Wikipedia:Reference desk/Archives/Science/2006 August 26

< August 25	Science desk archive	August 27 >

Humanities Science Mathematics Computing/IT Language Miscellaneous Archives

The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions at one of the pages linked to above.

Jamming the shutter button

I have a Canon Powershot A620 camera. I want to use its continuous shooting function (which requires me to always have the shutter button depressed) for longer than I'm willing to stay with the camera. How do I jam the shutter button in the depressed position? (Of course, I need to be able to restore the button back to normal!) --Bowlhover 06:54, 26 August 2006 (UTC)

Would sellotape work? smurrayinchester^{(User), (Talk)} 08:24, 26 August 2006 (UTC)

Blutack Gaffer Tape Ohanian 08:29, 26 August 2006 (UTC)

Judging by the photo on steve's digicams the shutter release doesn't stick out, so you could put a little ball of something (paper?) between the button and the gaffer tape. Don't use duct tape that leaves a sticky mess. Or use a rubber band. Maybe wedging a bit of wood in the side of the button would work, but that might damage it. DirkvdM 09:39, 26 August 2006 (UTC)

I did that once with my A70; I think I used a small piece of styrofoam and some masking tape. Just about any combination of a small object and tape should work, although some will obviously work better than others. If you have no adhesive tape, or just don't want to risk having adhesive residue on your camera, you could tie a strip of cloth around it instead. Or cut or tear a strip from a plastic bag and use that. Or a rubber band, as DirkvdM suggests above, though you'd need to stretch it pretty taut to make it hold the button all the way down. —Ilmari Karonen (talk) 01:30, 27 August 2006 (UTC)

Thanks! I used surgical tape and a piece of very thin cardboard. It works! --Bowlhover 04:01, 27 August 2006 (UTC)

A C-clamp with some cloth between to avoid damage HighInBC 03:58, 28 August 2006 (UTC)

about new energy source

is this possible to transform the energy of friction of shoes to our usable energy source to charge mobile or like that any other —Preceding unsigned comment added by 202.56.224.18 (talk • contribs)

If you buy a Rolex walking will wind your watch. pschemp | talk 08:47, 26 August 2006 (UTC)

Not friction, which only eats up energy, but yes, the walking motion should yield enough harvestable energy to charge your mobile phone. I'd be amazed if someone doesn't have a patent on this already. --Lambiam^Talk 08:51, 26 August 2006 (UTC)

In theory, the heat differential produced by friction could allow for the generation of small amounts of electricity. However, it's also impractical with current technology. There are other ways to derive electricity from walking, however, as mentioned above. StuRat 09:05, 26 August 2006 (UTC)

I remember reading a while ago about some device that could be somehow incorporated into your pants legs, so that when you walked, a small electrical current was generated - possibly by inducing an electrical current (one leg) with a moving magnetic field (other leg). My memory's a bit scratchy on the details. BenC7 10:43, 26 August 2006 (UTC)

Using friction/forward motion would have an effect somewhat like those old dynamo-generator bicycle lights - as soon as the circuit is loaded, the work that needs to be done increases. So any tapping of energy from forward motion would increase the required effort. But what about gravity? Every time one pushes down on the soles of one's shoes, to elevate oneself in preparation for the drop forward, we work against gravity, and when the foot lands on the ground afterwards, energy is transmitted throught the feet to the ground again. That amount of work is related simply to our mass (and velocity, OK), not to what happens to the force between the soles of our feet and the ground or whatever we walking on. Or is it? If we tapped that energy, would it mean more work for the walker, or would he just be "walking more lightly"? Would a device that converts compression to electrical current work without increasing energy expenditure? At the extreme, would it be like walking on dry soft sand? --Seejyb 11:19, 26 August 2006 (UTC)

• I recal reading about something like that a few years ago, it used a memory metal, coiled in the heal of a boot, and was supposed to be able to store enough energy to run hand held electronics, and they were even suggesting that soldiers could wear them in combat boots, and they could power all of their equipment. But again, nothing to do with friction--71.247.243.173 12:19, 26 August 2006 (UTC)

Friction isnt energy. Therefore cannot be converted into other energy. Philc _T^E_C^I 12:39, 26 August 2006 (UTC)

• The heat produced by friction can be converted into other forms of energy, much as the heat produced from the Sun can be converted into other forms of energy. However, friction isn't a "source" of energy, but rather a way of converting energy from one form (kinetic energy) into another (heat). StuRat 19:47, 26 August 2006 (UTC)

• As Robert Heinlein said,"There Ain't No Such Thing As A Free Lunch (TANSTAAFL). " Many clever persons have come up with ideas for creating "new energy sources" via such methods as installing generators in shoes to produce electricity by pressing down on piezoelectric material in the shoe sole, or some such. One inventor proposed having the sidewalk or stair treads be metal plates which were pressed down when someone stepped on them, spinning a generator. Others proposed hooking generators to turnstyles and revolving doors. Certainly any such device could produce electricity surely as by spinning a crank on a generator, but additional power out would require additional power in, and the effort of walking would increase. If one wanted to burn 400 calories per hour walking instead of 300 to lose weight or improve fitness, the additional effort would not a problem. I saw a jogger who was punping iron with handweights as he ran, and I have spent quality time jogging on a treadmill, so why not produce electricity but extra effort? But one would find walking while generating electricity more tiring than walking in conventional shoes, whether it is friction or vertical motion. The unstated premise of these proposals is that somehow the electricity would be produced without extra effort, which I do not believe. Edison 15:46, 26 August 2006 (UTC)

To generalize that answer, if you want to increase the energy output of a system, you must increase the input. Therefore, nullifying the point of increasing the output in most cases. Philc _T^E_C^I 17:25, 26 August 2006 (UTC)

For normal walking, the increment in energy expenditure per kg of extra load is about 3 W, the same as the power consumption of an operating cell phone. If the energy-harvesting apparatus is highly efficient, the burden on the walking person is about the same as for carrying an extra kg (about 2 lbs). --Lambiam^Talk 18:38, 26 August 2006 (UTC)

Your idea is sound, and there are some good prototypes already working. This site says: SRI International of the US, for example, has developed a resin voltage conversion film, and used it in a prototype pair of shoes which generates electricity while walking. When the sole contacts the ground, pressure is applied to the voltage-conversion film in the heel. In the prototype, the film was mounted in a volume about 6cm in diameter and 2.5cm tall, and generated between 1 and 1.5W from normal walking. A source at SRI International explained that film material and shoe sole design could be altered to boost generation to about 5W. The Applied Physics Labs at Johns Hopkins seem to be keen on marketing something too. There is work on a pain-relieving TENS machine which not only uses your gait to adjust the stimulation, but also to charge itself. --Seejyb 23:37, 26 August 2006 (UTC)

Optical effect

I've noticed something in the last few years: If my field of vision is dominated by one colour (say, blue) for a period of time and then if it stops being so dominated, I (temporarily) see everything with a tint that's around the opposite of the original colour; the strength depends on how long the domination went on for. What is this called, and is it something normal or should I have my eyes examined? CameoAppearance 11:39, 26 August 2006 (UTC)

Sounds normal to me. Please check out Afterimage. Bunthorne 14:01, 26 August 2006 (UTC)

Neural adaptation? EdC 15:03, 26 August 2006 (UTC)

Shortest lifespan

Hi!
I was just wondering what is the shortest known life span of an animal (and by that I'm including insects)? --Fir0002 12:42, 26 August 2006 (UTC)

Mayfly? --Shantavira 15:29, 26 August 2006 (UTC)

I think that's correct: only 1 day. – ClockworkSoul 15:34, 26 August 2006 (UTC)

The adults may only live for a day or two, but the nymphs and eggs are around for ages. Since they are still alive, they are still included in the lifespan. I have no idea to the answer of this question, and I doubt anybody does. --liquidGhoul 15:38, 26 August 2006 (UTC)

The best guess from my knowledge would be Caenorhabditis elegans, which has a life span of 2-3 weeks, or a relative. Insects have such a complex life-cycle. They have to undergo a few molts or metamorphosis, and this takes up a lot of time. Also, they tend to live in environments which vary due to seasons. They therefore have to fit their lifecycles into a year. Whether this be achieved by living for a year, or laying an egg which lives for almost a year. The best guesses are simple animals which live in a constant environment. --liquidGhoul 15:46, 26 August 2006 (UTC)

Of course, in the case of mayflies, the above response only begs that extremely controversial question we've all had on our minds for so long about mayflies and ethics: When does life begin for a mayfly? At conception? When the egg is laid? When the egg hatches? If a mayfly is killed in its fetal state, (i.e. after the egg is laid but before it hatches,) does that constitute insecticide? A very difficult ethical dilemma indeed. Loomis 15:56, 26 August 2006 (UTC)

Wait, I thought that insecticide was the stuff you used to kill insects, unless that is also what you use to commit insecticide. Does that mean that the general term for chemical weapon agents should actually be homocide? – ClockworkSoul 16:17, 26 August 2006 (UTC)

Only if the agent is being used to kill a being of the same type and the same sex as the killer. JackofOz 04:07, 28 August 2006 (UTC)

The parasitic nematode Strongyloides ratti (or at least the females) has an average lifespan of about 3 days. (Michael P. Gardner, David Gems, Mark E. Viney. 2004. Aging in a very short-lived nematode. Experimental Gerontology 39:1267–1276.)  --Lambiam^Talk 18:58, 26 August 2006 (UTC)

Note that many single-celled plants and animals which reproduce by mitosis (splitting in two) are excluded from this question, because they don't have a defined "life span", for two reasons:

1) Since both "daughter cells" are identical to the parent (except in cases of mutation), reproduction doesn't appear to constitute death of the parent. Thus, one could argue that the age of any individual is the age of the entire species, or perhaps strain, of such single-celled organisms.

2) Simple one-celled plants and animals (and some multi-celled, as well) don't appear to have a programmed death age, unlike more complex organisms, like us.

What you could compare, I suppose, is the average time from mitosis to mitosis, and call that a "life span". StuRat 19:37, 26 August 2006 (UTC)

The vaporization temperature of Salvinorin A at sea level

I am trying to find the temperature that Salvinorin A vaporises so that it can be inhaled. The article has the melting point, but not the boiling point. --Crazy Wolf 18:53, 26 August 2006 (UTC)

• If the melting point is 240°C (464°F), then the vaporizaion point would be considerably higher. Unless you want to cause some serious damage to your lungs, I would most definitely not recommend inhaling vaporized Salvinorin A. – ClockworkSoul 18:36, 26 August 2006 (UTC)

When using a vaporizer, you are not inhaling pure hot gas. You simply have to vaporize the chemical so that it can seperate from the plant matter and then it will be cooled by the air and form a mist that you inhale. For comparison, the end of a cigarette burns at about 1,000 degreens farenheit, and salvinorin A can be safely inhaled by smoking the plant. So it must vaporize at a temperature lower than the burning temperature of the salvia plant. So my question still stands --Crazy Wolf 18:53, 26 August 2006 (UTC)

Hmm, I found a source stating that the temperature is around 300 C, and that others have had success vaporizing it. But it wasn't a particularly reputable sourec. If anyone sees anything reputable, I'd appreaciate them dropping a link. --Crazy Wolf 19:00, 26 August 2006 (UTC)

I see where this is going. Take a look at vaporizer and/or the Erowid Salvia Vault. A word of advice, however: although this plant isn't currently regulated, its effects can be potentially dangerous. Please, use common sense and be careful. – ClockworkSoul 19:02, 26 August 2006 (UTC)

I will. Thanks for the concern. --Crazy Wolf 19:12, 26 August 2006 (UTC)

Daniel Siebert at www.sagewisdom.org suggests in his FAQ vaporizing at 275 C. I believe he's one of the experts in the field of Salvia Divinorum research. He is one of the few people who has been capable of reproducing salvia plants from seeds and collects genetically diverse strains (the majority of plants around are actually clones).

Removing packing tape adhesive

How can I remove packing tape adhesive from a piece of furniture that I don't want adhesive on? The tape has been ripped off, but it is still really sticky. I want this in science, not misc, becuase this is actually a chemistry question! — [Mac Davis] (talk) (Desk|Help me improve)

Propanone is sometimes very effective - nail varnish remover. --G N Frykman 20:14, 26 August 2006 (UTC)

You can try other solvents such as isopropanol (rubbing alcohol); but you might want to avoid solvents altogether. Both Isopropanol and propanone (acetone) can potentially remove the furniture's finish, damaging the surface. Try a mild soap-and-water solution. You can also use petroleum jelly such as vaseline or other lotions (try to avoid colored or fragrance-filled ones). Then, rub the surface vigorously until the sticky adhesive is removed. Finally, wipe off with a cloth. Nimur 00:59, 27 August 2006 (UTC)

I second the petroleum jelly approach. Solvents don't always work well, or hurt the surface. I find plain vegetable oil works well on most adhesives - apply with paper towel, rub adhesive to dissolve. After you're done, you can clean up the oil with soap & water or a little rubbing alcohol (isopropanol). -- 22:35, 29 August 2006 (UTC)

Try using an eraser. Anchoress 04:06, 27 August 2006 (UTC)

This was asked a little while ago and the answer I gave there was that I found two things to work. One is turpentine, but that might damage the furniture. I suppose that whichever solvent is used in the glue will work best. Another is using (the same?) sticky tape - put it on and pull it off again, several times. That should remove at least part of it. Not a chemistry solution, this last one. Sorry. :) DirkvdM 10:20, 27 August 2006 (UTC)

In my experience, the second technique, i.e. using the same type of tape and repeatedly putting it on remnants of adhesive and ripping it off, works very well. --71.123.61.112 15:12, 27 August 2006 (UTC)

Limonene spray removes all sticky adhesives and smells better than turps or whatever. Eh-Steve 18:27, 27 August 2006 (UTC)

Right, lemon juice also has a tendency to clean thing. Whatever you try, try it on some spot that is out of sight first, to check if it doesn't damage the furniture. DirkvdM 08:40, 28 August 2006 (UTC)

I once had a similar chore, and borrowed a series of solvents from a chemist and an artist. What is desired is to soften the adhesive without removing the finish. TEST ON A SMALL INCONSPICUOUS AREA! Neither Wikipedia nor we will be liable for any damage to readers, their pets, children or neighbors or their furniture for ill effects of solvents. Use safety glasses, chemical-proof gloves, plenty of ventilation, keep away from flames, etc etc don't be stupid in your experiments. The furniture finish might be lacquer if it is fine furniture(dissolves easily in many solvents). It might be shellac (dissolves in alcohol and many other solvents)if it is old cheap furniture. It might be polyurethane if newer and for informal use. Polyurethane is very resistant to many solvents. If you are lucky, the finish will be polyurethane. Lacquer thinner might selectively remove adhesive from polyurethane. Mineral spirits is an old standby for cleaning varnished furniture. Edison 15:13, 28 August 2006 (UTC)