The 144.8m "drop tower" in Bremen, Germany, is not a rocket disguised as a building, but a giant hollow tube used for experimentally dropping things — letting go of objects, watching them plummet toward the ground, and using those nearly 10 seconds of free-fall as a way to study the effects of weightlessness.
Fear not that scientists simply drop lead weights or billiard balls. No — they are much more interesting than that. They also drop fish.
The structure — only 109.7m of which is actually used for dropping — has been put to work with the fantastic goal of "inducing motion sickness in fish", as zoologists R.H. Anken and R. Hilbig explained in a 2004 paper published in Advances in Space Research.
Indeed, Anken and Hilbig point out, previous experiments performed elsewhere had already shown that fish "reveal motion sickness" when they "transition from 1g to microgravity." They thus did the next most obvious thing — what any of us would have done — they rigged a "camcorder-equipped centrifuge" and they started dropping fish.
Image courtesy of H.F. Wiebe Group.
Because it can be both difficult and expensive to test the effects of microgravity on human subjects, "other vertebrates such as fish are therefore used as model systems," Anken and Hilbig explain.
This means, specifically, that a little fish falling inside a tower in Germany is being studied — or, rather, "the microgravity-induced behaviour of [that] fish" was under investigation — for what its descent might reveal about human astronauts in space.
For example, do the fish get dizzy? Do they spin around? Do they swim in loops?
Our trusty zoologists were not to be outdone, however. They thus rigged-up another experiment five years later — this time dropping catfish.
Catfish waiting for the drop; image via Advances in Space Research.
Intent on learning more about the "behaviour of the upside-down swimming catfish at high-quality microgravity," as they write in their later paper, Anken and Hilbig realised that, because the species is already known for swimming upside-down and successfully functioning in a state of spatial disorientation, it made an excellent candidate for the drop tower.
The catfish body — looping, turning, rolling, falling — thus offered a great platform for understanding "space sickness" in human beings.
The zoologists thus left their offices in Cologne, heading for Bremen, bearing catfish.
Diagram via Endeavour, Volume 15, No. 2, 1991.
In any case, it's not all fish, all the time — not just some elaborate Monty Python sketch in the name of gravitational science.
The tower, which was completed in September 1990, basically functions as a kind of grounded version of the International Space Station. In other words, because of the brief periods of weightlessness it offers, things like material density, surface tension, thermal convection, and more can be studied without having to blast things off the Earth at great expense (or fly aeroplanes in dangerous, parabolic loops, simulating antigravity). Crystals, organisms, liquids, gels — anything that can be dropped can be studied during its 10-second fall.
You simply ride an elevator up to the top of the drop tower, hook your chosen subject matter to the frictionless "capsule sled" that helps to guide its rapid descent, and you let go: dropping things 109.7m in the name of science.
Top image courtesy of the Bremen Tourism board.