John Oliver hosts a mathematically representative climate change debate, with the help of special guest Bill Nye the Science Guy, of course.
All about earth.
The striking transformation of a caterpillar into a colourful, winged butterfly is one that has captivated scientists for years. The metamorphosis involves the breakdown of most of the caterpillar’s tissues before reassembling to form a butterfly. It therefore seems unlikely that butterflies or moths would remember experiences from their caterpillar days. However, scientists have now established that not only can a moth retain memories formed while it was a caterpillar, but that experiences gained during these early stages can have drastic impacts on adult life.
Memories live long
Moths and butterflies undergo drastic changes throughout their life-cycle, not just in their outward appearance, but also in their diet and overall lifestyle. Metamorphosis occurs within the pupal case. During this period, the larval brain stimulates the release of enzymes which dissolve most of its tissues into their constituent proteins through a process called histolysis. Then a group of specialised cells called histoblasts proceed to reconstruct the broken-down caterpillar body into that of a butterfly or a moth.
A few years ago, Martha Weiss and her group at Georgetown University discovered that aversive memories formed in the tobacco hornworm caterpillar (Manduca sexta) persisted throughout metamorphosis and were retained in adult moths.
Weiss trained caterpillars to avoid the odour of ethyl acetate, a chemical commonly used in nail polish removers. Caterpillars and moths are usually indifferent to the smell of ethyl acetate, but by pairing exposure to the odour with mild electric shocks, the scientists successfully taught these caterpillars to avoid the odour.
When given a choice of air or ethyl acetate, 78% of the caterpillars carefully avoided the odour in favour of air. Then, when adult moths developed from the pupae of trained caterpillars a month later, they continued to show a strong aversion to the smell, with 77% of the moths choosing air over ethyl acetate. Notably, the majority of moths choosing air as adults had also made the same choice as caterpillars, suggesting that individual preferences survived metamorphosis.
h/t (and image source): Google’s Venn diagram doodle is where logic and whimsy intersect (engadget.com).
Wingtip vortices are a result of the finite length of a wing. Airplanes generate lift by having low-pressure air travelling over the top of the wing and higher pressure air along the bottom. If the wing were infinite, the two flows would remain separate. Instead, the high-pressure air from under the wing sneaks around the wingtip to reach the lower pressure region. This creates the vorticity that trails behind the aircraft. I was first introduced to the concept of wingtip vortices in my junior year during introductory fluid dynamics. As I recall, the concept was utterly bizarre and so difficult to wrap our heads around that everyone, including the TA, had trouble figuring out which way the vortices were supposed to spin. A few good photos and videos would have helped, I’m sure. (Photo credits: U.S. Coast Guard, S. Morris, Nat. Geo/BBC2)
These pictures were created using long-exposure photography, which involves leaving the camera shutter open for up to an hour.
If I were a supervillain, I’d want my name to be Vantablack. Unfortunately, that moniker is already taken, but not by a Hollywood bad guy. No, its owner is even more dark and mysterious: Vantablack is the darkest material ever made.