Why do stars twinkle ?

Stars twinkle. Planets shine steadily. Why? Stars twinkle (scintillate) because they’re so far away from Earth that, even through large telescopes, they appear only as pinpoints. And it’s easy for Earth’s atmosphere to disturb the pinpoint light of a star. Thus the stars twinkle. They can even appear to move around a bit in the sky. As a star’s light pierces our atmosphere, each single … Continue reading Why do stars twinkle ?

How Acacia Trees Prevent Elephant Attacks: With Armies of Ants

  It’s a classic David and Goliath story, except there are 90,000 Davids and they all have stings. On the African plains, the whistling-thorn acacia tree protects itself against the mightiest of savannah animals – elephants – by recruiting some of the tiniest – ants. Elephants are strong enough to bulldoze entire trees and you might think that there can be no defense against such … Continue reading How Acacia Trees Prevent Elephant Attacks: With Armies of Ants

Red Tide, Blue Tide: Bioluminescence in the Ocean

Red tides, which often contain harmful algal blooms , are caused by chemical reactions that occur between algae and other substances. Red by day, blue by night, this colorful ocean phenomenon is a relatively rare natural occurrence that has spawned a number of imitations in movies and literature, the most recent example being a rather striking scene in the visually-driven movie Life of Pi. Although naturally occurring, … Continue reading Red Tide, Blue Tide: Bioluminescence in the Ocean