Okay, I need some discussion. I love love love reading about the universe and such. All the stars and planets out there, it’s amazing to me! But I’ve never been able to understand light years. Like, we could be looking at something in the sky and be all “Ooooh that’s a bright star!” But it’s 100 light years away and for all we know the star is actually dead and we are seeing the light as it had been traveling to us but died previously. This just goes right over my head. How do we just determine all these objects in the sky are so far… how do we know how far the light from thst object has been traveling? Please help lol! How do we also see planets so far away… I know we have amazing technology but damn… that’s insane to be able to see objects just so far away! I also think there must be some form of life out there. There’s no way we are the only planet with something living on it! Thanks for your input!
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>how do we know how far the light from thst object has been traveling?
This is the core of your question, so I’ll cut right to it.
Have you ever noticed when you’re driving down a highway, that objects closer to the car seem to move faster than objects moving farther away? The road sign passes in the blink of an eye, but the mountain in the distance barely seems to move!
This is due to the fact that the road sign is closer, and a given distance traveled by the car covers a larger angle.
This phenomenon is called *parallax,* and it’s what astronomers rely on to determine stellar measurements.
If we draw a line from Earth that passes through the star we’re interested in and lands on the distant background of stars, we can then draw another line six months later, when we’re on the opposite side of the Sun, and then calculate the angle (really, half of the angle) between the measurements. From there, since we know the distance from the Earth to the Sun, the distance to the star in question is simple trigonometry.
>How do we also see planets so far away…
We can’t. Not really, anyway. We can tell they exist by the effects they have on their parent stars — gravity wobbles, how they impact the light, etc — but we don’t have a way to directly visualize them.
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