Why are some things not visible…

Ralphie, of Topeka KS, asks,

Why are some objects not visible to your naked eyes?

There are many possible reasons.

  • The object is too small – for instance, a virus, or Snooki’s brain.
  • The object is too far away given its size – for instance, the planet Neptune (if you’re on Earth), or Jimmy Carter waving to you from a 747 as it flies over your house.
  • The object is completely transparent – for instance, a bunch of air, or the motivations of someone who wants schools to teach “Intelligent Design”.
  • The object has the same color and refractive index as the medium surrounding it — for instance, a pyrex rod in becel oil.
  • The object is too dim – for instance, a black hole, or Rush Limbaugh.
  • Your view is blocked – for instance, your pelvic bone (at least I hope your view is blocked).
  • The object does not exist – for instance, Superman or delicious zero-calorie ice cream.
  • The object does not exist at the moment, like George Washington, or yourself doing the macarena (unless you have both the bad taste and the agility to be doing the macarena at the same time you’re reading this).
  • You are looking in the wrong direction – for instance, the back of your head.
  • The object is conceptual – for instance, the hole in a donut (in case you feel like arguing that you can see the hole: what you’re really seeing is the edges of the donut. Or you’re looking through the hole, in which case you’re still not seeing the hole itself; if you can see clear through something you’re not seeing it).
  • The room is dark.
  • You are blind (or need glasses).
  • You are paying attention to something else – for instance, you’re watching the right hand of the magician while with her left hand she hides the object she supposedly made vanish.

That’s all I can think of at the moment, but perhaps my readers can suggest more.