Computer Science = ideas

Ideas are powerful.You up for it?

tim@menzies.usOct’12

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Don’t say you were not warned

• If you want knowledge: bite the apple.– Welcome to responsibility and shame.

• Make a choice– Take charge– Leave paradise

• Would you want it any other way?– If Eden then no sex– no anesthetics (anyone you know had a baby? had a tooth pulled?)– no air travel (no spring break in Miami)– no space program (we landed on Mars? wow)– no internet, no smart phones, no Xbox

Case study 1

How computers won WW-II

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Convoys, sunk by U-boats

The enigma machine

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Enter computers• Bletchley Park,

England

• Massive banks of computers – looking for

patterns in German radio signals

• Massive kludgey machines – run by an army of 10,000 woman– Winston Churchill: “The geese that laid the golden eggs - but

never cackled.”

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The programmer

• Alan Turing: mathematical genius– Defined what it means

to be computable.

• By the way, he was gay– we’ll get back to that.

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The curse of information

The power• Thanks to Turing,

– the allies knew the location of the U-boats

• But they had to be careful– If the Germans knew they

knew, they change the codes– Take years to break the new

ones

The shame• So they had to let (some)

boats get sunk and (some) bombs fall on England– In order to mount the

invasion and win the war

• Dead sailors• Dead civilians• Bletchley Park hastily

dismantled post-WW2, records quickly forgotten

Case study #2

Computers and hydrogen bombs were developed by the same people

at the same time for same reason

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How to build a thermo-nuclear bomb(don’t try this at home)

1. separation of stages into a triggering "primary" explosive and a much more powerful

2. "secondary" explosive, compression of the secondary by X-rays coming from nuclear fission in the primary, a process called the "radiation implosion" of the secondary,

3. heating of the secondary, after cold compression, by a second fission explosion inside the secondary.

Btw,All in a microsecond

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Enter computers

• To design "radiation implosion" – Need massive simulations

• Enter the king of the shock wave– John Von Neumann

• Built computers at Princeton – using Turing’s designs– Ran the sims– Built the bombs

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His favorite computer programmer

• His wife, Klara von Neumann– Famous ballerina– Bored by her first husband (a banker)– Left him for Johnny, moved to America

• Gifted– While Johnny wined and dined the

generals– She ran the clunky computers back at

Princeton

• Did not do well when Johnny died

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The curse of information

The power• Thanks to Von Nuemann,

– American got the h-bomb first

• Which leads to the arms race and the cold war

The shame• Global annihilation • Nuclear proliferation• In this case, it is not true that

– “someone would have done it”

• Von Neumann’s Princeton team was … unique

Case study #3

Turing’s “reward”

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Alan Turing won the war• Taught Von Neumann how to build computers• His theories are the basis of all modern computers

• And his reward?– Persecuted to death– Homophobic rejection in the 1950s – Security clearance revoked– driven to suicide … by apple (sprinkled with arsenic)

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2009: A public apology in Parliament

• British Prime Minister Gordon Brown– issued a public apology for the British

government's "appalling" actions,– after an online petition seeking the same gained

30,000 signatures and international recognition.

– “The debt of gratitude he is owed makes it all the more horrifying, therefore, that he was treated so inhumanely.”

And what is the future?

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Turing’s challenge to us all:• Be responsible.• Leave the shame behind us. • Build a different future.

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CS = building blocks

• In times past, computers were very expensive– Tools for the military– For code breaking and designing bombs

• Computers today are cheap – $30 for Raspberry Pi– Now, computers are tools

for everybody– What will do with that?

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Alan Turing:We do more if we do it together

• Alan Turing, 1939:– “The well-known theorem of Godel (1931) shows that every system of logic is

in a certain sense incomplete, but at the same time it indicates means whereby from a system L of logic a more complete system L may be ′obtained. By repeating the process we get a sequence

L, L1 = L , L2 = L1, ... ′

– each more complete than the proceeding. A logic Lω may then be constructed in which the provable theorems are the totality of theorems provable with the help of logics L, L1, L2...” .

• Translation– We are all incomplete– We all know part of the answer– We know more if we work together

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Teams, working together

• Linus Torvalds– a guy sitting on his Mum's lounge room floor – invented a way to build software – that now powers the internet.

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Groups, interacting

• Mark Zuckerberg– Some guy in his dorm room at Harvard – created a web site used daily by a billion people.

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Welcome to Science 2.0

Computer Science = ideas

Ideas are powerful.You up for it?