Observing the Sun, the moon and the stars has led us to wonder about the passage of time. But what exactly is time? Does it even exist? Back in the day, we used to rely on natural cycles like changes from day to night, changes in seasons to make calendars until a more convenient time-keeping devices came along to make more sense of our perception of time.
Watch this TED-Ed video, based on a lesson by Andrew Zimmerman, as it investigates if time is something that exists or not.