Wikipedia:Reference desk/Archives/Science/2014 November 24

= November 24 =

Bio-Printing Live, Healthy Human Infants: Will This Eventually Be Possible?
I apologize if this question offends anyone here, but I do think that it is a legitimate question: Would it be theoretically possible (based on what we currently know) to eventually (as in, say, several hundred years from now) bio-print (as in, using 3D printing) live, healthy human infants? Honestly, I have previously never thought about this possibility before, but someone on a forum which I post at suggested this possibility a day ago, arguing that after bio-printing organs, bio-printing simple organisms and then bio-printing complex organisms such as humans would eventually be the next (logical) steps to bio-printing. Also, I would like to point out that I am not asking about the ethics and/or morality of this here, but only about the theoretical aspects of this, specifically whether or not this will eventually be possible to do. (Of course, something such as this, if it is done well and if it eventually becomes cheap enough for most or all people, could also obviously dramatically change the way in which human beings reproduce.)

Thoughts on this? Futurist110 (talk) 01:31, 24 November 2014 (UTC)


 * How do you intend to keep the netherbits like the brain or feet alive before you've printed the heart and an unleaky circulatory system? The body works as a whole, as an organism.  It's not a product of construction, but of ontogeny.  Best I can see is you assemble some genes and have the retrovirally inserted into a gamete or zygote. μηδείς (talk) 01:40, 24 November 2014 (UTC)


 * It may be possible to 3D print, but you may have to do it in conditions where the baby is not fully alive. For example it could be done at a lower temperature so that the brain can survive without the heart.  Or perhaps things could be printed in a different order, rather than from the soles of the feet to the crown of the head. Graeme Bartlett (talk) 01:46, 24 November 2014 (UTC)


 * Would it (eventually) be possible to put all of these body parts together into a living human infant without causing any negative consequences and/or side-effects for this human infant, though? Also, could bio-printing a live human infant at a lower temperature actually (eventually) be fully/completely successful (as in, succeeding in doing this without any negative consequences and/or side-effects for this human infant)? Futurist110 (talk) 02:04, 24 November 2014 (UTC)


 * "We don't answer requests for opinions, predictions or debate". You are asking us to make a prediction about whether something will be possible "several hundred years from now". AndyTheGrump (talk) 02:13, 24 November 2014 (UTC)


 * Yes, but I am asking you to do this based on the information which you currently know and/or have available to you. Also, to be fair, this might be more of a theoretical question as opposed to a prediction. Futurist110 (talk) 02:17, 24 November 2014 (UTC)


 * Every prediction is based on something currently known. One thing I know is that every negative experience of a person's life is a direct consequence of being born, and nobody's lived a fully happy life yet. So these instant babies will also be doomed to uncertainty. Frankenstein's monster was quickly miserable for being shunned, and it'd arguably have been more positive for all if he'd died instead. So there's that uncertainty in definition, too. The future's full of it. InedibleHulk (talk) 04:35, 24 November 2014 (UTC)


 * I have to agree that there's some pitfalls here with regard to verifiability that are inevitable in any answer to this question, owing to the open-ended, "will it ever" nature of the question, but I do believe there are some conclusions to be drawn which follow almost absolutely from the biophysical properties of human physiology. has hit the nail on the head with this one in noting that a human being if formed by more than just a number of independent parts slapped together; rather it is the outcome of those many systems developing together, influencing one-another and guided by morphogenetics, epigenetics, and other massively complex classes of mechanisms essential to ontogeny.  To take just one of countless examples, consider the innervation of the motor system or any other aspect of the peripheral nervous system; the neurons which control muscle function develop even as the muscle itself does, integrating with it and becoming more robust with development and use.  At the same time, parallel structures are developing in the brain which allow it to control volitional motor acts, and indeed most reflexive motor acts as well.  Without that biochemical interplay (the complexities of which I have almost completely glossed over here) developing these systems in tandem, you just wouldn't get a functioning system.  Now, all of that being said, the phrasing you use leaves a lot of wiggle room in that we are asked about what might be possible with the advances of hundreds of years to our bio-engineering capabilities.


 * So yes, technically I can conceive of it being feasible for such an advanced science to create a living homo sapien sapiens, as we know it today, from completely engineered components, but here's the aside: by the point it would be possible to accomplish this with biological printing, it would almost certainly have long before become feasible to create an identical person using accelerated generative processes that none-the-less do not depend on conventional gestation.  That is, I can't fathom that an advanced technician capable of integrating every system (and indeed, every cell) together on a molecule-by-molecule basis wouldn't be able to instead accomplish the same end by utilizing generative/developmental processes that are vastly more efficient and (by comparison) much more self-organizing.  Imagine for a moment that, for some reason, you wanted to convert all of the water present in a vapor state in a closed flask into a block of ice.  Which would be simpler method, trying to isolate each molecule mechanically and forcing it somehow into the matrix of a frozen mass, or simply controlling the temperature and pressure of the flask and relying on cohesion, gravity, and other self-organizing processes to do all the meticulous work for you? A human being is vastly more complex and less homogenous system, but at it's core is still a collection of chemicals which obey physical processes that follow naturally from their molecular traits.  Of course, we are a long way off from a complete understanding and control of these processes, but they remain predictable in the sense that they are universal and inevitable.


 * Again, what it comes down is that, if a being possessed the biochemical understanding, capability for calculation and the ability for control of microscopic phenomena necessary to put a human being together cell-by-cell (or even to just create the major organ systems and then integrate them on a molecular scale as necessary), then they would almost certainly be able to create the same human using a fraction of that knowledge and effort by re-purposing and adapting normal human developmental principles. In other words, if a human being ever was created in this piece-meal fashion by a far-future entity, they would be less likely to be a scientist breaking a barrier in the science of bio-manufacturing and more likely something like an artist making a statement.  Bottom line, Leeloo would have been more realistically grown in a tank than put-together in cross-sections.  But still, can you imagine babies with that hair? How cute would that be!?  S n o w  talk 08:58, 24 November 2014 (UTC)


 * Agree if any changes are to be made it will probably be easier to do a bit of genetic engineering than trying to do such a job with a 3D printer. I see it being necessary in the not too distant future to produce babies using artificial wombs as I can't see any other practical way for people to get to the stars. Dmcq (talk) 12:08, 24 November 2014 (UTC)


 * Christopher Nolan would seem to agree...sort of. But it really all depends on which science (bioengineering vs. astronautics) develops quickest, doesn't it?  Depending on how viable the technology to artificially gestate a human being has become, mankind might determine to make their first efforts with a generational ship.  For that matter, while I tend to agree that cryogenics and wormholes are massively overused (and typically oversimplified) sci-fi tropes (the brilliance of the afore-references Nolan film not withstanding), the former at least could plausibly come before baby-in-a-box.  Further, it is worth noting that there are a number of subluminal and yet incredibly fast theoretical ships that could, especially combined with relativistic principles, easily put us within reach of systems neighbouring our own, though most within that range show little to no indications of possessing an exo-planet suitable to the purposes of a colony -- which is rather what I assume you meant when you said "get to the stars", rather than a purely scientific mission for which the participants would likely be giving their life.   S n o w  talk 15:13, 24 November 2014 (UTC)


 * The key here is to define "printing". A simple application of 3D bioprinting means putting together in roughly the right positions... but not with the right synapses or even the right gap junctions for heart function, for example.  But if you keep cells alive in a nutrient solution with the right O2 and CO2 levels maybe they make these things.  But you can't immerse a whole infant in that solution the way you might immerse a bioprinted bladder or piece of skin.  Of course, you might make your printer better and better, print tiny pieces of cells under individual control so you can make those elements work, print cells with cytoskeletal elements and membranes all neatly joined up and fully functional...  who knows what might be done?  But not easily! Wnt (talk) 22:54, 24 November 2014 (UTC)


 * Right. The (rather speculative) obvious answer to Futurist's original question is a pretty solid "maybe" -- and I would argue that you could tack on, "If human bioscience continues to advance consistently at a rate close to what it does at present over all of those centuries -- probably."  But the query is such that it begs the question of why such an advanced engineer would approach the problem of replicating a human in that way and you've touched upon that issue again.  If an entity were capable of assembling a brain synapse by synapse (and not for nothing, it's worth repeating that old chestnut that there are more individual connections between neurons in the brain than there are atoms in the observable universe), and arranging them as such that the resulting person was a fully functioning, healthy and at least generally cognitively neurotypical individual, then it seems impossible to conceive of that engineer as anything but an organism that had already moved well beyond the mental faculties of a modern human being, it's understanding of the organizational principles would have to be so vast.  And again, this capability would almost certainly come long, long after the same human could be generated by co-oping existing ontogentetic mechanisms.   In other words, it would be a non-optimal way to create a very-likely out-of-date model of human.   It is an interesting line of thought nonetheless -- and one I've considered more than once over the last decade and a half as both practical developments and fiction in the domain of bio-printing have ramped up -- but also one fraught with speculation, which I suppose we rather ought to be avoiding.  I say as the person who has done the most speculation (albeit from what I find to be almost certain principles).  And I think the last time I was on the Ref Desks, months back, I was actually chastising a regular contributor for speculating too liberally.  ~digs toe in ground~  S n o w  talk 23:46, 24 November 2014 (UTC)


 * Printing is a relatively crude technique. It could never address the requirements that have already been addressed in even the simplest forms of life. Bus stop (talk) 01:44, 25 November 2014 (UTC)


 * Well, that's not necessarily altogether true. We already engineer tissue samples that are in themselves more complex than many simple organisms, including a great number of eukaryotes.   Construction of varieties of fungi using a modified approach of the layering techniques already utilized for tissue printing, for example, would hardly go down as the most monumental development in bio-engineering, but again we would encounter the same issue discussed above: why use this method when a slime mold can already be generated, and convinced to grow to meet a particular morphology, through other means with relative ease?  Organisms in Animalia are another question entirely, of course -- and humans even more so.   To be honest, I'm not sure exactly the nature of the processes Futurist had in mind, with regard to whether he meant to suggest the entire infant would be printed in cross-sections starting from the head and moving down or that each major organ and system would be printed separately and then fused, and you could argue that the latter would not qualify as printing.   Both are of course utterly infeasible with anything resembling contemporary capabilities, but when someone asks what would be possible with 800 years of steady advancement in biotech science, it's hard to speak with any degree of certainty about what would not be possible.   The point I am trying to emphasize here is that, even were it possible,  it would never really make sense to create a complex animal in that manner when you could create an identical one with a fraction of the effort and understanding using a generative approach.   S n o w  talk 03:53, 25 November 2014 (UTC)

Human Power Techniques
The human powered helicopter uses bicycle pedals and cranks for hands and feet. Has anyone compared the output from different techniques, such as rowing? Or maybe pulling, like a horse? Okay, I'm sure someone has. What were the results? 50.126.104.156 (talk) 03:19, 24 November 2014 (UTC)
 * Human power has numerical data for pedaling, but does not seem to consider mention common athletic modes. If someone finds info (either specific data, or else analysis that the mode of motion is not a relevant factor), please update it. DMacks (talk) 03:26, 24 November 2014 (UTC)


 * Just an observation, comment, etc. Human powered helicopters take quite a bit of effort to get off the ground.  Therefore, the helicopters are kept as light as possible.  Taking a cranking motion such as pedaling and channeling it into a turning motion of the rotor blades is fairly easy from a mechanical point of view.  Taking the power of a rowing motion and, I'm assuming through some fly-wheel sort of apparatus, turning that back and forth motion into the turning motion would add more complication to the mechanics.  That complication would mean more weight which you don't want.  So pedaling or cranking seems like the obvious choice of motions to use.  Dismas |(talk) 07:08, 24 November 2014 (UTC)


 * See it as a bicycle you pull your and the bicycles total weight, weight up by a load over block and tackle to lift over time of flight. --Hans Haase (talk) 00:51, 26 November 2014 (UTC)

silly tank circuit question
what is the difference, electrically and practically, between a tank circuit with large L and small C and one with large C and small L, assuming the product LC, and hence the resonant frequency (via w=1/sqrt(LC)), are the same? what are the criteria for choosing one combination over the other? Asmrulz (talk) 21:07, 24 November 2014 (UTC)
 * The primary consideration is the Q factor of the circuit - the width of the resonant peak. For an "ideal" circuit, $$Q = \frac{1}{R} \sqrt{\frac{L}{C}}$$ - so, to get a high Q factor, we need high L, low C, and (most importantly) low R.  In general, larger inductors have higher resistance, so increasing L will also increase R; this makes finding the theoretical maximum Q factor for a given frequency fairly easy, if we know how R depends on L.  There may be other factors which determine component usage; for example, most vacuum-tube wireless sets used a standard air-dielectric variable capacitor in the RF stages, which restricts the choice of inductor for a given frequency range.  Parasitic capacitance might also be a factor leading to the use of an inductor less than the theoretical max-Q value.  And, as always, cost is a consideration for commercial designs - it may be cheaper to use a large capacitor and small inductor and put up with a reduced Q-factor in some applications. Tevildo (talk) 21:48, 24 November 2014 (UTC)


 * I see. Thanks! Asmrulz (talk) 12:23, 25 November 2014 (UTC)

How many times the water (liquid) has density compared to water gas (vapor)?
or in other words, how much water and how much water gas I can enter to the same vessel (in the same pressure of course) 213.57.99.239 (talk) 23:26, 24 November 2014 (UTC)
 * See Steam and Steam table. At 100°C and atmospheric pressure, the density of steam is 0.5974 kg/m3 and the density of water is 958.35 kg/m3, so the mass of the liquid water at the same temperature and pressure will be about 1600 times that of the steam. Tevildo (talk) 23:58, 24 November 2014 (UTC)

One mole of an ideal gas occupies ~22.4 liters at STP. One mole of liquid water occupies ~18ml. μηδείς (talk) 00:03, 25 November 2014 (UTC)
 * Except water vapor condenses (mostly) at STP to liquid water and then to ice. If I have a 22.4 L container of water vapor, and maintain it at STP (the ST is easy, the P would require the addition of an inert gas like N2 or Argon) then the water would first condense and then freeze.  At standard temperature (273.15 K) water will start to freeze.  At that temperature, water's vapor pressure is only 0.611 kPa (atmospheric pressure is about 100 kPa). If you want to be scrupulously correct about this, use the ideal gas law for 373 K and 1 atm rather than STP, because at room pressure, the liquid-vapor equilibrium (aka the boiling point) only tips in favor of vapor over 373 K.  -- Jayron  32  01:28, 25 November 2014 (UTC)


 * Water exists at 0C unless you remove the heat of enthalpy of fusion, which I was not assuming. Even then it is still at STP.  Of course, the solid is simply a little less dense, 19.8 cm^3 compared to the 22.4 liters for a mole of spherical cow gas.  We're looking at a ~50th of a liter solid or liquid versus ~22.4 liters--not exactly an order of magnitude in difference; indeed, over a thousandfold difference, right? . μηδείς (talk) 02:16, 25 November 2014 (UTC)
 * Indeed. You're numbers are fine for the back-of-the-envelope calculation; Tevildo gets there via another path.  In general, the difference in density between any gas and one of the condensed phases (solid or liquid) is generally on the order of 10^3 for any given substance.  -- Jayron  32  02:22, 25 November 2014 (UTC)
 * Of course at the triple point the gas, liquid and ice would have the same density. Dmcq (talk) 12:29, 25 November 2014 (UTC)
 * Do you have a reference for that? Certainly at the critical point the difference between liquid and gas (and hence the difference in density) disappears, but as I understand it, the triple point is just like the freezing point/boiling point - all three phases can exist and have their own distinct properties. The only difference between a triple point and a melting/boiling point is that it's three phases instead of two. -- 160.129.138.186 (talk) 18:57, 25 November 2014 (UTC)