For us to see with a telescope. It just keeps going on and on.
But if say, everywhere is dark, and someone lights up something in one part of the world, it wouldn't even go beyond that city. And one won't be able to use a telescope in the other end of the planet to get the images of the area that's lit.
So how does stellar light keep moving for space telescopes to capture the images and everything?
Getting my point?
Clive
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Yes it does. ALL light never stops travelling until it hits something and gets reflected or absorbed.
However, it spreads out until it becomes too dim to see, depending on what light detector you're using. Eyeballs are quite small and telescopes are bigger, which is why we need them to see more distant stuff. The bigger the main lens or mirror, the more of this spreading light we can pick up Even so, to see REALLY distant, you need a long exposure to collect more photons on your film or CCD and get a good picture. When Hubble took photos of distant galactic spectra and concluded they're ALL red-shifted so the universe must be expanding, it took him ages - basically he could only get one photo per night when he was looking at galaxies billions of light years off. Research can get really boring! (It also goes wrong a lot because you're doing new stuff - do not do a PhD if you don't have lots and lots of patience. My best friend at university took 7 years to finish his and it's only supposed to take 3.)
Laser light, by the way, is collimated so it doesn't spread out so much and the light from a not so powerful laser will be visible further away, but you won't see it unless it's pointing directly at you. Stars, fortunately for being able to see them, send out uncollimated light in all directions.
What you've forgotten in your example is that planets are round. You can't see more than a few miles because anything further than that is below the horizon because of the planet's curvature. If the world was flat, you would have a point. But it's not, it's round, so this is easily explained.
It may help to go extreme - if you're American, as you clearly are from your spelling, how do you expect to see Australia? Obviously you can't because you're on the other side of a big ball. You could see it from underneath on a transparent Earth. But Earth is not transparent to visible light. And light travels in straight lines, and a straight line to Aussie-land goes through it. A straight line to anywhere more than a few miles away does too.
It also doesn't help that the atmosphere scatters light. Which is why the Hubble Space Telescope was put in space. Put your telescope out there and you get much less blurry images. (That is, once it was repaired... the main mirror was a tiny bit out of shape and when they saw the first images, everyone connected with the project looked at the blurry blobs and went "oh sh**". Millions of dollars down the drain unless it could be fixed - and a Space Shuttle mission DID fix it. Oh boy - just imagine the political repercussions on NASA if they goofed again.)
Ronald 7
Because Cities have too much Light Pollution
Bulldog redux
No, I'm not getting your point.
daniel g
You strike a match, the light goes to the infinitum of the universe unless absorbed, reflected, or refracted. Intensity reduces by square law so not very bright say ,on our moon.
Daniel H
Light will travel until something blocks it. Dust particles in the air, trees, curvature of the earth, ... limit how far you can see light. Curvature of the earth limits you to around 3-4 miles.