Activity for HDE 226868
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
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A: Is a jet dragon possible? 1.Can fly to the altitudes of modern airliners (around 10 000 meters or 32808 ft). Take a look at this graph: At 10,000 meters, the air pressure is about 25% of its value at sea level. Wikipedia notes that pressures this low and oxygen levels this low can cause some problems: The lower pa... (more) |
— | almost 10 years ago |
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A: Could gas giants exist as a contact binary? Probably not. A direct quote from here would be nice, but I'm not sure if there's any relevant copyright on the text, so I'll just summarize. Here are the steps to forming a contact binary star system: A binary star system forms After billions - perhaps only millions, in larger stars - of years, o... (more) |
— | almost 10 years ago |
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A: Is a spherical core and magnetic field possible in Cube world No. At the moment, I can't answer the part about the shape of the core. I can answer the part about the magnetic field. The Earth rotates, and because of that its shape is that of an oblate spheroid, so any body that rotates must take this shape. Now, you can object, saying that the body in questio... (more) |
— | almost 10 years ago |
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A: Sapience Pulsar - Could Intelligence Come in Waves? You wrote I'm thinking for instance that the next post-human pulse for instance would have a lot less coal and oil. That's it. You hit the nail on the head. Each re-generation is inheriting a completely different planet than the last. Some things that would change: Fossil Fuels: As you said,... (more) |
— | almost 10 years ago |
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Arctic Airships, Part 2 - Navigation This is the second question in my Arctic Airships series of questions. The first one is Arctic Airships, Part 1 - Generating Electricity. The setting is outlined in Part 1, but I'll rehash the premise here. The premise: An Earth-like planet plunged into an ice age roughly 2,000 years prior to the ... (more) |
— | almost 10 years ago |
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A: Buying energy from the sun? A city planet Take Coruscant, from Star Wars. It's a planet covered entirely by one large, sprawling, complex city. I'm not sure if there's a canonical reference to how high the tallest buildings are, but from the seeing aerial$^1$ views it looks like they're taller than cities on Earth. Taller buil... (more) |
— | almost 10 years ago |
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Arctic Airships, Part 1 - Generating Electricity This is the first question in my Arctic Airships series of questions. The second one is Arctic Airships, Part 2 - Navigation. The premise: An Earth-like planet plunged into an ice age roughly 2,000 years prior to the story. The ice sheets extend to a latitude of about 50 degrees above and below the... (more) |
— | almost 10 years ago |
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A: Brown Dwarves: Dyson Spheres in disguise? No, you could not. Temperature probably isn't an issue, but a Dyson sphere shouldn't show the proper spectral lines. The-best case scenario This site gives the formula for the temperature of a Dyson Sphere as $$T=\left( \frac{E}{4 \pi r^2 \eta\sigma} \right)^{\frac{1}{4}}$$ where $E$ is the star's ... (more) |
— | almost 10 years ago |
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A: Energy source for a generation ship The Bussard ramjet idea could very well work - if you plan your route correctly. You're worried about the low number density of hydrogen atoms/ions in outer space. This table shows that this is indeed quite a big problem. There is a solution, though, which is to travel nearly exclusively - when poss... (more) |
— | almost 10 years ago |
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A: How long to freeze a planet? Here, it is useful to treat the planet as a black body. The Stefan-Boltzmann law states that a black body will have a luminosity $L$ directly related to its temperature $T$ and radius $R$: $$L=4 \pi R^2 \sigma T^4$$ where $\sigma$ is the Stefan-Boltzmann constant. We have to be careful picking $R$ an... (more) |
— | almost 10 years ago |
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A: Can a planet's moon rise at the same time every night? In order for this to be possible, the moon would have to be in the same place relative to the planet and the star throughout the day - in other words, if you drew a line from the center of the star through the center of the planet, then drew a line from the center of the planet through the center of ... (more) |
— | almost 10 years ago |
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A: Creating a species with birdlike bone structure From what I've found, they'd be less prone to injury. Bird bones are hollow and therefore lighter than solid bones of the same size, which is a boon to flying. However, they're also extremely dense. This does add weight - quite a lot, it fact - but it makes the bones incredibly strong, stronger than... (more) |
— | almost 10 years ago |
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A: If Earth spin decreased, how can I get it spinning faster? Remove much of the Earth's mass. The giant impact hypothesis states that about 4 billion years ago, when Earth was but a wee protoplanet, a Mars-sized object dubbed "Theia" hit it at an angle of 45 degrees, moving at 4 kilometers per second. This Destroyed Theia and knocked a bunch of material fro... (more) |
— | almost 10 years ago |
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A: How to Mimimize Air Loss in Space-Based Cities? Stick yourself in a rock and hope for the best. That's literally the best approach. It's a bit more elegant than that sentence might make you think, but it's something. I'll tell it like a story. You're strapped into the transfer shuttle, nervously waiting to enter your future home. You'll be s... (more) |
— | almost 10 years ago |
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A: Habitable moon of a gas giant: working out the sizes and distances Let's work out some factors. Luminosity You gave the radius of the inner edge of the habitable zone as 1.976 AU and the outer edge as 2.808 AU. From this, we can calculate the luminosity of the star. There's an explanation of how to do this on Planetary Biology. The formulae are $$ri=\sqrt{\frac{L... (more) |
— | almost 10 years ago |
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A: What technologies and sciences are needed to detect a star going supernova? When people think of supernovae, they often only think about the visible light emitted during and after the explosion. However, if you restrict yourself to observing in the optical part of the electromagnetic spectrum, you'll lose a whole lot of information. There are a few different astronomical mes... (more) |
— | almost 10 years ago |
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A: What would be the effects of a Chicxulub-sized impact on Earth's magnetic field? Earth's magnetic field is caused by movements in its core. Its outer core is roughly $2,890,000 \text{ meters}$ below Earth's surface. Therefore, to directly interfere with Earth's magnetic field, this thing is going to have to make a crater $2,890,000 \text{ meters}$ deep. Issac Newton figured out ... (more) |
— | almost 10 years ago |
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A: Effects of high magnetism? Actually, the strength of the field would change at the planet's surface. If we model the field as a dipole, it is described by the equations $$Br = -B0 \left(\frac{RE}{r} \right)^3 \cos \theta$$ $$B{\theta} = -B0 \left(\frac{RE}{r} \right)^3 \sin \theta$$ $$|B| = B0 \left(\frac{RE}{r} \right)^3 \sqr... (more) |
— | almost 10 years ago |
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A: What would life on Earth be like if the Sun was replaced by two blue giants? Blue supergiants are massive. Really, really massive - up to dozens of times the mass of the Sun. They are also extremely hot, large and luminous. They live much shorter lives that stars like the Sun, and may die spectacularly. All of this means that they aren't great stars to host habitable planets.... (more) |
— | almost 10 years ago |
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A: Can a gas giant have its own habitable zone? Really awesome answer by ckersch. I want to add in some math to get an idea of how large this kind of habitable zone would be. Formulas are from here and here, if you want to investigate them further, though I'll try to explain them here. We may assume that the source of energy is gravitational pote... (more) |
— | almost 10 years ago |
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A: How would human society develop if humans had gills? There are one or two chronological things which I should like to clear up before proceeding here. This graphic shows the geographical distribution of members of the genus homo over time: Image courtesy of Wikipedia user Conquistador under the Creative Commons Attribution 2.5 Generic license. It ... (more) |
— | almost 10 years ago |
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A: Energy manipulating superhero -- how would it work Here's what your guy would have to do: manipulate time and space Well, actually, we all do this, because we all have mass and therefore all exert a gravitational force. But to manipulate things at will, he'll either have to: Create new mass and/or energy at a given point. We've had questions ... (more) |
— | almost 10 years ago |
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A: Evolution of a non-human species with no concept of gender? Why not make them parasites - on their parent? Take, for example, the parasitoid wasp. Female adult wasps lay eggs in or on another creature - the host. The young them develop inside the host, feeding on it and taking in some of its nutrients. Eventually, the host dies and the young come out through... (more) |
— | almost 10 years ago |
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A: Planetary Scale Artworks Hmm. How about a nebula? Pavel Janicek mentioned it briefly in his answer, but I want to elaborate on it a little. You have a bunch of choices if you want to pick a nebula: Dark nebula: As you can imagine, dark nebulae are - well, dark! They block light from objects behind them. They're made of du... (more) |
— | almost 10 years ago |
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A: Could a manned maneuvering unit provide artificial gravity? Alert: Mathematics ahead. Just being humorous. I know that not everyone likes math, so I figured I'd add that in. Just so I can say 'I told you!' if you complain about the math. In which case just read DonyorM's answer. Anyway . . . The dimensions of the MMU are as follows: $0.846 \text{ meters}$... (more) |
— | almost 10 years ago |
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A: What would the problems with / consequences of a torus shaped planet be? There are a lot of cool effects - and some problems. Formation Planets form after a long, drawn-out process that starts with grains of dust colliding and forming planetesimals. These then become protoplanets, which can be kilometers across. More collisions result in small, rocky planets, some of wh... (more) |
— | almost 10 years ago |
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A: How long until a small black hole makes the sun fail? Good analysis by the others, but I want to add in some math here, because I'm really that nerdy. We can model the growth of a black hole by the matter it accretes. Normally, a black hole accretes matter via a (surprise, surprise) accretion disk. Analysis of this type of object is nice because it's t... (more) |
— | almost 10 years ago |
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A: Can we identify black holes in our path flying between the stars? Barring the presence of an accretion disk surrounding these black holes - unlikely, in the absence of a compansion object - our best bet is likely to exploit gravitational lensing, the bending of light from distant objects by a massive object in front of the source. Typically, the massive object is a... (more) |
— | almost 10 years ago |
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A: Open Polar Sea feasibility? There has to be some sort of heat source for this to happen, and it can't be something temporary. Here are some ideas: Volcanic Activity. Vodolaz095 beat me to posting this, but I was already working on it, so I can't claim priority but I can expand on it. For volcanic activity, you need a source. ... (more) |
— | almost 10 years ago |
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A: How could humans survive in extremely high gravity? Ha! An obscure question I asked somewhere else now becomes relevant! A while ago, I asked this question on Biology about liquid breathing. It's currently unanswered, and may stay that way forever, but it's now applicable here, which I think is cool. Anyway. . . Liquid breathing is (as Wikipedia put... (more) |
— | almost 10 years ago |
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A: Would a planet with very small temperature variation (between 17 and 21 degrees Celsius) be possible? There are three huge reasons for temperature fluctuations on a planet: The parent star, axial tilt and the curvature of the planet. The star. There's normally a huge difference on temperatures between day and night on a planet. On the side facing the star, light radiated from the star heat up the p... (more) |
— | almost 10 years ago |
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A: What would make real life "undo" possible? This isn't possible without a huge uptick in technology. You certainly can't go back in time, because that would violate, among other things, causality. Also, going back in time wouldn't help, because you'd still have the past you screwing up the answers to those questions. The alternative, by the wa... (more) |
— | almost 10 years ago |
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A: How could a smaller planet than Earth have a higher gravity? I think the others have done a good job of answering the main question of what it would be composed of (I'd have said iron, too, or something similar), so I'll address some of the other stuff. The BY Draconis system is young. Really, really, young. Components A and B certainly aren't well developed,... (more) |
— | almost 10 years ago |
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A: In a created planetary system, how many planets can fit in the goldilocks zone with stable orbits? It depends on the size of the habitable zone. Whether or not a planet's orbit is within the (circumstellar) habitable zone (aka the Goldilocks zone) depends on a wide variety of factors determined primarily by the star. Here's the Solar System's habitable zone compared to the habitable zone around t... (more) |
— | almost 10 years ago |
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A: Can a moon "skim" a ring? The problem here isn't really about whether or not a moon could "skim" a ring, but whether or not rings could form around Earth. There are three ways planetary rings can form. All three involve material coming inside the Roche limit of the planet. The rings of Saturn have a mass of about $3 \times 1... (more) |
— | almost 10 years ago |
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A: Under what circumstances would it be possible to harvest aurora for either energy or matter? I don't think we could directly harness the energy transferred to particles in auroras. However, we could probably captured the energy from the phenomena that caused auroras. Wikipedia notes that the primary cause of auroras is an interaction between the Sun and the Earth's magnetosphere. Here are s... (more) |
— | almost 10 years ago |
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A: Do different star systems experience time differently? You wrote: Just to give the background...I have the vision of an ancient race who's star saw it's end. They relocated to a star moving significantly slower than the majority of those in the galaxy, and as such the galaxy around them aged quickly while they saw a relatively short time span pass. ... (more) |
— | almost 10 years ago |
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A: Could a rogue planet be the host of a planetary system? I'll first address Cha 110913-773444 specifically. Checking the Wikipedia page yields some interesting information: Mass: 5-15 Jupiter masses. This means that it is likely a planet - extremely low-mass brown dwarfs are typically in the mid-20s, in terms of Jupiter masses Spectral type: L-dwarf. Th... (more) |
— | about 10 years ago |
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A: Could planets switch orbits like Janus? Before we get into seasons, life, etc., we have to address the question of whether or not such a configuration could exist. At first glance, I see no reason why two planets couldn't orbit a star in the same way Janus and Epimetheus orbit Saturn. It could be a bit tricky if the planets are gas giants,... (more) |
— | about 10 years ago |
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A: How could a planet have a 40 hour day cycle with its nights only lasting 3 hours? Yes, but not in the way you imagined. Vincent mentioned a Worldbuilding question which directly addresses the possibility of a figure-8 orbit. No offense intended, I don't think any of the answers there properly addressed the question - although Vincent may have decided against addressing it because... (more) |
— | about 10 years ago |
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A: Could a civilization as advanced as humans exist on a planet/dwarf planet like Pluto? No. I hate that that's my token response to things like this (I really should be more creative), but it seems pretty unlikely for a few reasons: Low surface gravity: Pluto's mass is 0.00128 times that of the Earth. That means that it's really hard for it to keep a lot of matter on it. Sure, it's b... (more) |
— | about 10 years ago |
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A: What would be the major changes to our body if we were herbivores? As far as I can tell, the major changes would be to the human digestive system, as well as to all body parts involved in processing food. Teeth The teeth of carnivores and herbivores differ because they eat different things, which require different techniques to chew. Plant matter is a lot differen... (more) |
— | about 10 years ago |
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A: Is it possible that a gas giant of similar size to Jupiter could harbor life? I don't think we're going to find any evidence (like TimB did for this question) that life does exist on extrasolar gas giants, but we can at least use some logic to figure it out. No. First, the cores of gas giants are nothing like asteroids, comets, or even terrestrial planets. Jupiter's core is ... (more) |
— | about 10 years ago |
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A: Is a Jupiter-sized planet plausible in a habitable zone? Absolutely. This would only take a few simply steps, and a small bit of luck. Here's how it could happen: A protostar forms from a collapsing gas cloud. A giant sphere of gas and dust collapses upon itself. The pressure is so great that the sphere begins nuclear fusion, and it beings to emit light... (more) |
— | about 10 years ago |
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A: Use Physics to prove Ragnarök has already occurred Yes, but you'd have to get lucky. If you want to use celestial bodies, you're best bet would be to study the effects of something that closely interacts with the Sun. Really, this rules out much of the solar system. Even Mercury, the closest planet to the Sun, is 46 million kilometers away from the ... (more) |
— | about 10 years ago |
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A: Could two planets be tidally locked to each other so close they share their atmosphere? Ahh, here we go. No. But yes. I'll leave the stuff about the Roche limit for Vincent; after all, it was his idea. Assuming he writes up an answer, you'll learn why these planets cannot be tidally locked and so near each other. This means that you won't see two planets coming really close to each ot... (more) |
— | about 10 years ago |
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A: Is there any likely reason why personal DNA tinkering machines would become widespread? This is my favorite question in a while, so I hope it's okay if I bend a slight rule in order to answer it. The question explicitly says "likely", so chances are my answer is completely invalid. I don't think there's much of a chance this would become likely anytime soon without some drastic change i... (more) |
— | about 10 years ago |
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A: What proof could Ragnarök leave behind? There is - believe it or not - a loophole that could show give solid evidence that Ragnarok happened. It involves a black hole (or a very massive body). One of the coolest effects of general relativity is that mass and energy can bend light. It's known as gravitational lensing, and it often is shown... (more) |
— | about 10 years ago |
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A: By what mechanism could a planet be locked into permanent solar eclipse? Note: My original answer was incorrect; tidal locking would not produce such a scenario. For an excellent explanation of why this is the case, see smithkm's answer. I want to leave in some notes regarding what would happen if there was somehow an object between the planet and the star. Not, though, t... (more) |
— | about 10 years ago |
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A: Can a spaceship traveling close to light speed be knocked off course by a gamma ray burst? Let's first do some math, the first part taken from this pdf regarding (solar) radiation pressure (the formulas should be applicable from any source of electromagnetic radiation). The intensity $I$ depends on the power $P$ and the distance from the source $r$. We can write the expression $$I=\frac{P... (more) |
— | about 10 years ago |