Internet

How Internet works?

In a nutshell, Internet is a network of networks which connects computers to each other and allows to transform data between them. Internet is a huge entity and to understand how it works we will look at it as at the system with key components.

 Firstly, you need to have hardware: everything starting from cables to satellites. There are machines data being stored on - servers, endpoints, such as smartphones - clients and connection points - nodes, eg. routers. Between the hardware devices you need to have transmission lines. They can be either physical - optic fibre cables or wireless signals from satellites, cell phone or 4G towers, or radios.

Most large communications companies have their own dedicated backbones connecting various regions. In each region, the company has a Point of Presence (POP). The POP is a place for local users to access the company's network. POPs are connected to each other through Network Access Point (NAP). T1 and T3 in the picture are the types of backbones. For example, T3 operates 45 Mbps (45 million bits per second). The backbones are typically fiber optic trunk lines. The trunk line has multiple fiber optic cables combined together to increase the capacity.

 In order to make this data transformation possible and computers “understand” each other there are protocols. Protocols are sets of rules that machines follow to complete tasks. They make the communication between devices possible. There are dozens of different protocols for different purposes. One of most important is, for example, Internet Protocol (IP). It is the pre-defined way that someone who wants to use a service talks with that service. The "someone" could be a person, but more often it is a computer program like a Web browser. There are also IP addresses, so one machine could find another.

 Data (also conversation, using voice over internet protocol, VoIP) between machines is transferred in packets. Packets are are parts of a file that range between 1,000 and 1,500 bytes. Packets don't necessarily all take the same path -- they'll generally travel the path of least resistance.

How data travels trough the air ?

Data travels across the internet in packets. Each packet can carry a maximum of 1,500 bytes. Around these packets is a wrapper with a header and a footer. The information contained in the wrapper tells computers what kind of data is in the packet, how it fits together with other data, where the data came from and the data's final destination.Information through the internet are transmitted by two basic methods: wires and frequency waves through the air. Microwaves are high-frequency waves that travel through the air in order to transmit data. Microwaves can travel directly through the air to each individual host, or are relayed all around the world through satellites.   

 Satellites

Satellites are used to transfer information through microwaves over farther distances. Satellites orbit approximately 22,000 miles above the earth's surface. Satellites are a means of redirecting straight microwaves from only satellite dish to another. Satellites located all over the world and has the ability to transfer vast amounts of data to almost anywhere in the world.

Satellite Internet generally relies on three primary components: a satellite in geostationary orbit (sometimes referred to as a geosynchronous Earth orbit, or GEO), a number of ground stations known as gateways that relay Internet data to and from the satellite via radio waves (microwave), and a VSAT (very-small-aperture terminal) dish antenna with a transceiver, located at the subscriber's premises. Other components of a satellite Internet system include a modem at the user end which links the user's network with the transceiver, and a centralised network operations center (NOC) for monitoring the entire system.

 Microwaves

The information travels through the air and into satellite dishes where the data in decoded and sent through copper lines to a host. Microwave transmission is only of the faster ways to transmit information, but are only useful for distances up to 30 miles. Because microwaves travel in a straight path, the curvature of the earth only allows the information on travel short distance.

Microwave links carry signals which are pulse code modulated (PMC). PMC is a form of digital modulation in which the microwaves are switched on and off in pulses of varying length. The length are arranged in binary code.

Matter and energy

Matter:

The common definition of matter is anything that has mass and volume (occupies space).For example, a car would be said to be made of matter, as it occupies space, and has mass.

Energy:

In physics, energy is a property of objects, transferable among them via fundamental interactions, which can be converted in form but not created or destroyed.

How the matter is structured?

Atoms are made from a nucleus of protons and neutrons and a cloud of electrons. Electrons are in constant motion around the nucleus, while the protons and neutrons move within the nucleus. Neutrons and protons are each composed of three quarks. As far as scientists can tell at the moment, quarks and electrons are among the most fundamental forms of matter.

What kind of forms energy can be?

Energy can exist in many different forms. All forms of energy are either kinetic or potential. The energy associated with motion is called kinetic energy. The energy associated with position is called potential energy. Potential energy is not "stored energy".

Kinetic energy:

Potential energy:

Light and matter

1. How does Light interact with Matter?

Light can interact with matter in three ways: absorption, transmission, and reflection. Visible light exists in waves, with distinct frequencies (wavelengths)specific to a corresponding color. Similarly, the electrons in an atom (responsible for interactions with light) vibrate at specific frequencies too, called natural frequency. It is the contact between the frequency of the light wave with the frequency of the electron’s vibration that determines whether light is absorbed, reflected, or transmitted.

1. ABSORPTION – When a light wave with an identical frequency to an electron’s natural frequency “impinges” upon an atom, the electrons will begin to vibrate as a result (almost like they are “set in motion”). The electrons will absorb the light wave (because it has the same vibrational frequency) and turn it into a vibrational motion (sort like it “matches” with the vibrational waves). The electrons, in turn, bump up against neighboring atoms, which changes the vibrations into thermal energy (think of when one cheering section at a baseball game starts doing the “wave”, which prompts all the other section to join in the fun).  This thermal energy is not turned back into light energy, thus that particular light wave never leaves the object again. This is ABSORPTION.

2. REFLECTION – This occurs when the frequency of the incoming light wave does not match that of the electrons’ natural frequency. If the object is opaque (not see-through/solid color), the electron vibrations are not “passed down” like during absorption. Rather, the surface-level electrons vibrate briefly before emitting that wave back out (as light). This is REFLECTION.

3. TRANSMISSION – Transmission works along the same lines as reflection, except it involves transparent or semi-transparent objects. The atoms take in the wave, vibrate briefly (but at a small amplitude – not like during absorption, when they vibrate with large amplitudes), transfer the vibrations throughout the body of the material, and then re-emit the wave as light out the other end. This is TRANSMISSION.

1. Why does Matter interact with Light?

Light is a manifestation of electromagnetic force.  Matter is made up of charged particles due to the nature of atoms, being composed of a positively charged nucleus surrounded by electrons that are in motion.  The nuclei in molecules also move with respect to each other.  In other words, these are charges that are in motion, and everytime charges are in motion, there will be an electromagnetic force that will be changing with time.  Light is an electromagnetic field that is oscillating.  It is a wave that can be characterized by a frequency.  But light is also a particle - its particle is called a photon and each photon carries a packet of energy that is proportional to the frequency.  Matter can absorb the energy from a photon.

1. What does Matter do with Energy from Light?

It depends on what kind of light.  There is a whole spectrum of light.  Light with very low frequencies (or long wavelengths, such as radio waves) have photons that are not too energetic.  This energy magnitude corresponds to nuclear spin levels.  Light with frequencies in the range of a gigahertz (109 per second or Hertz) correspond to microwaves.  These have enough energy to cause molecules to rotate faster.  Even higher frequencies (1012-1014 Hz) have enough energy to make molecules stretch and bend their bonds.  Light that we see corresponds to a very narrow range of the spectrum, 400 - 750 nm in wavelength.  For some molecules, photons in this range have enough energy to excite electrons, promoting them to higher energy levels.  Since these molecules will only absorb a specific frequency, what reaches our eye is no longer white light, but is now colored (It's white minus the color that the molecule absorbed).

How are matter, energy and light related to the Internet?

Attempts to quantify the energy used by the Internet have been made. In 2011 researchers estimated that the Internet consumed between 170 and 307 GW, less than 2 percent of the energy used by humanity. This estimate includes the energy needed to build, operate, and periodically replace the estimated 750 million laptops, a billion smart phones and 100 million servers worldwide as well as the energy that routers, cell towers, optical switches, Wi-Fi transmitters and cloud storage devices use when transmitting Internet traffic.

Internet is transferred through optic fiber cables. Cable consists of transparent core where light travels and transparent cladding with low refraction rate. Light is kept in the cable with total internal reflection. Optic fibers are good for extremely fast conductivity and little loss.

Sources:

http://en.wikipedia.org/wiki/Matter
http://en.wikipedia.org/wiki/Energy

http://www.nobelprize.org/educational/physics/matter/1.html

http://physics.info/energy/

http://segoianphysics.wordpress.com/2010/01/15/how-does-light-interact-with-matter/

http://bouman.chem.georgetown.edu/S02/lect10/lect10.htm

http://web.stanford.edu/class/msande91si/www-spr04/readings/week1/InternetWhitepaper.htm

http://computer.howstuffworks.com/internet/basics/internet-infrastructure5.htm 

http://electronicdesign.com/communications/understanding-modern-digital-modulation-techniques  
http://www.gizmag.com/air-waveguides-light-data-transmission/33109/ 
http://gizmodo.com/5575784/how-data-travels-from-a-wireless-device 
http://www.physics.udel.edu/~watson/scen103/projects/95f/voltage/project1-net.html 
http://www.groundcontrol.com/How_Does_Satellite_Internet_Work.htm 
http://computer.howstuffworks.com/ip-convergence2.htm