Wikipedia:Reference desk/Archives/Science/2013 December 15

= December 15 =

How much would it cost to build the space colonies from Mobile Suit Gundam?
I'm sure someones asked about the mobile suits themselves, but I'm curious about the orbital colonies from the original series. I know people have estimated the cost of the Deathstar in U.S. dollars, but space colonies sound more practical, if potentially devastating when dropped. I assume asking how much science costs is a science question. CensoredScribe (talk) 04:26, 15 December 2013 (UTC)


 * Ummm, just in case some of us were a little ... rusty ... about this Mobile Suit Gundam, could you explain where and what they are? I see something about an O'Neill cylinder in that article but tell us how big you want it. Wnt (talk) 04:48, 15 December 2013 (UTC)

Sure thing, according to the setting notes from Sunrise (company), 36 million people can live inside of a cylinder 32 kilometers long and 6.3 kilometers in diameter; these space colonies are situated at the Lagrangian points. Lets say the power is being provided by nuclear fission instead of nuclear fusion, as we don't have nuclear fusion reactors that provide net energy yet. They can only use electric cars and electric rails; and have enough water and agricultural land for the colony to comfortably sustain it's self. It's a shame they never let you do something as cool as building this in SimCity; thank you for answering this question. CensoredScribe (talk) 23:40, 15 December 2013 (UTC)

The biggest cost of building space colonies is lifting raw material off the face of Earth. You can keep the cost down by using raw material from Asteroids instead of raw material from the Earth's surface. Furthermore you can keep the cost of the colonists down by sending them up when they were sperm and ovums as these are pretty light. Then raise the colonists using robots until they achieved adulthood. And this is the cheapest way of building the space colonies. 202.177.218.59 (talk) 04:01, 16 December 2013 (UTC)


 * But would a person raised by robots be fully psychologically developed? I strongly suspect that, at the very least, such a person would completely lack emotional intelligence and would have major problems interacting with other people -- which would lead to severe social problems in the colony in the long run! 67.169.80.238 (talk) 05:40, 16 December 2013 (UTC)


 * Maybe these robots raised spacenoids would want to drop space colonies and big rocks on Earth. Sieg Zeon! 202.177.218.59 (talk) 06:05, 16 December 2013 (UTC)


 * See also Embryo space colonization.-- Auric    talk  23:27, 16 December 2013 (UTC)


 * The short answer is that no amount of money can do it - I don't think anyone has plans to build a 20 km span of more or less unsupported suspension bridge anytime soon, which is what that space environment is (at least, if it has gravity anything like Earth). The somewhat longer answer is that we'd build it out of space resources, which would be on their own monetary system.  For example, there's only a very limited amount of water at the poles of the Moon.  If it ends up being owned by, say, the PRC, then they can use it for free, nobody else can use it at any price.  So you'd have to have a market, and then it would depend on exchange rate, which could vary greatly.  The value of a ton of water in space is pretty much "a ton of water in space" :)  The idea of taking that many resources out away from Earth is absurd though - if we had the technology to use that much stuff in space, we'd have the technology to make it in space. Wnt (talk) 05:05, 18 December 2013 (UTC)

Formation of memories
If I give you a sequence of numbers to remember, say 1548, what changes in your brain (in the space of a second!) so that you can recall that sequence? Surely no new synapses form in that space of time? Gene expression also, can't respond so quickly? — Preceding unsigned comment added by 78.148.110.243 (talk) 16:38, 15 December 2013 (UTC)
 * I haven't kept up well with developments here, but still references a 2008 publication  which is free with registration.  Only somehow I forgot the password, so until I check my e-mail I'll leave it there.  (Come to think of it, odds are it was whatever it said in the last forgotten password note sent to my email...)  The gist, though, is that you can let calcium ions into the cell.  My impression is that in general, calcium ions are a sort of alarm signal of a damaged cell membrane, because if allowed to lurk around long enough they would tend to create problems (insoluble compounds) and so every cell pumps them out.  But in cells that respond to stimuli (not just neurons, but many other types) they can also be used then as a way of giving a signal that something has changed, and then the cell works pretty quickly to get them back out, but it still can be slow enough to take many seconds. Wnt (talk) 18:11, 15 December 2013 (UTC)


 * (ec) The answer is not well known for humans. You can start at this section of our article on human memory.  Generally, most scientists believe that there is a biochemical change at the very micro-microscopic level; and a corresponding emergent change in electrical response and cell-structure at the cellular level (still microscopic, but much larger than the former).  But this topic is difficult to study, and answers are subject to change as scientists learn more.
 * Contrast this with a computer, which is much simpler (and for which we know the design): memory is committed and stored when a finite state machine uniquely addresses a specific part of an array of storage circuits - and this allows the circuit to store electrons on a capacitor (or to magnetize a crystalline substrate, or to etch a visible mark in a reflective layer). In these machines, there is always a state machine that controls where information will be committed; there is always some physical change that occurs at a specific spatial location; and the information is stored in serial form, one bit at a time.  This is very convenient for the design of machines, and as a computer scientist, I commonly make similar assumptions about human memory; but in fact, we have no present ability to prove that human memory is addressable, or serialized, or spatially localized; and we cannot prove exactly which physical change corresponds to storing memory.  Nimur (talk) 18:15, 15 December 2013 (UTC)


 * As Nimur says, surely something physical changes, at at least the molecular level, for you to be able to store and recall memories; however we're really unsure how it works exactly. There is a Wikipedia article titled Neuroanatomy of memory which does give you some broad strokes.  -- Jayron  32  22:28, 15 December 2013 (UTC)


 * To begin with, you have to be aware that there are short-lasting forms of dynamic memory that allow information to circulate long enough to affect brain structure. One of the most basic is the so-called phonological loop -- a fancy term for the fact that we can hold information in our minds for a period of time by repeating it to ourselves over and over again. The best candidate for a long-lasting synaptic change mechanism is a process called long-term potentiation, usually abbreviated LTP. LTP can be induced by signals that last less than a second, though longer-lasting signals produce much stronger traces. It has two phases, an early phase that lasts a few hours and does not depend on protein expression, and a second "consolidation" phase that does depend on protein expression and can last for months or longer. Looie496 (talk) 00:38, 16 December 2013 (UTC)
 * This reference should answer the question (it's open access). Arnsten et al. (2010). Dynamic Network Connectivity: A new form of neuroplasticity. Trends Cogn Sci. 14(8):365-75.. The primate experiments are based on spatial working memory but it's very likely that verbal working memory works in a similar way in terms of synaptic fundamentals. Markr4 (talk) 10:26, 16 December 2013 (UTC)

Libido
Is libido reduced by only chronic tiredness or can it also be affected by temporary tiredness after alot of physical activity, lack of sleep etc? — Preceding unsigned comment added by Clover345 (talk • contribs) 22:12, 15 December 2013 (UTC)
 * We cannot give any advice or diagnosis of any medical conditions, in the specific or in the general. You can read the Wikipedia article titled Libido which discusses things which affect libido.  -- Jayron  32  22:25, 15 December 2013 (UTC)
 * I wasn't asking for medical advice. It's a general question related to human biology. — Preceding unsigned comment added by Clover345 (talk • contribs) 23:54, 15 December 2013 (UTC)
 * The answer is so obviously yes that I have a hard time seeing anything evil about the question (or anything valuable either)> Looie496 (talk) 01:22, 16 December 2013 (UTC)
 * And what is the biochemical reason for this? Clover345 (talk) 14:03, 16 December 2013 (UTC)
 * Have you had a look at the article libido? Dmcq (talk) 14:55, 16 December 2013 (UTC)