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How astronomers “see into the past” by looking at dim stars, and how bigger telescopes see farther back in history?
by audiometry 5y ago
How astronomers “see into the past” by looking at dim stars, and how bigger telescopes see farther back in history?
- adamhp 5y agoYou probably know that light has a speed, right? It takes time for light to get from point A to point B. Even from our Sun, light takes around 8 minutes to reach us. From that, you are actually viewing the Sun (relative to yourself) from about 8 minutes ago, by the time the light reaches you. If the Sun just disappeared magically, you wouldn't really know it for about 8 minutes while the light traveled from where the Sun used to be, to your eyes on Earth. So, expand that concept to distances that are billions of not just minutes, but years. A "light year" is just how far light travels in an Earth year. So, we can see about as "far" as 13.5 billion light years away. Which also implies we can see as "far back" (in time) as 13.5 billion years ago.
- audiometry 5y agoYeah, I understand that the photon hitting my eye right now was ejected from the sun 8 minutes ago. And if I could see it, a photon hitting my eye now from the big-bang was ejected 13bn years ago. But if I have some super telescope here on earth, and I'm looking through it now, the photon that hits the eyepiece of the telescope also was ejected 13bn years ago. I don't see how magnification allows me to see even older photons.
- burntoutfire 5y agoMaybe there's fewer of those old photons reaching us from any particular angular slice of the sky, so you need a more sensitive detector to see them?