How does the James Webb Space Telescope see so far into the past?

The James Webb Space Telescope looks far into the past because light takes time to travel, so looking at distant stars is like looking at old photographs.

When you watch a video call with your grandparent across the ocean, the image you see is actually from just before they spoke because the signal took a moment to arrive. Light behaves exactly the same way. It does not jump instantly; it zooms through space at a specific speed, roughly 186,000 miles per second. That sounds super fast, but space is gigantic.

Imagine you throw a baseball toward a friend who stands very far away. Even though the ball moves quickly, it takes a little bit of time before your friend catches it. While that ball is flying through the air, nothing about the event of throwing it changes, but you are seeing an event from the past when you finally catch it.

Webb captures this "old" light. It looks at stars and galaxies so far away that their light has been traveling for billions of years to reach us. When Webb snaps a picture of a galaxy 13 billion light-years away, we see the galaxy as it looked when the universe was much younger. We are essentially looking back in time.

Think of space like a giant timeline frozen in place. The closer an object is, the newer its image. The farther away it is, the older the image. Webb’s big mirror acts like a super-powered camera lens that collects these ancient photons. It does not physically travel back to the past; instead, it waits for the light from those distant events to finish its long journey and bring the story to us. So, every time Webb sends a new picture down to Earth, we are peeking at history just as it happened, preserved in beams of light traveling through the dark void.