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

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November 21

Methods to measure change

Can someone suggest a method or two one might be able to use to measure the amount of change on an object? Any help would be great! 174.93.63.116 (talk) 02:02, 21 November 2011 (UTC)

Easy enough -- take the change off the object, sort the coins by denomination and count them. Or did you mean something else besides change (like charge)? 67.169.177.176 (talk) 02:51, 21 November 2011 (UTC)

I think the appropriate instrument is probably a typometer - which was of course named after the well-known astronomical misprint Typo Brahe ;-) AndyTheGrump (talk) 04:11, 21 November 2011 (UTC)

Make a measurement before, and a measurement after the change. Then you can take the difference or the ratio of the two readings. If you want to measure charge, you could put the object in a hollow conducting sphere, measure the voltage and divide by the capacitance of the sphere, which can be calculated by its size. Alternatively you could discharge the charge though an integrating ammeter and get a readout. Graeme Bartlett (talk) 05:58, 21 November 2011 (UTC)

(Edited to add: If you intended to type "charge" rather than "change, then) "An Electrometer would be the obvious instrument, unless you are supposed to conjure up some improvised method. Otherwise you might measure the attraction to a charged or uncharged object hanging from an insulating thread and use basic physics to calculate the force from the angular displacement, then the charge from the force. Possibly you could transfer the charge to a capacitor of known capacitance, ten measure the charge on the capacitor with a high impedance voltmeter. A simple formula then tells you the charge on the capacitor. Edison (talk) 20:10, 21 November 2011 (UTC)

Braeme and Edison assume the OP meant to write charge instead of change in both the question and its title. However if the intended meaning was change in mass then a different answer is needed. Cuddlyable3 (talk) 00:29, 22 November 2011 (UTC)

True, but the hint was the preposition. Mass is seldom described as "on". Dbfirs 07:39, 22 November 2011 (UTC)

Marburg virus

I just read the hot zone book. This virus seem to be around for almost half a century now. It's very lethal and i wonder if we have found a cure for it yet?Trongphu (talk) 05:24, 21 November 2011 (UTC)

Marburg virus disease#Treatment says there is no current effective therapy. Clarityfiend (talk) 05:55, 21 November 2011 (UTC)

Man i feel like we, humans, kind of get left behind in medicine. There are some lethal diseases that have been known for ages and we haven't figure out how to cure it and where they come from. Lucky that those diseases didn't spread worldwide, otherwise there is possible that most of the people in this entire world get wipe out.Trongphu (talk) 03:06, 22 November 2011 (UTC)

Actually, that article should be updated: there's an experimental vaccine that can be used as a treatment if used in time: [1] Acroterion (talk) 03:53, 22 November 2011 (UTC)

... in monkeys. So you're still outa luck. Clarityfiend (talk) 04:26, 22 November 2011 (UTC)

True, in monkeys, but it's a matter of time before it's used in humans, assuming the treatment is found to be non-toxic to humans (and most people would run the risk, I suspect, if the alternative was developing Marburg symptoms). Acroterion (talk) 04:59, 22 November 2011 (UTC)

It's hard to get a vaccine certified for use in humans when no humans catch the disease naturally and your ethics prohibit exposing a few to it in the name of science. Alas, this was not the case for Marburg in Angola as of the 2004-2005 outbreak; the prototype vaccine was taken along by researchers in case of needle-stick injury. ("Of 86 needle-stick involving Ebola or Marburg virus and medical staff, there have been no survivors" !!!) But before such a vaccine is available to the people of Angola, some capitalist must look down from his noble heaven and smile upon the venture. [2]

"right-hand-side" hypothalamus?

i just read in "biological substrates of human sexuality" that activation of the "right-hand-side" hypothalamus initiated sexual arousal in males.

what is the meaning in "right-hand-side" hypothalamus?, is it the right-wing appearance of the hypothalamus?, or maybe the writer means that it's the hypothalamus of people who's brains are organized in the "right-hand-fashion" ?.. thanks. — Preceding unsigned comment added by 81.218.145.251 (talk) 09:33, 21 November 2011 (UTC)

As you will see from this page, the hypothalamus has two lobes. --TammyMoet (talk) 13:14, 21 November 2011 (UTC)

We don't have an article called biological substrates of human sexuality, so I don't know what the OP was reading. Male arousal is associated with activity of a small portion of the hypothalamus called the sexually dimorphic nucleus, which exists on both the left and right sides of the brain, but I'm not aware of any publication that says the two sides differ from each other. Looie496 (talk) 16:38, 21 November 2011 (UTC)

Object in the night sky

At work, middle of the night and there is a black and white monitor to my right that shows the end of the runway. In the bottom right of the monitor is a white blob that is actually a red light on top of the VOR/DME and is the only thing the monitor sees in the dark. Earlier I noticed that slightly to the lift and above the VOR/DME there was another light source. I assumed it was a snowmobile but thought it was moving to slowly. I went out to get a better look and realised it was in the sky, a reddish colour and moving slowly northwest in a straight line. I came back in started up Stellarium (computer program) to see if I could identify the object but wasn't able to find anything. It was moving too slow to be a satellite and was too bright. Any ideas what it was I saw? BTW it is obvious that it's the same object a co-worker saw last week and actually filed a report on it as a UFO. However, I'm not thinking of the opinion that it is a UFO. CambridgeBayWeather (talk) 13:23, 21 November 2011 (UTC)

Jupiter has been up the last few weeks; it will be visible as a very distinctive and bright object in Northern Canada and most of the Northern hemisphere in the middle of the night. If you have binoculars, try to spot the object again; if you can see four moons, you're certainly looking at Jupiter... if you can't positively identify the object, you could be looking at "something else.". Nimur (talk) 15:59, 21 November 2011 (UTC)

Jupiter wouldn't visibly move (well, it moves with the whole night sky as the Earth rotates, but I wouldn't expect the OP to have noticed that movement with the naked eye). --Tango (talk) 18:57, 21 November 2011 (UTC)

Since you're at an airport, the obvious answer would be that it was an aeroplane, but I'm guessing you wouldn't make that mistake! It could be a very distant plane, though - that would explain it's very slow movement. What did it look like? Was it a single point of light? Or a diffuse glow? --Tango (talk) 18:57, 21 November 2011 (UTC)

By definition it remains a Unidentified flying object because you can't identify it. Aircraft such as the Skyship 600 move slowly. At night they are often internally lit with bright halogen lamps to show the advertising on their translucent skin. In windy conditions one can see that their flight is slightly erratic as they get blown around. If so it will be fitted with a transponder which can be picked up on amateur equipment such as this: [3]. Which gives a display like this: [4]. A scanner tuned to the local air traffic feq. may also pick up the chit-chat with the craft and ATC. --Aspro (talk) 18:53, 21 November 2011 (UTC)

Could it have been a stray Chinese lantern? --TammyMoet (talk) 19:20, 21 November 2011 (UTC)

If it was a Chines lantern wouldn't it have been a weddish colour ?--Aspro (talk) 19:45, 21 November 2011 (UTC).

You could be seeing the early proving flights in your area connected with this airship.[5]. I think air certification takes a minim of 5,000 flying hours, so it would be around this time when you see it appear in the skies -if the contract is to be signed on time. You could phone them up, ask to be put through to their pubic relations department for confirmation. Should this be right, you can ask for some publicity material/ glossy brochures (possibility of complimentary fights?) etc., which they will be happy to send you. PR departments love people taking an interest, that is the whole reason for their being.--Aspro (talk) 19:41, 21 November 2011 (UTC)

I did think of Jupiter but Stellarium showed it right on the horizon, a bit too low. Also I couldn't see any moons around it with binoculars. I did wonder if it was an aircraft. We see 2-3 a month flying the great circle route but most of those are north to south and tend to be flashing lights rather than a glow. I'd forgotten about the airship but I don't think they will have one built until 2012, Hybrid Air Vehicles. The video of the model looks interesting, here I think but that's not working right now. It could have been a non-commercial aircraft. CambridgeBayWeather (talk) 21:11, 21 November 2011 (UTC)

Betelgeuse? Count Iblis (talk) 03:51, 22 November 2011 (UTC)

If its movement is obvious to the naked eye over the course of a few minutes or less, (and it doesn't zip across the sky in a couple of seconds or less) then it's nothing astronomical. It could possibly be a large artificial satellite like the International Space Station, but they only appear reddish for a few seconds when they're fading while moving into the Earth's shadow (to them it's like sunset).

If a colleague has seen the same thing it's unlikely to be a random event like a Chinese lantern release. I imagine you'd know about any weather balloon releases in the area!

My money would be on an aircraft of some kind. From my own experiences (living near RAF Leuchars and visiting the vicinity of other such bases) your description fits very well distant military aircraft taking off and using their afterburners. If the orientation of runways and flight paths happens to be right, you can see these many miles away, well beyond where you would hear their sound, and because they're be moving almost directly away from you they appear slower than you'd expect an aircraft to be. Can you establish whether there's a (military) airfield in that direction within, say, 25 miles? {The poster formerly known as 87.81.230.195} 90.197.66.40 (talk) 04:21, 22 November 2011 (UTC)

I thought about Betelgeuse but it looked to far south and wasn't moving on Stellarium. I should have mentioned where I live, Cambridge Bay, and work, Cambridge Bay Airport, 69°06′29″N 105°08′18″W. The closest airport would be Gjoa Haven, 68°38′08″N 095°51′01″W, and it's 350 km (220 mi) east. To the southwest is Kugluktuk, 67°49′00″N 115°08′38″W, about 450 km (280 mi) and Ulukhaktok, 70°45′46″N 117°48′22″W, a bit further away to the northwest. The only airports with a military presence would be Iqaluit Airport, 63°45′23″N 068°33′21″W, Rankin Inlet, 62°48′41″N 092°06′57″W, and Yellowknife Airport, 62°27′46″N 114°26′25″W, which are forward operating bases for the McDonnell Douglas CF-18 Hornet. Although not stated in the article I get the impression that the afterburner would not be on for 15-20 minutes which was about how long I saw the object. The balloon release is at 11:15 Z and 23:15 Z. They look nothing like what I saw and can't be seen in the dark. Also by the time I posted this the balloon had burst and the guy who released it had just called me. CambridgeBayWeather (talk) 05:30, 22 November 2011 (UTC)

The airships to meet this order won't be built until next year but I'm talking about the proving flights that take place (with exiting airships) before production begins. Cambridge Bay Airport has an SSR and whilst this object is probably well out of its range, the operators are likely to be aware of what type of air traffic is operating further out. The existence of airship flights, moorings sites, (or other things that could account for this sighting) etc., might even be mentioned on the local NOTAMs. They should be able to tell you who is walking about airfield with an up-to-date copy stuffed in his shirt pocket. In your area I would guess that helicopters have to fly at just above ground level in some poor visibility conditions. A moored airship would present a very unpleasant surprise to these pilots so such sites would certainly be mentioned on NOTAMs. --Aspro (talk) 10:04, 22 November 2011 (UTC)

We don't have a Secondary surveillance radar, in fact because we have a Remote communications outlet about .5 mi (0.80 km) away we don't even have the Aircraft emergency frequency (121.5). I work at the Community Airport Radio Station, that's for the Yukon but its the same as us. We check the NOTAMS daily and there hasn't been anything on there. The object was not making any noise that I could hear so it would have had to have been more than 5 NM (9.3 km; 5.8 mi) out and that puts it beyond the Mandatory frequency. If a mooring for an airship had been built it would have probably been big news and put up some place easily accessible like Hope Bay Aerodrome. And it was back again this morning in what appeared to be the same place. CambridgeBayWeather (talk) 13:35, 22 November 2011 (UTC)

I was just leaving work and as I drove away from the airport I was staring at the old DEW line site. They don't have a SSR but they have or did have a long range radar, see List of DEW Line Sites (search for CAM-MAIN) and here. But they no longer monitor it onsite and haven't for at least 16 years. It is monitored remotely but I'm not sure where, possibly CFB North Bay. CambridgeBayWeather (talk) 14:48, 22 November 2011 (UTC)

According to this [6] the Department of National Defence has long range radar and short range radar based at Cambridge Bay still operating in 2008. As you say it is likely to be unmanned these days and since 9/11 it is likely to be difficult to get anything out of them anyway. I don't know if they are official allowed in Canada are but I'm wondering if someone has a 'complete and detailed' list of the frequency allocations. A scanner (if they are legal where your are) could then be set to sweep those freqs automatically, looking for radio traffic. Might be worth putting up a request for sightings on your radio stations notice board. If you can get some fool interested enough who has a night-rating, then maybe they'll go up and chase it – then sell the shot footage to a news organisation. Even if it turns out mundane it should make a good story. As far out as 5 NM, the navigation lights should have been easily visible with binoculars so I agree it was likely much further away (presuming it to be a terrestrial aircraft). --Aspro (talk) 15:11, 22 November 2011 (UTC)

Thinking about it. If there are enough curious witness to this same phenomena, then the airport manger might find that justification alone to make inquiries to the North Warning System – just for good public relation reasons and the fact that its distracting his employees :-) Also, from his point of view as a PHB, he wouldn't like to think that his subordinates has discovered there is something that he does not have an answer for. --Aspro (talk) 16:32, 22 November 2011 (UTC)

Now that I've slept on it I suspect that Edmonton ATC can monitor the radar. The Canada Flight Supplement has all the frequencies and I didn't think about it until you mentioned a scanner. All I need to do is open the Airport Managers office and turn his scanner on. CambridgeBayWeather (talk) 22:41, 22 November 2011 (UTC)

Have you considered that it might have been a fireball? If it was moving roughly towards or away from you, that could account for its apparent slow motion. Astronaut (talk) 06:41, 23 November 2011 (UTC)

If it had been a one off then possibly but this is now the third consecutive night. This time I got a couple of pictures of the monitor showing the light but I had no success outside. I also had the scanner on but it only picks up our frequencies along with 121.5 and 126.7. I can't get it to monitor any of the military frequencies. It is higher and about an hour earlier than the last two nights. I think that it is moving away from me as it has got dimmer over the last 45 minutes. I mentioned it to another co-worker as he has friends at the DEW line site who checked and said there was nothing. But they would probably say that anyway and now I have to put up with "Seen any flying saucers?" Ah well, this is my last night shift so probably won't see it again for a while. CambridgeBayWeather (talk) 12:54, 23 November 2011 (UTC)

Brain size/body size and intelligence

Is there any correlation between brain size and body size when it comes to intelligence in living creatures? 58.109.41.190 (talk) 14:03, 21 November 2011 (UTC)

Yes, but like all things biological it is complicated and there are caveats. But check out our article on brain-to-body mass ratio and the related-but-more-useful encephalization quotient. --Mr.98 (talk) 15:24, 21 November 2011 (UTC)

Certain Mormyridae (a fish) have higher Brain-to-body mass ratio than man, followed by woman. Cuddlyable3 (talk) 00:20, 22 November 2011 (UTC)

Human men and women have mostly comparable brain-to-mass ratios, though with very small men or women the results get skewed. I wouldn't read a lot into that, though. As stated, this is as best a rough metric. And with very small things (birds in particular) the results are really off. Ditto that particular fish. But in general there is a correlation. The EQ ratio is a better correlation, but it too is just a hand wavy correlation, not an absolute law. --Mr.98 (talk) 12:00, 22 November 2011 (UTC)

Simple explanations for the recent neutrino experiments

There are a number of simple explanations coming to my mind about the OPERA neutrino experiment which apparently produced faster-than-light neutrinos. I wonder because I couldn't find them in the discussions and articles about it.

First of all, I understand this does not mean a significat faster than light travel, so we would not travel 100 times faster than light with it... The difference was only a few nanoseconds, so what if...

1. we measured the speed of light wrong? The definition is "speed of light in vacuum", but space is not a perfect vacuum. What if neutrinos travel exactly or just below the speed of "light" (as defined by relativity), but photons travel a little slower? We all know light travels much slower in certain substances, and that neutrinos react much more weakly with matter than photons. Did we measure the speed of light accurately? Was it in perfect vacuum? Is vacuum without any matter actually perfect, or maybe there is something undetectable or barely detectable like dark matter or something similar, which photons (even if barely) interact with, and neutrinos don't ?
2. The speed of light changed slightly since the last time we measured it. Who kwnos, expansion of the Universe, some large blob of dark matter passing through our galaxy, God just being in the mood of changing a cosmological constant, or basically any sensible or silly explanation we don't understand yet? We know that the speed of light was not always constant, because the known Universe is bigger than its age would indicate, so once in the past it had to expand faster than the current speed of light, assuming our model of the Big Bang is not horribly wrong.
3. Is it actually possible to transmit information with this experimet? If not, then it's just one of several known cases of something traveling faster than light.

Is there something which might be plausible, and if not, where am I wrong? — Preceding unsigned comment added by 91.23.232.169 (talk) 18:39, 21 November 2011 (UTC)

There have been lots of experiments to measure the speed of light and they have all agreed, so I doubt that is the issue. If we were get our vacuums wrong then we would be getting them wrong in different ways each time, so we wouldn't get the same answer. If the speed of light is changing that quickly, then, again, we wouldn't keep getting the same answer. I can't see why you couldn't transmit information with these neutrinos (although the bit rate would be incredibly low!) - the experiment seems to be showing that the individual neutrinos are actually travelling faster than light, this isn't just a group velocity vs phase velocity thing. --Tango (talk) 18:52, 21 November 2011 (UTC)

How do whe know they are the same individual neutrinos, and not just some case of entaglement or something similar? --91.23.206.55 (talk) 18:57, 21 November 2011 (UTC)

You can measure the energy and origin direction of the neutrino, which tells us that they are from CERN. CERN creates them in small bunches. Given that we know when they are created, and how far they have to travel, we can predict when they will arrive, but the ones that were observed appear to have arrived a little too soon. Dragons flight (talk) 19:24, 21 November 2011 (UTC)

So if we used it in a practical way to transmit information, how exactly could it send infomration to its own past? Af far as I know that's the biggest paradox with FTL communication. --91.23.206.55 (talk) 19:36, 21 November 2011 (UTC)

Tachyonic antitelephone shows a general construction (subject to several untested assumptions about how faster than light travel works). In order to transmit information into your own past using this system you require a physical relay that is moving relative to the sender at nearly the speed of light. If the neutrinos travel at (1 + 2.5×10⁻⁵)c then the relay must move at least (1 - 3×10⁻¹⁰)c. Not very practical, but physically possible. Dragons flight (talk) 19:57, 21 November 2011 (UTC)

If there were something (call it dark matter, dark energy, aether, or anything) which slightly interacts with photons but not with neutrinos, that could still mean that all our measurements of the speed of light are incorrect, and still give the same results. So the "speed of light" might be better represented by the speed of neutrinos, and photons are just a little slower? Has the speed of light ever been calculated theoretically, without actually measuring photons in some way? --91.23.206.55 (talk) 19:45, 21 November 2011 (UTC)

As discussed in Speed of light#measurement, the speed of light has been measured both directly (by time of flight) and indirectly via measuring other physical properties of light (e.g. simultaneous wavelength and frequency, permittivity / permeability of free space). Could all these properties be confused in some way? Maybe. But that's almost certainly a long shot compared to some other more mundane error in the OPERA result. Dragons flight (talk) 20:15, 21 November 2011 (UTC)

As speed of light I was referring to "c", as defined in special relativity, not the actual speed of photons. What if the two are not exactly the same, just very close? It might be a silly idea, but it seems more plausible to me than being able to send information to the past. --91.23.206.55 (talk) 20:51, 21 November 2011 (UTC)

Well, the most plausible thing is that this is an error of some sort, at this point. And divorcing c from the speed of light in a vacuum would make a perfect conceptual mess of SR. Setting c to be an arbitrary concept that is equal to the speed of light in a vacuum except with regards to neutrinos would be physically abhorrent. --Mr.98 (talk) 21:29, 21 November 2011 (UTC)

Not necessarily divorcing it. c would still remain the maximum speed limit, only that photons can only reach 99.999998% or similar percent of it, just like they move slower through water or glass. Maybe there is something in vacuum that does not make it 'perfect' vacuum. No one did ever create completely perfect vacuum, and even in the deepest space there is intertellar hydrogen and maybe other things we don't yet know. Or maybe photons interact weakly with "dark something" better than neutrinos? Neutrinos are famous that they can pass through light year thich solid lead, something photons cant quite do... Of course, it might be an error in the experiment, but it was repeated. A hoax is highy unlikely, with such a large number of scientists involved. A systematic error? Are there any plans to measure the speed of light again in the near future, maybe with specific regards on information gained from this experiment? --91.23.206.55 (talk) 21:47, 21 November 2011 (UTC)

The experiment was not repeated independently — the replication was done by the same team. All it did was rule out one of many sources of error. The experimental result is not in any way something accepted by most scientists as legitimate at this point. Nobody thinks it is a hoax. --Mr.98 (talk) 03:13, 22 November 2011 (UTC)

If the speed limit of general relativity is not equal to the speed of actual photons, then it would require most of our understanding of relativity to be revised. It would be as surprising as finding neutrinos that go faster than photons. Also, given the dozens of detailed tests of general relativity over the years, I would be very surprised if existing observations don't already exclude that possibility with a sensitivity substantially greater than the OPERA claim. Dragons flight (talk) 21:37, 21 November 2011 (UTC)

Well, it wouldn't really require relativity to be revised, necessarily; it could just mean that photons have nonzero (rest) mass. If I am correctly informed, that's inconsistent with a lot of what we think we know about particle physics, but not about relativity.

However the experimental upper bound on photon mass is pretty small. --Trovatore (talk) 01:46, 22 November 2011 (UTC)

4. Software error. Getting the time difference right is a tour de force. Two different clocks are involved, the neutrinos detected at CERN are given a time stamp using th clock there, the neutrinos detected at LNGS are given a time stamp using the clock at LNGS. You need to make sure that the clocks are synchronized, or at least be able to tell when an event happened according to the clock at LNGS when you know the time according to the clock at CERN.

Also giving a time stamp takes time, which one has to take into account. When neutrinos cause a reaction then that leads to an electronic signal, which travels through electric of fiber optic cables, at some node you add to it a signal that originates from the clock. But the time stamp given in this way will not be the actual time the neutrino caused the reaction, you will be off by the time difference between the time it took for the signal from neutrino detector to travel to the node and the signal from the clock to travel to the same node.

All such effects are taken into account automatically, but a small error somewhere can easily lead to a 60 ns error. Count Iblis (talk) 22:53, 21 November 2011 (UTC)

The guy who stamps the time on the neutrinos needs little teeny hands. --Trovatore (talk) 23:38, 21 November 2011 (UTC)

To help understand "small" error in context, light or any other electromagnetic signal travels 18 meters in free space during 60 ns. Cuddlyable3 (talk) 00:11, 22 November 2011 (UTC)

This just in. {The poster formerly known as 87.81.230.195} 90.197.66.40 (talk) 04:34, 22 November 2011 (UTC)

Can't say I'm terribly impressed. I mean, I'm certainly not an expert in this area, but to me it looks like just another theoretical reason why what has apparently been observed, can't be happening. But we already have plenty of those. What we need is an explanation for why what was observed was in error, or else a careful repetition of the experiment that either does or does not confirm the outcome. --Trovatore (talk) 09:16, 22 November 2011 (UTC)

Another good reason for doubtingf it is at these rates the neutrinos from SN 1987A would have arrived four years before the light. Dmcq (talk) 16:28, 22 November 2011 (UTC)

That is a good reason, but as OPERA neutrino anomaly#Previous measurements notes, SN 1987A's neutrinos were of a different type than OPERA's. As we can't definitively reject the hypothesis that different kinds of neutrinos travel at different speeds, SN 1987A doesn't necessarily invalidate the OPERA results. -- Finlay McWalterჷTalk 16:35, 22 November 2011 (UTC)

The difference that seems most interesting to me is that the SN 1987A neutrinos travelled through empty space, whereas these are moving through the Earth. Rampant Speculation: It's well known that matter can slow the speed of light that passes through it - is there any conceivable way it might also be able to increase it? I'd think it would have to be the matter, not just gravity or even electric fields, because the 1987A neutrinos would have gone through quite a few of those on the way here. But nuclei are only 1/(100,000)³ of the volume of matter, so the neutrinos would have to be doing more than just skipping across nuclei at a faster pace. Are they affected only by the super-strong electric field inside individual atoms, or reached by some weak-force effect that blossoms out from the nucleus? It does get more interesting the more it's replicated, but it's still probably some absurd but incorrect detail: GPS using the wrong shape for the Earth, incorrect estimate of the density and gravity field of the Earth at varying depths below the surface etc. Wnt (talk) 18:29, 22 November 2011 (UTC)

Interesting idea. We all talk about the speed of light in vacuum, but what is the speed of light in solid and non-transparent matter? No photons can pass through, so how can we measure it? Is in this case the speed of light zero, or is it just different than the speed of actual photons? --91.23.224.49 (talk) 19:18, 23 November 2011 (UTC)

The speed of light through rock can be measured as the mineral crystals composing it (eg feldspar, quartz) have a refractive index which always reduce light speed. Graeme Bartlett (talk) 11:15, 25 November 2011 (UTC)

Oxide world

What will be the diffrent between an earh-like world that instead of 21% of oxygen, will have 100% oxygen in the air(of course)? Exx8 (talk) 20:10, 21 November 2011 (UTC)

If there were anything flammable, it would burn until either the fuel or the oxygen got completely or nearly completely consumed. Would our Earths atmosphere be composed of 100% oxygen, al life would end very quickly in a fiery death, maybe except some heat tolerant anaerob bacteria deep down under some volcanoes. --91.23.206.55 (talk) 20:12, 21 November 2011 (UTC)

There could be star systems where oxygen far exceeds the amount of the heavier elements. You may end up with a water world; or if hydrogen was somehow depleted, something even stranger made from solid oxygen. Graeme Bartlett (talk) 22:39, 21 November 2011 (UTC)

A 100% pure oxygen atmosphere seems to rule out there being any gaseous products of combustion. It also rules out all the life processes that depend on the Nitrogen cycle so if any life evolved on such a world, it would not be Life As We Know It. Visitors from Earth would be in danger of Hyperventilation on arrival and, if they survived (oxygen becomes toxic under pressure), Decompression sickness on leaving. Cuddlyable3 (talk) 23:59, 21 November 2011 (UTC)

Before life on earth there was very little if any "free oxygen", it's the 3rd most abundant element in the universe but it's highly reactive, so I doubt any planet would be "pure" enough to prevent any free oxygen from being bound up into other molecules. For one, the planet would need to have no hydrogen, or far less at least, which seems unlikely since hydrogen is the most common element. Oxygen#Occurrence touches on this a little. Vespine (talk) 01:47, 23 November 2011 (UTC)

Digestion of Monosaccharide

Hi, I would like to know: 1)Are all of the Monosaccharide sweets? 2)Are all of the Monosaccharide digestable? Exx8 (talk) 20:11, 21 November 2011 (UTC)

The first is answered in the lead section of our monosaccharides article. Maybe an answer to the second lies therein as well. Search, you should. --Ouro (blah blah) 21:23, 21 November 2011 (UTC)

1. (edit conflict) No, as stated in the third sentence of Monosaccharide, "Some monosaccharides have a sweet taste." Since some is not a synonym of all, that means that not all of them are sweet.
2. No, some monosaccahrides are fairly undigestible. See this google search, where you can find many references. --Jayron32 21:28, 21 November 2011 (UTC)

Sorry for ec-ing You, Jayron. --Ouro (blah blah)

Is there a sweet and non digestable one? Exx8 (talk) 23:45, 21 November 2011 (UTC)

Depending on how expansive your definitions of "monosaccharide" and "non-digestable" are, erythritol may be one example, as it "is 60–70% as sweet as table sugar yet it is almost non-caloric". -- 140.142.20.229 (talk) 02:44, 22 November 2011 (UTC)

Curiosity

i was watching curiosity with stephen hawking in discovery channel on Did god created the universe?, at one point they discuss on how can something came from nothing without divine intervention, turns out it is possible because of negative energy, and we sum up eveything in the universe, it will equal to zero. i read somewhere that nature tends to use as minimal energy as possible, for example the bee hive structure, (i hope its a good example), im not an expert but why is it then that unviverse began assuming that its more work rather than nothing?i hope somebody gets my question. MahAdik _usap 21:24, 21 November 2011 (UTC)

Other beginnings to consider apart from balance of energy is information/entropy and cause. Graeme Bartlett (talk) 21:51, 21 November 2011 (UTC)

First we have to agree on a definition of "God", but I assume here we all talk about the omnipotent God as in the three major Abrahamic religions, and not just some guys with super strength like in Greek or other pagan mythologies. For such an omnipotent entity anything is possible, so it is not in our capability to either prove or disporove it. It doesn't even require negative energy, an omnipotent God can just create anything, and can violate the laws of the Universe, like if you write a computer game, implement a cheat code, and you can create anything in that game out of nothing. Now comes an interesting part if some of your characters in that video game would gain sentience, and would start doubting that they are in a video game, and that their wold was created by a programmer... --91.23.206.55 (talk) 21:58, 21 November 2011 (UTC)

You bet. And then they would have many debates on whether there really is a Programmer, and if so, how would you prove it? Or could you? Maybe it would have to be based on faith. And instead of belief in one Programmer, there could be poly-progammerists who believe there are many of them. And so on. Nifty idea. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:26, 21 November 2011 (UTC)

Nifty idea? Disney already been there, done that.. Cuddlyable3 (talk) 23:38, 21 November 2011 (UTC)

Primitive men thought thunder was a god grumbling, medieval men thought god held up the Moon and there are still a few 19th century leftovers who think dinosaur fossils were made by a god to deceive us. As actual knowledge grows, the scope for godly intervention diminishes towards zero. The question about the source of the energy of the Universe need not be answered with superstition if one can visualize the system as an enormous loss-free resonant cavity. The sum of energies and mass stays constant, and can be called "zero" just because there is nothing to measure it against. However the flows of mass/energy exchanges are huge and chaotic enough at the microscopic level to give us curious experiences. Cuddlyable3 (talk) 23:33, 21 November 2011 (UTC)

Yes, part of the question is how you define "God". Discovery of an "architect" or at least a catalyst or a definite non-random origin does not automatically prove the veracity of any of our human gods, including that of the Abrahamic religions. Proponents of creationism and intelligent design often conveniently ignore the fact that when a watchmaker makes a clock, he isn't necessarily concerned with what happens to the clock, nor does he talk to the clock, or care what the fates of the gears in it ultimately are (though he may repair it every now and then). The shepherd analogy is also morbid in its irony - the shepherd nurtures his flock only because he benefits from them, and he may even eat some every now and then. Who knows, the entire universe may actually be something as mundane as a power source in some unimaginable higher reality. Designed, but no more special than the watch on your wrist.

As for polytheistic religions, they aren't necessarily merely superhumans, remember that in most polytheistic religions, the gods are personifications of natural forces. Replace Zeus with "lightning", replace Hephaestus with "volcano", replace Artemis with "moon", and you begin to realize that the mythologies are really simply stories about nature adapted to the human culture. Even the Abrahamic religions are in truth, polytheistic. They have two gods - god is the personification of human moral good, and satan is the personification of human moral evil. Religion is not unlike science in this regard, but instead of objective observations, they dress it up through the filter of human experiences. And thus why the Abrahamic god is male, lives in the sky, and has a mean temper. For an omniscient being, he now resembles a Middle Eastern culture human father simply because those were the limits of our imaginations and all that we knew back then. This is also why religions are sometimes hostile towards new discoveries, because it illustrates the inadequacy of their explanations and relegates their god to a god of the gaps. The unknown has always been a fertile blaming and attributing ground for religions (as well as science, except that science actually tests it out). Taking away the mystery weakens this. Interesting side-note: the forbidden fruit in Genesis is that of the tree of knowledge. That raises a lot of red flags. Since when was ignorance a virtue?

It is a very valid scientific question, however. The truth might actually be even curiouser. We still have yet to explain consciousness, for example. But practically, it really is something we do not possess the means to understand now and most probably ever.-- Obsidi♠n Soul 04:54, 22 November 2011 (UTC)

Note that it doesn't matter whether you think God created the universe, in any case you always end up with either something springing from nothing or something having always existed (whether the universe is that something or God is). StuRat (talk) 03:31, 22 November 2011 (UTC)

A way out here is to assume that the universe only exists in a mathematical sense. I.e. all that exists are abstract mathematical models. One such model describes our universe and us. According to the model describing our universe, the universe can be finite in time, but the description itself (which is what really exists), is timeless. Count Iblis (talk) 03:40, 22 November 2011 (UTC)

Well, rather the universe really exists, but all we as humans can do is create models of it. We have our personal model of the world, which allows us to interact with it in useful ways (like, our intuitive sense of how gravity works, or how a solid object will respond to manipulation, etc.), and there are also well developed scientific models which describe how the universe works. However, they are still all models; reality exists, but human perception is only capable of representing reality inside our minds (individually and collectively) as models, and as George E. P. Box so eloquently put it "All models are wrong, some models are useful". --Jayron32 03:54, 22 November 2011 (UTC)

Box meant All Quadratic polynomial models are wrong... and we should try to think outside the box. Cuddlyable3 (talk) 18:27, 22 November 2011 (UTC)

I think that the archetypal example is the conception and birth of a child. By now the scientific explanation is pretty well known, even to teenagers; but this does not make it any less miraculous. Wnt (talk) 14:14, 23 November 2011 (UTC)

Measurement of sweetnewss?

In this article there is a table of how many sweetness there is in the metrials. How do they measure sweetness? Exx8 (talk) —Preceding undated comment added 23:50, 21 November 2011 (UTC).

The most common method is to give tasters samples with different concentrations and ask them to compare -- or just to ask how high a concentration it takes to detect the presence of the sweetener. Looie496 (talk) 00:07, 22 November 2011 (UTC)

If you are looking for a more scientific method, you may want to check the article on brix (sweetness units). I guess the table in the article you refer to should have included the type of units and not just numbers (not sure what unit the editor had in mind when making the table). If you find out, you can contribute by editing the article, or adding a post to its corresponding discussion page. DI (talk) 13:09, 22 November 2011 (UTC)

There is no unit. It is 26X sweeter than sucrose, 0.16X sweeter, etc. Rmhermen (talk) 15:02, 22 November 2011 (UTC)

Excellent. Then, technically, the unit is "times sweetness of sucrose".85.200.249.178 (talk) 07:18, 23 November 2011 (UTC)

Note that the Brix units don't report directly on sweetness but on sucrose (or total sugar, depending on the method and sample) content. Instead, they give the apparent concentration of sucrose – 1 Brix unit equals 1% sucrose – as derived from a physical measurement of density, refractive index, or optical rotation. Unless you're comparing Brix numbers for solutions containing the same sugars (in the same relative proportions), two solutions with the same Brix value can have very different levels of perceived sweetness. For example, a 2°Bx solution of sucrose will taste sweeter than a 1°Bx solution of sucrose—but that 1°Bx solution of sucrose will taste quite a bit sweeter than a 2°Bx solution of lactose. TenOfAllTrades(talk) 17:08, 22 November 2011 (UTC)