Wikipedia:Reference desk/Archives/Science/2012 June 25

Science desk
< June 24	<< May | June | Jul >>	June 26 >

Welcome to the Wikipedia Science Reference Desk 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 on one of the current reference desk pages.

June 25

Help needed to identify tiger breed

Could someone please identify this tiger? Any information helps! Leave a talk back template on my talk page if you leave a message though as my watch list gets flooded often. Cheers, Riley Huntley _talk No talkback needed; I'll temporarily watch here. 00:04, 25 June 2012 (UTC)

He looks like Tony in 7B? Actually, the subspecies differ in size and striping patterns so even if a definite identification were possible it might take a full body foto to do it. Eye color might be a hint. See Tiger#Subspecies μηδείς (talk) 02:27, 25 June 2012 (UTC)

Looks like a 3/4 grown Siberian to me, but remember , with zoo animals, that there has been a lot of cross breeding between races. — Preceding unsigned comment added by 124.191.176.130 (talk) 06:29, 25 June 2012 (UTC)

Thanks for the help. I do remember the zoo guide saying it is pure breed. Cheers, Riley Huntley _talk No talkback needed; I'll temporarily watch here. 20:44, 27 June 2012 (UTC)

Big Bang (not TV show) kickoff

Saw Hawking's TV show on cable the other day, where he points out that, just as time stands still inside the event horizon of a black hole because of the enormous gravitional field, so time would be stationary at the enormous density of the universe at the time of the Big Bang, thus questions such as "what was there before the Big Bang?" are meaningless. New argument to me, and fair enough. But...... if time was stationary, then by definition, how could anything "happen" to either kick off the Big Bang, or for it to spontaneously occur; or to put it another way, given that something changed, then it would be absolutely incorrect to say that time was stationary. Given that the whole thrust of his argument was to point out that the supernatural actions of a Deity are not necessary to explain the creation of the universe, and that I'm sure as heck incompetent to pick holes in his theoretical physics, there must be some loophole here.... ? Gzuckier (talk) 03:29, 25 June 2012 (UTC)

Perhaps rather than saying that time didn't exist, it might be better to say it was undefined. In a world without matter (or with one singularity containing all matter), how could the passage of time be marked ?

Also note, that, since the cause of the Big Bang is unknown, the cause of time being unknown doesn't really make it any worse than it already is. StuRat (talk) 04:59, 25 June 2012 (UTC)

Thanks for the reply. But I do think that having the cause of the BB be unknown is one thing, but having it operate within an environment such that time is stationary is quite another... Although Hawking didn't seem to think it needed comment, so I figured there must be something obvious I'm missing. Gzuckier (talk) 06:08, 25 June 2012 (UTC)

Nothing can really be properly explained before the end of the inflationary epoch. We don't know why there was cosmic inflation or why it stopped and our best job of papering over that hole is to say "different laws of physics applied back then". Really smart people might even start talking about the vacuum undergoing a phase transition to cause those differences in the laws of physics, but that doesn't make it any easier to know what the hell they were.1.124.255.232 (talk) 06:35, 25 June 2012 (UTC)

These are just my own personal thoughts, but I like to think that time exists (past tense) before the Big Bang. I don't know if anything existed or happened a billion years before the Big Bang, but if nothing did, then I would assume that prior to the Big Bang there was nothingness. That's just an assumption though. InforManiac (talk) 06:54, 25 June 2012 (UTC)

Let me add a little bit more to the comment I just posted up above. From a multiverse point of view, it especially makes it easy to think that time existed before the Big Bang. Even if the Big Bang took place 13.75 billion years ago, going back 15 billion years on a timeline, there just might not be anything happening in this particular universe. InforManiac (talk) 07:11, 25 June 2012 (UTC)

When talking about such things one has to be very careful what one means by "time." In Einsteinian physics, time is not a transcendental property that exists separate from space (see spacetime). There is no "universal time" running in the background under this model, there is no "clock of the universe." This is but one of the reasons that talking about time prior to the existence of space (much less matter and energy) is often assumed to be somewhat meaningless — no space, no time. Regardless, time is a tricky concept — it seems much more obvious than it is. --Mr.98 (talk) 16:24, 25 June 2012 (UTC)

For a long time Hawking has been pushing a no-boundary model of the early universe, where instead of there being a beginning of time, the time dimension fades smoothly into a fourth spatial dimension, and the "beginning" is just a region of four-dimensional space that's like a portion of the surface of the earth. No particular point of it is "before" any other point, and it doesn't begin anywhere, just as the surface of the earth doesn't begin anywhere. If this show really was quoting Hawking, he was probably talking about that. But saying that this is like the event horizon of a black hole makes no sense to me, because it isn't like that at all.

It's worth mentioning that Hawking is more popular with the general public than with other physicists. Most of his ideas are pretty far from the mainstream. This no-boundary idea, in particular, has never been part of standard cosmology. -- BenRG (talk) 08:06, 26 June 2012 (UTC)

Absolutely. Time in black hole and time at big bang is just for analogy, not to be taken literally. High density alone does not cause time to slow down, it is Stress-Eenergy_tensor that causes time dilation. Time began at big bang, everything before is speculation. manya (talk) 08:21, 26 June 2012 (UTC)

Thank you all. This has been most stimulating, Wikipedia at its best. Gzuckier (talk) 13:35, 27 June 2012 (UTC)

Do choanoflagellates have distinct personalities?

Do choanoflagellates have distinct personalities? It is said that they are "considered to be the closest living relatives of the animals" and that a "number of species such as those in the genus Proterospongia form simple colonies," so do any have buddies or rivals? InforManiac (talk) 03:36, 25 June 2012 (UTC)

Yes. μηδείς (talk) 04:08, 25 June 2012 (UTC)

You're joking, right ? I can't imagine such a simple organism having a complex social structure. Perhaps a simple social structure, like bees, or ants, but I don't think of them having personalities, either. StuRat (talk) 04:52, 25 June 2012 (UTC)

What does personality have to do with social structure? 1.124.255.223 (talk) 04:56, 25 June 2012 (UTC)

Well, it's part of a complex social order, where different relationships are formed with each individual in the group, and personalities determine how each individual relates to the others (some are bullies, some are friendly, etc.). Absent any social interaction, a "personality" is harder to define, although I suppose you could say "this lizard prefers to bask on the rocks while that one likes to swim". StuRat (talk) 05:03, 25 June 2012 (UTC)

Of course I was referring to simple personalities. Subtle differences. InforManiac (talk) 05:09, 25 June 2012 (UTC)

Would it be fair to say that you wanted to know if they possess individuality?

No. I just wanted to know if they have any kind of varying simple personality traits. InforManiac (talk) 05:21, 25 June 2012 (UTC)

On second thought, I guess you could call it individuality. I'm just curious about whether any two from the same colony would have differing behavior patterns. Even the slightest of differences. InforManiac (talk) 05:29, 25 June 2012 (UTC)

Well if you're going to adopt behaviorism for this question, which is wise, then (my guess is) sure, they would definitely display consistent differences in behavior, due to both genetic and environmental reasons. The genetic part is kind of the basic assumption of evolution, after all. Gzuckier (talk) 06:14, 25 June 2012 (UTC)

Thank you. I've been wondering about this for quite some time. InforManiac (talk) 06:18, 25 June 2012 (UTC)

Resolved

Thank you for answering my question. InforManiac (talk) 04:18, 25 June 2012 (UTC)

Actually, if you are talking about members of the same colony, they will be clones. Individuals derived from different zygotes will potentially show genetic variation resulting in behavioral differences. μηδείς (talk) 17:22, 26 June 2012 (UTC)

While clones are more similar in behavior, they are not guaranteed to be identical. Identical human twins, despite the name, do not always exhibit identical behavior. This is presumably due to slight differences in environment. In the coral example, different temperature or salinity of the water, different amounts of sunlight, and different food and predators on each side of the coral could change their behavior patterns. StuRat (talk) 17:30, 26 June 2012 (UTC)

I never really thought of this aspect before. Are all choanoflagellates clones? Are all colonies consisting of clones descending from an original choanoflagellate, or was there sexual reproduction somewhere along the line to create zygotes? InforManiac (talk) 20:08, 26 June 2012 (UTC)

I am finding all of this to be very interesting and informative. Thank you, everybody, for all of your input. InforManiac (talk) 19:12, 26 June 2012 (UTC)

I'll keep checking back from time to time to see what else has been written here. This is all very good. InforManiac (talk) 19:20, 26 June 2012 (UTC)

Any updates on Lake Vostok search for life?

I'm sure scientists have had a chance to put some of the water samples from Lake Vostok under a microscope. Has there been any news about if they've found any life in those samples? I haven't been able to find any good updates about it. InforManiac (talk) 04:09, 25 June 2012 (UTC)

From the article you linked to in your question, "Samples of the freshly frozen water in the ice well are expected to be collected at the end of 2012 when the new Antarctic summer starts." 1.124.255.223 (talk) 04:43, 25 June 2012 (UTC)

Thank you for bringing that to my attention. For some reason, I must not have seen that sentence. I'm kind of surprised that they didn't get at least a little bit of fresh water when they first reached liquid water. I thought I read before that they did gather some, but I am probably mistaken. I will be waiting anxiously for 2012's end to find out. InforManiac (talk) 05:00, 25 June 2012 (UTC)

The water only remains liquid when it's under pressure. Removing the drill allows the pressure to drop and it freezes. By the time they could get something down there to get a sample it would be ice. They'll be back to collect that ice later this year. 1.124.255.232 (talk) 05:34, 25 June 2012 (UTC)

That makes sense. Thanks for the info. InforManiac (talk) 05:40, 25 June 2012 (UTC)

Have they figured out how to prevent contamination of the lake with outside organisms ? StuRat (talk) 04:49, 25 June 2012 (UTC)

"According to the head of Russian Antarctic Expeditions, Valery Lukin, new equipment was developed by researchers at the St. Petersburg Nuclear Physics Institute that would ensure the lake remains uncontaminated upon intrusion. Lukin has repeatedly reassured other signatory nations to the Antarctic Treaty System that the drilling will not affect the lake, arguing that on breakthrough, water will rush up the borehole, freeze, and seal..." 1.124.255.223 (talk) 04:51, 25 June 2012 (UTC)

"rush up the borehole, freeze, and seal".. Is that one of those "eats shoots and leaves" things? Gzuckier (talk) 06:17, 25 June 2012 (UTC)

They'll need to be very careful about what they find under the Ice. μηδείς (talk) 17:19, 26 June 2012 (UTC)

Plant identification requested

I would like some help in identifying two plants growing in my suburban garden in south London. Both of them (as far as I can remember) were planted last year on the basis of being annual bedding plants, but both seem to have survived the winter and are currently flourishing. See http://www.flickr.com/photos/19482747@N00/7439490128/ and http://www.flickr.com/photos/19482747@N00/7439489884. My records of what I planted last year don't seem to give much of a clue. One plant has pretty pink flowers about 1 cm across. The other doesn't have any flowers at present (I think there were some flowers at some time last year) but has green leaves edged with white about 1 to 2 cm across. It overgrew the other plants in its bed last year, seems to send out shoots that root, and is trailing along underneath a wall. Both photos were taken today. Any help welcome! --rossb (talk) 11:53, 25 June 2012 (UTC)

The first one looks to me like a Diascia cultivar. Compare the image here. Deor (talk) 12:17, 25 June 2012 (UTC)

I think the first one is a Mimulus and the second one is a Plectranthus. --TammyMoet (talk) 12:19, 25 June 2012 (UTC)

Agree first is Diascia possibly a cultivar called Sunshine. (or maybe not). Second is Plectranthus, possibly "amboinicus variegata", so-called varigated Cuban Oregano. Richard Avery (talk) 15:07, 25 June 2012 (UTC)

No, the first photo shows identical plants to the photo shown in the Mimulus article to which I linked. --TammyMoet (talk) 18:28, 25 June 2012 (UTC)

Sorry, but I disagree, Tammy. The OP's flowers don't look at all like Mimulus to me. I'm also dubious about the Plectranthus identification; that genus seems to have rhomboid-to-ovate leaves with pinnate venation, whereas the OP's plants clearly have palmate venation and are more cordate/reniform in shape. Deor (talk) 22:49, 25 June 2012 (UTC)

OK I'll give you the Diascia, but I still think the photo in the Mimulus article is remarkably similar. Plectranthus is quite diverse and as our article on it says, a reassignment of certain plants to and from that genus has taken place recently - certainly after I last bought a plant sold as Plectranthus, which I still have and looks just like the OP's picture! --TammyMoet (talk) 09:33, 26 June 2012 (UTC)

Is it theoretically possible to make an artificial sweetener that tastes exactly like sugar?

Topic says it all. ScienceApe (talk) 16:02, 25 June 2012 (UTC)

I recall reading something in high school about measurement of sweetness. While I think that the same value of sweetness may be artificially obtained, making all the other parameters of taste equal to that of sugar might be difficult. Different reaction rates, different solubilities etc. might lead to a difference in overall taste. I'm just shooting in the air over here; might be worth to wait for a more qualified answer. Lynch7 16:16, 25 June 2012 (UTC)

Well, not all. Let's make this a slightly more scientifically refined question: Is it theoretically possible to develop a compound which the human tongue finds indistinguishable with sucrose yet the human body does not metabolize in a way that results in significant food energy OR is so potent that metabolically insignificant amounts are necessary to replicate the flavor of sucrose? (Most artificial sweeteners are far more sweet than sugar; the entire game is to make something that is highly sweet for the amount of calories it conveys, so you only need tiny, tiny amounts to get an equivalent sweetness to sugar.) I don't know nearly enough about how the tongue distinguishes between very similar molecules, though, to say for sure, assuming you are ignoring the difficulty of fabricating arbitrary molecules in useful quantities. --Mr.98 (talk) 16:18, 25 June 2012 (UTC)

I don't see why it wouldn't be theoretically possible. I doubt if we have perfect detection of sugar. Such a substance would have to exploit whatever imprecision exists for sugar detection. It would have to elicit the same response that sugar does. Bus stop (talk) 16:22, 25 June 2012 (UTC)

Left-handed sugar. --TammyMoet (talk) 18:26, 25 June 2012 (UTC)

Good point, Mr 98; aren't artificial sweeteners just other kinds of sugars that the body can't break down? Nyttend (talk) 18:26, 25 June 2012 (UTC)

Some of them seem to be, but others are just much sweeter than sugar and thus less of them are necessary. The articles we have on the specific ones are not always clear to me as to which they are (or whether it's a mixture of both). --Mr.98 (talk) 19:13, 25 June 2012 (UTC)

How about ambidexterous sugar, that way you avoid suffering from diarrhea when consuming large amounts of laeft handed sugar? Plasmic Physics (talk) 03:14, 29 June 2012 (UTC)

Note that even if you had such a perfect sugar substitute (tastes exactly like sugar, but has zero calories and side effects), this still might not help anyone on a diet. Current artificial sweeteners don't seem to help, because your body expects to be fed when you taste sugar, and if it isn't, it kicks your hunger into overdrive until it gets what it expected. This would still happen with even a perfect sugar substitute, unless it has an appetite suppressant built-in, too. StuRat (talk) 19:21, 25 June 2012 (UTC)

If I have this straight, the distinctive taste of cane sugar comes from the impurities that remain in it after refinement. It's basically the taste of molasses, but greatly attenuated. I suppose in principle you could duplicate that taste by removing the sucrose from molasses and adding a little bit of what remains to an artificial sweetener. Sucrose per se, as far as I know, does not have a distinctive taste. Looie496 (talk) 04:19, 26 June 2012 (UTC)

That doesn't sound right to me. I don't believe molasses remains in any detectable quantity in cane sugar. We can, of course, taste sucrose itself. With artificial sweeteners we also taste whatever else comes with them. (And they also make me feel lousy after.) StuRat (talk) 04:28, 26 June 2012 (UTC)

Yeah no, that's not right. Commercially available cane sugar is very very pure. I did an industrial visit as part of my undergrad degree at a sugar refinery's quality control lab in Bundaberg, and the sugar crystalls have basically no inclusions. 112.215.36.172 (talk) 00:23, 27 June 2012 (UTC)

Agreed. The white color indicates that no significant quantity of the black molasses remains. StuRat (talk) 00:28, 27 June 2012 (UTC)

@op...did you look at sugar substitute?Smallman12q (talk) 20:22, 28 June 2012 (UTC)

water cooled centrifugal chiller delta pressure across dooler/condenser

dear all, with reference to the above mentioned subject, i request you to clarify my question.

in the design data sheet of chiller, the pressure drop or pressure difference across cooler and condenser is provided by manufacturer, this press.drop is to be maintained for chiller accurate performance or this is the pressure drop to be considered for calculating pressure head for pumps across chiller (chilled water/condenser pumps).

for chiller performance is delta p important of flow to be maintained is important? please advise. regards, wikichilleraaminah — Preceding unsigned comment added by Wikichilleraaminah (talk • contribs) 19:56, 25 June 2012 (UTC)

To the last question, Yes delta p is important. See our artcle Chiller for many other things that are important. Without seeing your application and data sheet, asking the manufacturer is probably your best source of information. DriveByWire (talk) 21:51, 25 June 2012 (UTC)

HEMOLYSIS IN BLOOD SPECIMEN

I WORK IN A ER,IN A HOSPITAL.THE QUESTION I AM ASKING,CAN A COMPREHENSIVE PANEL BLOOD TEST HAVE HEMOLYSIS IN 3 OF 21 TEST ON A REGULAR BASIS — Preceding unsigned comment added by 206.205.82.3 (talk) 21:40, 25 June 2012 (UTC)

Go and ask your boss. We don't give medical advice. SmartSE (talk) 21:55, 25 June 2012 (UTC)

I work in an ER also, and there's no way easy answer here. I'm guessing you're not happy with your laboratory making you re-draw labs for being hemolysed. There's no way of knowing how frequent it will be, as there are too many variables. Likely A) whoever is drawing the blood did it incorrectly, B) the vials were compromised after draw, or C) there was a failure in the lab which ruined the specimen. This article from 2002 is the closest I could find to a proper study. — The Hand That Feeds You:^Bite 20:55, 26 June 2012 (UTC)

Telescopes one and two - new or used? what resolution?

The National Reconnaissance Office recently gave NASA two telescopes that it doesn't need that are apparently "better than Hubble". This NYT article makes it sound as if they were previously in space, rather than being kit that was never used. If that's the case, how could they have got them down? Secondly, they have 7.9 m mirrors - is it possible to guesstimate what kind of resolution would be achieved by having that point down at Earth? SmartSE (talk) 22:02, 25 June 2012 (UTC)

To me, the NYT article doesn't make it sound at all as though the telescopes were previously in space. It calls them "spare, unused 'hardware'" and "'bits and pieces' in various stages of assembly". Sounds to me like stuff that was intended to be sent into space but wasn't because of redundancy, because the spooks developed even better technology, or for some other reason. Deor (talk) 22:36, 25 June 2012 (UTC)

It says 7.9 FEET, not metres! 7.9 foot is 2.4 metres. Vespine (talk) 22:40, 25 June 2012 (UTC)

Which is the same as the Hubble. The Hubble Space telescope is supposed to be diffraction limited, which gives it a resolution of about 0.05 arcseconds for visible light (see the graph on the first linked article, which includes a line for the Hubble). Pointing at earth from an orbit of, say, 300 km, this limit corresponds to about 7 cm. The telescope also has to see through the Earth's atmosphere, so in practice, the true resolution is probably somewhat less than the diffraction-limited resolution (but probably on the same order of magnitude - good enough to see a person, but not to read the classified documents that he's carrying). Buddy431 (talk) 23:28, 25 June 2012 (UTC)

These "stubby hubbles" are either unused KH-11 Kennan or unused prototypes of its abortive replacement, Future Imagery Architecture. It's long been suspected that Hubble and KH-11 where very similar airframes - both were integrated by Lockheed Martin and shipped from their Sunnyvale, CA plant in very similar containers. These two ex-NRO birds are indeed physically broadly similar to Hubble, with the same primary mirror size. The KH-11 article does the same maths that Buddy431 did, and comes to much the same answer ("6 inches") neglecting the distortion from the atmosphere. If you're curious what this might tell you about capabilities of the current NRO, probably not too much. Very little is publicly known about Misty or Misty-2, and both appear to be shrouded (literally and figuratively) to conceal their position and characteristics. The Hubble's 2.4m mirror is a big piece of glass, but Delta IV can have a payload fairing of 5m, which would allow for a single-glass mirror of maybe 4.3m. Beyond that they'd have to do something like the James Webb Space Telescope and have a segmented mirror which they unfurl on orbit (which wouldn't be that surprising an achievement). -- Finlay McWalterჷTalk 00:12, 26 June 2012 (UTC)

If it's so stubby then maybe the field of view is wider and they gave it more megapixels to compensate, due to a lower focal ratio. Sagittarian Milky Way (talk) 19:09, 27 June 2012 (UTC)

As Deor notes, these devices weren't ever in orbit. Had they been, it is (at least in theory) possible for them to be retrieved from orbit by the STS (doing this to fix Hubble was one idea toyed with). Indeed, the technical synergies between Kennan and Hubble signpost the deeper influence the NROs spacecraft had on the shuttle design itself. The final shuttle design was larger and heavier than NASA needed, but they had to work with the USAF to afford the thing, and USAF had to launch NRO's systems. So the shuttle is big enough to launch a Kennan (but turned out to be too heavy to put one in a polar orbit, to the NRO's chagrin) and its predecessor, KH-9 Hexagon. I don't think it's publicly acknowledged who built the primary optics for KH-11, but for KH-9 it was PerkinElmer, who also built Hubble's big mirror. So Hubble was built by the same people who built spy satellites, and designed to launch (and maybe be fixed or retrieved by) an STS designed to do the same for spy satellites; so conversely it's not a big surprise that an unneeded spy satellite might make for the foundation of a decent Hubble. This article in The Space Review has some interesting stuff about the influence of NRO on the shuttle, and their fears and unhappiness regarding it. -- Finlay McWalterჷTalk 00:52, 26 June 2012 (UTC)

Would the Hubble mirror have been ground the same way as the other mirrors? Bubba73 ^{You talkin' to me?} 01:27, 26 June 2012 (UTC)

Very possibly by the same people on the same machine, but I don't think to the same curvature. Hubble's flaw (which they did detect, but discounted) was bad setup, bad QA, and bad procedure - they didn't just forget and put a spy satellite mirror in an astronomical instrument. -- Finlay McWalterჷTalk 01:39, 26 June 2012 (UTC)

That is exactly what I was wondering! At the time of the Hubble error, they said that the mirror was precisely made but to the wrong specifications. I knew that it must be very similar to those used in spy satellites, so I got to wondering if perhaps the spy satellite mirrors are ground one way to focus a few hundred miles away whereas the Hubble mirror was supposed to be ground to focus at infinity. Bubba73 ^{You talkin' to me?} 06:02, 26 June 2012 (UTC)

I'd just be speculating if I said anything about optical spy satellite optics beyond "big mirrors good". But note that the orbits of some of the KH-11s are (relatively) eccentric (e.g. perigee 408 km apogee 931 km), and at these relatively low altitudes their orbits will decay and have to be reboosted (like that of the ISS). And the Earth is very far from spherical; for something in a highly inclined orbit the oblateness of the Earth is the biggest factor that varies actual altitude). So they have to work with a range of altitudes between the instrument and its target, not a perfect fixed distance. -- Finlay McWalterჷTalk 10:49, 26 June 2012 (UTC)

And PerkinElmer's wasn't the only Hubble mirror made, just the only wrong one. NASA got Eastman Kodak (themselves no stranger to overhead reconnaissance optics) to build a spare. Of this backup the Allen Report (linked above) says "The backup OTA primary mirror was polished at Eastman Kodak Company using both a refractive and a reflective null corrector of a completely different design from the Perkin-Elmer version. This mirror matched the templates of the two null correctors to better than 0.014-wave rms wavefront error at 632.8 nm, and the Board has every reason to believe it is the correct hyperboloidal shape." p4-6 -- Finlay McWalterჷTalk 11:04, 26 June 2012 (UTC)

Hard contact lenses vs soft lenses

Hello signori i cognoscenti :) I have heard that hard contact lenses are generally recommended for higher presciptions and soft lenses are generally prescribed for lesser prescriptions, all other things equal. Now considering only minus prescriptions (i.e., to correct myopia), approximately what is the general lowest (or cutoff, or border, etc.) prescription for which hard lenses would be prescribed over soft (not taking into account other factors such as general eye health, age, sensitivity, etc. though an optometrist normally would)? Thank you. 152.97.171.80 (talk) 22:16, 25 June 2012 (UTC)

Here's an article on them, but there isn't a specific cut-off point: [1]. StuRat (talk) 22:23, 25 June 2012 (UTC)

Wikipedia has the article Contact lens. For individual attention which strangers on the Internet cannot give, ask a qualified optometrist. DriveByWire (talk) 22:28, 25 June 2012 (UTC)

If it helps, I've had soft contacts for a -6.2 prescription. I have no idea how much further past that they go. I think they're continually improving them. 209.131.76.183 (talk) 12:14, 26 June 2012 (UTC)

How to improve chandelier efficiency ?

I have a lighting fixture with 12 candelabra base incandescent "flame tip" clear 25 watt bulbs, at present. That's 300 watts total, at 110-120V. It's on a dimmer switch. It puts out a small quantity of rather yellow light and a great deal of heat with those 300 watts. I don't want to replace the entire fixture, and would like to be able to continue to use the dimmer. I was considering getting 12 candelabra base to medium base converters, and then putting in 40 watt equivalent CFL bulbs (which actually use around 9 watts each). However, most CFLs don't work well with dimmers. Those that are "dimmable" apparently only dim 10-25%. This site warns that you can't use regular CFLs and just always keep the dimmer on maximum: [2].

1) Why is that ?

2) How else can I improve efficiency ?

3) Is the situation any better with LEDs ? StuRat (talk) 22:51, 25 June 2012 (UTC)

Some LED lamps can be dimmed, and those that are will dim over the full range. But LEDs are still expensive, so 12 of the will cost quite a bit (my brief browsing of Amazon suggests $80 ish). -- Finlay McWalterჷTalk 01:12, 26 June 2012 (UTC)

Is that $80 for one (which is terrible) or $80 for 12 (which is great) ? StuRat (talk) 06:46, 26 June 2012 (UTC)

I found some for around $10 each, which are 40 watt equivalent and dimmable, and I could just do 6 instead of 12 (that would give me 240 watts equivalent instead of 300). However, these use a medium base, so I'd also need the converter from the candelabra base for each. Also, these bases are pointing upwards, and LEDs are like spotlights, so they would light up the ceiling, leaving the dining room table beneath it in shadows. So far, this seems to be the best option for saving electricity, though. StuRat (talk) 04:04, 26 June 2012 (UTC)

Good advice from Finlay, and you're right about dimming CFLs being dicey. As for "how else" I'll add that I rent a few of these fixtures, 4-8 bulbs x 25-40 watt (what a crappy design :-/). I have taken to only filling ~1/2 of the slots with incandescent bulbs, and that usually meets my lighting needs. It has low initial investment, and saves considerable power. Maybe worth investing in the LEDs if you're in it for a longer haul. SemanticMantis (talk) 02:06, 26 June 2012 (UTC)

That's exactly what I've done as an interim solution. However, 150 watts of dull yellow light and heat still isn't very acceptable. StuRat (talk) 04:07, 26 June 2012 (UTC)

Related question: do empty sockets use 0 watts? SemanticMantis (talk) 02:06, 26 June 2012 (UTC)

To a very good approximation, yes. I think if you are really particular, the socket is a very bad capacitor, so for AC, some very little current will go in- and out of it, which results in some loss to resistance. But this would not be measurable without very good instruments. --Stephan Schulz (talk) 10:35, 26 June 2012 (UTC)

You could also replace the incandescents with quartz halogen globes. At least in this country (Australia) they are available in a wide range of bases, wattages, and some different shapes. There are dimmable and give a good white light. Unfortunately they are only about 25% more efficient than standard incandescents, and cost is quite high. Ratbone58.170.176.182 (talk) 02:10, 26 June 2012 (UTC)

Halogen bulbs with increased efficiency over regular incandescents have started to become available in the U.S. as incandescents are being phased out. I'm not sure if they are available in a 40 W candelabra base bulb, though.--Srleffler (talk) 04:04, 28 June 2012 (UTC)

What if I do replace the chandelier ?

I'd still like to be able to get a variable amount of light out of it, but dimmer switches seem to require expensive LED lights. So, do they make chandeliers where you have switches that can turn each bulb on and off individually, and each has a medium base, so I can use cheap CFLs ? StuRat (talk) 18:56, 26 June 2012 (UTC)

well, without thinking it all the way through; home depot and (i assume) elsewhere have ceiling fan remote controls which are actually little wireless transmitter/receivers, where the receiver end mounts under the appliance baseplate and has a single AC circuit in, but two different AC circuits out (for fan and for light). the fan output has 3 remote selectable settings plus off, the light is continuously dimmable; my thinking is that the fan side could certainly be used for half your individual bulbs and the light side for the other half. they have different kinds of remotes; the slick one has a universal tv remote built in (but died within the year; apparently that's not unusual, and isn't in the store any more), the other kind is the same size/shape as a wall switch and is intended to replace it in the wall, but is acutally self contained and runs off a 9 volt battery so i just use it as a regular remote that i carry around and lose under the couch, etc.

but also; do they really make candelabra base to regular base adapters? i would think there might be a wattage overload safety issue?Gzuckier (talk) 20:27, 26 June 2012 (UTC)

Yes they do. Here's the cheapest one I found: [3] (better ones are made of ceramic). And yes, if you put a 100 watt incandescent in there, you might well have a problem. However, as I intend to use CFLs, and a 100 watt equivalent CFL is only 23 watts, that's under the 25 watts of the current incandescent bulbs, so should be fine, and give me way more light. (I'd probably only use 40 watt equivalent CFLs, which use 9 watts, so I can save energy and get more light/less heat).StuRat (talk) 20:34, 26 June 2012 (UTC)

ok, experimental data: happened to pass by the local job lot store which was selling "U Lighting America" brand (i.e. cheap brand i never heard of made in china 2 for $6) dimmable 23 watt mini cfls (not very mini, about regular bulb size, spiral cfls) so i got a pack and replaced one of the 40 watt incandescents in the ceiling fan attached to the aforementioned remote fan/light dimmer to see how much dimming can a dimmable fluorescent dim (if a dimmable flourescent can dimly flouroesce). Three observations; 1) at full blast the 23 watt cfl is a heck of a lot brighter than a 40 watt incandescent, as expected, 2) at lowest level the cfl is maybe slightly less bright than the 40 watt incandescents at full brightness, I'd say closer to 25% bright than 75% bright, and 3) what i didn't expect, at lowest level with the cfl in one of the 4 bulb sockets, the other 3 incandescents wouldn't go down all the way anymore, i.e. whatever impedance/reactance thing prevents the cfl from going all the way down to zero also works on incandescents in parallel. But my takehome is that maybe you should give a set of dimmable cfls a try. If you want really really bright light i imagine a dozen 23 watters oughta do it, if your concern is more just a reasonable amount of light and dimmable to a reasonably low level but not 0 then smaller cfls. Gzuckier (talk) 00:43, 27 June 2012 (UTC)

The safe limits of operation of a fixture do not depend just on the electrical power consumed. A fixture that is rated for a 40 W maximum incandescent may well fail if used with a 23 W CFL. The reason is that an incandescent bulb dissipates a lot of the energy it consumes as infrared radiation. A CFL or LED dissipates almost all of its waste energy by heat conduction through the base of the bulb and convection carrying heat away from the surface. The 23 W CFL may dump more heat into the fixture than the 40 W incandescent.--Srleffler (talk) 04:10, 28 June 2012 (UTC)

•  Comment: In a perfect world all of our lighting would be fibreoptic from one source. The streetlights outside your house would be cheapest. Someone should invent a chandelier that is 6-20 fibreoptic strands to each light point and run them all from one LED that is on a dimmer. I think the cheap dimmers now still don't increase efficiency. They just dissipate the unused power in heat. CFLs are still a problem with all the mercury, 1-5mg per lamp. Workers in China are getting poisoned in the lamp factories from it. You also may be able to replace the sockets themselves to the larger size and save the cost of adaptors.--Canoe1967 (talk) 22:57, 26 June 2012 (UTC)
  • the solid state dimmers are (i assume) still based on the triac tech that we used to homebrew such things with 50 years ago when they were cutting edge technology, and they actually do not dissipate the excess in heat; they are basically switches that are adjustable for what portion of the AC cycle they conduct. As with any kind of switching circuit, they are highly efficient because when they are on, the voltage across them is very low, and when they are off, the current through them is very low, so the total power, as I*E, across them is always very low except during the very short periods each cycle while they are in the actual process of turning on or off. Gzuckier (talk) 00:43, 27 June 2012 (UTC)

• OK, I was scared off of dimmable CFLs by that statement that they only dim 10-25%, but if you say you tested them and they are decent, I'll give them a try. StuRat (talk) 04:19, 27 June 2012 (UTC)

UPDATE: I found some dimmable, 25 watt equivalent (5 watt actual) CFLs that fit in a candelabra base, eliminating the need for an adapter to change it to a medium base. They dim about as Gzuckier described in his test, and have a "torpedo" shaped clear bulb around the spiral (you can still see inside). The light is whiter than the incandescent's yellow light, which is good. However, at $7 per bulb they are a bit pricey, so I've decided to only get 6 (if they were 100 watt equivalents, I probably could have gotten by with 2). I will use the 6 CFLs in summer, when the heat is a big negative, and switch back to incandescents in winter, when the heat is appreciated. StuRat (talk) 04:33, 30 June 2012 (UTC)