Physics 155

Physics Behind the Internet

Why Study This?Why Study This?

• Teach Physics in a Context

• Its important for citizens to know how stuff works

• A technological society can not afford to be ignorant and believe in magic

• Communications/information has large scale societal consequences

Themes of This Course

Communication, Information, Communication Networks and Bandwidth

What are the rules of information?

How does information propagate?

How do you ensure the integrity of information?

How is information encoded?

Device PhysicsDevice Physics

How does electricity work?How does electricity work? How do you make a circuit?How do you make a circuit? What’s a transistor?What’s a transistor? What’s a semi-conductor?What’s a semi-conductor? How does a computer work?How does a computer work? How does my digital camera work?How does my digital camera work? How does my cell phone work?How does my cell phone work?

Photons versus ElectronsPhotons versus Electrons

Why are lasers an essential part of Why are lasers an essential part of communications networkscommunications networks

Why does my DVD player have a laser?Why does my DVD player have a laser?Why is photon encoded information so Why is photon encoded information so

much better than electron encoded much better than electron encoded information?information?

Why should I invest money in Photonic Why should I invest money in Photonic Devices?Devices?

Internet Routing and Internet Routing and ChaosChaos

• How do networks work?How do networks work?• How does routing work?How does routing work?• What’s a packet?What’s a packet?• What’s packet loss, latency, What’s packet loss, latency,

collision?collision?• How can the internet even function How can the internet even function

as it grows exponentially – won’t we as it grows exponentially – won’t we run out of addresses?run out of addresses?

Social Issues

Is the Internet a net good to society or a net evil?

Does it encourage social isolation? Does it improve or degrade personal

communication skills? Who should control the Net? What’s the end game evolution of the Net? Do we want that?

OverallOverall

• This course is not so much a physics course (although you will be exposed to more physics than you realize) – rather it’s a course about science, technology and society.

• Assignments will be done as mini-research projects by teams of students. Learning how to collaborate is essential.