How is it possible for us to see stars that are millions of light years 'APART' from one another with the naked eye when we look at in the night sky from horizon to horizon? (i.e., pick any stars light on the right side of the sky and then another as far to the left side of the night sky as you can see).Their millions of light years apart, right? How can we see objects that are 'light years' apart from one another and away from us? I beleive it, I just don't uderstand it! The best answer I've heard is 'perspective'? OK, that's pretty vague, what does that mean? We can't travel those distances but we can 'see' those distances with the naked eye? There has to be simple explanation but I just don't get it!? Can anyone run it through the old 'simplifing machine'? Thank you.
closed as unclear what you're asking by John Rennie, Gert, GiorgioP, Kyle Kanos, Jon Custer Mar 2 at 3:03
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
"Seeing" something is the same as light travelling from that thing and into your eye. When you see your hand it is because light has been reflected off the hand and into your eye. When you see the stars it is because light has traveled from them, through the galaxy and into your eye. Light travels extremely fast, 300.000 m/s, and crosses the distance of a light year in the timespan of a year. Stars can also be extremely old (billions of years) and extremely bright in all directions.
This means that a large amount of light will be launched in your direction at any given time. The light of a star one light year away only has to travel for one year to reach you. And it does. Therefore you can see the star. We cannot travel that fast. Therefore we can see the stars, but not reach them.
The reason you can see two stars at the same time even though they are far apart is indeed because of perspective. Consider these two trees:
If you stand at a distance, you can see them both. If you stand very close to them, you will have to turn to see both. Now think about you and the two trees as the three points of a triangle. If you extend the points corresponding to the two trees to a larger distance, the distance between them will seem smaller. If they are really far away, they will seem like they are basically in the same point. So the distance between two objects far away from you seems small. In fact it seems smaller the further away the objects are. For something as far away as a star, the distance between two stars may look small, but is indeed about as large as their distance from you.
Photons travel, photons hit your retina and thus you have the ralisation of seeing a star. The fact that we can see objects far away is caused by the fact, that they are very bright. As the universe is isotropic in every point it doesn't matter in which direction you look to see said object.
Edit: as made clear in previous comments, of course the objects at thus distances are not stars, but galaxies, supernovae and other bright objects. Also you might not be able to see them with naked eye or even in visual wavebands. But this shouldn't get the inherent problem of your question, if i got it right.
If the core of you answer is maybe that your puzzled by the optical horizon of the universe caused by the finite speed of light coupled with the finite age of the universe, than the answer is simply that the optical horizon of the universe is, as far as we can proof, only optical and not a real border of the universe. Thus we can detect a light source 30*10⁹ lightyears away 'to the right' and 30*10⁹ lightyears away 'to the left', eventhough they are 60*10⁹ lightyears apart and the visible universe only spans ~42*10⁹ lightyears (in one direction). So eventhough they can not see each other, we can see both. For the same reason, both objects can see areas of the universe, which we can not see. Of course for a positive curvature of the universe we would possibly reach a point in the future where this is not completely true, but we would see said area simply on the other side.