Let’s suppose for a minute that two teenagers are engaged in some active, energetic activity (let’s suppose they are discussing philosophy) in the back of a parked car. After a few hours of intense philosophical discussion, the windows of the car have completely fogged up. What is the scientific reason for this? I know it has something to do with water vapor and condensation, but can anyone give me a more detailed answer?
-Outrider
A car is not well ventilated. Once you’ve turned off the A/C, the air inside is not going to be replaced with much outside air. With people inside engaged in energetic conversation, you’ll see an increase in both the air temperature and humidity, relative to the outside air temperature. Since the windows are usually cooler than the inside air, the now increasingly moisture-laiden air will condense on the glass, causing the look so familiar to horny teenagers and overly officious cops.
Funny that you mention the cops. A cop interrupted one of my philosophical discussions last night. Good thing my discussion partner and I had not started getting into the details of Nietzche and Kant and were only discussing the subject in broad terms. Nevertheless, the cop told us: “get out of here.” I guess he was just jealous that he couldn’t keep up with the conversation.
I’ve always wondered why cops do that. Is there some sort of law against it? Or is it just a version of droit de signor?
Just a WAG but I’m pretty sure it’s against the law in most places. Basically society wants you to keep that stuff behind closed doors. What the specific law that would apply I have no idea (Public Indecency or something like that I’d guess).
Is it even legal for teenagers to have sex (assuming both are under the age of 18)? Not that I’ve heard of anyone getting busted for that (they could pretty much incarcerate 90% of all high school students on the spot). Just curious…
I don’t know if it’s actually against the law (there are laws against public display, but with the windows steamed up, that shouldn’t be an issue. 
)
However, people don’t like the idea of it, both because of teen sex and because they just don’t like the idea. I don’t know of anyone every being arrested. A knock on the window is usually enough to stop it, and it’s not very likely the participants are going to want to make an issue of it.
How did we get to sex from philosophy? You people have sick minds
…and now humor.
Cop drives past a parking lot late at night, sees a parked car, and pulls in to investigate.
In the front seat is a young man, reading a magazine. In the back, a young woman, engaged in knitting a sweater. Cop knocks on the driver’s window and the young man opens it.
“You all right?” the cop asks.
“Sure thing, officer,” the youth replies.
“How old are you, son?”
“Nineteen, sir.”
“And the young lady in the back?”
The youth checks his watch. “Eighteen, in about ten minutes.”
Basically: