I’m Nora, the station’s science and environment columnist, with a chronicle about how a laboratory experiment measured time without an outside clock.

A chronicle is a written or spoken account of events.

A physicist at the University of Birmingham used about 24,000 ultracold atoms to test a different way to measure time.

These are atoms cooled to extremely low temperatures.

Instead of using an external clock, the experiment tracked changes inside the system.

Here, tracked means watched and recorded how the changes happened.

The result offers a controlled way to test ideas about how time might be measured from within a system.

Here, controlled means carefully set up so researchers can study the test in an orderly way.

The observed region repeatedly expanded and contracted, while the distribution of atoms changed.

The region repeatedly grew larger and then became smaller.

The observed region repeatedly expanded and contracted, while the distribution of atoms changed.

The distribution is the way the atoms were spread across the system.

The researchers used those changes to define what they called “entropic time.”

Entropic time is a way to mark the order of events by changes in how matter or energy is spread.

Entropy is a measure related to how matter or energy is spread within a system.

Entropy measures how matter or energy is spread within a system.

It also showed that the measure could advance at different rates as entropy changed.

Here, entropy means a measure of how matter or energy is spread in the system.

The experiment instead tested whether changes within a small quantum system could order events without referring to an outside clock.

Here, order events means show which events happened before or after others.

The study, published in Physical Review Research, found that this internal measure could order events across repeated cycles.

Here, order events means show which events happened before or after others.

It also showed that the measure could advance at different rates as entropy changed.

Here, advance means move forward as a measure of time.