Today’s post is a special A to Z Challenge edition of Sciency Words, an ongoing series here on Planet Pailly where we take a look at some interesting science or science related term so we can all expand our scientific vocabularies together. In today’s post, F is for:
They say it’s cold in space. That’s not quite true. First off, how do you define what temperature means in a vacuum? That’s a much harder question that you might think.
But secondly—and more importantly for today’s post—a lot depends on where you are in space, because if you happen to be anywhere near a star, I guarantee you will feel the heat.
If you read enough scientific literature about space, you’ll eventually encounter the term “frost line,” and you’ll probably be able to guess from context what it means. Objects on one side of the line are close enough to the Sun for ice to melt (or more likely, sublimate), while objects on the other side are far enough away that ice remains frozen.
In our Solar System, the frost line is usually placed somewhere in the middle of the asteroid belt.
But there’s a lot of disagreement about where specifically the frost line is, in large part because there’s a lot of disagreement about how, specifically, the term should be defined.
Some astrophysicists define the frost line based on temperature conditions in the Solar System today. Others define it based on conditions from back when the Solar System was still forming. Also, there can be different frost lines for different chemicals, because the freezing point of water is different than that of methane or nitrogen or carbon dioxide.
This is a case of how some scientific terms are more clearly and precisely defined than others. And yet despite all the ambiguity about the frost line (or lines), it is still an incredibly useful term to help describe the layout of the Solar System. Which is why, if you read enough scientific literature about space, you are bound to come across this term eventually.
Next time on Sciency Words: A to Z Challenge, where did the word gravity come from?