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Anders Sandberg Profile picture
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6 Mar, 4 tweets, 2 min read
Looking at the dynamics of classic vortices it looks like they might be able to form a billiard-ball computer. Might be that vortex pairs work as signals.
There is a very neat theory for these vortices stretching back to Helmholtz. Positions can be treated as points in complex plane, and everything is very integrable. vtechworks.lib.vt.edu/bitstream/hand…
The main problem I see is that stationary structures are too easily moved by vortex pairs: discrete space is so much more forgiving for error-correction.
One can make fun pair accelerators. But conservation of vorticity in the basic model makes it impossible to make true glider guns.

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More from @anderssandberg

Anders Sandberg Profile picture
5 Mar
#FridayPhysicsFun - Is water stable or potentially explosive? The answer may depend on whether one can construct a computer out of fluid.
Fluid motion is described by the Navier-Stokes equations. They are non-linear and really tricky to solve.
quantamagazine.org/what-makes-the…
One problem mathematicians would like to solve is whether an initial state of finite fluid velocities will remain finite, or whether it could evolve into something with a singularity.
Read 15 tweets
Anders Sandberg Profile picture
29 Jan
#FridayPhysicsFun - Last week I gave a talk about Karl Popper's critique of historicism and how this strikes at macrohistory and future studies. But what does physics say we cannot predict?
Classical mechanics has "Laplace's demon" (born in 1814): it knows all the positions and momenta of every particle in the universe, the full set of mechanical laws, and should then in principle be able to predict the future state at any point in time.
en.wikipedia.org/wiki/Laplace%2…
Like most thought experiment demons (Descarte's, Maxwell's, Darwin's, and so on) it mostly exists to be exorcised. newyorker.com/books/under-re… springer.com/gp/book/978331… degruyter.com/princetonup/vi…
Read 21 tweets
Anders Sandberg Profile picture
5 Dec 20
OK, what is it that I am missing when people go on about environmental impact of ML? Strubell et al estimate of 284 tons CO2equiv for big transformer training is about what you get for 300 tons of steel: short railway bridge. Industrial countries produce megatons steel annually.
My guess: original point "your computation actually has environmental impact and cost" got transmuted - by not comparing to other *industrial* things - into "your computation is a serious environmental issue".
Energy cost of computation/comms *as a whole* does matter (Koomey's law needs to be speeded up), but the ML focus seems more be to knock something with currently high prestige compared to corporate database management or webservers.
Read 4 tweets
Anders Sandberg Profile picture
4 Dec 20
#FridayPhysicsFun - One of the weirdest physical effects I know about is the Casimir effect (in my mental ranking it is just a step down from the Aharanov-Bohm effect). physicsworld.com/a/the-casimir-…
If you place two uncharged conductive surfaces close together in vacuum, there is an attractive force between them. Why? Because the vacuum between them has less energy than the vacuum outside them. en.wikipedia.org/wiki/Casimir_e… scholarpedia.org/article/Casimi…
Empty space, according to quantum field theory, is full of possible electromagnetic waves and they all have a finite zero-point energy. However, normally the only thing that matters is differences between this energy and fields with actual waves.
Read 12 tweets
Anders Sandberg Profile picture
24 Nov 20
New paper out by Andrew E. Snyder-Beattie, me, Eric Drexler and @mbbonsall about how the timing of evolutionary transitions on Earth suggests intelligent life is rare: liebertpub.com/doi/full/10.10…
There is life on Earth but this is not evidence for life being common in the universe! This is since observing life requires living *observers*. Even if life is very rare, the observers will all see they are on planets with life. Observation selection effects need to be handled!
Observer selection effects are annoying can produce apparently paradoxical effects such that your friends on average have more friends than you or that our existence "prevents" recent giant meteor impacts. But one can control for them with some ingenuity! fhi.ox.ac.uk/wp-content/upl…
Read 14 tweets
Anders Sandberg Profile picture
20 Nov 20
#FridayPhysicsFun - Today I made a loaf of bread. I also learned that bread spontaneously forms heat pipes that move heat and moisture more efficiently. And that the internal structure kind of imitates the large scale structure of the universe.
The heat pipe info is from Nathan Myhrvold and Francisco J. Migoya in their book Modernist Bread, based on earlier research by food scientists.
physicsworld.com/a/the-physics-…
When you heat dough in the oven, at first the surface heats up and starts to dry out. Water diffuses outward, and there is likely some capillary action causing wicking too.
Read 14 tweets

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