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Q&A: General Astronomy and Space Science
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Q:
As rays of light leaving a distant sun progress farther and farther out in space, would they not also grow more distant from each other? I picture a sphere covered in pins sticking out in all directtions. The distance between the pins at their tips is greater than at the base. If you were not in direct line of sight of one of these rays, would you not see that star at all? The farther away from a sun that you get, would there not be vast reaches of space that would never receive even one ray of light from a sun?
Anticipating that your answer might be that light also acts as a wave, then wouldn't that wave become spread so thin at some point, so as not to be visible?
A:
It's true that the light rays grow more distant from each other as they travel out from the Sun, and also that the light waves lose intensity as they travel further and further from the Sun. However, you should think of the light rays as an infinite number of pins sticking out in all directions so that no matter how far away you go there will always be at least one pin aiming right at you.
The problem is detecting the light. If you go too far away from a shining object then you will have a hard time making a detector to catch the few light rays that are coming towards you.
As you can imagine if you know some physics, the intensity falls off quickly as you move further away from the object, in fact it goes as 1 over the distance squared. For a brief note on radiation intensity diminishing with distance, scroll down to the Inverse Square Law section on this webpage:
http://www.physicalgeography.net/fundamentals/6f.html
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