Wikipedia:Reference desk/Archives/Science/2007 June 9

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[edit] June 9

[edit] Magnesium ribbon

Why should a magnesium ribbon cleaned with sandpaper before burning it in air ?

The effect of a sandpaper scouring would be to strip off the thin surface layer of Magnesium oxide that forms when magnesium is exposed to oxygen. I'm not positive of the reason you'd want to do so; one possibility is that the magnesium ribbon may be harder to ignite with the protective G"
I know from experience that it's harder to light. I couldn't light a strip of it with a normal lighter and had to pull fggesfzgfb out my cigar torch to light it. Yea yea, I was in high school once too. --Wirbelwindヴィルヴェルヴィント (talk) 04:26, 9 June 2007 (UTC)
When you burn it, the entire piece of metal becomes magnesium oxide, so it makes no difference for your health. —Keenan Pepper 23:12, 9 June 2007 (UTC)
Agreed, the reason to strip off the oxidized Mg is that it won't burn. Think of a log that is charred on the outside, you might want to remove the charred portion to get the wood underneath to burn. StuRat 15:23, 11 June 2007 (UTC)

[edit] What gull is it?

I looked around, but I need help finding the name of this gull. ( I can't get the picture into this question, but it is called: SpottedGrayGulloftheCaliforniaCoast.jgp. Go to the recent uploads, and it was uploaded around 3:44 UTC) Thanks!

nd2010 04:01, 9 June 2007 (UTC)

Or I can link it for you... --Wirbelwindヴィルヴェルヴィント (talk) 04:24, 9 June 2007 (UTC)

the gull is quite dangerous if it is right clse to u and you do not move it can somimes do a bad thing to you like hit you or stratch you

A juvenile version of some gull? This should belong to the seagull desk though :p. Where's Kurt when he's needed... --antilivedT | C | G 08:34, 9 June 2007 (UTC)
I honestly couldn't tell you for certain, sorry. I'm terrible at identifying juvenile gulls - they're all much of a muchness to me. If the photo was taken in England, I'd probably say that it was a 3 year old Herring Gull. --Kurt Shaped Box 10:48, 9 June 2007 (UTC)

This is probably a first-year Ring-billed Gull. Note the pink bill with the black tip, the pinkish legs, and the scaly pattern on the wing coverts. It could conceivably be a second-year Herring Gull, but Ring-bills are much commoner in California. --134.186.103.3 17:53, 9 June 2007 (UTC)

I thought it was a sea-gull, but then again, I could be wrong... ;) Spawn Man 05:29, 12 June 2007 (UTC)

In common parlance it is a "sea-gull", but for birders and ornithologists and other such pedants, it is a "gull" without the "sea". Ogden Nash had something to say on this subject: "Hark to the whimper of the sea-gull;/He weeps because he's not and ea-gull./Suppose you were, you silly sea-gull./Could you explain it to your she-gull?" --63.201.4.254 15:49, 12 June 2007 (UTC)

[edit] study of electron microscope

what is an elctron microscope? what is it made of? what does it work on? how does it work? what are its disadvantages? what are its advantages? who invented it? diagram of elecrton microscope? types of electron microscope?

May I sugest you read our article on Electron microscope's before you ask questions here? It seems like a preety good article at a glance. -Ĭ₠ŴΣĐĝё 07:10, 9 June 2007 (UTC)

[edit] Spider identification?

I'm observing an unusual spider walk around on the office walls. It seems to be sometimes walking on all 8 legs, and sometimes only using its hind 6 legs to walk, keeping its two front legs in the air almost as antennae. It has two things that hang down from its head or mouth, the ends of which seem darker and fuzzier. It has a slightly reddish colour, especially the legs. Its body is kind of in the shape of a mosquito.

I wish I could identify it.--Sonjaaa 10:42, 9 June 2007 (UTC)

could be a jumping spider (family Salticidae): they wave their front walking legs in the air sometimes. That usually means that there is another spider on the wall somewhere. You can tell them by a large pair of eyes looking forward, and by the way they move ( walk - jump - walk ). Jumping spiders are harmless, and very smart (for a spider, that is). They use silk threads as safety when they jump, but they don't make nets for catching prey. Let us know if the description fits. The "things that hang down" are pedipalps. If they are thicker at the end it's a boy, if not it's a girl. Cheers, Dr_Dima.

[edit] Patient Zero

How does finding a Patient Zero help when trying to fight a disease? Is it simply because by finding the index case you can track back the progression and help stop further outbreaks? Or is there something special about Patient Zero such as (as is sometimes alluded to in TV and movies) that Patient Zero maybe an asymptomatic carrier? If so why? Caffm8 13:29, 9 June 2007 (UTC)

Some of your surmises are correct: a tried and true method of stopping outbreaks of some condtions like STDs is simply painstakingly tracking down all contacts to offer treatment. There are other reasons. There is a Patient Zero only in relatively new diseases or outbreaks, when there are often questions about mode of transmission or even the nature of the illness. Finding out what happened to Patient Zero might tell you what will eventually happen to other people in earlier stages. It is rare for there to be something unusual about Patient Zero, but it might happen. For most infections, there are asymptomatic carriers by two mechanisms: (1) individual variations in susceptibility, or (2) a fairly long asymptomatic but contagious stage but the patient gets ill. alteripse 14:26, 9 June 2007 (UTC)

It also might help to find the non-human source of a disease. For example, AIDS is thought to have come from a non-human primates in Africa. Those primates can then be studied to see how they cope with the disease. StuRat 15:17, 11 June 2007 (UTC)

[edit] Genetic Linkage

Is this a mistake? http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=hmg.box.1391 This book/website says that for family A, there are five recombinants and one nonrecombinant, but I think it's the other way around. You can click where it says 'Figure 11.4' in the title, to see the diagram. Thanks --83.84.74.28 14:10, 9 June 2007 (UTC)

That looks correct. Recombination in general is likely. 12.127.48.250 05:38, 10 June 2007 (UTC) mrdeath
But for diagram B, where you don't know that A1 was inherited with the disease, it says "If she inherited A1 with the disease, there are five nonrecombinants and one recombinant." If we look at diagram A, we can see that she (II-1) did inherit A1 with the disease - surely this page contradicts itself? --83.84.74.28 14:43, 10 June 2007 (UTC)
I think you are right, that there five nonrecombinants and one recombinant in family A, and that the main text contains a typographic error about this. --169.230.94.28 07:50, 11 June 2007 (UTC)

[edit] hiiiiiii

where the status of scientific research in Germany and is Anwanao can email correspondence by —The preceding unsigned comment was added by 81.10.71.28 (talk • contribs).

An article which may provide some information on science in Germany is Science and technology in Germany. There are also pages which can be found through google, such as [1] and [2] which also discuss German funding of and advances in science. I may be misunderstanding you question, so feel free to clarify if need be. Thanks, --TeaDrinker 15:38, 9 June 2007 (UTC)

[edit] Is there any way to change the color of you're eyes if a person is Indian?

I know there is contacts but I was wondering if there is anyways, some Indian people have blue/green eyes, but how do they get it?

Isn't brown eyes tthe dominant trait?

Is there any point in time all indians had a eye color other than brown? —Preceding unsigned comment added by 68.210.35.208 (talk • contribs)


You should search the Reference Desk archives for any of the many times someone (you, perhaps?) has asked this question before. --TotoBaggins 18:27, 9 June 2007 (UTC)

[edit] Altering DNA

Will we ever be able to alter DNA?

To combat diseases, reverse symptoms like Down Syndrome, change features such as race, I.Q., ETC. —Preceding unsigned comment added by 68.210.35.208 (talk • contribs)

See gene therapy. Rockpocket 19:16, 9 June 2007 (UTC)
Also, as the gene therapy article states, it is mostly used for somatic cells. Germline engineering with Human artificial chromosomes for instance would be much more powerful, as it would potentially effect every cell in the body, and controversial. --Rajah 18:25, 11 June 2007 (UTC)
It depends on your definition of race. And for a lot of things people might want to change, introducing proteins/hormines into the right place would have the same effect. -Anonymous
It also depends on your definition of "alter." If you mean, change the DNA sequences OR add new DNA which, "combat[s] diseases" etc., then yes, we will be able to do that. Because we have already done it. From the gene therapy article: "Scientists at the National Institutes of Health (Bethesda, Maryland) have successfully treated metastatic melanoma in two patients using killer T cells genetically retargeted to attack the cancer cells. This study constitutes the first demonstration that gene therapy can be effective in treating cancer. The study results have been published in Science (October 2006)." Furthermore, Antisense therapy has resulted in a drug as well: Fomivirsen.--Rajah 21:26, 11 June 2007 (UTC)
Also, Down Syndrome isn't a "symptom" per se, but rather a trisomy (extra copy) of a chromosome. Fixing that would be harder. --Rajah 21:26, 11 June 2007 (UTC)
The main point I want to make is that what the questioner is getting at is most possible with what Lee Silver terms Reprogenetics and the editing of the germiline. Designer babies etc. Changing features such as skin color, neuronal plasticity, fast twitch muscle fibers etc. will probably be easiest when starting with zygotes or embryos in a petri dish, not with fully formed humans of 100 trillion somatic cells. --Rajah 21:26, 11 June 2007 (UTC)

[edit] Indian/white people/

How are Indians and Caucasians in the same race?

Is caucasian just applying to Norther India?


Can you tell me about the genetic similarities,differences, physical features, etc.

Thanks, sorry for annoying you with all these questions —Preceding unsigned comment added by 68.210.35.208 (talk • contribs)

It is readily apparent that you have not read the article Caucasian race. If you had read the article (even the first paragraph), you would not be asking such a question. --Kainaw (talk) 20:07, 9 June 2007 (UTC)
Or asking such questions, anyhow. — Rickyrab | Talk 20:30, 9 June 2007 (UTC)

So is it applying to just northern india or whole of india?

You may be interested in the article Australoid, which has old maps trying to outline the old-fashioned concept of "Caucasoids" (Caucasians) and "Australoids" (Aussie aboriginals and residents of some parts of India), as well as "Negroids" (black-skinned Africans) and "Mongoloids" (many Chinese, Japanese, Mongols, Vietnamese, etc.) The typology is outdated among anthropologists, though. — Rickyrab | Talk 02:37, 10 June 2007 (UTC)
Unfortunately, at the resolution of that map, you can't read the key. Does anyone have a better image ? StuRat 15:04, 11 June 2007 (UTC)

Also note that "races" tend to blend heavily, so there are no areas with 100% one race. StuRat 15:04, 11 June 2007 (UTC)

[edit] Noncompetitive Research Funding

I'd like to find a good way of funding my research non-competitively. The problem is that fellowships and other competitive sources generally either do not exist for my specialty or are awarding fellowships to people in more technical areas then mine (such as engineering new paving surfaces, etc.). (I am doing a Ph.D. dissertation on the equity of park-and-rides, and need a few thousand bucks for fuel, survey, etc., and other expenses.) — Rickyrab | Talk 19:09, 9 June 2007 (UTC)

I am in the United States, and am doing work on my home county of Middlesex, in New Jersey. — Rickyrab | Talk 19:14, 9 June 2007 (UTC)
I assume by "non-competitive" you mean that you do not want to go through the grant-writing rigmarole? Cannot blame you, but I do not know offhand of anyone doling out money without at least a (often lengthy) proposal. The obvious place to check is with your uni for in-house funding under the old 'this study will bring prestige to the institution, pretty-please fund me' rubric, but your advisor probably knows all about that. If you have not played around already on the NSF FastLane database, it is probably worth a look - your dissertation may not be overly technical, but they cover social sciences too. I have no experience with it myself, but the Department of Housing and Urban Development might be more up your alley. Personally, I am a big fan of the Carnegie Institute, and the MacArthur Foundation is also good. Here is a lengthy list of grant resources, and that site also has writing advice. You can also slog through the literature to see who gives everyone else their monies. Best of luck. Eldereft 08:36, 11 June 2007 (UTC)

You might also want to try to get the money from the county government or major cities. You would sell it by customizing the report for their jurisdiction. Since they likely subsidize the Park and Ride program, it's not unreasonable to think that they would also pay for a study of the program's equity. Approach the council members (or selectmen or whatever they are called there) individually, until you find one willing to propose it to the full council. StuRat 14:53, 11 June 2007 (UTC)

[edit] Why is the placement of our internal organs asymmetrical?

For example: Why is the heart in the left side? And Why is the liver in the right side? Any explanations in terms of evolutionary advantages? (If anyone is familiar, what are some aspects in the developmental biology that are responsible?) Any kind of answer is appreciated 128.163.171.68 20:02, 9 June 2007 (UTC)

See our evolutionary developmental biology article. The basic model for all vertebrates begins as a linear chain of segments that undergo differentiation by expression of some genes and repression or delay of others into the different sections of the body from head to tail. At an early stage there are a couple of "tubes" that run the length of the body (remember we are still talking mm at this stage) that become the gastrointestinal tract and the heart and great vessels. If you want even more details, read any of Sean Carroll's popular books. He is a scientist to keep an eye on. alteripse 21:38, 9 June 2007 (UTC)

(edit conflict) Interestingly, species become more asymmetrical as they evolve or develop (see V. Geodakyan's paper Asymmetrization of Organisms, Brain and Body). For example, humans start life as an egg, a near perfect sphere; they then become a gastrula with radial symmetry, then a simple embryo with bilateral symmetry, and then, when organs develop, an asymmetrical baby. This process allows more differentiation to occur within the body, hence reducing wasted body space. For example, the heart is biased toward the left side of the body (it isn't actually in the left hand side, but one of the ventricles extends a long way into the left side of the chest) because this side of the heart deals with the strenuous job of pumping blood around the body, while the right only has to send the blood to the lungs (a much shorter journey). As a result, the left side evolved very thick, muscular walls, while those of the right are much thinner. Asymmetry in one organ also causes a chain reaction, forcing asymmetry in others: the right lung is much bigger than the left because the extra-large left ventricle squashes the lung. The liver meanwhile is asymmetric because it is divided into several lobes which do different tasks. Some of these tasks are more important than others, and so evolution favours larger versions of these lobes. As the most important ones will be most strongly favoured, different bits of the liver evolved at different rates, leading to an asymmetric organ. This in turn forced other organs to be pushed around within the body. For a fuller answer, see Symmetry (biology). (As a interesting footnote, Geodakyan proposed that the most advanced species is the least symmetrical one: the humble sea sponge...) Laïka 21:52, 9 June 2007 (UTC)
I'm not sure that least symmetrical = most advanced. Human beings have 2 external plains of symmetry; Most trees have none. 12.127.48.250 05:33, 10 June 2007 (UTC) mrdeath

[edit] Information Transfer

How is information encoded into electromagnetic waves, and then read and translated in another area? Imaninjapiratetalk to me 21:51, 9 June 2007 (UTC)

Well, "information" is a pretty broad topic, to put it mildly. One way that it's encoded in one place and read and translated in another is when nuclear fusion in the Sun causes a photon to bounce around for a few million years, and then one day be emitted from the surface of the sun and travel as a wave of visible light for eight minutes, and then whack into a chemical in the eye of some creature on Earth, causing an electrical signal to travel to its brain which causes a cascade of other electrical signals which tell it that the Earth has revolved enough to move that critter's own portion out of the rest of the Earth's shadow, which means it's time to wake up and get on with the day's activities. If it's a very clever critter, perhaps some of those activities will include new ways of getting the physical world to measure up to the ideals of information theory. But more likely, it will just look for food and sex. --TotoBaggins 23:02, 9 June 2007 (UTC)
Haha, nice answer, and thanks, although it was not what I was looking for. I should have been more clear in my question. What I meant to say was how do we put information in an electromagnetic wave (such as a song into a radio signal) and then how is that information read and translated by us (such as our radio receiving and then playing a song). Imaninjapiratetalk to me 23:46, 9 June 2007 (UTC)
Try frequency modulation (FM) and amplitude modulation (AM) for starters. Very briefly, the info is encoded (for radio anyway) by varying the frequency or amplitude of the waves. It then gets decoded by the radio set. (That occurs in the free time left after all the activity Totobaggins described.) Clarityfiend 03:37, 10 June 2007 (UTC)
AM and FM are examples of analogue technologies. Information can also be transmitted digitally - see digital television, digital radio and Digital Audio Broadcasting. Gandalf61 10:00, 10 June 2007 (UTC)
Speaking of digital, there is of course also Morse code. It's probably one of the simplest examples of how to transfer information with an electromagnetic wave, since it simply consists of patterns of wave on and wave off. —Bromskloss 12:13, 10 June 2007 (UTC)
Here's a simpler encoding: display one powerful elecromagnetic wave emitter if the enemy is making a land-based sortie, or two emitters if their approach is via the ocean. :) --TotoBaggins 14:43, 10 June 2007 (UTC)


Morse sent wireless telegraphic signals by induction and earth conduction. Nathan Stubblefield just spoke into a telephone microphone hooked in series with a battery and a coil of wire. His voice was sent out at audio frequency as electromagnetic waves, and could be picked up by a similar coil hundreds of feet away hooked to a telephone earpiece. Thomas Edison and others sent electromagnetic audio frequency telegraph signals to and from moving trains (the "grasshopper" telegraph). Alexander Graham Bell sent voice messages considerable distance via amplitude modulated light waves. All before and without electronics per se, in the 19th century. The History of radioshows that in the early 20th century Reginald Fessenden sent amplitude modulated the radio frequency transmission from a high speed spinning electrical generator and sent voice messages. Much easier with 20th and 21st century techniques. Edison 20:08, 10 June 2007 (UTC)
In addition to encoding information in changes in the amplitude or frequency of a carrier wave, there is also phase modulation. And quite a few techniques that are new to me at just modulation. --Eldereft 08:48, 11 June 2007 (UTC)

[edit] Chemistry bewilderment

Yes, in chemistry class last week my class made soap using sodium hydroxide,vinegar, veg. oil, salt, distilled water, NaCl and tools to heat it all up. It all went according but I have been having major trouble trying to find information on FUNCTIONAL GROUPS of GLYCEROL, STEARIC ACID, and VINEGAR. And I also need help finding 1 molecule of Glycerol + three molecules of stearic acid react to form ---> one mole of ester and ?? I am unable to find a site that will let me input a chemical reaction and tell me what it makes....... and lastly the vinegar we used was to rinse excess NaOH off the soap however I need to draw a structural formular of the ACTIVE INGREDIENT in vinegar- If i could get this information on Functional groups, active ingredients and what 1 molecule of Glycerol(OHCH2CH(OH)CH2OH) + 3molecules of stearic acid (3CH3(CH2)16COOH I checked esters and I think (R1-c(=O)OR2 is the one produced, i will continue checking for the information online (as I know this will not be answered for some time)

anyhow thanks for any help —Preceding unsigned comment added by 74.98.58.4 (talk • contribs)

This information should all be in your textbook. You do have a textbook, don't you? There's no such thing as "a site that will let [you] input a chemical reaction and tell [you] what it makes", because sometimes it's not easy to predict what will happen. Sometimes you mix two chemicals and nothing happens; sometimes a complicated mixture of many products is formed. In this case, however, it's pretty straightforward. Keep in mind that water is a very stable molecule, so its formation is a driving force for many reacions. See Saponification for more information. —Keenan Pepper 23:20, 9 June 2007 (UTC)
Have you read our articles on glycerol, stearic acid, and vinegar? You should be able to find structures for these molecules from there, and identify the functional groups. TenOfAllTrades(talk) 00:43, 10 June 2007 (UTC)
The first thing to do is to learn what a functional group even means. It's not complicated - it's just a structure of a few atoms arranged in some consistent way. Our article concisely summarises: "specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction(s) regardless of the size of the molecule it is a part of." Nimur 19:57, 10 June 2007 (UTC)

<sniff> <sniff> This smells like homework. --Tbeatty 21:15, 10 June 2007 (UTC)

[edit] Seasonal Distribution of Precipitation

Hello. Why do continental climates have a summer maximum precipitation and maritime climates have a winter maximum precipitation? Thanks. --Mayfare 22:13, 9 June 2007 (UTC)

For maratime climates, water gets sucked up into clouds over sea and rains when it blows onto land. Hotter seasons mean more water can be held in the cloud (cf water cycle). Continental climates - sorry, I don't know: try looking up continentality in your text book (Wikipedia's article is quite poor) --h2g2bob (talk) 01:25, 10 June 2007 (UTC)
The page Continental climate says precipitation occurs mostly in the summer. My understanding is that few climates have more precipitation in the winter than in the summer, with the notable exception of Mediterranean climate and some regions of Oceanic climate (aka "marine west coast climate"), like the Pacific Northwest's coast. The Köppen climate classification system uses seasonal precipitation patterns as part of its climate definitions. That page has a lot of info on climates and precipitation patterns, although the text is pretty dense in places. Pfly 02:33, 10 June 2007 (UTC)

[edit] Go back in time?

After reading the time article, can we ever go back in time? —The preceding unsigned comment was added by 68.210.35.208 (talk • contribs) 23:25, 9 June 2007 (UTC)

If you could do it before reading the time article, I see no reason you can't do it after. But I suppose that depends on the details of the mechanism you're using to go back in time, about which I am ignorant. --Trovatore 23:32, 9 June 2007 (UTC)
Well, some cartoon characters seem to be suspended in the air until they look down and realize the depth below them (see cartoon physics). Also, in The Hitchhiker's Guide, Arthur (and others) can fly by forgetting to fall down. Perhaps reading the Time article can make one realize that you normally travel forwards in time, and that has a similar affect to going back in time. I'm only guessing though. – b_jonas 23:45, 9 June 2007 (UTC)
You may want to read the article on time travel in the Usenet Physics FAQ. – b_jonas 23:45, 9 June 2007 (UTC)
See also time travel --h2g2bob (talk) 01:12, 10 June 2007 (UTC)
The most basic answer to the question is "no" for now and perhaps "yes" in the future. It boils down to the lack of time travelers in our current past. If nobody in the future can travel into our past, why should we expect to be able to do so? However, there may be an event (such as a new invention) in the future that allows time travel into the past up to that point - which is currently in our future. So, until then, the answer is "no". Then, you get the people who argue that perhaps it is possible for some sort of time-cops to perform elaborate cover-ups whenever someone does travel into our past. I suppose they believe that governments will suddenly get better in the future even though they've changed very little in the last 5,000 or so years. --Kainaw (talk) 01:18, 10 June 2007 (UTC)
Wow, that's an interesting solution to the "lack of visitors from the future" problem. So we should be able to construct a kind of savegame if we discover that we all live in some kind of simulation? :) --V. Szabolcs 10:00, 10 June 2007 (UTC)
The 'butterfly effect' means that the idea of 'time cops' who go back in time and fix up problems caused by irresponsible time travellers simply isn't going to work. It's also clear that any of the proposed/hypothetical mechanisms for time travel (involving difficult stuff like wormholes, black holes, etc) don't allow you to travel further into the past than the day you first got the time machine working. That neatly explains why we don't see any time travellers. Of course you can imagine the scene if someone ever did get such a thing working - you'd turn it on, expecting to step off into the future - only to find your lab fill up with tourists, suitcases, etc travelling from the future. The impact on local economy would be spectacular! SteveBaker 14:33, 10 June 2007 (UTC)
I don't see why you couldn't go back in time before the time machine was invented.. there's no relationship whatsoever between someone sketching schematics of the first time machine and the actual physics of time. And I might point out that there's an awful lot of unexplained phenomena that could be future time travellers! (ball lighting and st elmo's fire in the 19th century, UFOs in the 20th, and umm dark matter? in the 21st) --frotht 17:14, 10 June 2007 (UTC)
The St. Elmo's fire is not at all unexplained. And about the "up to that point" idea, it was not about someone sketching schematics, but about creating something (wormhole, save point, whatever). The grandfather paradox and the lack of visitors from the future are very strong arguments against time travel. Unless our model of the known universe is entirely wrong... --V. Szabolcs 18:43, 10 June 2007 (UTC)
There is also the rarely mentioned paradox of inventing the time machine. Say that I invent it and show it to a friend. He will use it to travel back to before I invented it and say that he invented it. Then, someone will use it to travel to a time before he invented it to claim that they invented it. This will continue because in a world of over 6 billion people, there will always be at least one person willing to travel back to a time before the time machine is invented just so they can claim the invention. Because this continuation does not end, someone will eventually travel to a time earlier than today and claim that they invented the time machine. That has not happened - so such a machine must not exist. Of course, it does not limit a two-way device that lets you travel from a future device to a past device. Of course, someone has to invent and turn on the past device first. Then, nobody will be able to travel further into the past than the point in time when the past device is first turned on. --Kainaw (talk) 18:54, 10 June 2007 (UTC)
Unless you don't show it to your friend, or he doesn't copy it, or his friend doesn't copy it, ad infinitum. There might be a minefield of paradoxes, but who knows, maybe it's navigable. IIRC in Rainbow Earth, if you did something to screw up the past then several hours after you return (the "change wave" took awhile to propogate through time) you'd die and it wouldn't make any sort of paradox. The grandfather paradox doesn't seem very convincing- I guess you'd kill your grandfather and soon (immediately?) after drop dead yourself. Doesn't prevent you from going back and killing him since you're in your own little timeline --frotht 13:42, 11 June 2007 (UTC)
You appear to be missing the point of the paradoxes. For example, in the grandfather paradox, it is not an issue of "can you kill him quickly even if it means you will die too?". It is an issue of "if you kill your grandfather before he has sex with your grandmother and conceives your mother or father - how were you ever born?" You must have both a mother and father to exist (we aren't discussing Jesus here). If you ensure that either your mother or father do not exist by killing your grandfather, then how do you exist? It is not an issue about dropping dead after you kill him.
As for the "showing it to your friend" - that is only one part of it. If "we" are to be able to travel back in time, then "we" must have access to some device to allow us to travel back in time. Therefore, the inventor must make it available to us. As soon as it becomes available, someone will travel back to before it was invented and claim the invention for themselves. Then, someone will travel back before that time and claim the invention. Then, someone will travel back before that time and claim the invention - until it was invented so long in our past that the people of that time simply don't have the mental capacity to operate it.
On to the butterfly effect - that is merely an assumption that small things change other small things which in turn change other small things until large things are changed. For example, I purchased one of the monster-sized packs of diapers for my baby. I put them next to the changing table. My wife was changing him. She turned around to get a wipe and when she turned back, he pushed himself off the table and onto the big pack of diapers. He was not injured in any way because the fall was short and the pack acted as a large pad. What if I didn't place them by the changing table? He would have fallen further and onto a hardwood floor. What if the store didn't have diapers in stock because: there was a sale and they sold out, or there was a defect and they were recalled, or the manager forgot to order them, or the truck delivering them was in an accident... What if I simply didn't go to the store because: I blew my money earlier on a PS3, or I wanted to get home for some show, or there was an accident and I didn't want to wait in traffic... There were so many little things that resulted in the fact that those diapers were there when he fell that any one of them could be changed and the result would have been terrible. --Kainaw (talk) 18:45, 11 June 2007 (UTC)
I understand the premise of the grandfather paradox but it assumes a single continuous timeline. If I go back in time and kill my grandfather then uh oh I guess future Froth is screwed but too bad for him. Good thing I'm not in the future, I'm right here in the present. If I were to return to my previous timeline then I be in trouble, but there doesn't have to be a future froth to go back in time if i'm right here, now. That's the way it works in that book anyway. --frotht 23:53, 11 June 2007 (UTC)

I can go back in time in my dreams. It's true! - 210.49.223.249 08:00, 10 June 2007 (UTC)

I once left my paycheck on the shelf in a phone booth. Then, when I was eating lunch, when I realized what I had done. Fortunately, I went back in time, and it was still there. No one had found it yet. Is that what you meant? Edison 19:58, 10 June 2007 (UTC)