Is the starlight we see really old?

On a clear night, you can see tiny points of light above the rooftops. They seem to sparkle right here, right now. But is the starlight we see really old?

The journey begins at a star, far out in space. The star makes its own light and sends it out in every direction. Some of that light heads toward Earth, where you live.

Light travels incredibly fast, faster than any rocket. Still, it cannot jump from a star to your window in no time at all. Light needs time to cross the space between the star and you.

To talk about that enormous distance, we use a word: light-year. A light-year is the distance light travels in one year. Think of a whole year’s journey stretched out into one long path.

For our journey, let’s choose a star ten light-years away. Its light has ten of those year-long stretches to cross before reaching Earth. How many years do you think that journey takes?

Ten years! Light from a star ten light-years away travels for ten years to reach you. The light arriving tonight started its journey before you were born, and kept going as you grew.

When that light reaches your eyes, it shows you the star as it looked ten years ago. That is because the light left the star back then, not tonight. You see a view from the past.

Stars farther away send us light that takes even longer to arrive. Some starlight reaching your eyes tonight has traveled for hundreds or thousands of years. A longer journey means older light.

Light-year. Yes, the starlight you see is old because stars are so far away that their light takes years to reach you.

Tonight, you can look up at the stars and enjoy the quiet wonder of light from long ago.