Ever stop to think about the meaning of the word “old”? When you think about it, what comes to mind? A grandmother or grandfather? A large, gnarly tree? The boulders on a mountain, or perhaps the mountain itself?
If you walk outside on a clear night and look up, you will see things far older than most of what you can find on Earth: the light of distant stars and galaxies. Photons, the particles of light emitted by those stars, began their journey up to 12 million years ago. If you have a chance to look through a moderately-sized telescope, you can see light that is about 2 billion years old. For reference, the current estimated age of the universe is nearly 14 billion years old.
Source: Hubblesite.org
What’s especially interesting about this is that, even though you are seeing very old light from a very old object, the image you see is the object as it was in the very distant past, when it was younger and the light was first emitted or reflected.
So in one sense, when you look at a distant star, you are seeing an old object, but in another sense, you are seeing a young object. When you recognize this paradox, it makes for truly awe-inspiring views of our cosmos.
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