The following explanation is taken from https://news.ycombinator.com/item?id=49622607 : Alan Kay performs an improvisational avant garde layered audio feedback loop about Claude Shannon, live online…

150 points•behoove•5 days ago•36 comments•
The following explanation is taken from https://news.ycombinator.com/item?id=49622607:

Alan Kay performs an improvisational avant garde layered audio feedback loop about Claude Shannon, live online during Kristen Nygaard's 100-year birthday celebration.

Alan was scheduled to talk about how encountering Simula sparked his early thoughts about objects. During setup, somebody had the live stream playing out loud near an open Zoom mic, so his own voice kept arriving back in his ears about 21 seconds late, over and over.

What he said was not random: "Shannon gave us a way of dealing with noisy channels." And: "I think about that almost every day. I realize what the fuck is going on and it's just so amazing." Shannon's noisy channel coding theorem is the math for exactly the kind of channel that was garbling him as he praised it.

Alan joked it was "being rerouted to Mars and back." At the speed of light, a 21 second round trip is about 3 million km one way -- eight trips to the Moon and back, but only about a seventeenth of the way to Mars at closest approach.

This is an accidental Zoom performance of Alvin Lucier's "I Am Sitting in a Room" (1969), where Lucier re-recorded his own voice in a room until only the room's resonance remained. Here what remains is the network: delay, compression, dropouts.

Bonus noise: YouTube's auto-transcript bleeps Alan's enthusiasm into [ __ ]. So the full chain is: Alan's voice, Zoom, stream, room, Zoom again times three, my screen recording, YouTube's speech recognizer, a censored transcript.

The fix: "Just turn off the audio at your end on Zoom."

I Am Sitting in a Room: https://en.wikipedia.org/wiki/I_Am_Sitting_in_a_Room

Alvin Lucier on "I am sitting in a room": https://www.youtube.com/watch?v=v9XJWBZBzq4

36 comments

MarkusWandel5 days ago
Did he though? TMK Shannon did specifically not give a way to deal with noisy channels, no. He invented a way to quantify what could be sent on a noisy channel if you figure out the optimal way to do it. This is very similar to "no matter what you figure out about faster travel, you can't go faster than light in a vacuum".

Calculating the limit is easy with Shannon's theorem. Approaching it in practice is hard.

PunchyHamster5 days ago
> Calculating the limit is easy with Shannon's theorem. Approaching it in practice is hard.

Many modern modulations already operate basically on Shannon's limit for a given band/SNR. Well, on raw data, the encoding almost always use some kind of error correction so the decoded bitrate is few % lower than the wire one

tverbeure5 days ago
That’s understating the importance of the error coding. The modulation scheme is almost a side show, it’s the modern error coding algorithms (LDPC or Turbo coding) that allows you to get arbitrary close to the Shannon limit.
kragen4 days ago
If I recall correctly, he invented the optimal way to do it and published it in the original paper: use an arbitrarily long random code. The difficulty is that decoding a random code in the obvious way (compare the received codeword against each codeword in the codebook and decode as the one with the lowest Hamming distance) requires an exponentially large amount of both memory and computation. As I understand it, the advances since then have all been about how to get closer to the Shannon limit with reasonable amounts of computation by using codewords that aren't truly random.
ironqcold5 days ago
Fair distinction
dang5 days ago
The full talk seems to be at https://au.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=fe0..., but with a confusing interface (text chat flying by at speed, and no actual video of Alan, though you do get a prolonged view of a whiteboard). Maybe there's another copy that exists or will show up somewhere?
DonHopkins5 days ago
Yes it's a pretty klunky interface. Easy to miss that there are multiple camera icons to the right of the time slider, and you can switch to see different feeds like the speaker or their slides. It's still kind of hit or miss with some of the speakers, but at least Alan got a chance to test things out and debug all the glitches before his talk, so he didn't end up repeatedly interrupting himself!

Here is the full list of links from the video description to other related and interesting topics.

I can highly recommend smoking a joint and watching James "Doctor Chaos" Crutchfield's "Space-Time Dynamics in Video Feedback" film, which he made at UC Santa Cruz in 1984, building on Ralph Abraham's video feedback experiments there in the 1970s:

https://www.youtube.com/watch?v=B4Kn3djJMCE

https://en.wikipedia.org/wiki/James_P._Crutchfield

https://en.wikipedia.org/wiki/Ralph_Abraham_(mathematician)

Kristen Nygaard 100 Years, Celebration Symposium (Aarhus University, Aug 27 2026):

https://cs.au.dk/nygaard100years/celebration

Entire Nygaard Symposium Recording (Alan Kay's talk begins at 3:27:49):

https://au.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=fe0...

Alan Kay:

https://en.wikipedia.org/wiki/Alan_Kay

Claude Shannon:

https://en.wikipedia.org/wiki/Claude_Shannon

Information Theory:

https://en.wikipedia.org/wiki/Information_theory

Noisy-Channel Coding Theorem:

https://en.wikipedia.org/wiki/Noisy-channel_coding_theorem

Audio Feedback:

https://en.wikipedia.org/wiki/Audio_feedback

Video Feedback:

https://en.wikipedia.org/wiki/Video_feedback

Live Looping: The History And The Practice, by Stephen Garza:

http://computermusic2008.wikidot.com/live-looping:history-an...

I Am Sitting in a Room:

https://en.wikipedia.org/wiki/I_Am_Sitting_in_a_Room

Alvin Lucier on "I am sitting in a room":

https://www.youtube.com/watch?v=v9XJWBZBzq4

wood_spirit5 days ago
Aha i saw this video in a comment on another HN thread this week: https://news.ycombinator.com/item?id=49791117 Avoiding the babbling-idiot failure in a time-triggered communication system
aworks5 days ago
Alvin Lucier wrote other highly interesting, if unconventional works, although similar to John Cage's 4'33", this is the one that achieved meme status as conceptual art.
RobRivera5 days ago
Can someone please explain to me what this is all about?
DonHopkins5 days ago
My favorite part was how Alan's exuberant "I realize what the fuck is going on and it's just so amazing" got distorted by YouTube's speech to text transcription replacing "fuck" with "[__]", adding another layer of censorship noise and interpretation to the mix.

And how the conference's real time speech to text transcription honored Alan's "fuck", but would occasionally lapse into Danish, and say things like "We will eat your hands".

dang> Hopefully Don won't mind!

Of course not, and I hope Alan won't either, since in the recording he laughed and said "Yeah, this will be this will be fun."

thatspartan5 days ago
The way I've understood it is Shannon showed that it's possible to reliably send a signal even if you know the signal will get corrupted before arriving at the other end.

Shannon's theory is foundational to modern communication systems. You can expect to have WiFi remain functional even as other devices use the same medium. Up to a point, the Shannon limit in other words.

dang5 days ago
I've added an explanation to the toptext which is taken from a comment by DonHopkins, who recorded (but did not submit) the video: https://news.ycombinator.com/item?id=49622607.

Hopefully Don won't mind!

Read the full thread on Hacker News →

Related stories