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May 14

A method to scientifically test the existence of god

A lot of people have near death experiences, where in some cases they report seeing doctors trying to revive them and said they heard/seen things around them during the time "they died". if there was something very definite they can verify, e.g. putting a 6 digit number out of the sight of the dead body, but would be clearly visible from another angle, and if they can recall the number after they get revived, that would prove existence of afterlife and therefore of god. these tests can be run on death row inmates, kill them in a way that it's possible to revive them (e.g. anaesthetic overdose), and say if they can recall the number then they'll get life sentence instead of death (for some incentive).

This is the single most important question in human history, and we have the means to test it. So why haven't we done it? — Preceding unsigned comment added by Money is tight (talk • contribs) 00:33, 14 May 2016 (UTC)

Would you change your behavior if you would have proof that (a) god did or did not exist?

I don't think that that question is very important, it is quite irrelevant to me, and I don't think that the existence of an afterlife would be proof for the existence of a god or gods. People have scientifically tested the existence of a god, and the conclusion was that there is no reason to believe in a god or gods.

For example, back in 1872 Francis Galton concluded that prayer does not work, because the life expectancy of the British royals was not higher than that of the rest of the population despite weekly prayer for their health, and that churches burned down, got hit by lightning and destroyed by earthquakes at the same rate as other buildings of a comparable size. The Quixotic Potato (talk) 01:05, 14 May 2016 (UTC)

One of Isaac Asimov’s essays notes that when the lightening rod was invented, churches were reluctant to install them, as it would be attempting to thwart God’s vengeance. They gradually came around when they noticed the brothels and taverns being spared by the rod, while churches burned to the ground. Willondon (talk) 16:45, 15 May 2016 (UTC)

Or one could draw the conclusion that God wants to be worshiped in a rather different fashion than we imagined. It's not unprecedented. StuRat (talk) 16:40, 16 May 2016 (UTC)

(EC) Well, first, it has been done, though in a less grizzly fashion than you suggest - see the first three or so paragraphs at Near-death_experience#AWARE_study. As to your suggestion, there are major ethical problems in experimenting with death in the way you suggest, besides the whole idea being abhorrent. And then there's the point that even did the test pan out - near dead person sees something his body could not have seen - you have not proved god, but merely got yourself an observation for which it is difficult to construct an explanatory mechanism. All ethical and practical considerations aside, those who do not believe in god are unlikely to mount this test, since the anticipated absence of evidence (of god) is not evidence of absence - in other words, nothing gets proved by the experiment. Those who do believe in god are unlikely to put her to the test in this fashion. So the potential queue to perform the experiment is very very small indeed. --Tagishsimon (talk) 01:11, 14 May 2016 (UTC)

Houdini had a famous test where he told his wife some keywords that she had to memorize, and said he would tell them to any psychic who truly contacted him after his death. He died, and many psychics claimed to have contacted him, but none knew the keywords. Draw your own conclusions. StuRat (talk) 01:13, 14 May 2016 (UTC)

Houdini, dead ? What if the psychics could never have told her the special keywords ? ..the same result.. would occur.. --Askedonty (talk) 19:15, 15 May 2016 (UTC)

Some years ago a psychic was scheduled for an appearance on the local radio station. She arrived late, and said she was "caught in traffic." Apparently her psychic abilities did not include traffic reports. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:38, 15 May 2016 (UTC)

They usually weasel out of this by saying they can't predict everything, 100% of the time, which is of course true, if quite an understatement of what they can't predict. StuRat (talk) 16:35, 16 May 2016 (UTC)

@StuRat: Do you speak French? https://www.youtube.com/watch?v=rB33z6qFJqM

So, you say you are a clairvoyant, that you can foresee the future?

- Yes, I can see the future.

SLAP!!!

- And this? Didn't you see this coming? As you can see, it doesn't take much to expose a liar.

The Quixotic Potato (talk) 17:36, 17 May 2016 (UTC)

But again, that would only disprove a claim that they can see 100% of the future with 100% accuracy. They are smart enough not to claim that. Also, if they could do that, they would buy a winning lottery ticket, so wouldn't need to take money from their marks clients. A nice way around this is for them to say "You must be committed for me to see your future, and a contribution is a sign of this commitment". StuRat (talk) 17:56, 17 May 2016 (UTC)

a fundamental problem too is that any experience of God still runs into the problem of Descartes radical doubt: Cogito ergo sum 68.48.241.158 (talk) 02:04, 14 May 2016 (UTC)

How is Descartes' belief in his own existence a fundamental problem? AllBestFaith (talk) 13:52, 14 May 2016 (UTC)

it's related to the notion of radical doubt..that is, even if one had the experience of God appearing before her etc, there's no way to no for sure that this is really what is occurring...one could be being fooled by an entity other than God etc etc...just as our experiences could be something other than what they appear..see "brain in a vat" etc etc...68.48.241.158 (talk) 14:13, 14 May 2016 (UTC)

Far from succumbing to despairing that everything is doubtful as you suggest, René Descartes who was evidently a male person who served in the army and fathered an ill-fated illegitimate daughter Francine, turned his ability to doubt into the tool of methodological skepticism with the goal of sorting out true from false claims. Since Descartes considered himself to be a devout Catholic, though his attempt to ground theological beliefs on reason encountered intense opposition, you may be doubly mistaking him for an atheist female. AllBestFaith (talk) 14:48, 14 May 2016 (UTC)

you seem to somehow have confused my use of the female pronoun in my example as suggesting Descartes was himself female...this would be an instance of poor reading comprehension..regardless, what I describe is accurate and has relevance..68.48.241.158 (talk) 15:00, 14 May 2016 (UTC)

There is no reason to assume that an afterlife requires the existence of God, or vice versa. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:33, 14 May 2016 (UTC)

Agreed. The OP needs to think about what the hypothesis is and what the experiment is here. It is possible to picture a worldview in which there is an afterlife without God, or without a noticeable God. It is also very possible to imagine an afterlife that does not involve having some kind of disembodied vision. I mean, think about it - the colors we see are the product of red, green, blue receptors of a certain frequency. Our vision has a certain acuity, fails to pick up far infrared or (usually) ultraviolet. For that vision to be replicated after death by something that is invisible - i.e. which does not absorb light - seems extraordinary. Testing this kind of remote viewing has been attempted by some very unexpected agencies - see Project Stargate; there's no reason to assume a person would have to be dead to do it, if these disembodied eyes are part of some soul that exists in a living person also. Wnt (talk) 02:47, 14 May 2016 (UTC)

posting of banned user removed. The Quixotic Potato (talk) 12:27, 16 May 2016 (UTC)

Because a car manual contains accurate and useful information, it is not a work of fiction. The Quixotic Potato (talk) 09:46, 15 May 2016 (UTC)

The Bible is the designer's manual for use by humans? That view clearly reflects the belief system you have been given, and adopted, but your belief system is just one that has been created to date, and it is significantly different to the belief systems adopted by many others around the world. Dolphin (t) 10:58, 15 May 2016 (UTC)

Whether we could prove "scientifically" that God exists, in the end, You will either believe Him without such proof, or You won't, and I do not believe such proof can be found in this Age, since the Just shall live by Faith. Chris the Russian Christopher Lilly 09:21, 15 May 2016 (UTC)

The motor manufacturers set out to provide practical information in their manual. Why would you assume that the object of the people who put together the Bible was to tell a fairy story? As for the efficacy of prayer, if you pray that you will win the lottery you might not have much luck, but if you were to pray that a close relative be delivered from a serious illness you might be more successful.

posting of banned user removed. Fut.Perf. ☼ 08:15, 16 May 2016 (UTC)

Are you trolling? Shouldn't you be a lot more humble? Are you allowed to judge others? I noticed you haven't apologized yet. Praying for a sick relative is a waste of time. It is far better to bring them to a hospital, or call an ambulance. In the hospital they don't pray for the patient, they actually do useful stuff, like giving them medicine. There is a reason that god does not heal amputees. Your idea of god is just as made up as all the others. It is 2016, why do you still believe that nonsense? The Quran, Torah and Bible are all the same story about the same idea of a god, and the differences between them are quite small. I've read all three, maybe you should too! God loves atheists. The Quixotic Potato (talk) 12:03, 15 May 2016 (UTC)

“ Fuck me Sam, what are the odds
That of history's endless parade of gods
That the God you just happened to be taught to believe in
Is the actual God and he digs on healing,
But not the AIDS-ridden African nations
Nor the victims of the plague, nor the flood-addled Asians,
But healthy, privately-insured Australians
With common and curable lens degeneration ” — Tim Michin

posting of banned user removed. Fut.Perf. ☼ 08:15, 16 May 2016 (UTC)

Translated into English????? What are you talking about? You have not answered my questions. Are you trolling? Shouldn't you be a lot more humble? Are you allowed to judge others? And you haven't apologized yet. Don't worry, I'll forgive you, and I will ask your god to forgive you because you obviously don't know what you are doing. The Quixotic Potato (talk) 12:56, 15 May 2016 (UTC)

posting of banned user removed. Fut.Perf. ☼ 08:15, 16 May 2016 (UTC)

I wrote: "Translated into English?????"... You seem to know very little about the Bible (you wrote: Part of the Bible is the Torah (translated into English).), and religion in general (you wrote: How can a religion not have "a god or gods"?). Have you read the bible? How old are you? People do continue to visit Lourdes even though they don't derive benefit from it (or, you know, no miraculous cures). You have not answered my questions. Are you trolling? Shouldn't you be a lot more humble? Are you allowed to judge others? Have you read my userpage? What is your accountname? You should read this and watch this and that and this too. Have you read [1], [2] & [3]? The Quixotic Potato (talk) 13:45, 15 May 2016 (UTC)

Can someone close this thread and collapse the against policy behavior of "Quixotic Potato" and whoever else he's been engaging with??68.48.241.158 (talk) 14:14, 15 May 2016 (UTC)

Hahahaha. Welcome to the Science reference desk mate. Your most recent block ended 2 weeks ago, maybe it is a good idea to improve some articles? The Quixotic Potato (talk) 14:15, 15 May 2016 (UTC)

Some of the comments above go beyond the scope of the original proposed method, but they have some of the same issues regarding their hypotheses. Testing the existence of God by praying for healing assumes, for example, that, despite creating it, God doesn't see any beneficial use for disease; it also assumes that the purpose of prayer is to make magic happen rather than, for example, to provide insight or inspiration. Reifying "the Bible" minimizes the fact that it is made up of different books by different people that were independently circulated. So there is much needless conflict produced because people are taking a very specific notion of religion and then saying either it is all true or it is all false, when maybe the most important bits are independent of the most testable bits. After all, the most significant form of healing is resurrection into a new and better universe, yet it is clearly not possible to tell whether such a thing could occur by ordinary scientific means of investigation. Wnt (talk) 18:59, 15 May 2016 (UTC)

FYI, an IP is yelping at WP:ANI about this section, if anyone wants to comment there. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:04, 15 May 2016 (UTC)

Actually, praying for the sick or for anything else does work. For sure, one must use the Medical Knowledge God has also allowed us, but the effectual fervent prayer of a righteous man availeth much, and thus Prayer is indeed useful, and may even accomplish what even Modern Medicine cannot. The Bible would not say such things if they were not true - and by the way, all of the Bible is true, does not matter what one can, or what one thinks one can prove "scientifically". What I see in some of these attempts to prove the Bible by Science ends up being reducing God's real Miracles to natural acts that can be explained away. As for judging, one can only do so if they are not doing the same things wrong. If one has genuinely turned to God, it should only be because they have first judged themselves in the Light of God's Word, as Judgment must begin at the House of God. But judging others should only be according to God's Righteous Judgment. Whether or not is 2016, and even that Number we use for this year is based on timing with respect to the Bible, that is to say, it is said to be about 2016 years since the Birth of Christ ( when I understand He might actually have been born around September, 4 BC ), whether or not indeed it is 2016, or whatever year it happens to be in any given moment, as people have said such things up to now, should have no bearing on our Belief in God, or any lack of it, since Jesus Christ is the Same, yesterday, today and forever, and whatever people think about Belief in Him being out of Date, it never is. His Word, which endureth forever, is just as valid now as it ever was or will be. It is also interesting that when things go wrong, People blame God, and yes, nothing happens that He does not ultimately allow, since if He wished, He could stop it, but the same People might not thank and praise Him for all that He has done and created that is Good - He gets a lot of the blame, but hardly any of the Credit, and think of it, if we live in a World which in general does not honour Him, does not run things in the Way He in His Wisdom knows and commands they should be run, we ought not be surprised if He allows unfortunate events to occur. But the thing is, if we all did turn to Him, He would hear us, and forgive us ( 2 Chronicles 7:14 ), because He does not bear a grudge against those of us here on Earth who still have a Chance to turn to Him. May God forgive us all for each and all of our own sins, for there is none that sinneth not, and I would not presume to speak of God if I had not acknowledged my own sins to Him. To finish - He knows and hears all, and whatever we say or write, we will give account, and I can only pray that if we have offended Him, we can admit that, and turn to Him. One way or other, in the end, when all is said and done, whether or not we think God exists, we will find out for sure. Chris the Russian Christopher Lilly 00:39, 16 May 2016 (UTC)

I'm late to the party, but no one has yet mentioned at least one serious attempt to approach this exact question God: The Failed Hypothesis by Victor_J._Stenger. If you are at all interested in this subject, I can recommend this book, I found it quite interesting and informative. Vespine (talk) 06:18, 16 May 2016 (UTC)

1. Any experiment involving killing human subjects is unlikely to pass ethical standards.
2. The experiment proposed wouldn't answer the question. At most it could prove that, at the point of death, your soul/spirit/consciousness leaves the body and can see things that you couldn't while still in your body. It wouldn't prove that the soul was immortal (maybe it evaporates a few minutes after body death), nor that it can "pass on" to some sort of after life, not that there is a God or gods. And it certainly won't prove which of the many proposed gods and after-lives is the correct one.
3. Also, the idea that your "soul" can see things after it leaves the body would raise some other problems. Like, why do you need eyes to see while your soul is still inside its body? If the soul can see without eyes, what is the point of them? And if the soul's movement is trapped by its body, and its vision is blocked by flesh, what else blocks it? How does it get out of the room to wherever it is supposed to go? Iapetus (talk) 10:45, 16 May 2016 (UTC)

There is no evidence that "praying for the sick or for anything else does work." At best, it can make the patient feel better psychologically, provided he knows about it. There is only one kind of prayer that works - praying for one's own spiritual strength. That works, if the patient is open to it. But praying for an event or any other kind of "thing" doesn't "work". If it appears to work, it's superstition - it's really just randomness that happened to turn out well. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:12, 17 May 2016 (UTC)

Could an asteroid be ring-shaped ?

I picture a spherical asteroid, struck dead-on by a small, fast moving object, that punches a hole through it. Somehow I doubt if that would work, though, either breaking the asteroid into many fragments or melting it, in either case allowing it to coalesce back into a sphere. Maybe if the asteroid was flattened out from a high spin rate and the object struck it right on the axis ? StuRat (talk) 01:41, 14 May 2016 (UTC)

If the spin rate an dcollision speed were fast enough for the material to not coalesce in a sphere, it would be dispersed entirely. Fgf10 (talk) 12:27, 14 May 2016 (UTC)

Toroidal planets are possible, but they are not highly stable. A large impactor will cause them to collapse. So such a body is possible, but it has to coalesce from a primordial cloud with a high spin, and can't be created by the specific method StuRat proposes. (I only just found this out recently, but couldn't recall my source.) μηδείς (talk) 16:45, 14 May 2016 (UTC)

For future reference (since the search results will likely change) the leading search results include [4], [5], [6]. I remain less than confident this is possible from what I've read so far, but they think so and I can't rule it out. Wnt (talk) 19:13, 15 May 2016 (UTC)

Couldn't an exceedingly improbable string of tiny impacts "sculpt" an asteroid a few meters wide into a ring? Sagittarian Milky Way (talk) 19:45, 14 May 2016 (UTC)

larva on Mentha

Hey everyone, I found this larva on my Mentha. I try to identify this creature. I would glad to some help. I think it is a Chrysodeixis eriosoma but I'm not sure. thanks alot, --Tomsky2015 (talk) 09:22, 14 May 2016 (UTC)

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Well, there aren't many characters I'm really using here: I see it has three pairs of prolegs, and it's green, and it moves like an inchworm or looper. Without looking at your suggestion (which also fell in this category), I noted that some loopers in Noctuidae have three pairs of prolegs, such as the cabbage looper. (That, like yours, seems too fat to my eyes) There are various Noctuidae that come up on Mentha, but so far I didn't see a green one - it's not really easy for me to search. Pending some insight on how to find a better key, I think I'll leave this for now. Based on the lettering, is this from Israel, or somewhere else? Wnt (talk) 11:17, 14 May 2016 (UTC)

Wnt, Yes, Israel. Thank you very much. I looked on internet to see if I will find it by myself. My best result was Chrysodeixis eriosoma but your suggestion look right. Thank you and good day. --Tomsky2015 (talk) 12:45, 14 May 2016 (UTC)

Formulaic relation between two units

Suppose we don't know the simple formula to convert Centigrade into Fahrenheit or vice-versa. But, some how , we do know two or three instances of relationship between the two units. For example we know for sure that 5°C equals 41.0 °F, 17°C equals 62.6 °F, whereas 45°C is equal to 113.0 °F. My question is that, using these few instances how can we come up with a simple formula that can be used to turn any value of C or F to it's corresponding equivalent. 124.253.250.54 (talk) 12:16, 14 May 2016 (UTC)

Yes, provided we know that there is just a multiplication factor and a constant offset. It then becomes a simultaneous equation problem:

We only need two equations:

   45m + c = 113
    5m + c = 41

Now multiply the 2nd equation by 9 and subtract the 1st equation from it:

  (5m +  c = 41)×9
  45m + 9c = 369
-(45m +  c = 113)
        8c = 256

Solve for c then plug that back into the 2nd equation to solve for m:

         c =  32

   5m + 32 = 41
   5m      =  9
    m      =  1.8

Note that temperature conversions are a bit unusual in that they have a constant offset (except the conversion between Rankine and Kelvin). Without that you only need one conversion to find the multiplication factor, m. Similarly, you only need one conversion to find the constant offset, if there is no multiplicative factor (in other words, if it is 1, as in a Celsius to Kelvin conversion or Rankine to Fahrenheit). StuRat (talk) 12:44, 14 May 2016 (UTC)

All correct, we only need use two equations IF we already suspect the relationship is linear with an offset. The OPs third equivalence serves to confirm that. AllBestFaith (talk) 15:41, 14 May 2016 (UTC)

Yes, it's always a good idea to check your work by plugging the results into all equations provided. StuRat (talk) 16:50, 14 May 2016 (UTC)

Side note is that the mathematical definition of "linear" is there is no offset. --DHeyward (talk) 08:22, 15 May 2016 (UTC)

Darn, I guess most of the linear equations I've been using aren't. —Tamfang (talk) 08:22, 17 May 2016 (UTC)

A Linear transformation or linear operator, often represented by a matrix, has no "offset"; it sends zero to zero, as defining property. A Line, expressed as an equation in slope-intercept form (Y=mX+b), does not represent a linear map when b is not zero. Rather, it constitutes an Affine transformation. "Linear equations", confusingly, are almost surely not linear maps. SemanticMantis (talk) 03:31, 18 May 2016 (UTC)

The only reason why you know there is a linear relationship is because Celsius (since 1948 the preferred term, even though the guy had the scale backwards) and Fahrenheit are defined the same way, just with different numbers. Wnt (talk) 10:58, 15 May 2016 (UTC)

Some people, especially less technical or elderly ones, need a Mnemonic to help them remember the conversions between °C and °F. They may remember the constants 5, 9 and 32 which appear in both formulæ but not how to apply them. That incomplete memory leaves one in this quandary about converting:

Subtract 32 or not ?

Multiply by 5/9 or by 9/5 ?

Add 32 or not ?

The rule that works is: Make the 3 choices above that each ensure numerical °F is "warmer" than numerical °C. "Warmer" here means more positive number, which is true for all temperatures except minus 40 degrees and below, which is colder than you want to think about. AllBestFaith (talk) 23:33, 15 May 2016 (UTC)

The choice is easy between 9/5 and 5/9. Celsius degrees are larger than Fahrenheit ones, so when changing from Celsius multiply by 9/5 and when changing from Fahrenheit multiply by 5/9. For those who have problems with adding or subtracting 32 there is a formula which makes use of the fact that -40 is the same in both scales. Using the fact that 10 degrees C = 50 degrees F and looking for easy divisions I reconstructed it as follows:

• Fahrenheit to Celsius

Add 40. Multiply by 5/9. Subtract 40.

• Celsius to Fahrenheit

Add 40. Multiply by 9/5. Subtract 40. — Preceding unsigned comment added by 5.150.93.133 (talk) 09:13, 16 May 2016 (UTC)

I think it's easier to remember that freezing is 0 C and 32 F. If you can remember that 212 F = 100 C and understand 212 = 180 + 32, you're golden. Wnt (talk) 17:00, 16 May 2016 (UTC)

It was shown that a linear equation derived from two data points also fit the third data point. But does that really prove that there is no higher order relationship between the two variables (in cases where it is two variables of unknown relationship)? Might there be higher order relationships which also fit the three data points? Edison (talk) 14:37, 18 May 2016 (UTC)

Possible, but unlikely, in the general case, and it would require some slightly more complex equations. Since we know these units are each linear, and don't follow such complex equations, it shouldn't be possible here. Perhaps where non-linear units are used, like star's absolute and apparent magnitudes, then that conversion issue might come up. StuRat (talk) 14:53, 18 May 2016 (UTC)

There are an infinite number of higher-order relationships, including an infinite number of different degree polynomials. A great example of students using Excel to "prove" something silly is when they curve-fit a scatter-plot of n data-points using a polynomial with degrees≥n. "It's a perfect fit, so that must be the physical relationship or equation I was trying to prove." Um, no. An infinite number of lines can pass through one point, an infinite number of parabolas can go through two given points, etc. It goes back to the number of variables (here, coefficients of each term) vs number of equations (points). DMacks (talk) 16:16, 18 May 2016 (UTC)

Would dynamic tension work in space?

Dynamic tension is about contracting your muscles and moving them against each other Dynamic_Tension Would astronauts be able to use it to stave off bone loss and keep healthy? Bastardsoap (talk) 16:20, 14 May 2016 (UTC)

Yes, but it might be difficult to keep tabs on them. You would need to put a strain gauge between their hands to tell how much force they are really exerting, while a stationary bike is easier to monitor. Also, dynamic tension exercises don't do as much cardio, and that's important, too. StuRat (talk) 16:47, 14 May 2016 (UTC)

It's not that hard to add cardio with dynamic tension, you just have to contract less and do more reps Bastardsoap (talk) 17:31, 14 May 2016 (UTC)

I'm skeptical that you can get your heart rate up and keep it up as long as on a stationary bike. StuRat (talk) 17:41, 14 May 2016 (UTC)

Try a ddp yoga workout and see for yourselfBastardsoap (talk) 17:59, 14 May 2016 (UTC)

Its not a substitute for gravity and therefor this is still a well known health issue for long missions. Besides that gravity also completely affects cords and tissue and you can not substitute all that just with "some gymnastics". For that you find extensive artificial gravity constructions in Spacevessels in better Sci-fi movies like 2001: A Space Odyssey (film). --Kharon (talk) 12:14, 15 May 2016 (UTC)

A better solution would be a rotation that creates a 1G force. Exercise may help certain muscle tone and bone density but balance seems more important. To wit, a 150lb, 6 foot man can walk. So can a 300lb, 6ft man. I wouldn't expect that giving a 150lb backpack to the 150lb man would make him equivalent to the 300lb man in their ability to function. Both have adapted to their condition. --DHeyward (talk) 09:15, 16 May 2016 (UTC)

There are several disadvantages to a ship rotating fast enough for 1g:

1) Unless it's a large radius, the difference in g force when you stand up will induce nausea.

2) You lose the advantage of astronauts being able to move large pieces of equipment on their own.

3) Docking can only happen at 2 points, along the axis, and then you still need to match the rotation.

4) EVA's on the outside of the ship to do maintenance while it's rotating are impractical, so then you need to be able to stop the rotation and restart it, using up fuel.

5) Solar panels and communications antenna need to be moved constantly, to keep them aimed at their targets, causing them to break down sooner. The communications problem could be solved by having a sister ship which doesn't rotate, to do all the long distance communications, but that would require station keeping to keep them apart, and maintenance wouldn't be easy there. StuRat (talk) 15:53, 16 May 2016 (UTC)

Well, a lot of sci-fi designs suppose a limited centrifuge space for exercise with large nonrotating sectors at either end, to which ships dock. The centrifuge has limited uses that don't require much heavy equipment or stuff on its outer hull. Of course, given the stress involved I'd think you'd still have to check that hull for cracks and fatigue, which involves EVAs; but in theory the angular momentum can be transferred to a flywheel or to one of the end pieces or a second centrifuge section (rotating the other way) without the need for propellant usage, just electricity. Wnt (talk) 17:04, 16 May 2016 (UTC)

There the joints between rotating and non-rotating parts become risky, and an astronaut entering or leaving the rotating part needs to spin up or spin down their body. StuRat (talk) 17:11, 16 May 2016 (UTC)

Risky, sure. But what part of getting into a rocket and being blasted into space and trying to live in a tin can surrounded by vacuum isn't risky? I'm sure they would think of ways to protect the joints and make them safely separable under various contingencies. Wnt (talk) 10:14, 18 May 2016 (UTC)

Sure spaceflight is risky, but this is why they need to minimize the risk at every step. And if a stationary bike is less risky, that's what they will choose. However, for long term space travel, like to Mars, they may need to rotate the ship because getting exercise alone just isn't enough over such long terms. But for low-Earth orbit, why rotate the ship when you can just rotate the crew ? :-) StuRat (talk) 14:59, 18 May 2016 (UTC)

It's not that simple. According to NASA "the risks of these problems occurring [bone loss and kidney stones] cannot be completely eliminated through physical exercise alone." [7] Richerman (talk) 22:45, 16 May 2016 (UTC)

Measuring calories

I heard somewhere that scientists determined the number of calories in carbohydrates, fats, and proteins by measuring how much heat the body produced after eating. I know scientists have burned carbohydrates, fats, and proteins in a calorimeter and found a discrepancy between how much heat is released when protein is burned in a calorimeter and how much energy is produced when protein is metabolized in the body. The body gets 4 calories per gram from proteins, but burning a gram of protein in a calorimeter yields considerably more energy. How do scientists know how many calories the body gets from a nutrient like protein?174.131.47.80 (talk) 18:37, 14 May 2016 (UTC)

Yes, there is a problem using a bomb calorimeter (or any other type), in that not everything that's flammable is digestible, with an obvious example being wood. I wouldn't think measuring heat produced by a person following a meal would work, either, though, as then you have confounding factors like the amount of food energy stored as fat to be burnt later, or retrieved from fat stored from previous meals. I would think using mice for this test would be better, since presumably they can digest about the same things we can, and you could feed them an all-protein, all-carb, or all-fat diet for their entire (short) life without violating medical ethics (although PETA might not like it). StuRat (talk) 20:34, 14 May 2016 (UTC)

The gross energy (GE) of a food, as measured by bomb calorimetry is equal to the sum of the heats of combustion of the components – protein (GE_p), fat (GE_f) and carbohydrate (GE_cho).

${GE}={{GE}_{p}+{GE}_{f}+{GE}_{cho}}\,$

Wilbur Olin Atwater 1844 - 1907 considered the energy value of faeces in the same way.

${GE}^{F}={{GE}_{p}^{F}+{GE}_{f}^{F}+{GE}_{cho}^{F}}\,$

to develop the Atwater system for calculating the available energy of foods:

${\text{Metabolisable Energy}}=\left({\text{Gross Energy in Food}}\right)-\left({\text{Energy lost in Faeces, Urine, Secretions and Gases}}\right).$

AllBestFaith (talk) 23:56, 14 May 2016 (UTC)

Amino acids are not completely cataboilized by animals. Therefore the bomb calorimeter significantly overestimates their biologically relevant energy content due to the energy remaining in urea. Ruslik_Zero 08:06, 15 May 2016 (UTC)

There are also whole room calorimeters that you can stick a person in, and control the gases and other materials coming in and out while also taking measurements. --OuroborosCobra (talk) 00:13, 17 May 2016 (UTC)

May 15

H2CL2

Why does this here [8] is 2HCL but not H2CL2 ? --Ip80.123 (talk) 01:02, 15 May 2016 (UTC)

It is dichloromethane, there is a "C" (carbon), that is not labeled, in the center of this skeletal diagram. And it's completely not true that the two H are "across" from each other or at right angles to the two Cl and vice versa. Our article has some nice 3D diagrams of the shape of this chemical, a detail that is easy to mis-understand in the image you found. DMacks (talk) 02:14, 15 May 2016 (UTC)

The Implicit carbon and hydrogen atoms section of the above article is the most important. LongHairedFop (talk) 16:54, 15 May 2016 (UTC)

Where are Salmonella bacteria are founded in the eggs?

Sometimes I hear about the risk to consume eggs in some places in the world since they contains a high level of salmonella. Where are Salmonella bacteria are founded or located in the eggs, are they founded on the shell from outside or into the eggs or maybe both places? (it matters for example, for case that we can wash well the eggs with soap)93.126.95.68 (talk) 06:18, 15 May 2016 (UTC)

See Salmonellosis#Causes, which says that an infected hen can transmit the bacteria to eggs she produces, or bacteria can enter the egg through the shell. Egg shells contain small pores to allow in air for the embryo to "breathe". --71.110.8.102 (talk) 06:59, 15 May 2016 (UTC)

The U.S., Japan and a few other countries do wash them for that reason but then you need to keep them refrigerated.[9] Rmhermen (talk) 12:52, 15 May 2016 (UTC)

If you wash an egg with soap then the soap can get inside... The Quixotic Potato (talk) 13:13, 15 May 2016 (UTC)

In Israel it's forbidden to wash eggs in water according to the health minister (this is for public places) and for the citizens it's not recommended, because the bacteria can get inside through the shell. I would like to know about other countries. 93.126.95.68 (talk) 03:23, 16 May 2016 (UTC)

Same here, in the Netherlands, it is not recommended (but I don't know if its forbidden in public places). Washing eggs is a bad idea. My brother has pet chickens. If you google "wash eggs" you will find many sites that all say something similar to this: "Eggs are laid with a natural coating on the shell that is applied as the last step in the laying process called the "bloom" or sometimes the "cuticle". This coating is the first line of defense in keeping air and bacteria out of the egg. Since eggshells are porous, if you wash your eggs as soon as you collect them, you are removing that natural barrier." [10] The Quixotic Potato (talk) 12:01, 16 May 2016 (UTC)

This PDF says: Current European Union legislation prohibits the washing of Class A eggs. The Quixotic Potato (talk) 12:09, 16 May 2016 (UTC)

Here are the recommendations from the Food Standard Agency in Ireland regarding egg washing.[11] DrChrissy ^(talk) 16:03, 16 May 2016 (UTC)

This is a rather informative, non-technical account of the pros and cons of egg washing.[12] DrChrissy ^(talk) 16:07, 16 May 2016 (UTC)

Looking for the Full List

Over ten years ago, I read a tract in which the Author spoke of seven, what I believed he called, principles of engineering, or principles of mechanics, and named them as the cog, hinge, lever, pulley, screw, spring and wedge. I think what we was saying was that these were the seven foundations of mechanical movement, and I wonder, whether there were more, and also, if anyone else has heard of such a list, and what it was called. I could think also of the wheel, the ball, a ball and socket joint, although that could kind of be thought of as some specialised kind of hinge, bearings, couplings, nails, chains, among other things. But perhaps the list was about such things at their most basic level, where these become the basic parts to more complicated machines. I suspect also that the rubber band is seen as a kind of spring, at least in a more basic sense. If anyone has any other information on this, that would be good. Thank You. Chris the Russian Christopher Lilly 06:34, 15 May 2016 (UTC)

Simple machines. Sagittarian Milky Way (talk) 06:39, 15 May 2016 (UTC)

Thank You for that.Chris the Russian Christopher Lilly 00:39, 16 May 2016 (UTC)

Nostrils--- one or two?

Both my nostrils have been clear for the last couple of months. ie I can breathe thro both of them at the same time. Is this normal? I seem to remember reain on a WP page that nostreils alternate in being clear for operation. Is that statement false? — Preceding unsigned comment added by 178.106.99.31 (talk) 17:44, 15 May 2016 (UTC)

Yes sorry I forgot to sign.,--178.106.99.31 (talk) 17:46, 15 May 2016 (UTC)

See Nasal cycle. However, although there is a regular alternation, most people are not acutely aware of one nostril being blocked and the other open. If you feel that one nostril is blocked for a longish period, you have a problem. 81.132.106.10 (talk) 17:55, 15 May 2016 (UTC)

Both my nostrils have been clear for a few months. Is that usual?--178.106.99.31 (talk) 17:57, 15 May 2016 (UTC)

It's unclear whether asking why no one has punched you lately or telling you to read our guideline against medical advice would be more helpful. μηδείς (talk) 19:03, 15 May 2016 (UTC)

I dont think my inferior turbinates are undergoing alternating complete turgescence as far as I can tell at the moment. Am I fooling myself,or is it that I am in the 20% of the population that does not exhibit alternating turgesence? Or is it possible that I only experience partial turgesence in either nostril?--178.106.99.31 (talk) 22:56, 16 May 2016 (UTC)

Gas analysis

Can it be told what is wrong with a persons body by analising the anal gas emanations?--178.106.99.31 (talk) 17:57, 15 May 2016 (UTC)

Possibly not what you are asking, but my sister-in-law who is a nurse has told me that they can tell what the difference is between a Clostridium infection, C.diff and gastro-enteritis simply by the smell of the stools. The human nose is, as always, a far superior organ to any artificial nose. --TammyMoet (talk) 18:45, 15 May 2016 (UTC)

I'm impressed that she can tell Clostridium from Clostridium difficile! —Tamfang (talk) 08:37, 17 May 2016 (UTC)

As for now, you mean. Robotic noses are surveillance technology, and nothing is being funded and developed so much as surveillance technology. Wnt (talk) 16:18, 17 May 2016 (UTC)

You can detect some diseases by analysing exhaled gases, which is close to the OP's question. [13]. LongHairedFop (talk) 21:03, 15 May 2016 (UTC)

Analyzing gases from breath and skin is well known and can be refined. Tuberculosis makes skin smells like bread, some myocardial infarctions make skin smell burned or like smoke. Some blood suggar problems make breath smell like aceton or paint thinner. --Hans Haase (有问题吗) 09:19, 16 May 2016 (UTC)

Animals have amazingly developed senses of smell. See [14] and Canine cancer detection. 5.150.93.133 (talk) 09:49, 16 May 2016 (UTC)

There was a larger studie on flatulence gas mixture analysis a read a few years ago (I thought about how the collection was done) and there a peolple with hydrogen as a main compound while others have methane as a main compound, most of it is carbon dioxide any way. But the studie did not mention the trace gases which could indicate the mixture of microorganisms in the digestive tract.--Stone (talk) 10:06, 16 May 2016 (UTC)

Flatus can be collected in a "flatal bag" and then analyzed, but this doesn't seem to happen much, presumably because there are more accurate ways to evaluate digestive system problems, such as a stool analysis, where the collection method is simpler. However, a sudden change in flatulence, without any obvious cause like a change in diet, might be reason to see a doctor. StuRat (talk) 16:08, 16 May 2016 (UTC)

The methane test is quite entertaining! ;)--178.106.99.31 (talk) 20:43, 17 May 2016 (UTC)

"Flatus bag" being the more standard name (as usual, WP articles tell us things). DMacks (talk) 03:52, 18 May 2016 (UTC)

its all about light

from where does the light gets its speed111111111us (talk) 18:19, 15 May 2016 (UTC)

The speed of light in a vacuum appears to be a universal physical constant of the universe. No practical answer to "why is it that way?" exists for such constants except for "because that's the way it is". — Lomn 18:46, 15 May 2016 (UTC)

Exactly. The speed at which light propagates can be decomposed into vacuum permittivity and vacuum permeability, which are fundamental constants that represent electric- and magnetic- components. Some physics books consider these properties to be even more fundamental constants than c (which can be derived from these other constants, based on our understanding of the way electric- and magnetic- fields interact). At the end of the day, they're still just constants that never seem to change, no matter how we measure them - and although we can study them from lots of perspectives, we don't actually have any specific explanation for why they take any particular value.

Nimur (talk) 20:42, 15 May 2016 (UTC)

The article Electromagnetic radiation also sheds some light on the subject. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:53, 15 May 2016 (UTC)

Surprisingly, the answer to scientific questions is sometimes "philosophy or religion". The science don't know. (besides "whatever it is, the current speed of light will not be one of the values that makes your species impossible"). Sagittarian Milky Way (talk) 20:51, 15 May 2016 (UTC)

I agree it's philosophy but i'm not sure why anyone would call it "religion", it has very little in common with religion. In fact, one of the major philosophical shifts of the scientific revolution was to stop trying to explain the world with answers to "WHY?" questions, using agency and motivation to explain natural phenomena, and instead explain it with answers to "HOW?" questions using mathematics and models. In this case, it's not that "science doesn't know 'why' light travels that fast", it's because that question does not have a useful answer. Of course we can scientifically answer a "why" question like "why does a ball drop when you let it go", but you can't "why?" all the way down, the buck HAS to stop somewhere, and with science, the buck stops at the natural explanan it, because Gravity IS that way, or light IS that way. Religion would always take it one step further and say because god MADE it that way, but that extra step doesn't actually ADD any explanatory power so science dropped it. Vespine (talk) 01:18, 16 May 2016 (UTC)

See also Non-overlapping magisteria for one viewpoint on this. --Jayron32 02:04, 16 May 2016 (UTC)

It's only religion for some people. Sagittarian Milky Way (talk) 03:09, 16 May 2016 (UTC)

It depends on what "God" means. If you equate "God" to "Nature", then "God made it that way" is totally valid. But as you say, it doesn't really add any new information. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:40, 16 May 2016 (UTC)

It's rather nonintuitive, but light doesn't seem to accelerate or decelerate, it just always goes the same speed (in a given medium), similar to how electrons jump from one energy level to another, without seemingly ever having been in-between. The proverbial "quantum leap". StuRat (talk) 21:56, 15 May 2016 (UTC)

There is mention of nanoseconds there, isn't this rather slow in consideration with light ? So you say that the electrons jump ( in a few nanoseconds ), generating light in the process - which does not accelerate but is a full c speed right from the beginning. Is it that the famous quantum leap ? --Askedonty (talk) 11:17, 16 May 2016 (UTC)

Yep. StuRat (talk) 04:11, 18 May 2016 (UTC)

Watch this video: [15] --71.110.8.102 (talk) 08:32, 16 May 2016 (UTC)

May 16

.1 (leading 0 is implicit)

Is .1 (leading 0 is implicit) always the same as 0.1? And even if mathematically they are the same, could a manual of style advise editors not to use the one or the other?--Llaanngg (talk) 01:37, 16 May 2016 (UTC)

yes and yes, seems obvious..is there a specific context for asking this?68.48.241.158 (talk) 01:44, 16 May 2016 (UTC)

It may not be the same if the "." in .1 is actually a blemish on the paper. Note that there could be infinite leading zeros, as there is no unit, no ten, no hundred etc.... Our style guide should have something to say on the matter. Graeme Bartlett (talk) 01:46, 16 May 2016 (UTC)

The style manual says to use the leading 0:Wikipedia:Manual of Style/Dates and numbers#Decimals. Graeme Bartlett (talk) 01:59, 16 May 2016 (UTC)

Indeed the mathematics and interpretation of .1 is the same as 0.1 - and style determines which to use. The leading '0' is a huge aid to readability - especially when you consider that there are parts of the world where the role of '.' and ',' are interchanged in their meaning within numbers. SteveBaker (talk) 02:17, 16 May 2016 (UTC)

I think Steve should have stopped before "especially". In areas where "," is the decimal point and "." is the thousands separator, neither ".123" nor "0.123" is a possible number; instead we would be talking about ",123" and "0,123", neither of which is a possible number where we live. --69.159.60.83 (talk) 05:51, 16 May 2016 (UTC)

The problem comes in when it is used cross-culturally. For example, if we wrote "Color was blue,and the quantity measured,123", that might be taken to mean 0.123 in a place where a decimal comma is used. Adding a space after each comma helps reduce this type of error. StuRat (talk) 16:30, 16 May 2016 (UTC)

Why is this question on the Science Desk? Joseph A. Spadaro (talk) 04:21, 16 May 2016 (UTC)

Species of deer fly

A deer fly with a centimeter scale

Can anyone identify the species of this deer fly (from near the Atlantic coast of Georgia)? Bubba73 ^{You talkin' to me?} 03:25, 16 May 2016 (UTC)

Not a very clear image - but it could be Chrysops vittatus (full description here - http://animaldiversity.org/accounts/Chrysops_vittatus/ ) 81.132.106.10 (talk) 20:44, 16 May 2016 (UTC)

Thanks. It is hard to take a photo of things that small. Here is another one. Bubba73 ^{You talkin' to me?} 02:54, 17 May 2016 (UTC)

Another view

Follow-up question

Why do the eyes change from one photo to the other? (It is the same deer fly.) Bubba73 ^{You talkin' to me?} 03:36, 18 May 2016 (UTC)

It's a still dead no eyed deer fly. Vespine (talk) 06:28, 16 May 2016 (UTC)

Not sure if it's the same as for fish, but their eyes cloud up after death, so you want clear eyes to get fresh fish. StuRat (talk) 15:06, 18 May 2016 (UTC)

That is probably it. The first photo was taken shortly after death - the other was several hours later. Bubba73 ^{You talkin' to me?} 22:31, 18 May 2016 (UTC)

Can a pregnant woman become pregnant again while still pregnant?

Can a pregnant woman become pregnant again while still pregnant? Just curious about that odd situation. If this were the case, the woman might give birth to a baby. And then, say, 4 months later, give birth to a second baby. Is this possible? Has this ever happened? Does this have a name? Thanks. Joseph A. Spadaro (talk) 04:23, 16 May 2016 (UTC)

Superfetation which has happened with human children conceived two months apart. This was very easy to find with google. μηδείς (talk) 04:59, 16 May 2016 (UTC)

It's possible, as noted, but very rare and abnormal in humans. Normally in humans, ovulation is suppressed during pregnancy by high levels of progesterone. Most hormonal contraceptives work the same way, by containing a progestin that has the same effects. --71.110.8.102 (talk) 06:30, 16 May 2016 (UTC)

It is worth noting that although there are a few recorded cases of a second conception (though only during the early stage of the first pregnancy - two months seems to be the longest recorded gap) the births in each case have been simultaneous. It seems extremely improbable that the first conceived child could be delivered, while the second one then continued to develop in the womb for a significant period. 81.132.106.10 (talk) 08:21, 16 May 2016 (UTC)

However, there are cases where twins are born some months apart because of danger to one of the babies. Do a Google search on "twins born some months apart" for examples. --TammyMoet (talk) 10:06, 16 May 2016 (UTC)

I believe these two cases can be reconciled by stating that it normally requires medical intervention to deliver only one of the babies without the other(s) being born soon after. A C-section, presumably, is the normal medical intervention. Not sure if this would be possible with identical twins, which share the same amniotic sac (could it be cauterized/sutured ?). StuRat (talk) 16:18, 16 May 2016 (UTC)

No, StuRat; monoamniotic twins are extremely rare. DMacks (talk) 16:37, 16 May 2016 (UTC)

Not that rare, "about 1% of twin pregnancies", according to our article. StuRat (talk) 17:17, 16 May 2016 (UTC)

No Stu. 0.00285714285714% to 0.0016666666666667% of pregnancies is extremely rare!--TMCk (talk) 17:41, 16 May 2016 (UTC)

I don't think it is. We wouldn't call a disease that was that common "extremely rare", as then up to 200,000 people worldwide would have it. But, again, you are taking the percentage of the entire population, while I was only talking about identical twins. StuRat (talk) 17:47, 16 May 2016 (UTC)

Sure. That's why you removed the inconvenient part of your post. Full of it as always.--TMCk (talk) 17:55, 16 May 2016 (UTC)

I didn't notice that they had stated the odds directly in the article the first time, and removed my math and replaced it with a direct quote as soon as I did. And keep the attitude off the Ref Desk, please. StuRat (talk) 22:52, 16 May 2016 (UTC)

While it isn't a "disease", the accepted medical definition of "rare" is covered at Rare disease, with definitions ranging from 1/1000 of 1/200,000 as being "rare". .002% is 1 out of 50,000 pregnancies. --Jayron32 17:57, 16 May 2016 (UTC)

Do they define "Extremely rare" ? StuRat (talk) 22:52, 16 May 2016 (UTC)

I actually believed something similar. But I also did what TammyMoet recommended. From there I read sources like [16] which suggest this can occur without apparent significant medical intervention medical intervention. In fact [17] suggests medical intervention in the opposite direction i.e. ensuring the second twin was delivered at the same time used to be more common.

Note also that the original discussion was about pregnancies with conception happening at different times. Monoamniotic twins are already rare enough. Monoamniotic non identical twins with conception happening at different times is probably as close to impossible as we get in biology.

Perhaps of more relevance to the original question is that in rare cases a women with double uterus have had successful pregnancies in both uterus simultaneously. StraighDope mention a few, another slightly more recent one is here [18]. Possibly conception happening at different times is more likely in these cases than in a more "normal" case although since there are so few of them, conceptions happening at different times would be more likely in more "normal" cases. (To be clear, I'm not saying conception at different times is likely if a woman has a double uterus, but rather the probability of it happening, low that it is, may be higher.)

Nil Einne (talk) 18:23, 16 May 2016 (UTC)

Would that be "double uteri" ? StuRat (talk) 22:56, 16 May 2016 (UTC)

Thanks. Let me follow up with a question of semantics. Let's look at two possible scenarios. Scenario "A": Two babies are conceived at different times, but both are born at the same time. For example, the first conceived is delivered normally today, but the second conceived is delivered early (prematurely), also today. Scenario "B": Both babies are conceived at the same time. One is delivered today, and the other is delivered some time down the road, maybe a month later (for whatever medical reasons). Are the babies in Scenario "A" properly called "twins"? And how about Scenario "B"? Thanks. Joseph A. Spadaro (talk) 03:56, 17 May 2016 (UTC)

(sorry, just an opinion, but I can't help myself): I think that if a woman spends a day with two babies (well, fetuses or embryos) inside her, she is carrying twins. And once a twin, always a twin. So I'd say A and B. Requiring the same moment for conception or parturition doesn't make sense because babies are rarely conceived nor born at precisely the same moment. (Well, identical twins are conceived at once, or fertilization might truly simultaneous, and maybe they can be "born" the same moment by Caesarian, but that's kind of stretching it) A consequence of this logic is that in theory baby 1 can be a twin of baby 2, and baby 2 of baby 3, but not baby 1 of baby 3. If someday that happens, I can live with that semantics. Oh, also I see the source used above actually uses "twins" to refer to staggered pregnancies two months apart in two uteri. Wnt (talk) 09:50, 17 May 2016 (UTC)

May 17

Parachuting

What special precautions (if any) must be taken when parachuting into a heavily forested area? 2601:646:8E01:515D:F88D:DE34:7772:8E5B (talk) 01:49, 17 May 2016 (UTC)

https://en.wikipedia.org/wiki/D._B._Cooper68.48.241.158 (talk) 02:30, 17 May 2016 (UTC)

That should be avoided if at all possible. The parachutist is likely to get hung up in a tree and need rescuing, so communication equipment and GPS would be needed, and water to drink until the rescuers arrive. Diapers might be a good idea, too. StuRat (talk) 02:34, 17 May 2016 (UTC)

Also, try to avoid carrying large satchels of money, as D.B. Cooper did. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:44, 17 May 2016 (UTC)

I wonder if a specially designed parachute could be made that would allow the occupant to lower themself down on a rope to the ground. Depending on the height of the trees, it could be hundreds of feet down. Of course, there would still be the risk that they would hit a branch and be killed or incapacitated. StuRat (talk) 02:47, 17 May 2016 (UTC)

Aside from pre-planning as you're suggesting, the best advice would be, "When parachuting into a forest, try to avoid trees." ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:49, 17 May 2016 (UTC)

That might not be as silly as it sounds. Obviously, where you have complete tree cover, avoidance isn't possible. But if aiming for a clearing in the middle of forested area, a stunt parachute may help to steer it into the clearing. StuRat (talk) 15:17, 18 May 2016 (UTC)

For unintentional tree landings in sport parachuting, see the "Trees" subsection of 5-1F (General Recommendations / Skydiving Emergencies / Landing emergencies) of the USPA Skydiver's Information Manual. -- ToE 03:20, 17 May 2016 (UTC)

For paratroopers intentionally targeting forested areas, see Treejumping. -- ToE 03:31, 17 May 2016 (UTC)

For forestry personal, I would have expected us to have something under Fire jumper, but alas that link is currently red. see Smokejumper -- ToE 03:36, 17 May 2016 (UTC)

I created redirects from Fire jumper and Firejumper to Smokejumper. --Guy Macon (talk) 10:24, 17 May 2016 (UTC)

Here's a publication from the FAA that includes both regulatory and advisory details on parachute landing areas (e.g., information about mandatory rules and optional decisions): from their advisory circular database, Report DOT/FAA/AR-11/30, Criteria for Parachute Landing Areas on Airports. In their section on hazards, they describe trees, and recommend sizes of areas at specific distances from dense trees. There are a lot of useful diagrams. More complex operations need more obstacle-clearance. The publication also references several Army sources for paradrop operations; if you actually do decide to go parachuting, those field manuals are sort of the "canonical" source of math and equations. For example, the FAA cites FM 3.21 Pathfinder Operations for equations on landing drop zone sizes. Obviously, consult your dive-master or parachute jump coordinator for more specific, current, local information.

More good reading: Advisory Circular 105-2D, Sport Parachuting; this government publication advises about hazard and obstacle avoidance, and references several other publications of the U.S. Parachuting Association as further reading. For example, here's the Skydiver's Information Manual, a lengthy 270-page book that includes the BSRs (Basic Safety Requirements). These are advisory rules - the Government doesn't enforce them, but FAA encourages you to learn from a reputable instructor, especially one affiliated with USPA, and to adhere to their safety rules. Per Federal Aviation Regulations parts 91.15, 105.21, 105.23, and 105.25, the Government doesn't really care what happens to you if you fall out of an airplane - as long as the pilot takes "reasonable precaution," and provided that you don't land on an airport, a congested area, or special use airspace. You can land on those things too, provided that you carefully comply with the rules. But if you splat on a tree, that's sort of on you; or, rather, you are on it.

Part 105 of the Federal Aviation Regulations does specify actual federal laws that pertain to parachute operations ("skydiving").

Nimur (talk) 04:26, 17 May 2016 (UTC)

Thanks, all! ToE was especially helpful. Now, a follow-up question: Does Baseball Bugs's advice about large satchels of money also apply to carrying weapons and ammo? 2601:646:8E01:515D:F88D:DE34:7772:8E5B (talk) 11:29, 17 May 2016 (UTC)

Well, the more weight you carry the larger the parachute would need to be to support that weight. At some point it would no longer fit in a backpack, but then an alternative deployment system can be used. Alternatively, ammo and supplies can be sent down on their own parachute. Not so good when there's just one jumper, because if he doesn't find and retrieve his supplies he is in rough shape. But with many jumpers, they will find at least some of the supplies and ammo. I wonder if a timed system could then be used to lower the supplies and ammo on a line after they hit the trees. (Some would get hung up, but not all.) StuRat (talk) 13:39, 17 May 2016 (UTC)

Good -- that's just what I needed to know! 2601:646:8E01:515D:F88D:DE34:7772:8E5B (talk) 04:38, 18 May 2016 (UTC)

Maybe read through the U.S. Army's Airborne School description. The life of an airborne infantryman is not an easy one. Before they let you jump at all, you have to be pretty prepared. Before they let you do a tactical jump with full equipment, there are a handful of requirements, including completion of Basic Combat Training (described in detail at the Army recruiting page). Weapons, ammunition, and jumping out of airplanes are each uniquely dangerous; there's a lot of prerequisite training to prepare yourself physically and mentally.

Nimur (talk) 14:02, 17 May 2016 (UTC)

“have to be pretty prepared.” Brain washed more like it! Here on Wikipedia many editors take exception to 'fringe science' . This is a good example of a 'so called' intervention that has not under gone any – repeat- any scientific randomised trials. Read: Parachute approach to evidence based medicine. So it also needs hating as we don't give answers to anything remotely medical in nature.--Aspro (talk) 19:30, 18 May 2016 (UTC)

bioengineering a space telescope lens

Could it be feasable or beneficial to develop a space telescope that incorporates biological material? For instance, using elecrowetting with synthetic electrolytes in order to create a superfluidic lens that can be spun in zero-G to generate a concave lense shape. Would this have an advantage over traditional designs (ie, self-repair in case of micrometeor strikes, curvature adjustability)?

119.171.79.241 (talk) 05:08, 17 May 2016 (UTC)

I'm not sure if it's me or you but I think you are mixing up some concepts which are not necessarily related. We have an article about Liquid mirror telescope which is directly related to what you are asking, but it does not seem like you need to involve biology, electrowetting or superfluidity. Unless you think somehow those factors would counteract the fact that I'm not sure simple spinning would stop the fluid from just floating off in zero G. Vespine (talk) 05:33, 17 May 2016 (UTC)

Aaand we also have this artcile Liquid mirror space telescope. Vespine (talk) 05:36, 17 May 2016 (UTC)

There is high energy radiation in space that even has an aging impact on tough construction materials. Any biological material would either have to be very tough in multiple senses or its simply put in a very wrong place. --Kharon (talk) 02:49, 18 May 2016 (UTC)

• Space telescopes need phenomenally precise lenses – the Hubble Space Telescope was very nearly ruined by just a 10 nanometer error in the mirror grinding stage – and I doubt you could get practically achieve that precision with biological growth (you'd basically need every cell to be in exactly the right place). A non-biological liquid mirror telescope is already adjustable and (since it's just liquid) largely self-repairing. Smurrayinchester 08:30, 18 May 2016 (UTC)

If you read that link more carefully, the 10 nm tolerance was fine, and the mirror met that tolerance. The problem was not the tolerance; it was the shape, which was off by more than 200 times the tolerance at the edge. --Trovatore (talk) 20:07, 18 May 2016 (UTC)

Go/no go thread gauge

When you have a pair of Go/no go thread gauges, is the go male thread gauge supposed to screw freely into the go female thread gauge?

There are 4 possible combinations:

1. go male + go female

2. go male + no go female

3. no go male + go female

4. no go male + no go female

Which of the four is supposed to screw freely into the other? Johnson&Johnson&Son (talk) 06:35, 17 May 2016 (UTC)

Yes. A "go" is essentially the "correct" version of the thread, so a go male will fit into a go female (case 1). A "no go" is the other test, it is NOT SUPPOSED to fit into the go thread, so case 2 and 3 should fail, (NOT fit more than 3 turns). Whether it is possible for a no go to fit into a no go is undefined to the test and i am not familiar enough with it to say if there is a 'common' or 'standard' resolution, i.e. if they "usually" do fit or usually do not fit, but it does not matter to their actual purpose. Vespine (talk) 06:47, 17 May 2016 (UTC)

• No it's not supposed to screw anywhere! They're both precise and hardened. Screwing gauges together like this is a route to damaging them. Especially when people "store" them screwed together like this (avoid all contact on the gauging faces in storage anyway).

The "go" gauge is intended to fit a workably sized thread. So the male go gauge should fit the female go gauge. The other combinations should not fit. The no go / no go combination won't work because the male is oversize and the female undersized, so it won't fit by two tolerances, not just one.

Note that it's not practical to use this sort of simple go/no go gauging to detect a faulty undersized male thread, or an oversized female. It is rarely seen that a "must not fit" gauge is produced where "no go" is then correct behaviour (ie an undersized female gauge used for detecting undersized male threads). These are rare though, as they create endless confusion with unfamiliar operators. Andy Dingley (talk) 10:32, 17 May 2016 (UTC)

Free gases

Are there any free gases floating about in the solar system between the planets?--178.106.99.31 (talk) 21:13, 17 May 2016 (UTC)

See Interplanetary medium. CodeTalker (talk) 21:16, 17 May 2016 (UTC)

(ec) sure, there is. See interplanetary medium. On the outskirts of the Solar System it transitions, via a heliopause region, into interstellar medium. All along, it's a mixture of dust, neutral and ionized gas, with varying composition. You may also want to read plasma (physics) article,. --Dr Dima (talk) 21:25, 17 May 2016 (UTC)

So are the gases differnt depending on which planet you are near?--178.106.99.31 (talk) 21:54, 17 May 2016 (UTC)

Yes. see Solar wind#Solar System effects. The solar wind interacts with the top layers of the planet's atmosphere, so that there is a persistent flux of matter from the planet's atmosphere into the interplanetary medium. The amount and composition of atmospheric material being stripped by the solar wind depends on the planet's mass, radius, orbit, atmosphere composition density and temperature profile, strength of the planet's magnetic field, and so on. Mars lost most of its atmosphere this way, while Venus, Earth, and the gas giants still have substantial atmospheres. I don't remember the Earth rate of atmospheric loss, but I'll add it here when I find it. --Dr Dima (talk) 22:57, 17 May 2016 (UTC)

Here you go: Atmospheric escape. You may also want to read Atmosphere of Earth#Evolution of Earth's atmosphere. --Dr Dima (talk) 22:59, 17 May 2016 (UTC)

May 18

Polypropelyne capacitor marking

I have some PP capacitors marked with the letters MKT. What do these letters mean?--178.106.99.31 (talk) 14:10, 18 May 2016 (UTC)

It's a code for the type of capacitor construction. As noted at the Wikipedia article film capacitor and at this table here, MKT is code for "metallized polyester foil". I don't know that the letters directly stand for anything. --Jayron32 14:21, 18 May 2016 (UTC)

Thanks. Couldnt find it in the article before, but found it now. So my capacitors are polyester not polypropylene. It seems the M stands for metal, the T is from polyester and the K means?? So polyprop would be marked MKP. :)--178.106.99.31 (talk) 14:31, 18 May 2016 (UTC)

These codes were the German ISO 41379 ; (declared obsolete, [19]). See altungen this(de) document: the 'K' would be Kondensator (probably not 'Keramik'). See also in: [20] (by TDK), as you want to cross-check your deductions. --Askedonty (talk) 15:51, 18 May 2016 (UTC)

• MKT "Metallisierte Kunststofffolie aus Polyester (Polyethylenterephthalat) als Dielektrikum"
• MKP "Metallisierte Kunststofffolie aus Polypropylen als Dielektrik"

Guess as last letter was already occupied for Polypropylen they picked T for Terephthalat. --Kharon (talk) 22:31, 18 May 2016 (UTC)

Seeking a Reference

Can I have some free links to references on continuous and descrete spectra (Quantum mechanics)?Sayan19ghosh99 (talk) 17:04, 18 May 2016 (UTC)

Can you be more specific? I'm not sure there's anything in quantum mechanics that wouldn't count as continuous or discrete spectra (of operators). -- BenRG (talk) 19:40, 18 May 2016 (UTC)

Acctim radio controlled clock module

Does anyone know how to access the 60kHz signal that these clocks operate on? --178.106.99.31 (talk) 21:59, 18 May 2016 (UTC)

Cat in a new home

Hi everybody, I have recently adopted an indoor cat from a lady who has had to return home to China. I was wondering what period of adjustment I should allow for the cat to get used to his new home and people, and if it would possible for him to be tempted to venture outdoors. I live in a fairly quiet part of the countryside in the UK, where it's normal for cats to go outdoors, and would like to give him the benefit of a natural cat lifestyle. Also, any advise on helping him to settle in would be appreciated. He is neutrered, microchipped, vaccinated and 9 months old. Thanks in advance --Andrew 22:16, 18 May 2016 (UTC)

He'll go out if he wants to, and vice versa. Fit a cat flap.--178.106.99.31 (talk) 22:44, 18 May 2016 (UTC)