Feature
- Life
The origin of biological clocks
Most of Earth’s creatures keep time with the planet’s day/night cycle. Scientists are still debating how and why the circadian clocks that govern biological timekeeping evolved.
- Animals
Some animals’ internal clocks follow a different drummer
Circadian clocks in some animals tick-tock to a different beat.
- Planetary Science
Pluto: A timeline of 85 years of discovery
Several observations in the last 85 years have given astronomers a little more information about Pluto, and the July 2015 flyby will offer the closest look yet at the solar system's far-flung satellite.
- Physics
The arrow of time
Gravity may explain how time always runs forward, even though the laws of physics should permit it to run backward.
