Light from the Past
You always see the past: the Moon as it was a second ago, the Sun 8 minutes ago, the stars years ago.
What’s going on
Light is the fastest thing there is, yet it still takes time to cross space. Moonlight reaches us in about 1.3 seconds and sunlight in about 8 minutes 20 seconds; light from the nearest star beyond the Sun takes over four years. A light-year is the distance light travels in one year. So the farther away something is, the further back in time we are seeing it.
Myth
Most of the stars you see at night have already died.
Fact
Nearly all the stars visible to the eye are relatively close, and still shining.
Learn more
NASA Space Place, “What Is a Light-Year?”; distances from NASA Science Moon and Sun fact pages.
Look up tonight
Next time you see the Moon, remember that you are seeing it as it was about a second ago.
Play Myth or Fact? Read out either the sentence on the card or the myth above. Can everyone tell which is true?
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