We’ve entered a new year for my Twitter #weirdscifacts!  The previous week’s facts are below:

291. Dec 29: In the late 19th century, paleontologist O.C. Marsh speculated that stegosaurus had a second brain in its rear! This was no so crazy at the time as it perhaps appears now.  Marsh noted that stegosaurus has a large canal in the hip region of the spinal cord, and this canal was significantly larger than the animal’s brain.  Because of the smallness of dinosaur brains, it was thought that perhaps a large animal like stegosaurus needed a second brain in the rear area to control reflexes back there.  This is no longer believed, but the canal’s purpose is still unclear.

292. Dec 30: The case study of a woman who (literally) feels no fear.

293. Dec 31: Placobdelloides jaegerskioeldi, a leech that only lives in the anus of hippopotamus. (h/t @DrBondar)  This is obviously a very specialized leech.  It has not been studied very much, due to the obvious dangers of not only working with hippos, but rooting around in a hippo’s rear-end!

294. Jan 01: Start New Year’s weird facts with a bang! The Tunguska blast and other similar events.  It is really striking, and a little frightening, how frequently meteorite airbursts occur with energies in the kilotons of TNT or higher.

295. Jan 02: Physicist Roger Penrose’s geometric work influenced the art of M.C. Escher.

296. Jan 03: Vampire bats: a 40g bat can drink 20g of blood in 20 mins — and pee most weight away in 2 mins. These bats are remarkably adapted: they drink so much blood that they can’t even fly with it all, but their bodies quickly absorb the nutrients and pee out the leftover liquid.

297. Jan 04: Soldiers can collapse a bridge simply by marching across it: ex. Angers Bridge, 1850. Such bridge collapses are an example of mechanical resonance.  Bridges, buildings and other structures tend to have characteristic frequencies of vibration, and external forces that vibrate in synch can produce massive oscillations of the structure that can lead to failure.  The most famous example of this is the original Tacoma Narrows Bridge, which collapsed due to wind forces in 1940.

In the case of the Angers Bridge, the resonance was induced by soldiers marching in lockstep across it.  The disaster led to soldiers being advised to break step when crossing bridges, though evidently this rule had been implemented by much earlier military groups and later lost.