
Scale-Free Vertical Tracking Microscopy, a.k.a. Gravity Machine - sohkamyung
https://gravitymachine.org/about/
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lmilcin
There is one problem, though.

The water column the microorganism travels is not uniform and endless. As it
travels, the conditions change. Some can be easily adjusted (for example
lighting), some would be much more difficult to get (pressure, chemical
composition).

So while the microorganism can travel it can't actually get anywhere.

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devindotcom
They have a method for imitating natural chemical, temperature, and light
gradients even in the otherwise sealed tube. So they can simulate a great deal
of those conditions and have observed some interesting behaviors at boundary
layers, if you check the gallery.

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lmilcin
Ah, missed it.

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cjhveal
I'm probably just misunderstanding the physics involved, but wouldn't moving
the container only impart movement on the fluid inside in proportion to the
viscosity of the liquid? And once the fluid is moving wouldn't stopping it
require movement in the opposite direction or waiting for friction to reduce
the inertia of the fluid?

I'm thinking of the behavior of the semicircular canals of the ear, and how
the inertia of the endolymph can cause dizziness after spinning for a while.

Maybe the critical part I'm missing is that the organism is actually sinking
in the fluid around it and the effect of fluid current if present is minimal
compared to the effect of gravity.

As an aside, the homepage for this project is quite nicely illustrated.

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devindotcom
I had this exact question, and the researchers said it was a serious
consideration. Turns out the critters at this scale move quite slowly and so
does the wheel. There's some effect certainly but it's small enough that they
can track a single organism for quite a long time. It wouldn't work in other
circumstances or scales for sure.

I wrote it up here, in case anyone would like to read about it in article
form: [https://techcrunch.com/2020/08/19/this-looping-aquatic-
tread...](https://techcrunch.com/2020/08/19/this-looping-aquatic-treadmill-
lets-tiny-ocean-creatures-swim-forever-under-the-microscope/)

