When we say something is 1000 light years away, or 100,000 light years away, how do we know how far light has traveled to reach us? How do we differentiate the distance between all the different sources of light we can see so accurately?
In: Physics
It’s actually kind of complicated. We see the light and can measure its intensity, but how do we know whether this is something dim and close by or bright and far away? The answer is the “cosmic distance ladder,” which astronomers have built up over time. The physical properties of certain astronomical objects ensure they will have a certain brightness that we know. These are “standard candles.” By looking in the vicinity of these standard candles for other hints about distance from Earth, we have built methods for measuring things even farther away.
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