Originally Posted by
Hypno Toad
Insults, not really, just talking with somebody that doesn't want believe the facts and testimony of multiple posters. Calculations are fine in the classroom, but real-world life experience is what I'm talking about.
I have seen no "facts" from any posters. My calculations are based on facts...real ones of known principles. If you have a different set of "facts", present them.
Originally Posted by
Hypno Toad
Therefore, we have more experience with sub-zero temps that most places in the US. With temps staying below 0F for days-on-end, there is very little moisture in the air (the air is drier than a dessert). There is far less moisture in the air than what is coming from the tailpipe of hundreds of cars. It would be very odd that the tiny amount of moisture left in the air would only form ice at places where cars are stopped, idling.
The amount of moisture in your air is probably higher than that here in Colorado. Our air can't carry as much water due to its lower pressure and our relative humidity...the ratio of water in the air to what the air could carry at any given temperature...is lower than many places in the US. We have cold temperatures and our tailpipes put out just as much water as yours do but we don't have this urban legend of the water condensing on the roads. We should be able to condense the water at much higher temperatures due to the lower carrying capacity of our air.
The dryness of your air doesn't help your argument either. As I've said above, if the air isn't saturated, the air can absorb the water vapor that is put out by the cars. Yes, the cars are going to have clouds of vapor around them while sitting still but those clouds will quickly evaporate into the air. The water won't go crashing out on the ground in any appreciable amount...largely because there isn't that much water in the fog.
Originally Posted by
Hypno Toad
Wouldn't that ice would form on sidewalks and trees and other surfaces? But it does not, it only forms on roadways where cars are stopped idling. The source of the moisture that is forming ice on the road surface is the cars exhaust.
Therein lies the problem. If the cars are the source of your ice, you'd expect the sidewalks and buildings at any given intersection to have a thicker coating of ice than elsewhere. There is nothing that would keep the water from condensing on every surface around the intersection. It wouldn't condense preferentially on the roadways.
Originally Posted by
Hypno Toad
There are dozens of source that state the exact same thing I'm saying. It's OK to say you don't have a calculation to explain this, we won't judge you, just stop saying we are wrong - that is insulting.
There are hundreds of sources that state the same thing you do. All of them state it the same way that the Wikidpedia article state it. That's not a creditable source. Like I've said before it has all the hallmarks of an urban legend. I can't find a single scientific article with data that backs up the claim.
It's not insulting to say you are wrong if you are wrong. You are wrong. There's just not enough gas burned nor is there enough water produced to do what you guys are saying happens.
Originally Posted by
tjspiel
Perhaps a very miserly car under ideal conditions burn that little gas in an hour. A typical car will burn 1/4 to half gallon of gas in an hour. Maybe even 3/4 of a gallon for something large. A school bus could burn as much as gallon. And as your chemistry magic showed burning a gallon of gas produces more than a gallon of water !
Got anything to back up the claim of that high a gasoline consumption? It's not hard to do the calculations yourself.
Originally Posted by
tjspiel
Of course an individual car doesn't sit at intersection for an hour but you have many cars idling at busy intersections all throughout the day. Of course they don't just idle either, they accelerate as they move on, burning more gas and producing more water than they would if they were idling.
Yes, the cars aren't going to idle for an hour. They are going to idle for a couple of minutes, as I've pointed out above. A thousand cars passing a point and idling for 2 minutes each are going to produce about 7 liters of water...a bit over a gallon and a half. That's still not much water.
Originally Posted by
tjspiel
You were convinced that any water vapor immediately rises up and out of the way. I showed you a picture that shows that is simply not the case. As they say, a picture is worth a thousand words and that same picture shows plenty enough water to cause problems.
Let's look at that picture. Yes, there's fog around the cars from exhaust. But there is also a lot of snow on the ground in the picture. The cars moving on the snow, compacting it and sliding on it are going to do far more to make the intersection slick than the car exhaust will.
Originally Posted by
alan s
The exhaust appears roughly equivalent to ground fog, and would most certainly cause black ice under the right conditions (low wind, mainly). Add to this the water condensate that comes out of tailpipes, and you have plenty of water to form black ice.
The "right conditions" is what is important. A moving car isn't a situation where there is low wind. The air around each one of those cars in tjspiel's picture is going to become turbulent the minute the cars start to move. That will stir the air, bringing low moisture air into the mix and move high moisture (warmer) air further up. the conditions would not be "right" for the formation of "black" ice.