SA Special Editions

The pace of living quickens continuously, yet a full understanding of things temporal still eludes us

From the fixed past to the tangible present to the undecided future, it feels as though time flows inexorably on. But that is an illusion

The concepts of time and change may emerge from a universe that, at root, is utterly static

Physicists can't seem to find the time—literally. Can philosophers help?

It wouldn't be easy, but it might be possible

Hypothetical twins who age at different rates suggest the answer is no

Whether they're counting minutes, months or years, biological clocks help to keep our brains and bodies running on schedule

Several brain structures contribute to “mind time,” organizing our experiences into chronologies of remembered events

What is time? The answer varies from society to society

Our conception of time depends on the way we measure it

The units of time range from the infinitesimally brief to the interminably long. The descriptions given here attempt to convey a sense of this vast chronological span

Atomic clocks are shrinking to microchip size, heading for space—and approaching the limits of useful precision

Some experimental optical clocks are so precise that even a small change in elevation or velocity makes them register the passage of time differently

Do the inner workings of nature change with time?

String theory suggests that the big bang was not the origin of the universe but simply the outcome of a preexisting state

A timely conversation with physicist Sean M. Carroll about how our one-way trip from the past to the future is entangled with entropy and the origin of the universe

We perceive space and time to be continuous, but if the amazing theory of loop quantum gravity is correct, they actually come in discrete pieces

Could time end? Yes. And no. Recent work in physics suggests a resolution to the paradox