Why do some airplanes leave contrails, while others do not?
Well done! The vast majority of the contrail is water. When you burn a hydrocarbon fuel (gasoline, wood, candle wax, etc.), it produces carbon dioxide and water vapor.
At high altitudes, you get very cold temperatures. On our flight today, the outside air temperature registered
-52C! At those temperatures, water vapor tends to condense into water droplets or ice crystals, producing a cloud. (See this week's video, A Watched Pot.)
If the air is very moist, the contrail can trigger more condensation, and the contrail will grow larger, sometimes expanding to cover large areas.
On the other hand, if the air around the plane is very dry, it absorbs the moisture, and the contrail disappears quickly, or may not form at all.
Also, if the plane is flying below the point where temperature/pressure/humidity will cause condensation, it will not leave a trail.
contrails
Where were you that is was 52C? Isn't that abominably hot?
The Andrews
Re: Contrails
It was -52C. The text was breaking, leaving the "-" on the end of the previous line. I have it fixed now.
-52C
Well, that was abominably cold. :-) Glad to be inside a modern day jet in that kind of weather!
Thanks for your reply.
The Andrews
Airplanes
The altitude of the plane determines whether the liquid water trail behind the engines will dissipate or freezes into ice.
?
Do they leave trails in different atmospheric conditions?
Krista
Engines
Maybe they have a different kind of engine, or runs on a different kind of fuel?
Rachel, Age 10
Motor
Some airplanes have different motors, or engines.
Sarah, Age 5
Wake
The part of the airplane on the back (the wings on the back) might make a wake like boats in water.
Emily, Age 7
contrails
Well, we just discussed that as the atmosphere thins, it also becomes colder. So, if a an airplane flies really high there will be a big contrast in temps between the air-cold and the contrail-hot. When you have a hot cup of chocolate in a cold room, you get steam. We think the exiting gases of high flying planes turn to "steam" sort of too. The answer then is some planes just fly at higher altitudes.
But that doesn't explain why some planes can write messages in low altitudes. Do they do it backwards? Do they put off cold fumes and since the air around it is warm, the fumes make a "cloud"?
The Andrews
Why do some airplanes leave contrails, while others do not?
I did a bit of reasearching and found out that contrails are created when the hot air from the jet engine mixes with cold air resulting in condensation which is basically is how clouds are formed.
This doesn't alway happen because the air temperature and the humidity have to fall into a certain range for a contrail to form.
question
hello i'm julia and my science teacher ms.Norton uses your site to do bellringers and stuff so thats how i found out and i really like this site and i wish i'd found it sooner.i have no idea about the planes though.also when i see a new science photo and answer i like to tell alot of people because 100& of the time its really intresting but when i asked her what was so strange about birds knees she just said they were backwards and would not listen to me becuase she too stubborn when she thinks shes right although she has no actual information and thinks that her way is the only way.it makes me really angry that she's so ignorant what should i do?
julia(p.s i'm sorry if i'm wasting your time)
(p.s.s what does p.s stand for?)
(p.s.s.s how do you find so manny intresting things,know so much about them and find the time to post it all?)
sorry again (age 12 sister 18)
Hi Julia
Well, the first thing is not to get angry. Over my MANY years of sharing the wonders of science, I have run into many people that disagreed with me on one point or another. Sometimes it was because I was wrong. Sometimes it was because they had learned a different answer. Sometimes it was because we were not communicating well, and did not really understand what the other person was saying. In every case, once you get angry, they usually stop listening to you. That is one reason that I wound up as The Happy Scientist.
I also find that it helps to be able to send people to books or websites, where they can confirm your facts. That does not mean that they don't trust you, or think you are wrong. People like to be sure of things, especially when the answer is not what they thought it was.
As for how I find so many interesting things, I have learned to look at things and wonder why and how. No matter where I am, if I relax and start wondering, I can usually find something amazing that I never really thought about before. Then I start researching to find the answer. It is fun to wonder, fun to find the answer, and fun to share it with others.
I hope that helps.
P.S. P.S. means post script. One of the meanings for post is after, so a post script is a it that you add after you have finished writing a letter.
Post new comment