User-Friendly Sparks

Factual Questions
1

Why don’t sparks from lighters or from the 4th of July “sparklers” burn when they come into contact with our skin?

2

My WAG is that they do burn your skin, but the surface area of the cinder is so small you don’t feel it, the same way you might not feel a hypodermic needle puncturing your skin.

3

because they are sparks and not too hot

4

There just isn’t enough energy there. The heat from a tiny spark transfers across a large area of your skin.
Try welding sometime. The sparks given off are larger (and heavier) and can burn your clothes, skin, etc…

5

Yeah, welding sparks can really mess up your day. Wear long pants.

The sparkler thing was an example in physics class of temperature vs. heat content. Temperature is just based on the average speed of all the molecules in a substance, while heat content is more like the sum of all their speeds (close enough in concept).

There’s just not much mass in each of those white-hot (1000F?) sparks, but they do leave small burned spots on your outer (dead) skin layer as UM mentioned. Since the total heat content of each spark is low, nothing much happens after that, since your skin easily absorbs that much heat.

A casserole fresh out of a 400F oven is not nearly as hot (lower average molecule speed), but we know better than to touch it because the high heat content (lots more total molecular motion) can certainly damage a lot of flesh.

Oh, here’s another: a 100mph paintball hurts, but a 20mph car can kill you.

I lead a boring life of relative unimportance. Really.

6
      • This reminds me of when I was a kid and near the 4th of July kids (boys, mostly) would have Roman Candle fights. If the shot just bounced off you it would only singe the hair on your skin, but if it stuck, , , ooooooOuch!!! If anyone saw it stick, they’d dropped whatever they had in your hands and brushed it off as fast as possible. Usually what they dropped was - a handful of just-lit fireworks.
      • OTOH, a bottle rocket is only a tiny bit of paper and bamboo, but if you got hit good, it would leave a bruise an inch across. It didn’t explode when it hit; it didn’t have to. Same with those damn “Witch Whistler” things - they came in fusillade boxes of forty - one wick set them all off one after the other, about a second apart. We preferred bottle rockets to them though because you couldn’t aim witch whistlers; often they would turn on the attacker, sometimes they’d hit him. The witch whistlers didn’t move quite as fast, but were a bit heavier. They both hit about the same.
  • You know, I used to wonder why most of my friends went through the service. Right now I’m wondering why I chose not to. - MC