Wikipedia:Reference desk/Archives/Science/2015 March 5

= March 5 =

Jet stream clouds?
Can a long, straight cloud like this be associated with the jet stream (upper left to lower right)? It went for as far as I could see in both directions. This was the widest I could get with the lens I had on. This is today's jet stream and the blue area in the southeast US is where I took the photo. (Sorry, it won't let me put in a shortened URL.) Bubba73 You talkin' to me? 00:39, 5 March 2015 (UTC)


 * That's a jet contrail, not a cloud. Clouds are never that long, straight, and narrow. &#8213; Mandruss  &#9742;  00:45, 5 March 2015 (UTC)


 * But jet contrails can cause clouds to form in their wake. Those clouds are initially long, straight, and narrow, but then tend to diverge in shape. StuRat (talk) 00:57, 5 March 2015 (UTC)

Thank you. Bubba73 You talkin' to me? 00:47, 5 March 2015 (UTC)

When I see such a long URL, I like to try deleting each field to see which of them are redundant. —Tamfang (talk) 08:59, 5 March 2015 (UTC)


 * I converted it to a tiny URL, but Wikipedia rejected it, saying that it was a blocked site. Bubba73 You talkin' to me? 00:26, 6 March 2015 (UTC)


 * A different type of "jet stream", apparently. On youtube I saw a clip that some alert person had uploaded, from a Daniel Boone episode, where someone says goodbye to Fess Parker and heads off into the distance - with a jet contrail clearly visible in the bright blue sky. There weren't really all that many jet airplanes in Boone's day, ←Baseball Bugs What's up, Doc? carrots→ 14:43, 5 March 2015 (UTC)

Risk of cancer from oral sex: Mark 2
Will I be able to find the lifetime risk for people with more than 5 partners (I misread the article) by simply adding 250 percent to 1.1 percent? — Preceding unsigned comment added by 199.7.159.115 (talk) 00:55, 5 March 2015 (UTC)


 * Lifetime risk of what ? What article ? StuRat (talk) 00:58, 5 March 2015 (UTC)


 * Apparent continuation of . There is no need to start a new section, just add to the existing one. &#8213; Mandruss  &#9742;  01:01, 5 March 2015 (UTC)


 * No, 250% increase means 2.5x more. So if 1.1% of the population has a condition, and some behavior shows a 250% increase, then you would expect 2.5x1.1% = 2.75% of the people who exhibit the behavior to develop the condition.  For this example, lets say that of 1,000,000 people, 1.1% develop cancer.  That would be 11,000 people.  If all 1,000,000 people performed the risk behavior, that would result in 27,500 people now developing the condition.  That doesn't, of course, mean that all 1,000,000 engaged in the risk behavior.  Let's say that only 1 in 10 exhibited the risk behavior, that would now result in an extra 2,750 people developing the cancer, on average, of our initial 1,000,000 people.  The numbers scale accordingly for your population.  -- Jayron 32 12:54, 5 March 2015 (UTC)
 * I'm not sure why the OP feels the need to duplicate their questions. But anyway, just to re-iterate a point I made above, I think it's safe to assume the average 1.1% risk includes people who have more than 5 partners/show the risk behaviour. So even if we ignore the problems combining different results (of uncertain reliability), simply multiplying the risk isn't going to I think produce an entirely reliable answer since the 1.1% would be lower if we take out those who have more than 5 partners.
 * Taking random numbers as examples here, it may be that if no one showed the risk behaviour/had more than 5 partners, the actual average risk would be 1%. So for 1 million people, 10,000 would developed cancer. Under this made up example, those who do show the risk behaviour would have a 2.5% average risk. The reason edit: the average risk is it's 1.1% or 11,000 people out of a million would be because some people are in the higher risk category and some people in the lower risk. (Remember of course we are only talking about one risk factor and averages, in reality, some people would be higher and lower regardless of how many sex partners due to other reasons.) If you do the sums for this random made up example, you end up with roughly 66,670 / 1,000,000 being in the higher risk category for us to end up with the earlier 1.1%. (Meaning ~933,330 people in the lower risk category of which ~9,333 develop cancer, and a further ~1,667 from the 66,670 developing cancer in the higher risk category.)
 * The numbers who are in the higher risk category are probably small enough that it doesn't make that much of a difference but you'd need to at least look in to this. If most people do have more than 5 partners already, then the number for the average risk for people with more than 5 partners won't be that much higher than 1.1%. Of course just to repeat one more time, combining results from different things like this is not likely to produce a good answer even if you take care.
 * Nil Einne (talk) 16:21, 5 March 2015 (UTC)


 * You're at exponentially much greater risk for STD's. ←Baseball Bugs What's up, Doc? carrots→ 14:36, 5 March 2015 (UTC)

Sounds like someone needs to learn joint probability. The way to find out if you get hit by A or B (e.g. cancer from him, cancer from her) is to take 100% - (neither A nor B). That's (not A) and (not B) and you can figure out those probabilities by just multiplying (bearing in mind of course that "percent" means "per 100", i.e. 100% == 1. So if something has a 1% chance of killing you, and something else 1%, and something else... for 100 times, that doesn't add up to a 100% of being dead.  Rather it is 1-( (1-0.01)**100 ) = 63.3%.  (To calculate things like this on your own I recommend downloading R programming language. You ought to do many wondrous programming tasks with it, meanwhile it makes a heck of a desktop calculator) Wnt (talk) 22:59, 5 March 2015 (UTC)

Venus and Uranus conjunction
There was a conjunction of Venus and Uranus today, when they were only about 0.1 degree apart (see List_of_conjunctions_(astronomy)). I tried to photograph (just my camera - no telescope) it about 5-1/2 hours after closest approach, but I don't know if I got Uranus or something else. I got something other than Venus. I measured the distance in the photo, considering my camera and lens, and came up with 0.29 degree separation. Since it was about 5-1/2 hours after the closest point, could they be 0.29 degrees apart, or was the next-brightest object something other than Uranus? Bubba73 You talkin' to me? 04:24, 5 March 2015 (UTC)
 * How long was your exposure? There is a very easy way to resolve this if you install a program like stellarium. I have it at home but won't be home for a few hours. In this program you simply put in your location and the time and it shows you exactly what the sky looked like. From there you shold be able to compare your photo and fairly confidently say if what you captured was in fact uranus or not. Vespine (talk) 05:56, 5 March 2015 (UTC)


 * The exposure times ranged from a fraction of a second to about 1 minute. I'll check out that program. Bubba73 You talkin' to me? 06:03, 5 March 2015 (UTC)


 * Ok, that is a nice program. That program shows that they had moved a little farther apart.  Uranus looked like the right direction from Venus, but the distance seemed wrong.  But there was nothing else it could be.  Then I realized that when I did my calculations based on my lens' field-of-view, I forgot to take into account the extra factor because the camera uses an AP-C sensor.  So it is Uranus.  Bubba73 You talkin' to me? 06:33, 5 March 2015 (UTC)
 * Well, i for one am impressed! can you upload the pic somewhere? I know it'll probably be just dots but i am a bit of an amateur astronomer (I own a 12" Dob telescope). Vespine (talk) 22:40, 5 March 2015 (UTC)


 * I don't need no stinkin' telescope! (Actually I have a 6" refractor, but I don't use it for photography.)  These were taken with just my camera and what my daughter calls my "big ass lens".  At first I could see Uranus only in long exposures were it made a streak.  But then I could see it in others when I enhanced them.  A link to dropbox.  Venus was 9,100 times brighter than Uranus at the time. I think I calculated that Uranus is about 3 pixels wide.  Bubba73 You talkin' to me? 00:52, 6 March 2015 (UTC)
 * Very nice! I especially like the star effect you're getting on venus there from your lens. Quite beautiful. Vespine (talk) 03:52, 6 March 2015 (UTC)


 * Yes, the star effect is from the stopped-down lens. I've seen Neptune in a telescope, but I don't think I've ever seen Uranus before.  Actually I only saw it in the photos.  I need to take the 'scope or binoculars while it is somewhere that I can perhaps spot it.  At first I could only see it as a streak in the long photos.  There were some thin clouds (as you can see in one of the photos).  Enhancing the shorter exposures brought it out.Bubba73 You talkin' to me? 06:25, 6 March 2015 (UTC)


 * I've added another one "Venus Low ....jpg" when they are low on the horizon (uncropped but enhanced). The light from Uranus is going through a lot of atmosphere, and it is a speck just barely visible to the left of a tree branch - just barely distinguishable above the camera noise.  Bubba73 You talkin' to me? 06:42, 6 March 2015 (UTC)

What is the thing that causes to contact lenses to be connected to the eyes?
Is it the surface tension?149.78.32.22 (talk) 10:57, 5 March 2015 (UTC)
 * Read this -- Jayron 32 12:55, 5 March 2015 (UTC)


 * If you mean very connected, read this. Usually dryness. InedibleHulk (talk) 21:16, 5 March 2015 (UTC)


 * See Wetting. Surface tension makes things worse, not better, because it decreases the contact area and hence the total adhesive force. -- BenRG (talk) 23:37, 5 March 2015 (UTC)

Is there an advantage to living in one location at all times?
Many animals live in the open. If they are always on the move, then there is less chance that lurking predators will prey on them and their young. So, why are humans different? Humans have two legs. They CAN move around, if they want to. But they usually stay in one location. Humans are apex predators, but even apex predators must move and follow the prey. Otherwise, they will starve. Perhaps, planting seeds forced early modern humans to settle down and guard the food supply? But what happens if the soil becomes eroded and can no longer support the same crops? What if the sky pours down heavy rain and drowns the crops? What if there is a volcano that destroys all the crops? What if a nearby population of humans spies on another population of humans and conquers the latter tribe and steal their crops? 140.254.136.149 (talk) 21:39, 5 March 2015 (UTC)
 * Check out Agriculture and Hunter-gatherer for possible insight on why a given culture might choose one or the other. ←Baseball Bugs What's up, Doc? carrots→ 21:58, 5 March 2015 (UTC)


 * And see drought, erosion, flood, famine and theft for what happens after those things happen. InedibleHulk (talk) 22:07, 5 March 2015 (UTC)


 * Sedentism seems appropriate. For the question, anyway. Better article within the article. InedibleHulk (talk) 22:23, 5 March 2015 (UTC)


 * Staying in one location allows you to build up the defenses there, for one. Castles don't make much sense if you don't stick around for a while. StuRat (talk) 06:44, 6 March 2015 (UTC)


 * Just ask the blue-throated Common side-blotched lizard, there are advantages and disadvantages. — PhilHibbs | talk 13:28, 6 March 2015 (UTC)


 * A huge number of animals give birth in a maternity den or live in burrows. Some go nocturnal for the sole reason that their predators aren't. If you can get food without exposing your tasty side, your species will outlive the ones it has delivered.
 * If we tear down the walls now, we wouldn't see the sort of "apex predator" you think we are. We only got that far by being cowardly. Relative to tigers, lions and sharks, anyway. Very few of us want to be persistent when we can set a trap or shoot from afar, and get back home. That's why they don't name "energy drinks" after us. Only "luxury drinks". InedibleHulk (talk) 21:38, 6 March 2015 (UTC)


 * Most of what's in structures built by animals applies to you, too. InedibleHulk (talk) 21:44, 6 March 2015 (UTC)