This was a shower thought.
- We usually define a topological space as connected iff there are disjoint open sets such that . Since they are disjoint, we have that .
- An alternative way of stating this is to consider two colors
C = {red, blue }with the discrete topology. - We use the discrete topology on
Csince we want the two colors to be "separate". - Now, a space is connected iff there is a continuous surjective function . That is, we can color the whole space continuously with both colors.
This is equivalent to the original definition by setting and :
- Pre-images of a function must be disjoint. Hence, .
- Preimages of and must be open sets since and are open and is continuous: continuous functions have pre-images of open sets as open. Hence and are open.
- Since is surjective, we must have that the pre-images cover the entire set . Hence .
I find this to be appealing, since it's intuitively obvious to me that if a space is disconnected, I can color it continuously with two colors, while if a space is connected, I should be unable to color it continuously with two colors --- there should be a point of "breakage" where we suddenly switch colors.