
How Feynman Diagrams Almost Saved Space - benbreen
https://www.quantamagazine.org/why-feynman-diagrams-are-so-important-20160705/
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kkylin
If you enjoy this, take a look at
[http://ctpweb.lns.mit.edu/physics_today/phystoday/Ether.pdf](http://ctpweb.lns.mit.edu/physics_today/phystoday/Ether.pdf)
.

~~~
gumby
Consider c to be the Mach number of the luminiferous ether.

After all special relativity works with any waveform in any medium -- it's all
about information transfer.

~~~
Koshkin
> _Consider_

The analogy is imperfect, as _c_ is not just the speed of light, it is also
the universal upper bound of the speed in general, whereas the Mach _can_ be
exceeded.

~~~
gumby
Yes, but as far as special relativity is concerned the mach number is by
definition the fastest way to propagate information (a signal) as a wave
through a given medium.

This is why if you squeeze a crystal the internal wavefronts interact
relativistically.

~~~
v_lisivka
> This is why if you squeeze a crystal the internal wavefronts interact
> relativistically.

Where I can read more, please?

~~~
thaumasiotes
I can't answer your question, but I had an uninformed thought.

This idea reminds me of what happens when you dangle a very long slinky and
then release it. The bottom of the slinky hovers in place until the collapsing
top finally reaches it. The information that the top end lost its support has
to propagate through the slinky.

~~~
lodi
That's something different. There's two effects going on:

1) Each 'slice' of the slinky, whether near the bottom, middle, or top, wants
to fall down under the influence of gravity.

2) Once the top is released, spring forces in the slinky want to compress it
so that the top and bottom both move towards the middle.

Therefore you'll briefly have one part somewhere in the bottom half (not
necessarily the "bottom"\--it depends on how strong the spring is), that's
being pulled up at 9.8m/s^2, which ends up matching the speed that the slinky
center of mass is falling down, thereby making it appearing to hover in place
for a moment.

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chillacy
I’ve always wondered if there was some analogous technique for drawing out
parallel programming from lock acquisition to atomic variables. I always find
them so much more difficult to reason about in code form due to all the ways
different threads can interact, it seems drawing them on 2D might help.

~~~
zwkrt
you already can do this in 1d by just writing out the possible sequences of
events. Feynman diagrams are used to help enumerate all possible particle
interactions, including 'virtual' interactions, but there are no virtual
interactions in multithreaded programming.

~~~
akvadrako
There are virtual interactions in multithreaded programming. Virtual in this
sense basically means internal - if two threads have a secret backchannel to
send messages and you don't have access to any of their internals, you can
model their behavior with "virtual" messages. To be general, it would even be
a mixture of all possible implementations.

Only those messages detectable from the outside are "real".

Besides, if you have threads separated by significant difference, there isn't
even a canonical ordering of events due to special relativity.

