How Do Airplanes Fly? What Neil deGrasse Tyson got wrong about Bernoulli | StarTalk

Summary

The video script features a critique of astrophysicist Neil deGrasse Tyson's explanation of aerodynamics on his popular podcast, StarTalk. It argues that Tyson's description of lift based on the equal transit time hypothesis is incorrect. Instead, the video presents NASA's view that lift is a result of the flow of air being turned by the wing, following Newton's third law of motion. The script debunks the common myth that lift is solely due to airspeed differences over the wing's curved surface, emphasizing the importance of understanding both Bernoulli's principle and Newton's laws to fully grasp how airplanes achieve lift.

Takeaways

• 😀 Neil deGrasse Tyson is an astrophysicist, writer, and science communicator who has studied at Harvard University, the University of Texas, and Columbia University.
• 👨‍🏫 Tyson served on government commissions regarding the future of the US airspace industry and space exploration, and was awarded the NASA Distinguished Public Service Medal.
• 🎙️ Since 2009, Tyson has hosted 'Star Talk', a popular podcast with nearly 3 million subscribers on YouTube, co-hosted by comic co-host Chuck Nice.
• 🚫 The script challenges Tyson's explanation of lift in his podcast, arguing that his understanding is based on a misconception about aerodynamics.
• ✈️ The common explanation of lift, based on the equal transit time hypothesis, is debunked with evidence showing that air does not travel at the same speed over and under the wing.
• 🔍 According to NASA, lift is generated when a moving flow of gas is turned by a solid object, creating an opposite reaction force, aligning with Newton's Third Law of Motion.
• 📚 The Bernoulli principle is not entirely dismissed but is used in conjunction with Newton's laws to explain the pressure differences that contribute to lift.
• 📉 The video by Holger Babinski, a professor of aerodynamics, visually demonstrates the flaw in the equal transit time hypothesis using smoke to track airflow.
• 🛫 During takeoff, pilots use flaps to increase the angle of attack, which increases the pressure difference and lift, allowing the aircraft to ascend.
• 🌬️ The script emphasizes that lift is not solely created by air hitting the underside of the wing, but by the complex interaction of airflow over and under the wing.
• ✋ The idea of comparing wing lift to holding a hand out of a car window is flawed, as most of the force felt is drag, not lift.

Q & A

What is the main topic of the podcast episode featuring Neil deGrasse Tyson?

The main topic of the podcast episode is the explanation of how airplanes fly, specifically addressing the common misconceptions about lift and aerodynamics.

What is the 'equal transit time hypothesis' mentioned in the script?

The 'equal transit time hypothesis' is a previously held belief that the air on the top of an airplane wing travels a longer distance and therefore must move faster to reach the end of the wing at the same time as the air on the bottom, creating lift. However, this hypothesis has been debunked as incorrect.

According to the script, what is the correct explanation for lift on an airplane wing?

The correct explanation for lift, as per the script, is that lift occurs when a moving flow of gas is turned by a solid object, such as an airplane wing. The flow is turned in one direction and the lift is generated in the opposite direction, following Newton's third law of motion.

What role does the Bernoulli's principle play in the generation of lift according to the script?

Bernoulli's principle is still relevant in explaining lift. It helps to calculate the velocity of an airstream when the static pressure is known and is useful for visualizing the pressure distribution above and below the wing. However, it is not the sole explanation for lift.

What does the script suggest about the importance of the angle of attack in flight?

The script suggests that the angle of attack, which is the angle between the airflow and the chord of the wing, is crucial for generating lift. As the angle of attack increases, the static air pressure over the wing decreases, leading to more lift.

Why do pilots increase the flaps on the tail wings during takeoff, as mentioned in the script?

Pilots increase the flaps on the tail wings during takeoff to create extra pressure that pushes the tail down, pivoting the nose upwards. This increases the angle of attack, which in turn increases the lift generated by the wings.

What is the significance of taking off into the wind, as discussed in the script?

Taking off into the wind is significant because it provides a headwind component that increases the airspeed over the wings, which is crucial for generating lift. This allows the aircraft to become airborne more efficiently.

How does the script explain the evolution of aircraft carrier designs, particularly regarding the flight deck?

The script explains that aircraft carriers evolved from having a straight deck to an angled flight deck. This change allowed aircraft to land and take off more safely by enabling missed landings to go around the deck instead of crashing into parked aircraft.

What is the purpose of having multiple runways at different angles in airports and on aircraft carriers, as described in the script?

Having multiple runways at different angles allows for aircraft to take off and land into the wind regardless of its direction. This ensures optimal headwind components for better lift and control during takeoff and landing.

What is the challenge issued to Neil deGrasse Tyson at the end of the script?

The challenge issued to Neil deGrasse Tyson is to make a new video about lift, correcting the misconceptions and incorporating the insights provided in the script, possibly with the guidance of experts like Holger Babinski, D. McEn, and Kristoff Foskett.