Maybe you've seen this ancient-looking video of cats floating weightlessly inside an airplane.
Since YouTube user AIRBOYD uploaded the clip on January 11, 2011, people have watched it more than 2.3 million times.
No real surprise there: The Internet loves cats doing ridiculous things, and so the footage — an excerpt of a public-domain video by Aerospace Medical Research Laboratories — was bound to be a hit.
When the American space program went into overdrive, primarily in response to the Soviet Union's launch of Sputnik — the first artificial satellite — scientists had very little idea of the effects of zero gravity on the human body. Or any body, for that matter.
Monkeys and mice were obvious choices for zero-gravity research, but cats' ability to right themselves in midair presented an opportunity for an extreme balance test: Would they be able rotate like this in microgravity?
The answer, it turned out, is no.
The Air Force researchers you see in the clip are riding in a Convair-131, the first of a series of planes that NASA would nickname "vomit comets."
On these flights, the pilot would take the plane up to 12,000 feet, then plunge it into a high-speed dive. After reaching 280 miles per hour, the pilot would pull up sharply to make an arc. At the top of the arc — as the plane began to free-fall — occupants would experience about 15 seconds at zero gravity.
Repeat many, many times, and you can rack up a few minutes of weightlessness for various experiments. Like tossing cats around.
In 1962, the Aerospace Medical Division included what they learned in a report, "Weightless Man: Self-Rotation Techniques." This particular technique mimics the twisting of a cat's torso to get control of one's position in space — though we doubt astronauts kick each other around their capsules, like one particularly cruel researcher did in the full video (see below).
A similar vintage video that Kelly uploaded, this one featuring weightless pigeons, hasn't garnered millions of views like the cats. But it's still fascinating.
If you want to join the weightless cats and pigeons, you're in luck.
Similar microgravity thrill rides operate publicly and privately, though at considerably higher speeds to squeeze more weightlessness out of each arc. The band OK Go even chartered a zero-gravity flight over Russia to film their jaw-dropping music video for "Upside Down & Inside Out" (at a cost of untold dollars and "58 puke events").
Check out the full DNews video for more on the first animals in space:
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NOW WATCH: OK Go shot their new music video in zero-gravity at a space training center in Russia