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Old 2009-11-13, 16:18   #1
Orgasmic Troll
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Default A CD player from scratch

Not so much a puzzle, more of a thought experiment:

The rough idea: How long would it take to build a modern device from raw materials, without any current technology?

The more precise version: Imagine an astronaut has crash landed on an Earth-like planet and all that remains from the ship is an audio CD containing the next steps of his mission, but he has no way of playing it and needs to build a CD player. Assume that all raw materials are available and nearby, but he has absolutely no tools. How long would it take him to build something that could play the CD (or otherwise extract the information and convey it to him in a useful fashion)?
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Old 2009-11-13, 17:06   #2
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That astronaut had better be inhumanly dedicated to his mission. I think a more useful application for the CD would be to break it into pieces, attach the pieces to strings, and hang them outside the door to a makeshift hut to help keep the indiginous popluation of the planet from eating him by distracting them with the diffracted light.

Otherwise he needs to start by considering how to construct a 780 nm wavelength laser using a pile of unprocessed silicon, boron, and antimony. He would need to construct envionmentally controlled processing facilities and laboratory instrumentation, each of which in turn require a huge amount of infrastruction which he would have to fabricate. Is there a simpler way? A magnifying glass, a steady hand, and a few million spare hours to manually record the pattern of pits and translate the resulting encoded binary sequence into raw data. The raw data itself might encode lists of frequencies and amplitudes, which he would then need to manually decode into speech.

I don't think this can be done in a single lifetime, so he better hope Eve the astronaut came with him.

Last fiddled with by bsquared on 2009-11-13 at 17:23 Reason: more speculation...
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Old 2009-11-13, 19:18   #3
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i think you could start with something easier. i couldnt imagine it being completed in an average lifetime.
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Old 2009-11-13, 19:30   #4
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Quote:
Originally Posted by Dougal View Post
i think you could start with something easier. i couldnt imagine it being completed in an average lifetime.
How many lifetimes then?
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Old 2009-11-13, 19:43   #5
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depends on they previous education of the person in question.
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Old 2009-11-13, 20:09   #6
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Quote:
Originally Posted by Dougal View Post
depends on they previous education of the person in question.
Assume he has all the knowledge that he needs
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Old 2009-11-13, 20:56   #7
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Quote:
Originally Posted by Orgasmic Troll View Post
Not so much a puzzle, more of a thought experiment:

The rough idea: How long would it take to build a modern device from raw materials, without any current technology?

The more precise version: Imagine an astronaut has crash landed on an Earth-like planet and all that remains from the ship is an audio CD containing the next steps of his mission, but he has no way of playing it and needs to build a CD player. Assume that all raw materials are available and nearby, but he has absolutely no tools. How long would it take him to build something that could play the CD (or otherwise extract the information and convey it to him in a useful fashion)?
This may not be a direct answer to your question,
but I arrived in this hell-hole (Milton Keynes) because I was asked
about error-correction while I was programming games at some
outfit in Lowestoft.
I went to the bookshop at the world-famous "UEA" and found three
good books (second-hand) on "discrete mathematics". One of them
was both entertaining and told me what I needed to know about
Galois Fields.
I got the job, and a year or so later, Martin Brennan (a sort of whizz
kid who had worked with Sir Clive Sinclair on the QL) interviewed
me with the idea of writing much of a CD player in software.
He explained that he had designed the hardware that could multiply
in the (2^8-1) field, but dividing was more time consuming.
I told him that I used logs, got the job, and together we designed
a customized chip.

Await the next thrilling installment
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Old 2009-11-13, 21:45   #8
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If one had a good microscope, knew the coding system, and disc layout, reading it may be possible. It would take a lot of patience, time, paper, and pencils.

Not me. After 30 minutes, I'd be done for.

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Old 2009-11-13, 22:05   #9
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Quote:
Originally Posted by storm5510 View Post
If one had a good microscope, knew the coding system, and disc layout, reading it may be possible. It would take a lot of patience, time, paper, and pencils.
That was my idea too. OT said assume he has all knowledge.
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Old 2009-11-13, 22:07   #10
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Quote:
Originally Posted by storm5510 View Post
If one had a good microscope, knew the coding system, and disc layout, reading it may be possible. It would take a lot of patience, time, paper, and pencils.
If I understand it correctly there are something like 6 billion features (pits or lands) to distinguish on a full capacity CD. Assuming you could examine, write down, and move to the next feature once per second this would take 190 years of continual examination to do by hand (neglecting the time it takes to blow the glass and forge the steel in the right shape to be able to magnify to the point of distinguishing something 1 micron square... oh, and create either an electrical generator or a 200 year supply of candles... otherwise one would have to only work during the day). It might be faster to beget a few generations of helpers and build the infrastructure to be able to create a laser, photodiode, microprocessor, amplifier, and speaker.
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Old 2009-11-13, 22:15   #11
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Quote:
Originally Posted by bsquared View Post
If I understand it correctly there are something like 6 billion features (pits or lands) to distinguish on a full capacity CD. Assuming you could examine, write down, and move to the next feature once per second this would take 190 years of continual examination to do by hand ...
There is far less information in the Bible, at least from a raw bit count standpoint, and 2000 years of continual interpretation has gotten us no closer to fully understanding its contents... what sort of belief system might spring up in the generations of descendants of the astronaut about their "holy text"? And imagine their disappointment when they finally are able to listen to... an hour long dissertation on the spectral characteristics of their atmosphere

p.s. nice puzzle... this is fun!

Last fiddled with by bsquared on 2009-11-13 at 22:17 Reason: p.s.
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