Wikipedia:Reference desk/Archives/Science/2012 November 7

= November 7 =

Making eggs on an industrial scale
How do egg farmers get roosters to service the massive quantities of hens on an industrial scale? Or do hens make eggs without getting any sex that cannot become chicks? Or can chickens reproduce parthenogenetically? 67.163.109.173 (talk) 00:10, 7 November 2012 (UTC)


 * hens make eggs without getting any sex that cannot become chicks. Dauto (talk) 00:19, 7 November 2012 (UTC)


 * What are you trying to say Dauto + OP? I suppose you both meant: "hens lay eggs without sex." — Preceding unsigned comment added by OsmanRF34 (talk • contribs) 00:24, 7 November 2012 (UTC)


 * You just have to insert proper punctuation to make it make sense: "hens make eggs – without getting any sex – that cannot become chicks". Someguy1221 (talk) 00:51, 7 November 2012 (UTC)


 * OK, that sounds like a cautionary tale about how important punctuation is. There is still the problem of saying "make eggs" instead of "lay eggs", as if the chicken were preparing the eggs. OsmanRF34 (talk) 00:56, 7 November 2012 (UTC)


 * I guess you're on my mother's side of a minor dialect divide between us: it grates on me when she says "make a potato" to mean "cook a potato". —Tamfang (talk) 01:06, 7 November 2012 (UTC)


 * If the hen doesn't make the egg, where does it come from? Of course the hen makes the egg (whether you are used to the phrase or not).  Laying (expelling) is just the final step, after forming/making the egg.  I see no basis for "correcting" that phrase.  -- Scray (talk) 04:17, 7 November 2012 (UTC)


 * I'd use parens: "Hens make eggs (without getting any sex) that cannot become chicks." Or, if we don't want such a clumsy sentence: "Unmated hens lay infertile eggs." StuRat (talk) 01:01, 7 November 2012 (UTC)


 * The hens will lay eggs without ever mating. Presumably they have been bred for enhancement of this trait. The vast majority of eggs you buy at the grocer's will be unfertilized and contain no embryo. At a low rate, unfertilized chicken eggs will begin development through parthenogenesis, but they almost always fail before hatching. We have little bit at Parthenogenesis. Someguy1221 (talk) 00:24, 7 November 2012 (UTC)


 * It's worth remembering that human females create eggs without having sex too. They're generally not much use though. (The eggs, not the females.) HiLo48 (talk) 00:43, 7 November 2012 (UTC)


 * Meh, the females aren't of much use either. Yes, but the intact egg never leaves a human female's body. It disintegrates in the fallopian tubes if it isn't fertilized within a day or so.  --140.180.252.244 (talk) 01:59, 7 November 2012 (UTC)


 * Egg farmers who supply eggs for hatching are advised to include one rooster for every 7 to 15 hens (depending on breed, and age and health of the roosters) to ensure fertility. Hens store sperm for a week or more, so daily sex is not necessary to produce fertile eggs. If there are too many roosters, they can injure the hens, or sometimes they fight and kill each other.    D b f i r s   18:23, 7 November 2012 (UTC)


 * Does that figure include that they want some actual chicks, to replace the hens and roosters as they die (or are eaten) ? StuRat (talk) 19:32, 7 November 2012 (UTC)
 * If I'm reading it right, that's the figure for farms that are mainly or wholly producing actual chicks, for sale to the egg-producing farms. AlexTiefling (talk) 12:43, 8 November 2012 (UTC)
 * Yes, though the eggs are often sold to hatcheries which then sell the males to be fattened for food and the females to farms that produce eggs for eating. The latter farms usually have no roosters (why would they bother to feed unproductive birds, and many consumers don't like to eat fertile eggs).  Hens are often purchased at "point of lay" by commercial operations, though some small farms might raise their own birds.    D b f i r s   13:51, 8 November 2012 (UTC)

USDA has a lot of information on poultry and egg production available here. Zoonoses (talk) 06:03, 8 November 2012 (UTC)
 * Whatever you do, don't let any renegade roosters mate with your eggs and fertilize them unless you want scrambled chicks with bacon. μηδείς (talk) 19:39, 8 November 2012 (UTC)
 * Mate a boar with your hens and have a complete breakfast in a shell. Gzuckier (talk) 18:57, 9 November 2012 (UTC)

The Sun
Why is the Sun's atmosphere layer so much hotter than the Sun's surface? Bonkers The Clown (talk) 07:16, 7 November 2012 (UTC)


 * See Corona. Plasmic Physics (talk) 10:53, 7 November 2012 (UTC)


 * It's not the "atmosphere" as such which implies the ions nearest the "surface" of the sun, but rather the higher-up ions which are excited by and accelerated by the stellar magnetosphere. They are quite "hot" but not very dense. μηδείς (talk) 22:54, 7 November 2012 (UTC)


 * Also, for the record, the outermost layers of the Earth's atmosphere are also the hottest (see Thermosphere), though at those densities, temperature has little meaning. Though it has a nominal temperature of 1500-2500 C, you'd freeze to death there as there aren't enough molecules to transfer enough energy to you to keep you warm.  -- Jayron  32  02:42, 8 November 2012 (UTC)
 * Is that really true, though? after all, your body generates heat, and if you were in an insulator (i.e. a vacuum) I'd guess (totally guesswork, admittedly) you'd have to heat up pretty good before your radiated energy balanced your metabolic output. being in a thin atmosphere of very hot gas wouldn't make it any cooler. Gzuckier (talk) 03:04, 9 November 2012 (UTC)
 * No, you radiate energy faster than you generate it (calculations here). The fact that you haven't dropped dead is mostly due to radiation returning to you from your surroundings (though to be fair the effects of convection and conduction are much more potent than radiation for room temperature objects, so you could probably do without the inbound radiation so long as you weren't in a vacuum). The insulative properties of your body/clothing have a relatively small effect, but it's difficult to estimate what it will be, especially since your skin will cool off much faster than the rest of your body when you get cold (we had a discussion about this a few months ago). Jayron's point is that the "thin hot atmosphere" isn't going to efficiently transfer heat to anything, or from anything. Someguy1221 (talk) 03:21, 9 November 2012 (UTC)
 * Someguy has what I was trying to say. In the vacuum of space, you emit more heat as radiation than a combination of absorption and internal heat sources can compensate for.  The thermosphere, despite its nominal temperature, is close enough to a vacuum to have little effect on transferring heat to you're body via conduction.  -- Jayron  32  06:17, 9 November 2012 (UTC)
 * Wow, I've had it wrong all these years. My fault for just assuming without doing the math, the exact thing I love to chide others for doing. So, those movies where the guy is ejected from the airlock without a spacesuit and freezes don't have it wrong after all. Thanks for straightening me out so I have fewer chances to make myself look dumb in public. Gzuckier (talk) 19:01, 9 November 2012 (UTC)

about electron configuration
can you please explain to me what are the rules to followed in deriving the electron configuration — Preceding unsigned comment added by Yukuri (talk • contribs) 11:34, 7 November 2012 (UTC)


 * Why don't you try googling "electron configuration", or even just enter "electron configuration" in the Wikipedia search box. Assuming you mean electron configuration of atoms of course. For all we know, you could mean electron configuration of molecules, or even the electron cloud configuration in an electronic device.  Then, come back to us if there is a particular aspect that you have difficulty with.  We are more likey to spend some time providing you with good help if we can see you have put some work in.  Wickwack 120.145.9.226 (talk) 15:32, 7 November 2012 (UTC)
 * I've linked all previous mention of electron configuration for the OP's benefit and convenience.  DRosenbach  ( Talk 22:09, 7 November 2012 (UTC)
 * I could have asked why you encouraged the OP's laziness by providing direct links to WP articles. However, you actually provided links to the wrong article each time except for one, so actually you are potentially misleading the OP.  Electron config in atoms is not the same as molecules, and is not the same as cloud configuration in electronic devices. Wickwack 121.221.230.208 (talk) 23:56, 7 November 2012 (UTC)
 * They all link to the same, and seeing how the OP asked about electron configuration, that's where I sent him. If he needs something else, he'll either figure it out from there or he won't -- I don't think that's anything to get upset about.  But either way, I provided him with direction, which is what I figure we're all here to do.  DRosenbach  ( Talk 04:07, 8 November 2012 (UTC)

What about sound in vacuum ?
We can hear the sound of a ringing bell on Earth but we cannot hear it in vacuum or on moon because sound needs medium through which it can travel. Suppose, if we bring a bell on moon and the bell is ringing, it will produce sound energy or not. If the bell is producing sound energy, what happen to this energy ? Suppose, if we hit moon's surface with something hard and a person touches the moon's surface with his ears, will he listen the sound produced in this case ? Here, moon's surface is material through which sound can travel (I think). Thanks, for answering my both questions. Sunny Singh (DAV) (talk) 12:20, 7 November 2012 (UTC)


 * You're correct - a person putting their ear to the moon's surface will hear the other person tapping. You can demonstrate this yourself as part of the famousalarm clock in a vacuum jar experiment - if the alarm clock is resting on a suitably hard table, you should still be able to hear it by putting your ear to the table.


 * Of course, I'm making a few assumptions in saying that someone would be able to hear tapping on the moon. First, that the listener could place their ear directly on the ground - that is, get their ear outside any helmet they might be wearing without suffocating or having their head explode. Secondly, that the distance between the tapper and the listener is not too great. Sound propagates through a surface in all directions, with the energy in any one direction being quite low. The amount of sound energy received by the listener will be inversely proportional to the distance from the source - possibly either by the inverse of the square of the distance, or even the inverse of the cube of the distance. (My maths has temporarily failed me on this point.) Thirdly, we assume that the moon's surface is of a suitable substance to allow decent sound propagation. If you think about it, sound travels better through a wooden table than through a cushion. The harder the moon's surface, presumably the better the sound will travel to the listener. - Cucumber Mike (talk) 12:46, 7 November 2012 (UTC)


 * Taking off the helmet shouldn't be necessary, if at least part of the helmet is rigid. Hm, have astronauts ever tried the old fictional trick of switching radios off and holding helmets in contact to talk privately? —Tamfang (talk) 17:11, 7 November 2012 (UTC)


 * (ec) :Your assumption about the moon's crust conducting the sound is essentially correct. If the bell is ringing at a substantial volume, a nearby astronaut might be able to hear it as the sound waves disperse across the moons surface and through the boots of his spacesuit. If, on the other hand, the bell is in pure vacuum and not in contact with any other body, the sound's energy will theoretically remain trapped within the bell itself indefinitely, though I suspect that the actual form of that energy (sound) would dissipate throughout the bell and equalize rather quickly, most likely taking the form of simple heat before too long. No energy would cease to exist over time or be sucked away to some phantom dimension; it all remains in the bell until the bell either impacts another body or ceases to exist. An actual waveform is not going to propagate indefinitely, however. Evanh2008 (talk&#124;contribs) 12:47, 7 November 2012 (UTC)


 * The Apollo missions each left the Apollo Lunar Surface Experiments Package on the moon. These experiments included active and passive seismic equipment.  Apollos 13, 14, 15, 16 and 17 deliberately crashed the third stage of the Saturn rocket into the Moon, and the seismic experiments detected the vibrations.  So, yes the moon's surface does conduct sound.  Astronaut (talk) 16:13, 7 November 2012 (UTC)


 * The Moon seems to be covered with a thin layer of dust, which would not propagate sound well. You'd need to make contact with the rock below, both with something connected to the bell, and something connected to the astronaut's helmet. StuRat (talk) 19:27, 7 November 2012 (UTC)


 * As for the more interesting question of a bell rung in a pure vacuum, I imagine it would continue to vibrate for a very long time. (The vibrations would eventually all be converted to heat, but that's much slower.) StuRat (talk) 19:29, 7 November 2012 (UTC)

Hover
How do you calculate the energy needed (by an helicopter or similar aircraft) to hover? Comploose (talk) 14:07, 7 November 2012 (UTC)
 * It's not really a matter of energy, because a stationary helicopter does not do any physical work. A stationary aircraft needs to create an upwards force that makes up for the gravitational force pulling down the aircraft, but it depends on the method of generating this force how much power/energy is needed for this. - Lindert (talk) 14:18, 7 November 2012 (UTC)


 * Lindert is completely wrong here with his inane answer. The helicopter is doing some work on the rotor, and obviously needs energy for that, which can be calculated. See the physical details [| here]. OsmanRF34 (talk) 14:33, 7 November 2012 (UTC)
 * If you bothered to read the link you provided, you will noticed that the person who calculated the necessary power came to the conclusion (correctly) that dE/dt = 0.5*M*g*v, where v is the velocity of the air that is being pushed down. As you can see, the energy is proportional to the downwards velocity of the air, or in other words, the slower the air is being pushed down, the less energy it will cost. Of course you need to compensate for the slow air by increasing the airflow, but essentially this means that if you increase the airflow to infinity, the energy will go to zero, so theoretically, no energy is needed, though this is not implementable in practice. The point of my post above, as you might have noticed, is not that you need no energy, but that the required energy is not a fixed amount, but rather depends on the kind of aircraft. - Lindert (talk) 14:51, 7 November 2012 (UTC)

It's not an insane answer. Imagine a large feather that falls in a still church and lands halfway off of a chair. Now we seal the church for millennia. First, what is keeping the feather from falling to the ground? It's the chair, doing work. So, when does it run out of work that it can do? After 1000 years? 10,000? A million? It never runs out, because it doesn't perform work. Theoretically, the chair could suspend the feather forever.

Likewise, if you are trying not to fall by suspending yourself in air, all you have to do is push down against something in the same way that the chair is connected to the ground - except instead of chair, you have air. Theoretically, there is no work that actually needs to be done. On a practical level, air will move out from under you whereas chair does not. But that is an implementation detail. --91.120.48.242 (talk) 15:12, 7 November 2012 (UTC)


 * And if Lindert had read the webpage Osman provided, he would have seen that it is for the case of a bird hovering well above the ground, ie high enough that any ground effect can be neglected, similar to a helicopter. This is not the case for a hovercraft.  A hovercraft only rises enough to let air out around the skirt.  In this case the viscosity of the air casues resistance to the flow of air out between the ground and skirt, such that the air pressure within the skirt is just sufficient to support the weight of the craft.  The energy (more correctly the power) required is that which is lost in the visocity friction around the skirt.  If the engine/fan supplies less than that, the hovercraft will sit on the ground.  If more than the required power is supplied, the skirt-to-ground gap will increase unnecesarily, allowing the air velocity to increase to maintain the same pressure, and the viscosity friction loss must increase to match the increase in engine/fan power.  The energy consumed by a hovercraft is thus a minimum at the minimum skirt-to-ground clearance, and increases with increasing clearance, until the machine is operating as a helcopter.  Wickwack 120.145.9.226 (talk) 15:22, 7 November 2012 (UTC)
 * There is no contradiction. The helicopter is not doing work by staying up - it is doing work by circulating air (and making noise, and heating the air, etc.).  To illustrate, suppose you build a "helicopter" out of thin, horizontal plastic wrap that is the size of the Earth, completely surrounding the entire atmosphere at a certain level.  It takes no circulation at all to hold up. Wnt (talk) 15:28, 7 November 2012 (UTC)


 * I'm sorry, but I see nowhere in the question that this is about a hovercraft. The OP specifically asked about a helicopter or similar aircraft, so this is perfectly analogous to a bird in the sense that it flies high above ground. - Lindert (talk) 15:33, 7 November 2012 (UTC)
 * You are right - I was off in fairy land for some reason. My appologies. You are correct. Wickwack 120.145.9.226 (talk) 15:38, 7 November 2012 (UTC)
 * No problem, I could easily see myself making the same mistake. - Lindert (talk) 15:42, 7 November 2012 (UTC)


 * (ec) Lindert, Wickwack, and 91.120 are spending a lot of time giving the right answer to the wrong question. Their calculation answers the question "how much work is being performed on a hovering helicopter?", which does indeed come out to zero.  What the OP asked for, however, is not how much work is done (or how much power is required) to hold a theoretical mass stationary in the air, but rather how much energy it takes to keep a real helicopter in the air.  That answer is greater than zero.
 * What would be useful here would be (one or both of)
 * a method of approximately calculating the amount of lift generated by a helicopter rotor as a function of input power (there's probably a rough equation floating around somewhere that takes the rotor blade length and angular speed, the number of blades, the density of air, and some kind of blade shape fudge factor as parameters); and/or
 * some actual numbers for some real aircraft. Numbers surely exist for the actual, measured power output of helicopter engines under hovering conditions, and they will give you some idea of how (un)reliable estimates based on an approximation formula might be.
 * Come on, people&mdash;we're the Reference Desk. Let's find some references. TenOfAllTrades(talk) 15:44, 7 November 2012 (UTC)
 * Not to be rude, but how do you manage to read the mind of the OP to see what he meant? I certainly understood it in a theoretical sense: 'how much energy is needed', as opposed to 'how much energy is actually used'. Nonetheless, I appreciate your effort to answer the question. - Lindert (talk) 15:53, 7 November 2012 (UTC)


 * Thanks for Osman + TenOfAllTrades for you answers. That's exactly what I wanted to know. Comploose (talk) 16:26, 7 November 2012 (UTC)


 * (ec)The real-world answer is that some kind of helicopter I found on Google uses 45 gallons per hour of what I'll assume is some kind of Aviation fuel.  The article says BP Avgas (I don't know that's the right type) contains 44.65 MJ/kg with a density of 690 kg/m3 = 0.69 kg/liter, i.e. 30.808 MJ/liter - assuming the gallons are US liquid that's multiplied by 3.79 liter/gal to get 116.762 MJ/h = 32400 watts.  (Although this is the power of only 22 hair dryers on high  apparently most of a hair dryer's energy goes into heat, so don't launch your lawn chairs until we work out the details) Wnt (talk) 16:29, 7 November 2012 (UTC)


 * Around here, they fly R22 and Robinson R44 helicopters and fill them with 100LL AvGas. As far as a reference: start with the Pilot's Handbook of Aeronautical Knowledge - which provides just enough balance between theoretical information and practical real-world knowledge.  The FAA also publishes an airplane flying handbook, but for helicopters, all I found is the Helicopter Instructor's handbook, which covers physics of flight in Chapter 3.
 * From first principles of mechanics or thermodynamics, you won't get very far. Helicopter flight is characterized by aerodynamic work against a non-conservative force.  What this means in practice is that the amount of energy or power required for a maneuver depends on the helicopter's configuration.  A helicopter pilot can independently control the collective, the cyclic, and also throttle the engine rpm.  The pilot can also change the attitude of the helicopter to maintain a hover at many different engine settings and aircraft attitudes.  Phrased another way, the angle of attack of the rotors can be varied to change the aerodynamic efficiency of the helicopter, while maintaining a level hover or a stable hover at an unusual attitude.  The blade pitch changes how efficient or draggy the blade is - and this directly affects how much lift is produced for a given amount of energy  So, the total amount of energy the engine has to produce is going to vary signficantly.  You can pull up the pilot's manual for an R22, or other helicopter, to see normal operating engine and control configurations for a hover.  I see the engine maxes out at just around 2600 RPM, which will hover the aircraft in certain conditions, and lift it in other conditions; of course, hover performance is affected by weight and atmospheric conditions.  The engine is rated for around 150 hp, but is designed to take off at around 120 hp, and can lift the aircraft at much lower power settings.  The yellow line starts at 60% on the tach, and you can convert that to produced horsepower using the charts in the aircraft manual. Nimur (talk) 21:46, 8 November 2012 (UTC)

G-Force
If you accelerate in a vacuum, would you experience G-Force? — Preceding unsigned comment added by 109.153.170.218 (talk) 18:16, 7 November 2012 (UTC)


 * You would feel a force, and you could measure that force scaled by units of g, the standard measure of gravitational acceleration at Earth's surface. I personally don't like the term "G force" because it conflates the units with the effect; and I have seen it used in various contexts to mean totally different things.  Nimur (talk) 18:42, 7 November 2012 (UTC)

Is there any way to prevent G-force/any circumstance you could travel at very fast speeds without being affected by g-force at all? — Preceding unsigned comment added by 109.153.170.218 (talk) 19:07, 7 November 2012 (UTC)


 * Yes, by having a large mass in front of you, which accelerates with you. It's gravitational attraction will thus counter the g's due to acceleration.  The denser and closer the mass is to you, the less mass is required.  Of course, there's no practical way to do this, at present and in the foreseeable future, as the mass would be huge. StuRat (talk) 19:18, 7 November 2012 (UTC)


 * I don't think you've worked that scenario out to its logical conclusion, StuRat. Nimur (talk) 19:30, 7 November 2012 (UTC)


 * Meaning that they would have to rapidly accelerate a mass on the order of the size of a planet ? Yes I have.  That why it's not practical in the forseeable future.  Perhaps with a mini-black hole, the mass could be far less, but then you have the issue of how to create the mini-black hole, keep it stable, and keep it from swallowing the ship, while accelerating the whole thing.  My much more modest design involves a massive linear particle accelerator which clamps on to a metallic asteroid.  The asteroid is kept in front, and acts as a shield, while it is mined and shot out of the linear accelerator at the speed of light.  If the asteroid generates a 0.5g gravitational attraction, then a 1.5g acceleration would only be felt as 1.0g, to those on the surface.    StuRat (talk) 19:55, 7 November 2012 (UTC)


 * Stu, I wanted to say that I think your planet-idea is brilliant, literally brilliant. No one has included this in the inertial-dampener discussion.  91.120.48.242 (talk) 13:03, 8 November 2012 (UTC)


 * that's basically how we are travelling through space right now, isn't it? just like the idea that you can buy a fusion powered boat which keeps the reactor a safe 93 million miles away and transfers energy by radiating it into a working fluid of ordinary atmospheric air, which is captured by a simple structure of large fabric vanes.... Gzuckier (talk) 03:10, 9 November 2012 (UTC)


 * There's a short story by Charles Sheffield about a ship whose nose is a big ball of neutronium. The passenger pod moves up and down a mast, adjusting its distance from the neutronium so that its gravity balances the acceleration of the engine (whose magic unlimited energy source I do not remember!) to within ±1g.  At maximum acceleration, a ratchet malfunctions so the pod gets stuck close to the neutronium, so the ship can't slow down ... —Tamfang (talk) 22:27, 7 November 2012 (UTC)


 * This story, but as I'm not strongly motivated to re-read it I don't guarantee that my summary is accurate in detail. —Tamfang (talk) 22:31, 7 November 2012 (UTC)


 * Also, you said "fast speeds", but I assumed you meant "fast accelerations". There's no problem going at fast speeds, as the g's are only caused by the acceleration.  Thus, if you accelerate slowly enough, you can go any speed you want, up to those approaching the speed of light, without excessive g's.  Accelerating at 1 g (normal gravity), for example, you can get close to the speed of light in about a year. StuRat (talk) 19:21, 7 November 2012 (UTC)

Thank you! Whats the maximum acceleration a human can withstand? — Preceding unsigned comment added by 109.153.170.218 (talk) 19:49, 7 November 2012 (UTC)


 * That greatly depends on the length of time and what precautions are taken, and if they need to remain awake and able to act or merely stay alive. For seconds in a pressure suit, a properly trained and evaluated test pilot might be able to take on the order of 10 g's, while an ordinary person might only be able to take 1.1 g, for months at a time. StuRat (talk) 19:59, 7 November 2012 (UTC)
 * Colonel John Stapp pioneered the use of rocket powered acceleration/deceleration sleds in the late 1940's to test seat restraints for aviation, and repeatedly withstood accelerations of 45G, though he broke a wrist and suffered retina detachment. Edison (talk) 01:06, 8 November 2012 (UTC)

Strong magnetic fields can be used to counter the effects of the G-force, see e.g. here.

"Whether an object will or will not levitate in a magnetic field B is defined by the balance between the magnetic force F = M∇B and gravity mg = ρV g where ρ is the material density, V is the volume and g = 9.8m/s2. The magnetic moment M = (χ/ µ0)VB so that F = (χ/µ0)BV∇B = (χ/2µ0)V∇B2. Therefore, the vertical field gradient ∇B^2 required for levitation has to be larger than 2µ0 ρg/χ. Molecular susceptibilities χ are typically 10^(-5) for diamagnetics and 10^(-3) for paramagnetic materials and, since ρ is most often a few g/cm^3, their magnetic levitation requires field gradients ~1000 and 10 T^2/m, respectively. Taking l = 10cm as a typical size of high-field magnets and ∇B^2 ~ B^2/l as an estimate, we find that fields of the order of 1 and 10T are sufficient to cause levitation of para- and diamagnetics. This result should not come as a surprise because, as we know, magnetic fields of less than 0.1T can levitate a superconductor (χ= -1) and, from the formulas above, the magnetic force increases as B^2."


 * But would that be useful for humans ? I tend to think that a strong enough magnetic field to exert a significant force on a person would cause medical problems, like preventing blood from circulating by exerting force on the iron in the hemoglobin. StuRat (talk) 20:22, 7 November 2012 (UTC)


 * Perhaps for short time intervals these effects are not a big problem. You can e.g. think of a magnetic air bag in a car that will produce a very strong magnetic field for a short time. You then also have to consider if you can tolerate the huge emfs generated by that. Count Iblis (talk) 20:38, 7 November 2012 (UTC)


 * Our own magnetic levitation article describes the levitation of a frog with an electromagnet. The frog seemed totally fine in the short term. I'm not sure if they ever did a long-term viability assay. Someguy1221 (talk) 01:29, 8 November 2012 (UTC)


 * And that's only 1 g on a small organism. I'd suspect that smaller organisms would be better able to handle it. StuRat (talk) 01:48, 8 November 2012 (UTC)

You could put the human inside a liquid-filled tank and also fill all air-containing spaces inside the human body with the liquid (see liquid breathing). The density of the liquid should be similar to the density of the human body, which prevents the lungs and other cavities from collapsing. The acceleration limit will be higher, but due to different tissues having different densities, there will still be a limit. With the bone density of maybe 1.5 g/cm3, the adipose tissue density of maybe 0.9 g/cm3 and the density of air of approximately 0, one would think that the tolerable acceleration is multiplied by a factor of (1.5 - 0)/(1.5-0.9). But that's of course a simplification, as a bone usually isn't directly surrounded by adipose tissue (and for what's inside the bone, you have to take into account that the bone is mechanically more stable than the lung). How would death or injury occur at high accelerations, given this liquid immersion? Icek (talk) 20:51, 7 November 2012 (UTC)


 * That gimmick was used in The Forever War, right? —Tamfang (talk) 22:32, 7 November 2012 (UTC)

Okay, Thank you! — Preceding unsigned comment added by 109.153.170.218 (talk) 20:59, 7 November 2012 (UTC)

Sorry I was a few comments behind there! Clicked edit, didn't see the new comments! This is all extremely interesting and useful! Do you know if anyone has already worked out the calculations on liquid breathing affecting the acceleration? Or are there any similar workings that could come in useful? — Preceding unsigned comment added by 109.153.170.218 (talk) 21:06, 7 November 2012 (UTC)

Stu, I wanted to say that I think your planet-idea is brilliant, literally brilliant. No one has included this in the inertial-dampener discussion. 91.120.48.242 (talk) 13:03, 8 November 2012 (UTC)


 * Thanks. You're quite welcome to use it.  Note that such a ship would have to find and clamp onto a new asteroid, when it arrives at it's destination, to be used for the return trip.  In other words, it would use multiple asteroids in Ceres. :-) StuRat (talk) 18:48, 8 November 2012 (UTC)

Generating energy without losing fuel
I am not sure about this but this question is revolving around my mind for several days. Suppose, in nuclear reactor, we are able to hit a proton with a neutron; proton will decay in neutron + positron + electron neutrino and neutron will decay in proton + electron + electron anti-neutrino. In reactor following may take place- Proton + neutron → neutron + positron + electron neutrino + proton + electron + electron anti-neutrino. In the above equation, positron is the antiparticle of electron and electron anti-neutrino is the antiparticle of electron neutrino. Annihilation will take place between particles and their corresponding antiparticles with the release of huge amount of energy. The above equation can now be restated as- Proton + neutron → neutron + proton + energy. Hence, energy is produced without losing fuels (i.e. proton and neutron). I am not sure whether this process is right or wrong. Is it possible to generate energy in this way ? Thank you! Sunny Singh (DAV) (talk) 18:58, 7 November 2012 (UTC)
 * What you are proposing is called perpetuum mobile. :) Ruslik_ Zero 19:00, 7 November 2012 (UTC)
 * Won't the neutron decay? So you'd effectively lose a neutron in the equation? --Wirbelwind( ヴィルヴェルヴィント ) 19:04, 7 November 2012 (UTC)


 * What you're missing is that the two component reactions you're adding together don't happen with ground-state protons/neutrons (at least the one starting with the proton doesn't). So the net reaction is really energetic proton + neutron → neutron + proton + energy, which shouldn't surprise anyone. If you carefully examine the conditions where each half reaction holds, you'll find mass-energy is conserved in each, so even if you were able to combine them somehow, mass-energy would still be conserved. The energy you get out is exactly the amount of energy you need to pump into the proton/neutron to get the reaction to start. -- 205.175.124.30 (talk) 19:34, 7 November 2012 (UTC)

Who created this picture of the thermoscope?
In this blog, there is a picture of a thermoscope that is taken from an unknown book (to me). I have no idiea on this book. Do you know who created it or in which origin book it's found? Thank you. מוטיבציה (talk) 20:21, 7 November 2012 (UTC)


 * This site attributes it to the 1832 Edinburgh Encyclopædia. Regards, TransporterMan  ( TALK ) 20:41, 7 November 2012 (UTC)
 * Thank you a lot, for the help. מוטיבציה (talk) 04:33, 8 November 2012 (UTC)