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Which Planet Is Closest?
- Someone 7y agoI guess the sun is ‘closer’ to earth than any planet, using this ‘metric’.
- testplzignore 7y agoI think Mercury might still win. When the Sun is closer than Mercury, there is a lot of time when Venus or Mars are closer than the Sun.
- vl 7y agoBut they take time from both Sun and Mercury. I think Sun will win: let’s say there is a planet A between Mercury and Sun, given math in video, A is better than Mercury. Planet B is between A and Sun. Repeat until you get to the surface of the Sun.
- mcv 7y agoOn average the Sun is closer than Mercury, because Mercury spends 2/3 of its time further away from us than the Sun, and only 1/3 closer to us than the Sun. Mercury is closer to us than any other planet entirely because it's the closest to the Sun, which is closer to us than any planet. On average.
- DoreenMichele 7y agoThe sun isn't a planet. It's a star.
- earthboundkid 7y agoWe redefined a planet as a star.
- labster 7y agoOh good, we can just use 星 for everything now. Much simpler.
- earthboundkid 7y agoSuper Mario 星 makes more sense than Galaxy.
- DoreenMichele 7y agoTrivia that will get booed out of existence on HN: "In astrology, the sun and moon are called luminaries." (Though Pluto throws a monkey wrench into everything. I like to call it "That heavenly body formerly known as a planet.")
- earthboundkid 7y agoIt bothers me that astro-nomy (the laws of the stars) is the regular science and astro-logy (the study of the stars) is the pseudoscience. This is clearly backwards!
- DoreenMichele 7y agoThe short version is that astrology came first and probably basically began as an attempt to predict the weather for purposes of things like deciding when to plant. Planting before an unseasonably late frost could be a deadly local apocalypse for a village. Somewhere along the way we began to distinguish scientific study of the stars from attempts at weather prediction and also from attempts at assuring ourselves that the sun will come out tomorrow because the omens are propitious.[3] So we began calling one part of our desire to look up to the heavens and wonder how it impacts our lives Meteorology ("the study of things high in the air" [1]) and another Astronomy and began turning our nose up the stuff we now call astrology even though all three of those used to be basically the same thing. You can see evidence of this in Farmer's Almanacs which still list things like phases of the moon.[2] [1] https://en.m.wikipedia.org/wiki/Meteorology https://en.m.wikipedia.org/wiki/Meteorology [2] https://www.almanac.com/astronomy/moon/calendar https://www.almanac.com/astronomy/moon/calendar [3] We remain intensely interested in trying to predict the future and in using that info to try to "bet the right way," we just have more respectable terms for it than signs, portents and omens. These days, we like to use terms like leading indicators, statistical analysis and professional opinion. If you think about it, it's really the exact same thing, we just have access to better data and tools. When an astrologer was someone kings used as advisors, they were basically relying on proxies. Now, we have satellite imagery of storms on the other side of the planet and we try to predict their path. A hundred years ago, hurricanes just showed up without warning and this lack of warning directly resulted in lost lives. But we scoff at astrology like "only a fool would take that seriously," completely forgetting that we have always been able to look up and infer relationships between things happening in the heavens and events here on the ground, but we didn't always have satellites and the like.
- 333c 7y agoThe comment you're responding to didn't claim that; rather, it claimed that the sun is closer than any planet by this metric, which is true.
- DoreenMichele 7y agoI'm aware of that. But the piece in question is literally titled Which Planet is Closest? So while it's possible that the sun actually is the winner, it's not an answer to the question being investigated. If they can pedant, so can I.
- Ygg2 7y agoThat's not the issue here. The video asks which planet is the closest, and presents its measurements as common sense. Then it gets controversial results. Imo the base setup is wrong and Sun and Mercury always being the closest is a demonstration of that. It should either measure the minimum or maximum distance between planets/stars, not the average. Or measure distance between two orbits.
- 333c 7y agoWhile this metric is technically the most accurate, it's (to me) uninteresting and not useful because it is essentially a constant function (the closest planet is always the one with the smallest orbit).
- tedunangst 7y agoWait til we redefine the moon as a binary planet.
- philipov 7y agoAfter reading tzs' comment, I'm convinced.
- deleted 7y ago[deleted]
- twright 7y agoI wonder if this is more due to Mercury's orbit being so frequent that it is more often able to occupy that "closest window" while other planets remain further away for longer. Would this mean the second closest for any planet is Venus being the planet with the second highest orbital period?
- Amorymeltzer 7y agoYes, that's what the video is saying and showing.
- ravar 7y agoMy guess is that as long as the orbital periods of the involved planets are sufficiently different (not being rational multiples of each other for example) , making the system ergodic . Then Mercury will always be the closest by the metric.
- gus_massa 7y agoSomewhat related: The three inner Galilean moons of Jupiter are in a 1:2:4 resonance https://en.wikipedia.org/wiki/Galilean_moons#Orbit_animation https://en.wikipedia.org/wiki/Galilean_moons#Orbit_animation https://xkcd.com/1300/ https://xkcd.com/1300/ Also, the ex-planet Pluto is in a 2:3 resonance with Neptune. https://en.wikipedia.org/wiki/Resonant_trans-Neptunian_object https://en.wikipedia.org/wiki/Resonant_trans-Neptunian_objec...
- ShteiLoups 7y agoSo which planet is mostest closest to Mercury? The next largest circle?
- kolla 7y agoYes, Venus.
- slimscsi 7y agoEARTH!
- sideshowb 7y agoCame here for this was not disappointed
- dyukqu 7y agoPrevious (from 7 months before) thread (with a different link): Mercury is closer to Earth, on average, than Venus [0] [0] https://news.ycombinator.com/item?id=19372323 https://news.ycombinator.com/item?id=19372323
- campfireveteran 7y agoClassroom factoids gonna factoid.
- tzs 7y agoThere are some decent arguments that the Moon should be considered to be a planet, which would make the Earth/Moon two planets sharing an orbit rather than a planet and its satellite. The Moon, if ever recognized as a planet, will of course be the closest one. Here are some of the ways the Moon is more like a planet than a satellite [1]. I also remember an essay by Isaac Asimov that brought up another one. For all the other satellites in the solar system, if you compute the ratio of gravitation force on them from the planet they orbit to the gravitation force from the Sun on them, that ratio is greater than one. For the Moon, it is less than one! The Sun exerts more force on the Moon than the Earth does. Related to this, if you look at the path traced out by all the other satellites in the solar system as their planet makes one orbit around the Sun, that path is sometimes concave and sometimes convex, as the satellite circles the planet. The planet takes a convex path around the Sun, and the satellite makes a little circle around it. An observer on the Sun would see the planet moving always moving forward, and see the satellite sometimes moving forward and sometimes moving backward. For the Moon, that path is convex. It's basically a rounded dodecagon, as is the path of Earth. They are out of phase with each other, so that when one is near a vertex of the rounded dodecagon, the other is in the middle of a side, and so can slip past the other. An observer on the Sun would see the Earth and Moon both always moving in the same direction, with them speeding up and slowing down, so that about 12 times in a year they trade the lead, and the overtaking one always passing on the same side. [1] https://blogs.nasa.gov/Watch_the_Skies/2009/07/10/post_1247240047519/ https://blogs.nasa.gov/Watch_the_Skies/2009/07/10/post_12472...
- chrisweekly 7y agoInteresting! Thanks for the new perspective. :)
- rolltiide 7y agoI’ve been thinking about this too, in the context of where the solar system ends. I had been thinking of “the solar system” as a noun for answering multiple choice questions in grade school instead of “objects that are most greatly influenced by sol than any other gravitational field” I think gravity itself can be taught differently and a lot of concepts would be more intuitive
- 7y ago
- liquidise 7y agoSomehow my fascination with the result here is my second favorite part of these videos. The curiosity and questioning of knowledge that is generally accepted as understood makes me wonder what else we accept at face value that is only partially correct. In many ways i find the same joys when building websites/apps. Even using the same technologies it surprises me how my approach to similar-in-theory projects changes year over year. Knowledge that i used to accept as gospel gets overwritten by experience or curiosity, for better or worse. I had no idea 6 minutes what i assumed were simple questions would invigorate my curiosity like this but color me pleasantly surprised.
- Symmetry 7y agoWhen we're wandering around on Earth we naturally tend to think of the "closeness" of locations in terms of distance because of the way we travel here. But if you're thinking of traveling to another planet you shouldn't be thinking of linear distance, you should be thinking of delta-v. And by that metric the planets form the same neat line you find in a classroom chart with Venus edging out Mars. https://www.reddit.com/r/space/comments/29cxi6/i_made_a_deltav_subway_map_of_the_solar_system/ https://www.reddit.com/r/space/comments/29cxi6/i_made_a_delt... Linear distance isn't entirely irrelevant. It affects light lag for instance. But it is mostly irrelevant.
- agildehaus 7y agoDelta-V at the time of optimal travel. Otherwise it's probably as all over the place as this video.
- sillysaurusx 7y agoDoes anyone know a simulation of the solar system corrected for delta-v? It would be neat to see visually how the planets compare. Like a 3D rendering, or a screensaver. You'd need to morph distance such that if a point takes less energy to travel to from earth, it appears either closer or larger. Bonus points if it accounts for time dilation somehow.
- GuB-42 7y agoNot exactly a simulation but it is a nice illustration, I think. https://xkcd.com/681/ https://xkcd.com/681/
- smallnamespace 7y agoI'm not sure whether this paper is a great overlooked observation or a trivial result that one can prove with a couple diagrams and no calculation at all. Maybe it's both :) If you assume all orbits are spherical, then the distance from your planet to the sun is 1 AU. Now draw a graph, with the sun at the origin, our planet P at 1 AU 'below' the sun, and the other planet P' going around in a circle at distance R around the sun. Now draw a right triangle, with the sun at a near corner, the other planet P' at the far corner, and one of the short sides pointed straight at our planet P. __x__P' (t2) | / y / | / |/ sun |\ y| \ | \ |_x_\ | P' (t1) P You can see that the y-distance of the planet from the sun exactly averages out to zero - half the time it's on the far side, half the time it's near. Therefore the y-distance from our planet to the other planet always averages out to exactly 1 AU. However, the x-component is sometimes to the 'left' and sometimes to the 'right' of P. We know from the triangle inequality that |y + x| >= |x|, so the x component always makes the distance between P and P' larger than it would otherwise be, therefore the average must be larger than 1 AU, and this discrepancy grows with the radius of the other planet P'.
- deleted 7y ago[deleted]
- zuminator 7y agoThat's only if P' is closer to the sun than P. In other words, the average distance between the two planets will be approximately the radius of the outermost planet's orbit.
- slg 7y agoThis is strangely apropos given its namesake.
- Iwan-Zotow 7y agoEarth