As long as people have been living on Earth, we’ve been looking up at bright stars in the night sky, trying to understand the universe and our place in it. Astronomers have long known that not all stars are alike. Some are almost as old as the universe itself, others are just now being born. They come in different colors: blue, white, yellow and red. Some shine brightly in the sky, and others are visible only with special telescopes. Some stars race through space in pairs or groups; others move alone. Some, like our own 4.8-billion year-old sun, are surrounded by planets.    One o...

Anyone who has ever gone fishing probably knows this general rule: Keep the big ones, throw the smaller ones back. The idea behind the rule is simple — the larger fish are assumed to be older. If you were to keep the smaller ones, they would not be able to reproduce, and the fish population would be in jeopardy. That rule may have done as much harm as good. Fishing out the largest fish from a population can have an unwanted consequence: Over time, fewer adult fish get really big. If only the smaller fish can reproduce, then future generations of the fish will tend to be smaller. This is an...

To see Albus Dumbledore’s memories, Harry Potter simply had to look into the pensieve, sit back and wait for the show to begin. For us Muggles, reading minds isn’t quite so simple. It may not be simple, but it may not be impossible, either. What if a brain scan could reveal your memories? A team of British scientists recently did just that — they used brain scans to look at spatial memory in four people. Spatial memory is the kind of memory you use to remember where you are. Rats, for example, use spatial memory to get through a maze. You use spatial memory to remember how to get from ...

If you gaze through a telescope at a distant galaxy, it may glow brightly with the light of hundreds of millions of stars. Despite all that light, most scientists think that at the center of a big galaxy lies something very dark: a black hole. A black hole is a region of space with gravity so strong that nothing can escape, not even light. What’s even stronger than a black hole at the center of a galaxy? Try two black holes, spinning around each other like deep-space dancers. Astronomers recently announced they have observed a faraway galaxy that may have at its center two black holes, v...

Crazy-colored, flat-faced fish does more than swim.

The taste of metal is sweet, spicy, bitter, delicious and perhaps other, mystery tastes.

An orbiting telescope records the universe’s most powerful explosions.

An aquatic animal provides a possible new kind of disease resistance.

Scientists report on the true cost of eating meat — it’s more greenhouse gases.

The absorbent stuff in diapers may help clean up after a terrorist attack.