Is there any semantic difference between these sentences? Does the article makes any difference?

As fast as light can go


As fast as the light can go


All light has the same speed; it is difficult to imagine a context in which it would make sense to single out some particular identifiable form of light (red? green? ultraviolet?) as a standard of comparison.

As fast as the light can go might be appropriate if you were using light as a mobile source of illumination: "Rob is running ahead with a light, and I'm having no trouble following him—I can bicycle as fast as the light can go."

  • Actually the speed of light varies, in which case you could refer to "the light traveling through a particular medium" (like air or water) or "the light as observed in a particular inertial frame". But this can get complicated. :)
    – Andrew
    Apr 4 '17 at 23:54
  • @Andrew, and that raises the question of whether you could distinguish the speed difference, anyway. All light is REALLY fast.
    – fixer1234
    Apr 5 '17 at 0:21
  • @fixer1234 as the link in my comment mentions, Foucault was able to measure the speed of light in various media back in 1850. Obviously it's faster than any unaided human can perceive, but even small differences can be detected with the right apparatus.
    – Andrew
    Apr 5 '17 at 2:58
  • @Andrew You're quite right. I will have to rethink this. Apr 5 '17 at 9:31

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