Can the James Webb Space Telescope really see the past?

Scientists want to use Webb to see the beginning of the universe. How is that possible?

On July 12, the James Webb Space Telescope (JWST) made history by releasing its debut image: a jewel-filled photo that’s been touted as the deepest photo of the universe ever taken.

Besides looking farther across space than any observatory before it, the James Webb Space Telescope has another trick up its mirrors: It can look further back in time than any other telescope, observing distant stars and galaxies as they appeared 13.5 billion years ago, not long after the beginning of the universe as we know it.

How is this possible? How can a machine look “back in time”? It’s not magic; it’s just the nature of light.

“Telescopes can be time machines. Looking out in space is like looking back in time,” NASA scientists explained on WebbTelescope.org. “It sounds magical, but it’s actually very simple: Light needs time to travel across the vast distances of space to reach us.”