I'm doing battle with someone in a debate and I need some help here as, perhaps, I'm not articulating my side well or he's just so stubborn that he doesn't want to learn the error of his ways. :) It's the stupid old riddle where if you have 1000 birds in a plane or a truck (or any enclosed vehicle) that each weigh 1 pound and suddenly they all start flying would the vehicle weigh less than when they were perched. My belief of physics on this and from everything I have read, the answer is no. The air they displace to stay in the air in the closed environment is equal to their mass so the vehicle, as a whole, would weigh the same. Someone posted this question on Facebook and there were a few people who responded yes and some no but one person in question was quite emphatic about his belief that the vehicle would weigh less. His background is that he has spent many years as a pilot and his background in avionics tells him that because the birds are creating lift (low air pressure under the wings, etc.). I've tried to explain, in every way that I can, that to keep something in the air you need thrust, and that thrust in an enclosed environment is equal to the mass of the object to keep it in the air so the weight does not change of the vehicle whether or not the bird is flying inside. The other individual keeps insulting me saying that I'm wrong because this all has to do with lift. I've cited numerous forums (this one included, including this link here): https://www.physicsforums.com/showthread.php?t=166425 I even went so far as to show him the link to the Mythbusters episode where they dealt with this specific question. No go. He cites how even encyclopedias can be wrong (guilt by association fallacy), how Mythbusters is a poor citation, and how people in science forums are just giving opinions. I tried to even explain Newtons 3 Laws of Motion and that was to no avail. Here is one of his rebuttals: You likely read Encyclopedia Britanica and World Book when you were in school, though I have no idea how old you are, so maybe not. But both have listings for GERONIMO. They say Geronimo is named "Goyathlay" which he clearly ws not. Geronimo was born Go-kla-yeh, named by his Grandfather Mahko, Chief if the Nedni Apache. It was later that Taza, the eldest son of Cochise nicknamed Go-kla-yeh... GOYATHLAY, because he thought GMO was lazy. When I contacted BOTH Encylopedias to tell them they were mistaken, they told me they knew, but that is how it had been for 80 years, they were not changing it now. BOTH publications, list Geronimo as a Chief of the Chiracahua Apache. NEITHER IS TRUE, Goklayeh was born to his mother Juana, a Be-don-ko-he Apache and his father Taklishim, a Nedni Apache, because the Apache are matriarchal, he took his mother's tribal heritage as a Be-don-ko-hey. When I pointed this out to Britanica and World Book, they again reminded me they knew I was right, but... it still reads inaccurately. BOTH BOOKS OF KNOWLEDGE used in virtually every school in AMERICA for 80 years say he was a Chief, which he never could be, as a mixed breed and Chiricahua which he never was. At age 19 or 20, he married Alope', the daughter of Noposo, the brother of Chief Chise-co-chise, better known as COCHISE. GERONIMO's association with his best friend NAICHE' youngest son of Chief Cochise and his marriage to Alope' were his only ties to the Chiricahua Apache. He was BEDONKOHE! He was never CHIEF OF ANY TRIBE OR BAND, he was at best a War Shaman, chosen to lead the attack on a band of Mexicans after the slaughter of his family at KASKIYEH, where his wife, children and parents were slaughtered. Since he had suffered the greatest loss, he got to lead the attack. THAT IS AS CLOSE as he ever become to any CHIEF, which he never was. SO YOU TELL ME OF YOUR CONFIDENCE IN YOUR SCHOOL BOOKS and MYTHBUSTERS and a few message boards with more questions than answers and I will tell you, do WIDER research, many of the things you learn in school ARE WRONG. Remember that head they had on T-REX for 50 years, telling us this was the head of T-REX, only to discover they were wrong, the head they told us belonged to T-REX was just another head of another creature found nearby. OOOPS! Do not imagine you have a clue what I know or do not know... that would be foolish on your part. BUT KEEP TELLING PILOTS THEY KNOW NOTHING ABOUT AERODYNAMICS... It helps them understand you, more than you realize. So, in my frustration, I came here. Is there any better way I can articulate my argument? Are there any people in here with some letters behind their name who can help me out here. :) Here is the last statement I made in the argument after explaining numerous times that lift and aerodynamics have nothing to do with this riddle at all, it just has to do with basic physics: The one factor [He] just cannot wrap his head around is the factor of thrust. The four elements to an airfoil are Lift, Weight, Drag, and Thrust. The reason that a plane does not fly when just sitting on the ground is that there is no thrust to push it into the air for lift to occur. No thrust, no lift. So when you exert thrust as a means of propulsion, you can get lift with a wing which creates a pressure flow which creates lift. The lift compensates for the weight and is counteracted by drag. The same thing occurs with a bird. But instead of an engine to create the thrust, the thrust is created by flapping a wing. In the motion of the flapping, thrust is occurring to then create the lift etc. But in the manufacturing of the thrust, you are pushing down against the inside of the airplane or the truck or the box or whatever enclosed environment the bird is in. That thrust is the same amount of force as the mass of the bird so it balances itself out. Just because you can create lift doesn't mean that you have an anti-gravity device, the lift has to be made by creating thrust. Again, Physics 101. So, can anyone help me with this? Thanks in advance!