army ant mill pheromone trail circle

Army ants can march in circles until they die

Army ants often navigate by following chemical trails left by other ants. If a group becomes separated from the main trail, individuals may begin following one another in a closed loop. The result is an ant mill: a rotating circle that can continue until the ants become exhausted. A useful navigation rule turns dangerous when every ant follows the one ahead.

Flying is safer per kilometer than bus or rail

About 10×

Measured per passenger-kilometer—the distance traveled by one passenger—air travel is about 10 times safer than bus or rail travel. Measured per journey, flying is significantly more dangerous than traveling by car, rail, or bus.

Energy survives when hot and cold water mix — but becomes less useful

Mix hot water with cold water and the final mixture contains essentially the same total energy, assuming none escapes. Yet you can no longer extract as much useful work from the temperature difference. The energy has not vanished; it has spread out. This is one way to understand why entropy increases in everyday processes.

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army ant mill pheromone trail circle

Army ants can march in circles until they die

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