[ExI] Bacterially induced megastructures

Bryan Bishop kanzure at gmail.com
Mon Apr 20 21:39:52 UTC 2009

On Mon, Apr 20, 2009 at 1:38 PM, Bryan Bishop wrote:
> On Mon, Apr 20, 2009 at 12:48 PM, mostromundo wrote:
>> Here's a neat little post from BLDGBLOG about using bacteria to
>> solidify sand into sandstone in about a week. It sounds like a pretty
>> neat use of biology, pile or pour some sand into the shape you want
>> and then flood it with the right bacteria, and in a week you have a
>> solid structure to live in!
>> http://bldgblog.blogspot.com/2009/04/sandstone.html
> What first came to mind when I saw this was ant and termite mounds.
> When studying ridiculously large ant mounds, what researchers do is
> pump some plaster throughout the entire structure and then let it sit.
> They then excavate it and look at the overall pattern. But using
> bacillus pasteurii might be more appropriate.
> I can't help but think of selective laser sintering, a method of
> printing 3D shapes. You have this giant bucket of "sand", you raster
> scan a laser and the polymer or 'sand' polymerizes or whatever special
> material you're using, and ultimately the result is the shape that you
> wanted. So, what about photoactivation of a regulatory circuit of this
> bacteria? Suppose you engineered a GRN in these bacteria such that the
> lithification only occured once a certain gene is activated by laser
> stimulation (chromophores?). Using a very specific wavelength of laser
> that can get through the atmosphere, you could use a laser in orbit to
> do selective laser sintering fabrication with deserts. You could
> literally do rapid prototyping of deserts- it would require a
> satellite in orbit, which is somewhat of a cost, although less costly
> than running a giant 3D printer around on the desert forever (rather
> than just positioning some mirrors up in orbit).

Wait, why would you have to be in orbit? Find yourself a mountain, or
build a tower, and just project and draw under the horizon. This would
be using the same mechanism of xy laser scanners that draw virtual
grafitti on buildings, which I've mentioned previously here--


.. except in this case the light would be activating the regulatory
circuits in the bacteria in the pattern that you describe. You would
need a flat surface, unless you have a perfectly sloped terrain and
know some basic trig, otherwise your result will be all skewed and
weird-like. There's an interesting phenomena associated with deserts
called singing sand.


"Singing sand, whistling sand or barking sand is sand that produces
sounds of either high or low frequency under pressure. The sound
emission is usually triggered by wind passing over dunes or by walking
on the sand. The sound is generated by shear stress ... the most
common frequency emitted seems to be close to 450 Hz. Singing sand
dunes, an example of the phenomenon of singing sand, produce a sound
described as roaring, booming, squeaking, or the "Song of Dunes". This
is a natural sound phenomenon of up to 105 decibels lasting as long as
several minutes that occurs in about 35 desert locations around the
world. The sound is similar to a loud, low-pitch, rumble, and it
emanates from the crescent-shaped dunes, or barchans. The sound
emission accompanies a slumping or avalanching movement of the sand,
usually triggered by wind passing over the dune or by someone walking
near the crest. Examples of singing sand dunes include California's
Kelso Dunes and Eureka Dunes, sugar sand beaches and Warren Dunes in
southwestern Michigan, Sand Mountain in Nevada, the Booming Dunes in
the Namib Desert, Africa, Porth Oer (also known as Whistling Sands)
near Aberdaron in Wales, Indiana Dunes in Indiana, Barking Sands in
Hawaii, and Singing Beach in Manchester-by-the-Sea, Massachusetts."

Here's a paper on working towards quantifying all this--

Surface elastic waves in granular media under gravity and their
relation to booming avalanches

"Due to the nonlinearity of Hertzian contacts, the speed of sound c in
granular matter is expected to increase with pressure as P^(1/6). A
static layer of grains under gravity is thus stratified so that the
bulk waves are refracted toward the surface. The reflection at the
surface being total, there is a discrete number of modes (both in the
sagittal plane and transverse to it) localized close to the free
surface. The shape of these modes and the corresponding dispersion
relation are investigated in the framework of an elastic description
taking into account the main features of granular matter: Nonlinearity
between stress and strain and the existence of a yield transition. We
show in this context that the surface modes localized at the free
surface exhibit a waveguide effect related to the nonlinear Hertz
contact. Recent results about the song of dunes are reinterpreted in
light of the theoretical results. The predicted propagation speed is
compared with measurements performed in the field. Taking into account
the finite depth effects, we show that the booming instability
threshold can be explained quantitatively by a waveguide cutoff
frequency below which no sound can propagate. Therefore, we propose
another look at a recent controversy, confirming that the song of
dunes can well originate from a coupling between avalanching grains
and surface elastic waves once the specificity of surface waves (we
baptized Rayleigh-Hertz) is correctly taken into account."

Why would this be useful? Well, what comes to mind is sonic
sculptures, which are sometimes used in sonic gardens, either made out
of bamboo, steel, wood, etc.

http://www.singingbridges.net/about/ `"Singing bridges" is a sonic
sculpture, playing the cables of stay-cabled and suspension bridges as
musical instruments. To create this work I will amplify and record the
sound of bridge cables around the world. Listening in to the secret
voice of bridges as the inaudible vibrations in the cables are
translated into sound.`

and in general: http://en.wikipedia.org/wiki/Sound_sculpture

What could we make, then? Giant vocal amplifiers? Whisper to the
desert? Largest instance of RIAA copyright violations, ever
imaginable? Making wind amplification tunnels for ultrasonic and
hypersonic studies? Largest dog whistle ever? Basically this is like
patterning really really giant brass instruments. Even if you could
somehow miraculously pattern out individual instruments with
individual tones per each structure, or something, I don't know how
you would be able to play specific symphonies or musical pieces
without using something other than sound and wind to block certain
instruments for some period of time. Very large pneumatic sand
circuits? Ok, ok, maybe housing for now per the original suggestion.

- Bryan
1 512 203 0507

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