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Circles are not always invisible. A circle made up by a closed-loop line source of photons would be visible. (They're kind of hard to make, though.) It's sort
by lutorm 15y ago
Circles are not always invisible. A circle made up by a closed-loop line source of photons would be visible. (They're kind of hard to make, though.)
It's sort of the question of what is the smallest thing a human can "see". Stars, for example, are extremely small, far below the resolution of the human eye (outside of the atmosphere, of course). Yet seeing them is not a problem, you just get an unresolved image.
- Benjo 15y agoThen it's the photons that are visible. A circle is a set of points, and a point is an abstract concept. Having a photon centered on a point does not make the point visible.
- baddox 15y agoAlso, a circle is an infinite set of points, so even if points were visible, you couldn't have a real circle without infinite points.
- lutorm 15y agoBy that definition, nothing is visible. You never see anything except photons.
- thebooktocome 15y agoThat's true; and sometimes, that definition is useful, as it is here.
- Benjo 15y agoVisible means "able to be seen." You can see things that emit or reflect light. Abstract concepts don't emit or reflect light. Real objects can only approximate a circle. The pedantic definition of a circle in this context is being used to make the point that you can't make a perfect circle with pixels.
- lutorm 15y agoNo. If you made an abstract object that emitted light, like the "linear light source" I hypothesized, it would be a perfect circle, and visible. It doesn't exist, of course, but if it did, it would be visible... ;-)
- spodek 15y agoRichard Feynman spoke well and humorously on this topic: http://http://www.youtube.com/watch?v=XpYhM4x4PmY http://http://www.youtube.com/watch?v=XpYhM4x4PmY