Blue is hot and Red is cooler

What if I told you that blue means hot and red means cool? I know that’s not the way it looks on my sink handles. There’s a reason why I ask the question because most of us generally assume that blue means cold and red means hot. This is almost like a previous post of mine when I was talking about why the word right can mean so many different things.

This blue and being hotter thing has to do with stars as well as earthbound examples of blue being hotter than red. Stars are extremely hot, duh! Apparently a teaspoon full of sun will cause some devastating effects over hundreds of kilometers if you dropped that on our earth. But our sun is considered a cool (red) sun. If you ever look up at the sky, and I hope you do, the stars aren’t all white. Let’s throw out the twinkling ones because our atmosphere is causing that problem. I’ll take one star as an example….Betelgeuse (pronounced beetlejuice by most people). It’s a very bright star we can easily see. It’s red! It’s not as hot a star compared to Sirius, a bluish star. By the way, these stars are massive, way bigger than our sun. Put Betelgeuse in place of our sun and it will smother us and maybe extend out to Jupiter. Stars have different colors during their life spans. The really hot blue ones don’t live as long either.

Here’s an example of earthbound blue being hotter than red. A flame from a propane or butane torch is hottest at the tip when it’s blue and the lower part of the flame is red. There’s a bit more to burning (combustion) and colors but let’s just leave it at that (high frequency=high energy=high temperature=blue flame). So red is “cooler” than blue. I’ll include a couple of links of some more scientific explanation at the bottom if you’d like to understand combustion, temperatures and flame color. I sure do like wikipedia and you can see that from all the links below.

So how did blue become known as cool on our water faucets and red become hot? I’m just guessing at the reasoning here. Maybe it’s because a fire is generally reddish looking and the stove also turns red when it’s hot. And blue looks like the color in a swimming pool or the ocean? You got me. But are you down with that?:)


Hertzsprung-Russell diagram