physical mediums.

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Today, we physically send bits by electricity,[br]light, and radio waves. To send a bit via electricity,

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imagine that you have two lightbulbs connected[br]by a copper wire. If one device operator turns

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on the electricity then the lightbulb lights[br]up. No electricity, then no light. If the

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operators on both ends agree that light on[br]means 1 and light off means 0, then we have

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a system for sending bits of information from[br]one person to another using electricity. But

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we have kinda a small problem, if you need[br]to send a 0 five times in a row, well how

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can you do that in such a way that either[br]person can actually count the number of 0s?

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Well the solution is to introduce a clock[br]or a timer. The operators can agree that the

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sender will send 1 bit per second and the[br]receiver will sit down and record every single

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second and see what's on the line. To send[br]five 0s in a row, you just turn off the light,

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wait 5 seconds, the person at the other end[br]of the line will write down all 5 seconds.

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For five 1s in a row, switch it on, wait 5 seconds,[br]write down every second. Obviously we'd like

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to send things a little bit faster than one[br]bit per second, so we need to increase our

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bandwidth - the maximum transmission capacity[br]of a device. Bandwidth is measured by bitrate,

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which is the number of bits that we can actually[br]send over a given period of time usually measured

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in seconds. A different measure of speed is[br]the latency, or the amount of time it takes

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for one bit to travel from one place to another,[br]from the source to the requesting device.

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In our human analogy, one bit per second was[br]pretty fast but kinda hard for a human to

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keep up with. Let's say that you actually[br]want to download a 3MB song in 3 seconds,

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at 8 million bits per megabyte that means[br]a bit rate of about 8 million bits per second.

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Obviously, humans can't send or receive 8[br]million bits per second but a machine could

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do that just fine. But now there's also the[br]question of what sort of cable to send these

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messages over and how far the signals can[br]go. With an ethernet wire, the kind that you

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find in your home, office, or school you see[br]measurable signal loss or interference over

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just a few hundred feet. For the Internet[br]to work all around the world, we need to have

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an alternative method to send bits really[br]long distances. We're talking like across

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oceans. So what else can we use? What do we[br]know that moves a lot faster than just electricity

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through a wire? Light. We can actually send[br]bits as light beams from one place to another

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using a fiber optic cable. A fiber optic cable[br]is a thread of glass engineered to reflect

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light. When you send a beam of light down[br]the cable, light bounces up and down the length

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of the cable until it is received on the other[br]end. Depending on the bounce angle, we can

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actually send multiple bits simultaneously,[br]all of them traveling at the speed of light.

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So fiber is really really fast. But more importantly[br]the signal doesn't really degrade over long

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distances. This is how you can go hundreds[br]of miles without signal loss. This is why

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we use fiber optic cables across the ocean[br]floors to connect one continent to another.

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In 2008 there was a cable that was actually[br]cut near Alexandria, Egypt which really interrupted

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the Internet for most of the Middle East and[br]India. So we take this Internet thing for

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granted but it's really a pretty fragile,[br]physical system. And fiber is awesome but

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it's also really expensive and hard to work[br]with. For most purposes, you're going to find

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copper cable. But how do we move things without[br]wires? How do we send things wirelessly? Radio.

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Wireless bit sending machines typically use[br]a radio signal to send bits from one place

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to another. The machines have to actually[br]translate the 1s and 0s into radio waves of

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different frequencies. The receiving machines[br]reverse the process and convert it back into

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binary on your computer. So wireless has made[br]our Internet mobile. But a radio signal doesn't

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travel all that far before it gets completely[br]garbled. This way you can't really pick up

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a Los Angeles radio station in Chicago. As[br]great as wireless is, today it still relies

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on the wired Internet. If you're in a coffee[br]shop using wifi, then the bits get sent to

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this wireless router and then are transferred[br]through the physical wire to travel the really

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long distances of the Internet. The physical[br]method for sending bits may change in the

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future, whether its lasers sent between satellites,[br]or radio waves from balloons, or drones, but

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the underlying binary representation of information[br]and the protocols for sending that information

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and receiving that information have pretty[br]much stayed the same. Everything on the Internet,

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whether it's words, emails, images, cat videos,[br]puppy videos, all come down to these 1s and

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0s being delivered by electronic pulses, light[br]beams, radio waves, and lots and lots of love.