Why is ketchup so hard to pour?

Ever go to pour ketchup on your fries…and nothing comes out? Or the opposite happens, and your plate is suddenly swimming in a sea of red? George Zaidan describes the physics behind this frustrating phenomenon, explaining how ketchup and other non-Newtonian fluids can suddenly transition from solid to liquid and back again.

Why do zebras have stripes? Scientists have the answer

Zebra

For years, scientists have debated the evolutionary reason behind a zebra’s stripes. Are they: a. Costumes for courtship? b: Camouflage to confuse lions and other predators? c: A natural way to cool off? d: Bug repellent? New research strongly suggests that they have evolved to deter parasitic flies.

If you answered “d,” you’d win the prize, at least in the eyes of Tim Caro, a biologist at the University of California at Davis. He and his colleagues report in Nature Communications that the geographic range of zebras and other horsey species with stripes overlap nicely with the range of bloodsucking flies.
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Why do we cry? The three types of tears

Whether we cry during a sad movie, while chopping onions, or completely involuntarily, our eyes are constantly producing tears. Alex Gendler tracks a particularly watery day in the life of Iris (the iris) as she cycles through basal, reflex and emotional tears.

Dead stuff: The secret ingredient in our food chain

When you picture the lowest levels of the food chain, you might imagine herbivores happily munching on lush, living green plants. But this idyllic image leaves out a huge (and slightly less appetizing) source of nourishment: dead stuff. John C. Moore details the “brown food chain,” explaining how such unlikely delicacies as pond scum and animal poop contribute enormous amounts of energy to our ecosystems.

The mystery of motion sickness

Although one third of the population suffers from motion sickness, scientists aren’t exactly sure what causes it. Like the common cold, it’s a seemingly simple problem that’s still without a cure. And if you think it’s bad on a long family car ride, imagine being a motion sick astronaut! Rose Eveleth explains what’s happening in our bodies when we get the car sick blues.