Re: [ontolog-forum] Rethinking Time in Distributed Systems

[TSchneider <tjschneider@xxxxxxxxx>]

David,

You've piqued my interest. Why "..., if troubling."?

I always found the current (and past) conceptions
of time problematic/troubling (but haven't had a
more coherent and consistent explanation).

-- 
Todd
+1.703.655.8826 (mobile)

On 3/2/2014 6:13 PM, David C. Hay wrote:

John,

Thank you for this.  It is very profound, if troubling.

Dave Hay

At  3/2/2014 07:05 AM, you wrote:

The subject line is the title of a talk that Paul Borrill presented
at Stanford a few years ago.  It's important for many issues about
time that have been discussed in Ontolog Forum.

In particular, he emphasizes the complexities of time, the difficulty
of defining time, and the disasters that have been caused by treating
time as a Newtonian linear sequence.

The talk:  http://www.youtube.com/watch?v=VKkGqNRlUJM

The slides:
http://www.stanford.edu/class/ee380/Abstracts/091111-RethinkingTime.pdf

The slides are useful for an overview, but the talk is much richer.
It's packed with examples and stories that aren't on the slides.

Three of many examples:

  1. For a multi-core chip, each core maintains its own clock. The time
     delays for signals passing across the chip make it impossible to
     keep the clocks exactly synchronized.

  2. For GPS, even special relativity is not sufficiently accurate.
     People on earth are sitting in a deep gravity well compared to the
     satellites.  GPS requires the corrections of general relativity.

  3. The disaster of the Challenger space shuttle, for which he was
     on the engineering team.

Borrill's conclusion:  Simultaneity is a myth.  Except for a single
local observer, don't assume a linear time.  In a distributed system,
never depend on clocks to serialize anything.

I also like the slogan of his company:  "Radical simplicity."
That is his recipe for designing reliable systems.

His final slide is a quotation by Leonardo da Vinci:
"Simplicity is the ultimate sophistication."

John
 
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