Explain xkcd: It's 'cause you're dumb.
Title text: We actually divorced once over the airplane/treadmill argument. (Preemptive response to the inevitable threads arguing about it: you're all wrong on the internet.)
Cueball has been thrown out of his house because he believes that Pluto should never have been a planet. Pluto was considered "the ninth planet" in our solar system between 1930 and 2006. (Jupiter was thought to be the ninth planet from 1807 to 1845.) In 2006 the IAU reclassified Pluto as a dwarf planet. The reasons are complicated, but the basic issue is, like Ceres, Pallas, Juno, and Vesta, Pluto is too small to function as a planet in the solar system. Here is a good explanation.
In the title text, the airplane/treadmill argument starts when someone asks whether an airplane can take off while it is on a treadmill that is opposing its progress (pulling it backward). The question usually leads to arguments because it is posed ambiguously. Properly defining the question shows that the airplane can indeed take off (because its forward motion is provided by its propeller/jet engine, not its wheels, which are free to spin at any speed) and experiments (such as Mythbusters') bear this out.
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- [Cueball laying on sidewalk outside a house, surrounded by his belongings.]
- She threw me out yelling, "You don't say those words. Not in this house."
- It's been two years. I thought the wounds had healed.
- But I stand by what I said.
- Pluto never should have been a planet.
The explanation says: "... Pluto has been the ninth planet in our solar system until 2006 ...".
It should says 'the tenth' isn'it?
SioD (talk) 14:52, 30 August 2013 (UTC)
- Pluto was discovered in 1930, and has been since the ninth body to be discovered and classified as a "planet". The sentence is a temporal rather than spacial reference, if that clears up any confusion. Thokling (talk) 12:04, 24 September 2013 (UTC)
- Actually, no. Using the temporal definition, Pluto would be number 13. It was discovered after Ceres, Pallas, Juno and Vesta, which were discovered, named and classified, but then quickly demoted, all about 120 years before Pluto. This was due to the fact that telescopes of the day were strong enough to see quite a bit of the asteroid belt in a relatively short time, unlike with the "previously mythical" Kuiper belt.
- Also, if any thing, the spacial discrepancy should be between eighth and ninth, as Pluto's orbit is squeezed enough to be inside that of Neptune, but long enough to extend outside it. Charon, Pluto's "moon" may cause additional worry, but is usually ignored.
- Anonymous 01:11, 4 December 2013 (UTC)
- I think we would all be happy if the astronomers would come up with a definition of a planet that reasonably included Pluto but reasonably excluded the other 'candidates' that have been found so far. You know, the ones without large moons. Or Pluto could just be grandfathered in. Exactly how would science be held back by this?? 18.104.22.168 00:00, 4 January 2014 (UTC)
The airplane/treadmill question is actually hard to define properly. In real case scenario, the plane would of course take off, but you can keep it in place if you assume really fast treadmill (much faster that the plane), friction in airplane wheels and that those wheels won't break off, catch fire or otherwise get destroyed under the stress much higher they are developed for. Oh, wait, actually the airplane WONT take off if the wheels break. :-) -- Hkmaly (talk) 12:01, 5 December 2013 (UTC)
- If you choose to model friction in the wheels, it would be simpler to model the airplane with NO wheels, and then ask whether it could take off. Well, 'Airplane!' notwithstanding, it couldn't. But that's not an interesting problem, right? And neither is the variation with friction in the wheels. 22.214.171.124 23:54, 3 January 2014 (UTC)