Each one had six wings; with twain he covered his face, and with twain he covered his feet, and with twain he did fly.
All insects have two pairs of wings, sprouting from the second and third segment of the thorax. Even insects that appear to have only one pair, like flies and beetles, really have two: in flies, the second pair of wings diminished to new structures called halteres, while in beetles, the first pair became the elytra. In cockroaches and bugs, the first pair only got halfway to elytra and are called hemelytra.
But! A 2011 paper in Nature gives morphological and genetic evidence that the helmet of treehoppers is derived from a third pair of wing buds on the first segment. Hox genes have suppressed wing expression on every segment but 2 and 3 for 300 million years. Hox genes control repetition of certain body parts. They are very strongly preserved, since they govern the gross body plan of a creature—in humans, for instance, they control how many vertebrae we have. The authors suspected that the treehopper hox gene no longer suppressed production on the first gene and inserted it into drosophila flies to see if wing primordia formed, but they didn’t. So somehow, despite the hox genes being preserved, treehoppers found a way around the inhibition of wing production and were able to evolve their fantastic helmets.
TIL: Till is not a shortening of until
‘Til is a corruption of till under the assumption that it is a shortening of until, but till is, in fact, an older word than until. Both till and until mean the same thing.
Journey to the black hole at the center of the galaxy
Here’s some context for the recent black hole image.
Shock diamonds and aerospikes
I was curious what caused the oscillations in rocket exhaust. I learned they’re called “shock diamonds”, among other names, and are due to the lateral pressure of the exhaust being mismatched with the atmospheric pressure. At low altitudes / high pressure, the exhaust is immediately pinched and then bounces off itself as the pressure increases, then becomes repinched as it expands again. At high altitudes / low pressure, the exhaust expands first, then gets pinched at the lower pressure. The bell-style rocket only has its maximum efficiency at one specific altitude; this is one reason for multistage rockets.
There’s a rocket design called an aerospike that effectively uses air for half the bell and then controls the flow to match the air pressure. It’s more efficient, but has had bad luck as far as deployment goes. Since fuel is about the cheapest part of a rocket, new space companies have opted for using known, proven designs instead. This is a good video about the history and development of the aerospike.
While looking for the explanation, I came across this wonderful paper that examines what happens when two laminar flows collide. Depending on the viscosity, surface tension, and velocity of the streams, you get several different “phases” of interaction.
Lightfield 3d photos from an inkjet!
Lumii uses multilayer Moire patterns to simulate lightfields. You print out the layers on a regular transparency from an inkjet printer!
Fantastic fossil find from dinosaur killer asteroid
Seismic waves from the Chicxulub impact set up enormous standing waves in a large inland sea in North Dakota. The waves hit the mouth of an incoming river, which focused the waves into a 30 foot wall of water that knocked down trees and put fish next to triceratops and hadrosaurs in the fossil bed. The fish’s gills were also clogged with tektites, ejecta from the impact made of hot glass spherules that set the world’s forests on fire.
https://news.berkeley.edu/2019/03/29/66-million-year-old-deathbed-linked-to-dinosaur-killing-meteor/?T=AU
reperiendi 
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