Mom, This! the internet.

Mom, This! the internet.

Mom, 

Lets start with the basics. This is something a lot of my friends don't even know. 

Do you know what is the internet is?

Like HOW it sends stuff and WHAT it is? No, mom, it's not magic.

The internet is like the post service.

The internet is a tangible, PHYSICAL system that was made to move emails, pictures and text messages around the world. It's pretty much like the the postal service, you know, that strange snail mail system you guys used back when I was a little kid. Writing stuff on letters and putting that sticky square stamp on the corner. 

The only difference is that the physical stuff that gets sent is a little bit different. The Internet ships a ton of things called bits. A bit is a pair of opposites like a yes/no or on/off. Usually we say “on” is a "1", and “off” is a "0" and because there are two possible states, we call it binary code. So 10101010 has 8 bits, since there are 8 "1"s and 0"s. 

So instead of envelopes and cardboard boxes, the internet sends a bunch of "1"s and 0"s. 

  • 8 of these bits (eg. 10101010) make up one byte.
  • 1000 bytes together make up a kilobyte
  • 1000 kilobytes make a megabyte, or 8,000,000 ones or zeroes!

Your favorite song is probably made of 3-4 megabytes or 24-32 million "1"s or 0"s. 

It doesn't matter if it's a picture, a video, or a song. Everything on the Internet is represented and sent around as these "1"s and 0"s or bits. But it's not like we're physically sending a piece of paper with a "1"s or 0"s on it from one place to another. 

You are probably asking yourself what the physical stuff is actually getting sent if its like the postal office?  

Well, here a short exercise, how might me and you physically communicate sending a single bit of information from one place to another? Not talking to each other or writing a letter, but me saying to you saying “yes” or “no” | “on” or “off”. 

So say that we could turn on a light for a "1" or off for 0", that would send one bit of information from me to you. A more complex system would look something like morse code, like the Sean Connery did in the The Hunt for Red October. 

This would definitely work!

But it would be rather really slow, you and I would have to physically sit there to receive the signal and no one would have time to make their beds, or take out the trash or do chores or cook dinner! 

That would be a horrible world to live in! We really need is a machine to do it for us, so we can do other more important son things and mom things. 

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 of information by electricity, light, and radio waves.

The internet sends info via Electricity. 

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 "1" and light off means 0", then we have a system for sending bits of information from one person to another using electricity.

Although they would have kind of a small problem.

What If you need to send a 0" five times in a row, well, how can you do that in such a way that either person can actually count the number of 0"s? 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 "1"s in a row.

Operator: Switch it on. wait 5 seconds. 
Receiver: Write down "on" or "off" for every second.

Obviously, this would still be slow, we'd want something a little bit faster than one bit per second. So we in a physical system we could increase the number of wires and lights, but that would take up a lot of space, so we instead change the range of frequencies at which we send information. This is our bandwidth, the maximum transmission capacity of a device.

Bandwidth is measured by bitrate, which is the number of "1"s or "0"s that we can actually send over a given period of time, usually measured in bits per second.

Different applications require different bandwidths.

  • An instant messaging conversation: <1,000 bits per second (bps);
  • An internet phone call (voice over IP (VoIP)) with me : 56 kilobits per second (Kbps)  
  • Standard definition video (480p): ~1 megabit per second (Mbps),
  • HD video (720p): ~4 Mbps
  • HDX (1080p): <7 Mbps.

We can also view internet speed as the time it takes for a "1" or "0" to travel from one place to another (from the source to the requesting device like a computer). This is latency. 

For just me and you, one bit per second was pretty fast, but kind of hard for us to keep up with. But consider trying to download a three megabyte song in three seconds.  At 8,000,0000 bits per megabyte is a bitrate of about 8,000,000 bits per second. I don't think our fingers could flip or tap a switch 8,000,000 times per second, but a machine can do that just fine.

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 you find connected to the WIFI box, you see measurable signal loss or interference over just a few hundred feet. So that wouldn't work across the globe.

This blue wire, Mom, with the clear plastic connector thingy

This blue wire, Mom, with the clear plastic connector thingy

For the Internet to work all around the world, we need to have an alternative method to send bits really long distances.

Like across all the oceans. So what else can we use?

Well, what do we know that moves a lot faster than just electricity through a wire?

Light.

The internet sends info via light waves

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. It's like those toys at Disneyland that they sell at night, except useful...

When you send a beam of light down the cable, it doesn't go straight down the middle. The light bounces up and down the length of the cable until it pops out 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 losing information or signal loss. This is why we use fiber optic cables across the ocean floors to connect one continent to another.

In 2008, the Middle East and India had interrupted internet, because of a cut cable near Egypt. We often take this Internet thing for granted and we forget it's a pretty fragile physical system.

Fiber is awesome, but it's also really expensive and hard to work with. For most purposes, you're gonna find copper cable. 

So now you are probably going to ask how do we move things without wires? That WIFI thingy. Ill explain more in about it in the next post. 

WiFi_ZONE.gif

For now, just digest some of this. any questions, mom?

love, 

your son.

Mom, This! Wi-Fi

Mom, This! Wi-Fi

MNIST + Softmax Regression + Multilayered Convolution Layer + TensorFlow

MNIST + Softmax Regression + Multilayered Convolution Layer + TensorFlow