Plane vs. Conveyer Belt: Hell Yeah the Plane Takes Off

UPDATE: Well, that'll teach me to blog about physics I don't fully understand! I have researched the issue and edited the post below, now that I understand the explanation from The Straight Dope.

Last night the Discovery show Mythbusters settled a longstanding debate: whether an airplane on a conveyor belt (running in the opposite direction as the plane) can take off. The short answer, as liveblogged by Jason Kottke:


It's a curious problem. As a thought experiment, it seems (at least to me) like the plane shouldn't take off, since it wouldn't gain takeoff velocity relative to the ground. But according to, you know, SCIENCE, the plane will still reach takeoff velocity -- the wheels will just spin twice as fast. This is because the wheels aren't providing any thrust, it's the engines (propellors) that are pulling the plane forward through the air. It's the velocity of the air relative to the wings that counts, which is generated by the action of the engines pulling the plane forward. So the conveyor belt will only stop the plane from gaining takeoff velocity if it creates enough friction to counteract the forward thrust of the engines (or propellor).

Despite explanations of this sort by physicists, the issue wasn't really settled until last night's Mythbusters episode -- they replicated the experiment on a small scale, then with a real airplane (albeit an ultralight), using a huge tarp dragged by a truck as the "conveyor belt." Even the plane's pilot thought the plane wouldn't overcome the power of the conveyor belt, and thus wouldn't gain takeoff velocity. When Jason Kottke first blogged about the issue last February, his comment thread was hot with controversy. So Kottke tuned in to Mythbusters last night and liveblogged the event, with results visible above. His exuberance over the plane's liftoff has resulted in a "HELL YEAH THE PLANE TAKES OFF" tee-shirt available starting at $18. Wow.

Watch the Mythbusters clip in question below.... (Note: if this clip is pulled down, I'll try to dig up another.)

Keep in mind that the issue here is partly semantic, and has to do with how you explain the theoretical problem. I explained it poorly in my first post, since I (like apparently many) assumed that air would flow over the wings as a result of the propellor spinning, and that would be enough to make the plane take off, even if it was stationary. This is not the case -- the plane is going to need to move air over its wings in order to take off. The point of the experiment is simply that yes, the plane will move despite the conveyer belt underneath it. And that movement (at least in this experiment) provided sufficient lift to get the plane off the ground.

Whale Sharks Can Live for More Than a Century, Study Finds

Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

Scientists Find a Possible Link Between Beef Jerky and Mania

Scientist have discovered a surprising new factor that may contribute to mania: meat sticks. As NBC News reports, processed meats containing nitrates, like jerky and some cold cuts, may provoke symptoms of mental illness.

For a new study, published in the journal Molecular Psychiatry, scientists surveyed roughly 1100 people with psychiatric disorders who were admitted into the Sheppard Pratt Health System in Baltimore between 2007 and 2017. They had initially set out to find whether there was any connection between certain infectious diseases and mania, a common symptom of bipolar disorder that can include racing thoughts, intense euphoria, and irritability.

While questioning participants about their diet, the researchers discovered that a significant number of them had eaten cured meats before their manic episodes. Patients who had recently consumed products like salami, jerky, and dried meat sticks were more likely to be hospitalized for mania than subjects in the control group.

The link can be narrowed down to nitrates, which are preservatives added to many types of cured meats. In a later part of the study, rats that were fed nitrate-free jerky acted less hyperactive than those who were given meat with nitrates.

Numerous studies have been published on the risks of consuming foods pumped full of nitrates: The ingredient can lead to the formation of carcinogens, and it can react in the gut in a way that promotes inflammation. It's possible that inflammation from nitrates can trigger mania in people who are already susceptible to it, but scientists aren't sure how this process might work. More research still needs to be done on the relationship between gut health and mental health before people with psychiatric disorders are told to avoid beef jerky altogether.

[h/t NBC News]


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