Wikipedia:Reference desk/Archives/Science/2011 April 21

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April 21

Venus

If people don't start protecting the environment from greenhouse gases, will Earth become like Venus (9 MPa CO2 atmosphere, 850 F surface temperature, sulfuric acid rainstorms, etc.)? --75.40.204.106 (talk) 02:07, 21 April 2011 (UTC)

Unlikely. For one thing, Earth's living systems are surprisingly resiliant, and are quite able to alter the atmospheric composition in dramatic ways. Don't get me wrong, humans impact on the environment, to change it from the world we know, into something far less friendly for us to live in, is a serious deal. We stand in real danger of making the world a less hospitible place for humans, and doing real harm on a timescale which is quite long on human measurements, but short on the Geologic timescale. Lets say we screw up the environment for the next 10,000 years. That's like 500 generations on a human timescale, and longer than there has been evidence of human civilization. It seems like a serious issue, and it is for us. However, 10,000 years is a minor blip on a geologic timescale. Consider that life on earth has existed for something like 2,000,000,000 years, and that 10,000 years seems insignificant to the Earth. And it is. The "earth" will recover, ultimately, from whatever we do to it. The question becomes, for me, if we will be around to enjoy it at that time... --Jayron32 02:15, 21 April 2011 (UTC)

Was Venus like Earth a long time ago until its life destroyed the environment? --75.40.204.106 (talk) 02:17, 21 April 2011 (UTC)

No, quite the contrary, there has never been life on Venus. Indeed, pre-life Earth used to look a lot more like Venus; the introduction of life drastically changed Earth's atmosphere in some very big ways. See Great Oxygenation Event where the atmosphere of the Earth changed drasticly. --Jayron32 02:56, 21 April 2011 (UTC)

According to Oxford Professor Fred Taylor, "In the light of the new data [from Venus Express] it is possible to construct a scenario in which the climates on Venus and Earth were very similar when they started out, and then evolved to the state we see now, like twins separated at birth. Billions of years ago there is even the possibility that Venus would have been habitable." Clarityfiend (talk) 03:01, 21 April 2011 (UTC)

Venus is significantly closer to the sun than is the Earth. (The average distance from the Earth to the sun is about 40% greater than the average distance from Venus to the sun.) The greater intensity of solar radiation on Venus has always represented a significant difference between the two planets and shows they could never have provided similar environments for living things, nor will they ever be similar. Dolphin (t) 03:02, 21 April 2011 (UTC)

(edit conflict) I can accept a similarity between Earth and Venus a long time in the past, but "habitable" does not equal "had life". I'm not saying you or your source said that. But it must be made clear that there's nothing there to indicate that there ever has been life on Venus. I could have married Jennifer Lopez. Doesn't mean it happened... --Jayron32 03:04, 21 April 2011 (UTC)

Hummmn. Got thing for J Lo huh?190.56.105.52 (talk) 04:50, 21 April 2011 (UTC)

People seem to disregard the fact that evolutionary processes are influenced by feedback-loops. So is climate evolution - an increase of atmospheric carbon dioxide will, through a chain of cause and effect, alter our rate of CO2 output.

For instance, assume that the only source of CO2 is industry. A drastic change in atmospheric CO2%, will eventually alter and reallocate sociological and economical priorities, including industrial sectors. As global industry shuts down a number of sectors, atmospheric CO2% decreases. Given a chance, the climate will heal itself and reajust to a new equilibrium. In short, alteration of the climate will automatically affect our ability to alter it.

I'm not argueing against global wariming, infact, I believe that at present the collective effort to change climate altering habits is insuffient to prevent the progress of global warming. Assuming that the effort remains unchanged into the future, then civilaisation will collapse, we will be forced to change our habits as it would no longer be energetically favourable to continue carbon dioxide producing technologies. Over time, global warming will naturally reverse, albeit slowly, as it is reabsorbed by ecogenesis and other minor processes.

Venus atained its current climate without the benefit of a negative feed-back loop, it actually suffered from a positive feedback loop. Plasmic Physics (talk) 11:47, 21 April 2011 (UTC)

Jayron, I don't think we can really make a statement like "there has never been life on Venus". In fact, I don't think that we can state with authority that it isn't there now. APL (talk) 14:00, 21 April 2011 (UTC)

I can't state with authority that I even exist. There's no definitive proof that Wikipedia itself is not a halucination that you are having as a result of being administered powerful mind altering chemicals placed in your tapwater supply by the CIA, and that this entire conversation isn't happening inside of your own deluded mind as you are actually, right now, lying on the floor in your living room drooling on yourself. Can you prove THAT to not be true?

Back to the life on Venus issue: Its the positive assertion that requires evidence to prove it, not the negative one. We don't assume every utterance a human could make to be true by default, and then require others to disprove it. I could make any number of rediculous assertations (Clouds used to be made of cotton candy, but they arent anymore!, Elvis Presley didn't die, he had plastic surgery and became George H. W. Bush! Grilled Cheese sandwiches cause pregnancy!), and there's no requirement that we give them any possibility of being true. You seem to be taking the stance that "any nondisproven idea must be at least considered to be possibly true". That's not necessarily the case, since I can present any number of statements that have not been disproven (to any arbitrary standard of proof I wish to demand) and then demand that you accept them as possibly true, no matter how rediculous they may be. A scientist has presented data that there may have been conditions on Venus, in the past, which may have been similar to conditions under which life on Earth is known to have existed. We can entertain that idea (we are not required to accept it as absolutely true, but we can entertain it) because the assertion is at least backed up with data. However, there is no need to entertain wild speculations that have zero data to back them up, for example, that there was actually life on Venus. Yes, you can say "you don't KNOW there was no life on Venus." But there's no need to prove the negative; the lack of any evidence is enough so far. Since you are making the positive assertion (there may have been life on Venus), you need to supply the evidence to make it. See Argument from ignorance, which is exactly the fallacy you are committing here. --Jayron32 15:34, 21 April 2011 (UTC)

You made a very definite assertion. I'm saying that it was almost completely unevidenced. It's not like you're saying "Many people have observed the Loch Ness, but no one has every produced evidence of a monster. It's safe to say that there is no monster." You're saying "No one has ever even been to Scotland, but we've got a dozen very low-res photographs, so There is no monster.". The first is a scientific statement, the second is not. You can't bluntly say that something doesn't exist because no one has produced evidence, if we haven't looked for that evidence! At that point you have to say that it's unknown.

Confusing the line between "Science is never 100% certain of anything." and "This particular thing is completely unknown" just gives fuel to the creationists and other anti-science types. APL (talk) 16:43, 21 April 2011 (UTC)

Agreed. As for the possibility of life on Venus now, if life can exist near hydrothermal vents at the bottom of our oceans, at extreme temperatures and pressures, then maybe it can on Venus too. Yes, the acidic environment of Venus is also harmful to life, but then so is free oxygen, yet life on Earth evolved to not only survive that, be to take advantage of it. And Venus does have a very reactive environment, with lots of energy available, which would promote both the creation of life and it's evolution. I have no problem imagining something similar to bacteria living on Venus. It may or may not exist, and I will make no definitive statement either way until I see some proof. StuRat (talk) 17:46, 21 April 2011 (UTC)

Here is what I remember having heard about venus. It is nearer to the sun and thus receives more solar energy than earth does. At times of the faint young sun this would have helped venus not to turn into a snowball. Venus is less massive than earth and I read somewhere (not on wikipedia, can't find it again now) that any planets less massive than earth cannot hold hydrogen by gravity. If so, venus, like mars, was bound to dry completely sooner or later. Venus does not have plate tectonics the way earth does. This way the exchange between the atmosphere and ground is limited. CO₂ would not be as dynamically released or bound geochemically like on earth. I think it was somewhere on wikipedia where I have read that the whole of the venus' surface was submerged in one single event. If so, there is no hope of ever finding any traces of life that may or may not have existed. 93.132.132.156 (talk) 22:11, 21 April 2011 (UTC)

I found part of the information here Geology of Venus#Global resurfacing event 93.132.132.156 (talk) 22:26, 21 April 2011 (UTC)

Bosch reaction

Is it endothermic or exothermic? --75.40.204.106 (talk) 02:16, 21 April 2011 (UTC)

According to the Wikipedia article Bosch reaction it is exothermic. You could check yourself with the data at Standard enthalpy change of formation (data table). --Jayron32 02:52, 21 April 2011 (UTC)

What would Earth be like if it was 82% more wonderful?

It's great that you're being creative and imaginative, but this isn't the correct place for it.
The following discussion has been closed. Please do not modify it.
I have collapsed this discussion. This is the science reference desk. On this page, we seek to improve the quality of our encyclopedia by helping people find scientific references. If you want help finding internet discussion forums or other outlets for your creative energies, you might find better answers on the Humanities or Miscellaneous desks. Nimur (talk) 04:21, 21 April 2011 (UTC) When people think of environments much better than those found on Earth, they invariably talk of Heaven and its variants, which are INCOMPARABLY better. Earth is amazing, wonderful, astonishing, charming, exciting and deep, but the world to which I refer is 82% more enhanced in all of these properties. What would such an Earth, one that is better but not incomparably better to the one we know be like? The immediate objection to this question will be that it is not “scientific” because the properties of “amazing, astonishing…etc” are subjective descriptions. This is so, but subjective evaluations can be quantified and measured by psychometric means. We don’t need to do that here; for the time being a respondent can estimate what features such a planet might have that would render it 82% more wonderful in every way to the one we live in. Not 100%, or 200%, but 82% - it is important that the last figure be the one under consideration, although respondents to this query might wish to compare their 82% ideal with what would be the case if the figure were much higher. For myself, I believe the following would be a reality in such an Earth: 1. There would be four sexes, male, female, devotrain and andila. Everyone would be male or female but also be either devotrain or andilian. A devotrainian male could make love to an andilian male without being homosexual. There would be an another entirely different kind of eroticism which would run parallel with the one we know. Human navels would become powerfully erotic organs which, when joined with another’s, would emanate fibres that would extend through the other’s body. When the moment of devotrainian or andilian orgams occurred, it would be felt from head to toe. 2. Humans would have eyes which, when properly trained upon the night sky for half an hour or so, can see the cosmos as clearly as the Hubble Telescope does now. Indeed, humans will be able to see in the infra red and unlta violet, and the brain will be hard wired to see two extra colours. 3. People will be able to glide for considerable distances, and death by falling will no longer occur. To fly like a bird, however, would require an Earth 128% better than the one we have. 4. There will be creatures like vast air ships, 10 times larger than the biggest whale, which will be tame and carry thousands of passengers across the seas in great comfort, requiring only some food and love. 5. The Earth will be 34% larger, but correspondingly less dense so that gravity is largely unaffected. There will be two extra continents. 6. We will share the planet with another species equal to our own in intelligence, and with whom we can communicate. 7. During the night when we sleep, we will be able to join in a universal dream in which all sleeping people of good will can partake, involving vast on-going dramas ranging from passionate love to intense adventure. Can you provide some more background for this world? Myles325a (talk) 02:54, 21 April 2011 (UTC) Wait, you've invented a fantasy world and now you want us to provide you with more information about it? The world is in your head. You can give it all the background information you want. The reference desks aren't really an appropriate place to try to write a crowdsourced science fiction novel. Do you have a specific factual question we can help you find answers to in Wikipedia articles? --Jayron32 02:59, 21 April 2011 (UTC) Op myles325a back live. Sigh...sigh...I DID say, above "The immediate objection to this question will be that it is not “scientific” because the properties of “amazing, astonishing…etc” are subjective descriptions. This is so, but subjective evaluations can be quantified and measured by psychometric means. We don’t need to do that here...". And so you go ahead and make exactly the same objection I had already tried to pre-empt. You very well might not agree with this pre-emption, but you could have at least acknowledged that I made it. A couple of other points. One: These questions are not just for people who can't use the Search function in WP. And two: It's not just IN my head. You are assuming that. The reality is more complicated. Myles325a (talk) 03:13, 21 April 2011 (UTC) You may be interested in Leibniz's 'Theodicy', which argues that we live in the best possible world (and hence it cannot be made 82% more wonderful). Or you may be interested in Voltaire's Candide, which was influenced by Leibniz's work, and largely ridicules this notion. SemanticMantis (talk) 03:15, 21 April 2011 (UTC) And no doubt this world has 82 percent more giant purple mushrooms.190.56.105.52 (talk) 04:01, 21 April 2011 (UTC) You realize you've basically described the movie Avatar right? Ariel. (talk) 04:09, 21 April 2011 (UTC) No ariel .I don't think Pandora had any giant air ship creatures that carried people across the seas in great comfort.190.56.105.52 (talk) 04:19, 21 April 2011 (UTC) OP myles325a back live. Thanks. You have ensured that everyone will want to see what has been censored by you, Nimur, just as surely as they will touch the wood where a sign says "wet paint". But I ask of these potential respondents. Please don't. Don't look at this question. It's just..not something you should see. I have conformed to the wishes of my betters. The question is now posed in the Humanities Board. Myles325a (talk) 05:14, 21 April 2011 (UTC)

Kindle 1 reflective scrolling — how does it work?

The first-generation Amazon Kindle has a visually fascinating way to select on-screen options. Above a scroll wheel is a long vertical grayish-white line which looks plastic or rubber. But as you turn the wheel, portions of this line suddenly become reflective, like a mirror — you can actually see (part of) yourself in it. The location of the reflective part tells you which line on the screen you'll select if you push the wheel down.

It looks like magic; even having owned this thing for a couple hours, I still can't wrap my mind around it. What exactly is it made of? How can something instantly go from "mirror" to solid gray/white? (To clarify, the line seems to respond to the computer input of the Kindle — it doesn't do anything if the Kindle is off, and larger or smaller portions of it become reflective based on the size of what is being selected.) ± Lenoxus (" *** ") 03:10, 21 April 2011 (UTC)

How is that any more "magical" than the rest of the screen where white turns into black (and shades of gray)?

I think the question is how the "mirror" works. (Normal pixels can't "mirror" -- presumably the e-ink allows for the use of reflective coloration, but I don't really know.) --Mr.98 (talk) 16:20, 21 April 2011 (UTC)

No, it's not e-ink. The "Cursor Bar" is not part of the main screen. It's a separate display next to the main screen that updates quickly like a normal LCD.

Except instead black/clear like a normal cheap LCD, the cells turn mirrored when they're on and clear when they're not on.

I have also wondered what kind of technology this is, and why they don't make digital watches with it. APL (talk) 16:51, 21 April 2011 (UTC)

[1] suggests it's as simple as an LCD with a mirror backing instead of a backlight. Nil Einne (talk) 17:06, 21 April 2011 (UTC)

That sounds plausible to me. It would make sense for a device that has no backlight — you'll need to have it in light of some sort anyway, so a mirror backing is a clever way to deal with the LCD lighting issue (like an old microscope). --Mr.98 (talk) 18:54, 21 April 2011 (UTC)

Thanks for the responses! I guess I'd never put much thought to exactly how a normal Liquid crystal display works either; it's pretty fascinating too. In reply to APL above, I would guess that a watch (or similar device, such as a calculator) which used "mirror" instead of black would be rather difficult to read. On the Kindle, you can simply tell that "stuff's there" on the LCD line; more detailed information would likely become difficult to parse, if it were mirror on gray. Although perhaps not mirror on black, come to think of it. I wonder why Amazon didn't go with that instead… ± Lenoxus (" *** ") 23:53, 21 April 2011 (UTC)

unknown herb

Hi, does anyone know the name of this herb: http://img816.imageshack.us/i/photo1jd.jpg/ 84.228.108.151 (talk) 11:24, 21 April 2011 (UTC)

Perhaps some variety of thyme? Note the the variety of thyme foliage, e.g. [2]. Aside from visual ID, you can taste / smell a few crushed leaves, and compare to any known herbs you may have in your kitchen. SemanticMantis (talk) 14:02, 21 April 2011 (UTC)

Looks more like a variety of mint to me. --ColinFine (talk) 16:13, 21 April 2011 (UTC)

Hard to tell from the picture, but mint (or something in the same family like basil or catnip) will have stems with square cross sections. That said, it looks very much like the pot of marjoram I have. (Marjoram smells something like a cross between thyme and oregano.) - Actually, following links tell me that thyme, marjoram, and oregano are also included in Lamiaceae, the mint family. Checking the pot, marjoram does indeed have a square stem cross section (only noticeable on the larger stems). -- 174.31.219.218 (talk) 16:27, 21 April 2011 (UTC)

Glow discharge creation

Whats the best way of creating a glow discharge betweem 2 parallel wires, and would it be better if one or both of the wires had a circular cross section?--92.29.203.164 (talk) 11:37, 21 April 2011 (UTC)

Besides the article you cited, see also Geissler tube and Neon sign. A glass vessel filled with low pressure gas of the appropriate sort and sufficient voltage (AC or DC) to produce ionization, with a resistor to prevent excess current when the gas starts to conduct, with airtight seal for the leads. The voltage to produce a discharge between electrodes decreases as the gas pressure is reduced down to some low pressure, below which the required voltage increases. A neon lamp presents a very high resistance until the voltage is high enough to ionize the gas. One demo was to have a high voltage battery in an RC circuit, which would gradually charge the cap until the conduction voltage was reached, at which point the neon light would flash. Do you have a vacuum pump and glassblowing equipment? I have pondered using a kitchen vacuum food preservation pump, with the plastic jars they supply, and sealing the electrodes through the lid with aquarium seal. This would not work for a long term use such as a a commercial neon sign, but might be ok for a demo or experiment. I would avoid using glass jars due to the danger of implosion and shards flying, and any high voltage has the potential to produce a dangerous shock. Old books on the subject suggest using mercury to pull a vacuum in the tube, which would be considered too dangerous for amateur experimentation now. A discharge tube under some circumstances might put out dangerous xrays, so home experimentation is not a good idea. An old reference on the subject is Townsend, "Electricity in Gases," (1915). The classic Geissler tubes used electrodes at either end of a cylinder or other shape of evacuated tube with a residue of gas. Your question was about parallel wires. We see that configuration in the common NE-2 neon lamp It ionized at about 90 volts. They can be used for lots of interesting projects. See [3] in particular.Edison (talk) 19:19, 21 April 2011 (UTC)

Oh, you're so punny... --Jayron32 19:51, 21 April 2011 (UTC)

I typed "potential" in all innocence and only on rereading noted the pun, so went ahead and bolded it. Edison (talk) 20:08, 21 April 2011 (UTC)

As for circular cross section: at least for high voltage conductors in air, a conductor with a large cross section and no sharp edges is less prone to cause ionization of the gas molecules in the air, and less corona discharge. For a gas discharge tube, the same is likely to be true. I would expect parallel small diameter wires to cause ionization of the trace gas at a lower voltage than larger radius conductors the same distance apart. A sharp edge might concentrate the current and cause more local heating if the current is larger. This is just my expectation, and I have not found a reference on it. Edison (talk) 00:20, 22 April 2011 (UTC)

Where have the "edit" buttons per section gone?

Normally there should be an "[edit]" button with each section. I don't see any any more. I have reloaded about 10 times now. What's wrong? 93.132.132.156 (talk) 21:37, 21 April 2011 (UTC)

They're right where they've always been for me. But I don't see how this is a science question... Dismas|^(talk) 21:39, 21 April 2011 (UTC)

Because I missed them here on this desk, I posed the question here. Why should this not be a science question? is computer science less a science? 93.132.132.156 (talk) 21:43, 21 April 2011 (UTC)

Normally computing questions go on the computing desk. But then again, normally questions about how Wikipedia works should go at the Help Desk. Anyway, it's possible that your CSS or something got messed up, or what Wikipedia just had a hiccup for you. If it's better now, I wouldn't worry about it. --Mr.98 (talk) 22:32, 21 April 2011 (UTC)

(ec) And now I have edit buttons. Do I have to ask a question first in order to see them? Doesn't make much sense. And I haven't altered anything with my browser or computer lately. 93.132.132.156 (talk) 21:43, 21 April 2011 (UTC)

Usually when that happens to me, I'm actually looking at a version from the page history. Those have a notice at the top that you're editing an old version, but on a long page like this you never notice. Wnt (talk) 22:34, 21 April 2011 (UTC)

At the top of the page, did you see the 'edit' tab or a 'view source' tab? If it's the later, it's been discussed before on the talk page and I've encountered it myself that for some strange reason the page appears as protected for anonymous users even though it was never (semi-)protected. Note that when reloading a page you should always try WP:BYC and probably even WP:PURGE since reloading 10 times is no use if your browser or the wikipedia servers just keep sending you the same cached content Nil Einne (talk) 23:54, 21 April 2011 (UTC)

It looks like a case for WP:PURGE. I saw 'view source' instead of 'edit' at the top. After I asked this question (instead of a null edit) it went away. Perhaps you know a workaround for yet another plague: lately some of the formulas display with an incomplete (west north) border that gives the impression of a square root. 95.112.196.91 (talk) 14:31, 22 April 2011 (UTC)

Cookie Monster ate them. Count Iblis (talk) 22:52, 21 April 2011 (UTC)

Same thing happened to me man. All the edit links are gone! When I logged in, they appeared, so this must be part of the movement to disenfranchise anonymous editors. Mac Davis (talk) 01:32, 22 April 2011 (UTC)

"Semi-protection" might do that for other pages, but the Science Refdesk isn't semi-protected, and according to the logs it hasn't been semi-protected, at least not any time this year. Wnt (talk) 06:47, 22 April 2011 (UTC)

See my comment above or check out the latest RD archive. Nil Einne (talk) 14:15, 22 April 2011 (UTC)

Digital signals in space

Analogue signals are broadcast out into space, and any aliens out there within 60 light years will be receiving them and can see/hear what we are like!:

1. would an alien civilisation be able to see/hear them in the same way as they could with the analogue signals, or would they not be able to decipher them?

I looked around for an answer but couldn't find any, so I hope someone can answer this for me!

Regards, -- PhantomSteve.alt/talk\^{[alternative account of Phantomsteve]} 23:18, 21 April 2011 (UTC)

The answer to #1 is unambiguously yes. We can't stop electomagnetic signals generated on Earth from leaving the Earth. However, this signal tends to degrade over time, due to two things: attenuation and the inverse square law which basically states that as a signal travels over space, it "spreads out" and becomes gradually weaker to the point where it becomes so weak it disappears. The answer to #2 is that we're not even sure that an alien civilisation would be able to decode our analogue signals. In the novel and film Contact, an alien civilization beams some our own TV signals back at us. There is, however, no need for them to have decoded them; they could just have reflected the signals back at us. However, given point #1 I made above, its not readily clear that any signals that have been generated at earth would even make it to the nearest star, let alone be able to be decoded... --Jayron32 23:27, 21 April 2011 (UTC)

While it's impossible to know how aliens will think, I'd bet they can make sense out of an analog TV signal. The signal, after all, consists of raster lines which are similar from one to the next, yet differ... before long, they're putting them side by side and realizing it makes an image. They might not know which color is which - yet I'd give them even credit for that, because the observant alien will see occasional rainbow icons and substances such as magma that can only come in certain colors on any planet. I would likewise give them good odds of making sense out of a digital signal because it can be worked over to produce recognizable patterns. I don't know if they'll work out the AACS key, but I wouldn't put it past them. ;) Wnt (talk) 23:52, 21 April 2011 (UTC)

Is that for when they land and take away some Blurays? AACS isn't used in broadcast television or anything but Blurays and the now defunct HD-DVDs AFAIK. Of course smarters aliens would just find it online. Nil Einne (talk) 00:01, 22 April 2011 (UTC)

They probably have a radio telescope made from a network of single-atom filaments, the size of the solar system. It zeroes in and logs every time Earthlings make a cell phone call, play a video, type anything that appears on a computer screen that isn't secured against Van Eck phreaking, or talk somewhere in the open within a hundred yards of a power line. They're supposed to be advanced - they're aliens. And how do you think they made this simulation you're enjoying now if they couldn't properly spy on EM signals? Wnt (talk) 06:53, 22 April 2011 (UTC)

That aliens would be able to figure out that analog TV signals, when arranged a certain way make images than can be "seen" assumes that aliens have vision and are able to see images like we do. Vision is not uncommon for Earthly species, but even here there are alternate ways of "seeing"--like echolocation. For all we know the first aliens to intercept Earthly TV signals live gas giants and "see" via magnetic fields or something similarly unlike human vision. Or perhaps they "see" some aspect of reality we don't even know exists and can't perceive light at all. The idea of aliens with eyes similar to ours strikes me as very unlikely. Seems they'd be as likely to know about Jesus Christ and hot dogs. Perhaps intelligent aliens capable of abstract thought might recognize TV signals as a curious pattern, and perhaps could figure out how to decode the signal into what we would call images. But it seems to me a huge assumption to think they would "see" the images in a way that made any sense, if they could "see" at all. The common stereotypical "alien" we picture is ridiculous anthropomorphic. I wouldn't be surprised if there are sentient aliens out there, but I would be very surprised if they were remotely similar to us--that we would even be able to recognize them as sentient beings at all (and vice versa). Even on our planet we have trouble recognizing sentience or lack thereof among birds, cetaceans, etc etc etc. Pfly (talk) 09:52, 22 April 2011 (UTC)

The eye has evolved almost from scratch many times on Earth. The mammalian eye, the cephalopod eye, the insect compound eye and numerous others each evolved separately (our common ancestor may have had some kind of light sensitive cells, but not a specific eye). That suggests an extremely strong and near-universal selection pressure toward vision. If so many different animals have evolved eyes on Earth, it is highly likely that any life-as-we-know-it on other planets will have eyes too. (Life-as-we-don't-know-it is a very different kettle of fish, and not one we can have any useful discussions about. We just don't have a starting point to understand how such life would work.) --Tango (talk) 13:48, 22 April 2011 (UTC)

As others have mentioned, typical early TV signals will be quite weak by now, but we have occasionally sent radio messages into space at much higher power, with the explicit intent of catching someone's attention. See e.g. the Arecibo_message. Note that in this message, as in the Voyager_Golden_Record, scientists have taken great care to encode the message in terms that are thought to be fairly universal. SemanticMantis (talk) 01:23, 22 April 2011 (UTC)

I would be very surprised if a human seeing the Arecibo message in isolation would be able to interpret it. It's just looks cool. That was the whole purpose of it. If it was actually intended to catch someone's attention, they would have made it much simpler and send it towards a nearby yellow dwarf star. Instead, they made it very complicated and sent it towards a very distant cluster. As our article says, it was just a demonstration of their cool new toy, not a real attempt at making contact with aliens. --Tango (talk) 13:48, 22 April 2011 (UTC)

But by sending it to M13, the signal arrives at all the few hundred thousand stars it is composed of. Count Iblis (talk) 14:54, 22 April 2011 (UTC)

That would be true if they had sent it to M13. They actually sent to where M13 was 25,000 years ago. They should have sent it to where M13 will be in 25,000 years time. Our articles explains this (with references to official press releases - they were perfectly open about the whole thing). --Tango (talk) 15:30, 22 April 2011 (UTC)

I see! This looks rather stupid :) . In Ref 1. where that fact is mentioned it is also clamied that the signal could still be received with similar equipment in M31. If that were to happen, ET would also get the message of just how stupid we are :) . Count Iblis (talk) 16:10, 22 April 2011 (UTC)

Yes, I agree it would be difficult for any single human to decode, and that it was a somewhat symbolic gesture (voyager record even more so). However, if the Arecibo message were given to a room of scientists that were well-educated (but ignorant of this message), I think they could decode it, given a little time and motivation. I believe decoding the Arecibo message or Voyager record would be easier than decoding a TV signal (assuming you could find the properly educated group of scientists with no prior knowledge), but this is potentially debatable. SemanticMantis (talk) 15:17, 22 April 2011 (UTC)

The issue is whether there is a single interpretation that makes more sense that any other. Figuring out the binary should be easy enough, but then why would you interpret the numbers as atomic numbers of elements rather than any number of other things? With a TV signal, there's really only one interpretation that makes sense. It may take a while to stumble across it, but once you have you'll know you've got it right. --Tango (talk) 15:30, 22 April 2011 (UTC)

Advanced civilizations will likely be machine civilizations. Now, intelligent machines can travel at the speed of light, simply by uploading themselves via electromagnetic signals to another machine. That's easy to do within one civilization, but then they can only travel to locations where they have build their machines. However, by contacting distant civilizations, they can travel to those civilizations, if these civilizations are able to download and run the code of the machines.

So, you can imagine that a civilization sends a simple message to catch the attention of other civilizations and then that message is followed by a message containing a schematic outline of a machine so that it is clear how a machine code is to be interpreted. Then the entire code of a machine is sent. This whole sequence of sending the simple message, the message containing information on how to interpret the code and then the code itself is then repeated over and over again.

Civilizations that receive this message do not send a reply, as no reply is expected. All they have to do is build a suitable machine, download the code and run it on the machine. Count Iblis (talk) 16:59, 22 April 2011 (UTC)

What do you mean by "machine"? Any lifeform is a machine, in a sense, but I don't see any reason why organic life forms can't form an advanced civilisation. The idea of mind uploading for interstellar travel isn't a new one, but trying to give instructions on how to build the receiving device to a completely alien civilisation by remote (especially without two-way communication) seems ridiculously difficult to me. --Tango (talk) 19:22, 22 April 2011 (UTC)

Consider our own future. The free market economy has a natural end point. When all human involvement in all production processes from raw materials to finished end product is fully automized, everything will be free of charge (while labor cost only form part of the costs of a product, the costs of raw materials, energy etc. are ultimately also due to labor costs.). In that end state you'll have humans living in a planned economy. Free enterprise will be outlawed, because you don't want out of control growth of machines, like in the grey goo-scenario. Humans are then more or less barred from doing anything productive. Only an elite will be in control of things. But that elite will find it more and more difficult to control things as the civilization becomes more complex.

As the machines get more complicated, the elite need ever more intelligent machines to control things, but then these intelligent machines will, at some point, be so much more intelligent than humans, that the elite won't really control anything at all. Humans will then be prisoners of the machines, much like most animals on Earth are now. Freedom is only tolerated up to a point: as soon as a wild animal interferes with our civilization (e.g. when a lion shows up in a city, claiming the teritory there, we remove the lion). Count Iblis (talk) 20:41, 22 April 2011 (UTC)

Man, CI, sad much? Maybe you need to take a day off and go walk in the sunshine? The doomsters have been around forever, but the world remains a good place. --Trovatore (talk) 06:49, 24 April 2011 (UTC)

You seem to have forgotten about the service economy. In the developed world, agriculture and industry are becoming smaller and smaller portions of the economy and more and more people work in providing services to others, not producing physical things. As some services become automated or obsolete, others become common. That's the trend that's been going on for the last 100 years and I see now reason why it won't continue. --Tango (talk) 21:09, 22 April 2011 (UTC)

You're all making great points, but isn't this straying into forum/soapbox/opinion? Are you editors any longer contributing to a cogent answer to the OP, or just musing now? Franamax (talk) 22:06, 22 April 2011 (UTC)