Wikipedia:Reference desk/Archives/Science/2014 June 13

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June 13

Why aren't magnets used to make pushing solenoids? (aftermath)

Here I asked why permanent magnets are not used to make pushing solenoids without the need of a spring (and consequently, more length). The answers that it wouldn't work were quite convincing. Yet I think I should report that stubbornness and the availability of magnets led to trying anyway, and that it does work. Maybe the permanent magnet will wear out or something like that, and we do need gravity to return to the base situation, but today the first magnet reached the ceiling. Yay! Joepnl (talk) 02:36, 13 June 2014 (UTC)

Isn't a pushing solenoid just a Gauss gun? --Jayron32 03:07, 13 June 2014 (UTC)

There are good permanent magnets now that can withstand repeatedly having an opposing magnetic field applied but they're expensive. Also it is hard to get the right type of relationship of force and distance with current. Using a spring is just so much easier and cheaper. One can always get more length using a tension wire and putting the solenoid somewhere else instead of trying to push. Dmcq (talk) 08:33, 13 June 2014 (UTC)

Absorption of Hyaluronic acid - Biochemistry

Taking Hyaluronan capsules with Raw Coconut oil or Raw Olive oil can improve their absorption? thanks. Ben-Natan (talk) 03:01, 13 June 2014 (UTC)

Hyaluronan doesn't seem to have much trouble getting absorbed,[1] even through the skin.[2] Because hyaluronan is hydrophilic, I wouldn't expect it to have much to do with any oil on the molecular level. I can't comment on whether the oil could affect some aspect of barrier function or metabolism, though. (there are some references I see on PubMed about emulsions for drug delivery, but that's vastly more sophisticated than swallowing capsules and oil and is basically aimed at absorption of some third entity) Wnt (talk) 21:18, 13 June 2014 (UTC)

Hello Wnt, Thanks for this wonderful, very detailed and swift&sound answer. you said there "emulsions for drug delivery", Could you please add a few words about this sentence? (Do you mean that better than water or oil would be some kind of emulsion?), Thanks! Ben-Natan (talk) 01:15, 14 June 2014 (UTC)

All I meant is that if you run [3] you come up with various references like [4] that use hyaluronan with some hydrophobic substance in drug delivery. (From a quick glance at the article it seems to slow the rate of release of a drug; in [5] a chemical derivative of HA apparently improves overall concentration of a drug.) Wnt (talk) 11:43, 14 June 2014 (UTC)

Does malaria affect mosquitoes

I know that mosquitoes can carry malaria, but one thing I'm still not clear on is if it is actually deleterious to them in any way or do they just passively carry it without it adversely affecting them. ScienceApe (talk) 03:42, 13 June 2014 (UTC)

According to Mosquito-borne disease, skeeters are not harmed by the disease. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:06, 13 June 2014 (UTC)

Tesseract rotation

What does a rotating tesseract appear as, from the 3D perspective (not a projection, but the collapsed form). Plasmic Physics (talk) 06:54, 13 June 2014 (UTC)

There's a number of different ways of viewing a tesseract. I'm not sure which one you're referring to as the 'collapsed form'. My personal favourite which I refer to as a perspective rather than a projection eliminates the hidden 3d volumes. Also a tesseract can rotate around two different axes at once. Probably the maths reference desk would be better for this. Dmcq (talk) 08:18, 13 June 2014 (UTC)

By "collapsed", I mean to refer to the form where true orthogonality is preserved. Plasmic Physics (talk) 09:02, 13 June 2014 (UTC)

I think you must mean an orthographic projection, that is, one in which there is no foreshortening depicted. If so, there is a javascript animation on this page which has only a small amount of foreshortening, so easy to imagine what it would look like without any. Perhaps our resident graphics projection expert user:SteveBaker would care to make us one. SpinningSpark 10:34, 13 June 2014 (UTC)

Draw a cube by drawing two squares, and connecting faces. Then draw a smaller cube in the same manner, so that it is centered in the original cube. Finally, connect the faces of the inner cube to the outer cube, so that you get something like the links above. Note that this does not preserve orthogonality of the originally orthogonal angles. But, it is roughly as close as you'll come (e.g. mapping parallel lines to parallel lines, but only for some. Some right angles come out as right angles, but not all). If you want to retain orthogonality of all angles, then you'll have to sacrifice something else for it to 'fit' in Euclidean 3-space. Note that, since a tesseract cannot be embedded in R^3, (it can only be immersed, you cannot have a 3D model that preserves all aspects of the inherently 4D object. SemanticMantis (talk) 13:56, 13 June 2014 (UTC)

Think about this for a moment. Our eyes have retinas that are two-dimensional viewing surfaces...much like a camera and a computer screen. We only see 3D objects as 2D projections on our retinas. Admittedly, we have two eyes, looking at the object from slightly different positions - but that only adds a little to the perception of a 3D object. Considering how 4D (or 5D or N'D) objects "would look" or "should look" is really *only* a matter of how those additional dimensions are removed in projecting them onto a 2D surface. We see 3D objects using our 2D eyes by effectively tossing out the third dimension with a simple X'=X.k/Z, Y'=Y.k/Z projection (where 'k' is a constant that depends on the focal length of our eyes).

So the question here is what do we do when we have a fourth dimension to eliminate as well as the third? Well, we can use perspective in that 4th dimension, or we can just throw it away like it never existed (which would produce an orthographic projection if you did that in 3D)....you can distort the object in all sorts of peculiar ways as you do so.

But what (I think) our questioner is asking ("What does a 4D object look like if you project it into 3D instead of 2D?") is meaningless because whatever the 3D representation you might end up with is projected further into 2D before we can see it. You might argue that if a tesseract were projected into a 3D sculpture - you could see it with both eyes and you could walk around it to use your 2D vision systems to understand the shape as if it were in 3D...but that's no different than rotating the 3D object before you project it into 2D on a computer screen.

There is REALLY nothing new that we can get from these processes. Every possible way of viewing a 4D object is a matter of how you take X,Y,Z,W and convert it into X' and Y' for display. That's trivial to play with in computer software - and the resulting projections are what you're already seeing in all of those tesseract viewers out there. Some of them map the fourth dimension into time - so you're effectively moving through slices of a 4D object that are projected down into 3D...and the result of doing that is about as illuminating as seeing progressive slices through a human brain made by a CAT scanner. You can get some sense of what the 3D brain might be like but only indirectly. That trick doesn't really work for 4D objects because we still only have one time axis to play with - so the third dimension still has to be projected down into 2D.

Also, if you've chosen to use time to "display" one of the missing dimensions, then you can't use it to show motion - and that means that you can't rotate the object while viewing the extra axis using time. So you can only ever get an appreciation of it when viewed from one direction...and that's similarly frustrating to our goal of appreciating the object more clearly.

Sometimes people ask what it would look like if we were suddenly dropped into a 4D world...and the answer is that with our 2D retinas - it would look exactly the same as the 2D renderings of 4D objects that you see on a computer screen. The only way that a 4D world would look noticeably different is if we magically acquired 3D retinas in the process. However we can't ask what THAT would look like because in order to process images from a true 3D retina, our brains would have to be totally different and we can't know what that would be like. Indeed, you don't need to wonder about the 4th (and subsequent) dimensions to think about that. What if we had direct 3D perception in our current 3D universe? If you can't figure that out (and trust me, you can't!) - then asking what 3D retinas would be like in a 4D world is impossible - beyond saying that it would be somewhat like a 3D projection into our 2D retinas.

Bottom line is that you're already seeing all that there is to see with the vision systems we are equipped with. There is no new insight to be had here.

SteveBaker (talk) 14:06, 13 June 2014 (UTC)

It is our minds that see, not our eyes. You are talking like those who say we're really seeing hings upside down because that's what's on the back of our retinas. If you put prisms in front of the eye to invert the image we soon see things the right way up again. The main problem with getting a good idea of 4D is that we have not grown up with it and perhaps we have some 3d intuition built in. Experience is needed for a reasonable sense of 4D. There are a number of ways of projecting the 4D down and what one want's to do is project it in a way the brain can learn to interpret well. I believe doing 4d occlusion is important and that is missed out in most representations. I think it would also help to have tactile feedback. Dmcq (talk) 17:33, 13 June 2014 (UTC)

You are certainly correct that it is our minds that "see" - but they see through the 2D interface that is the retina. So no matter how good we might get at understanding 4D, we're always going to be stuck with interpreting what we see in two dimensions. There is really no getting around that. As I said, everything that can be done to help us to understand 4D shapes happens via that 2D interface - and that means that there is no real magic here.

The question of occlusion in 4D is interesting. We'd have to imagine a 4D lightray being emitted by a surface, travelling in 4D and either reaching our retinas - or being absorbed by a 4D object. Easy enough to simulate in computer graphics - a 4D raytracer is really no harder to make than a 3D version. SteveBaker (talk) 21:27, 13 June 2014 (UTC)

Unless, I'm misinterpreting your answer, this is not what my question concerns. I do not desire to see the entire 4D object at once. I want to see how one 3D-face morphs into another as the tesseract is rotated. Plasmic Physics (talk) 04:27, 14 June 2014 (UTC)

For instance, a cube rotating around an axis that connects opposing faces, will produce a 2D-image of a quadrangle that oscillates between a square and a rectangle with an edge progressing from the short end of the rectangle to the other. Plasmic Physics (talk) 06:11, 14 June 2014 (UTC)

Or for an extra simplification, a square rotating around an axis perpendicular to its surface, will produce 1D-image of a line that oscillates in length. Plasmic Physics (talk) 06:38, 14 June 2014 (UTC)

Right - but that's what all of the standard visualizations of a spinning hyper-cube actually do. One of the cubic "faces" of the hypercube is just a cube. So if you spin it around the X, Y or Z axis, it looks exactly like a cube - and the entire hypercube looks like a bunch of cubes stuck together. But if you spin it around the W axis, then what you see depends ENTIRELY on how you choose to eliminate the W and Z dimensions in viewing it. The result could look more or less like anything depending on how you make that choice.

But this is true even for your 3D analogy. One face of a spinning cube will turn into a rectangle then back into a square as it rotates if you choose to eliminate the Z axis by simply ignoring it (an "orthographic" projection). Or you can eliminate Z using a more realistic "perspective" projection (where the X and Y dimensions shrink as the object gets further from the eye in Z) - in which case the sides of the cube will turn into trapezoids rather than squares. Those two approaches are the 'natural' way to view 3D objects on a 2D screen because they are a reasonable match the way that light travels into our eyes. But there is no reason (in principle) why you shouldn't pick some other way to project the image - a hyperbolic coordinate system, for example...which will result in some other peculiar Escher-like thing happening to the faces of the cube as you spin them. We make the choice to go with orthographic or perspective projections because those are most like what happens "in the real world" - and our brains are best able to understand the resulting image when we do that.

We have that same choice to make when viewing a 4D object - but now we have two dimensions to eliminate. Each one could be simply ignored or used to scale X and Y - or something else entirely. The problem now is that which of those things we do is not driven by "reality" or how our brains are best equipped to understand the 4D world - because we live in a 3D world, and that's all that our brains are able to comprehend. So there is not "right" way to do that projection of W and Z...and which one you pick is the ONLY thing that determines what a spinning tesseract looks like.

Your quest to understand what it "really" looks like is an impossible one - because what you're actually going to see depends entirely on how you tried to wedge those four dimensions (plus time) into the two dimensions (plus time) that your eyes can capture - and there is no obviously "right" way to do that.

SteveBaker (talk) 14:53, 14 June 2014 (UTC)

We cannot say that people see the same thing even in 3 dimensions since the seeing is in their brains. The best we can ask is that people be able to use it properly and have a feeling for what things are like. That's why I think that having something one could hold which gave tactile feedback on 4D would be so useful as well as just seeing a representation.

As to what an orthographic projection does it is just like squashing and then expanding again whatever the number of dimensions, a fairly straightforward extension of what one sees with a 3D cube projected that way. Even in 3D it hides more than it shows about a cube. Dmcq (talk) 16:01, 14 June 2014 (UTC)

If I think about my example then a possible extension for a tesseract could be a 3D-image of a hexahedron that oscillates between a cube and box with a square interface progressing from the one end of the rectangle to the other. At any one point during a rotation, only a maximum of two 'faces' of the tesseract is visible. Plasmic Physics (talk) 01:08, 15 June 2014 (UTC)

Caloric Intake, Muscle Growth, and Time Period

(Disclaimer: not seeking medical advice, just random interest - nutrition and bodybuilding seem interesting reading for the last few months...weird) Anyways, from what I've read, people seeking to build muscle require a caloric surplus to do this, but this can also lead to weight gain if not properly managed. However, if calories are very important, what would happen if you were to stay at your usual calorie intake, but take in a very large number of calories twice a day, let's say 40% of your daily intake, then randomly snack to make up the remaining 10%? After ingesting the larger meals, wouldn't some of that current excess be used to repair tissue, while at the same time not putting you above the norm - so that you could balance out losing some potential muscle gain with not gaining fat (or you could still go for a daily surplus, but not as high). At any rate, I'm sure there is a flaw to this logic, but I'm ultimately curious how your body would react to local surpluses that don't total to a global surplus. Thank you for any help, sorry for the lengthy explanation:-) Phoenixia1177 (talk) 06:57, 13 June 2014 (UTC)

I think you might be taking "caloric surplus" the wrong way. It doesn't mean "more than a person normally eats", but rather "more than a person needs to avoid starvation". Since most people already eat far more calories than this, you should be able to grow muscles just fine. What will happen is that some of the calories normally going to other activities will be redirected into building muscles. For example, you may feel tired after exercising, as you have lower blood sugar then, since some of that blood sugar was expended while exercising. Many of those "super weight gain formula" powders you see at stores that cater to exercise fanatics are really only appropriate for top athletes who exercise all day long and do, indeed, need more calories. For normal exercise, as you said, eating more calories than usual will just make you fat.

One thing you do need to do though is ensure that you are getting enough protein. So, if necessary, shift your caloric balance from less fats, carbs (starches and sugars), and alcohol to more protein. StuRat (talk) 14:10, 13 June 2014 (UTC)

If you look at those online calorie charts that show how many calories you burn in various exercises - you'll see that the human body is crazily efficient at those kinds of things. One metric I'm fond of is that you can run a mile on the energy contained in a single sugar cube. Most of the energy we need is for running our large, energy-consuming brains - and for maintaining our internally regulated body temperature. The other things take very little energy indeed. So a relatively sane amount of exercise requires only a tiny increase in calorie intake - an extra small snack or two each day should be more than enough. On the other hand, every 3,500 calories that you consume over what you burn adds a pound of fat...so messing around with eating more can very easily put you into fat gain rather than muscle gain. 3,500 calories is probably 20 extra 'snacks' (a bag of chips, a banana, etc)...so it doesn't take much extra intake to slowly put on pounds. It takes a HUGE increase in exercise to make a dent in that.

So, no easy answers. Exercise to build muscle, slightly increase your calorie intake if you notice that you're losing weight...but only slightly!

(That said, I saw on TV the other day the factoid that championship-level sled-dogs consume 10,000 calories per day...five times what a normal person needs! Since their body weight is about half or ours...that's an insane amount of food...but then they're surviving in frigid temperatures and running flat out for many hours at a time pulling a heavy sled)

SteveBaker (talk) 14:28, 13 June 2014 (UTC)

I'd modify your statement a bit from: "increase your calorie intake if you notice that you're losing weight" to "increase your caloric intake if you notice that you're underweight". That is, since most of us could stand to lose a few pounds, there's no need for most of us to eat more, if we start losing weight from exercise, until we become underweight. (If you lose weight due to a medical condition, then ask your doctor if you should eat more.) StuRat (talk) 23:54, 14 June 2014 (UTC)

Eating more or less during a particular meal doesn't matter. What matters for building muscles is whether or not you are getting the right nutrients, particularly protein. Also, if you are physically fit (i.e. have no difficulties running half an hour at a fast speed where "fast" means significantly faster than mere jogging speed), you won't gain much weight if you increase the calorie intake by a huge amount. Weight loss due to exercise does work when you are not physically fit despite the calory counting argument by Steve above suggesting that it won't work. What happens when you exercise and become fit is that your body will reconfigure itself toward maintaining its fitness and using the energy intake for that instead of being the huge fat carrying couch potato it used to be. Count Iblis (talk) 00:49, 15 June 2014 (UTC)

Hair

Is it true that human hair combing can cause baldness? — Preceding unsigned comment added by Carllica4 (talk • contribs) 11:18, 13 June 2014 (UTC)

In the rather trivial sense that hair often falls out as you comb it, I suppose the answer could be a half-hearted "yes", but in the normal scientific sense, most authorities would reply "no, it's hormonal". See Baldness#Causes for details of other causes including Traction alopecia. Dbfirs 11:24, 13 June 2014 (UTC)

Agreed. Combing only removes hair that would have fallen out soon, in any case. An exception would be if you have knots in your hair, in which case combing might rip the hair out by the roots. So, if it hurts when you comb your hair, then this might be happening. StuRat (talk) 13:57, 13 June 2014 (UTC)

Though, anecdotally, I know of an alopecia areata patient who was advised not to comb their hair to prevent the baldness from progressing—why would that be? הסרפד (call me Hasirpad) 18:24, 13 June 2014 (UTC)

Well, not combing the hair might slow down the balding process by a tiny amount, but that would have the undesired effect that the hair will fall out at other times, like in their food, whenever somebody runs their fingers through their hair, etc. The only point I could see in this is if the patient suffered from some condition which only temporarily loosened the roots, in which case keeping the hair intact during that period would be critical. StuRat (talk) 03:57, 14 June 2014 (UTC)

amp hours

Does "72 amp hours" mean that it can run for 72 hours at 1 amp and also 72 amps for 1 hour? — Preceding unsigned comment added by Carllica4 (talk • contribs) 12:02, 13 June 2014 (UTC)

Yes, theoretically that is. In practice there is of course a limit to the current that any power source can provide, and efficiency may depend on the magnitude of the current, but in principle, yes that is what ampere hour means. - Lindert (talk) 12:09, 13 June 2014 (UTC)

In other words, amps x hours = 72. --Shantavira|^{feed me} 13:44, 13 June 2014 (UTC)

You might want to read Battery capacity#Capacity and discharge. —Quondum 14:25, 13 June 2014 (UTC)

72A is a very high current and it is likely to damage the battery to such an extent that it cannot supply this current for an hour. The link provided by Quondum is a very good one - it explains that the number of amp-hours attributed to a battery is usually based on a time period of 20 hours. Using this standard, it can be assumed a 72 A.hour battery can supply a current of 3.6 A for 20 hours. Dolphin (t) 05:46, 14 June 2014 (UTC)

An amp is a flow of electrons. The units of an amp are coulombs per second. A coulumb is 6.241×10¹⁸ electrons. Therefore, an "Amp hour" is a measure of total electrons available or the capacity. Since batteries generally specify a constant voltage over varying load, it becomes an energy storage term once the voltage is established. A "1 volt, 72 amp hour battery" is simply 72 watt hours (or 72*60*60 Joules) The structure of a battery, the voltage/chemistry and external factors like dI/dt effects of an inductance can rate limit the discharge. The reason for using Amp-hours is because at some point, the battery voltage will be unable to maintain its specification. Amp-hour then becomes a way to compare batteries with the same voltage requirements. The concept of maintaining the voltage while using the stored energy is what separates a batter from a capacitor and why the same fundamental storage of electrons and energy is specified in different terms. Electronic devices like LED flashlights and cell phones shut off when the voltage falls below a threshold. The amount of electrons that can be moved out of the battery before it reaches the operating lower limit becomes the "amp hour" capacity of the battery. The instantaneous amount of current available is not part of the "amp hour" capacity just as the "kilowatt hours" you get billed for by the power company over the span of a month can't be converted to a single hour and expect your service can handle it.--DHeyward (talk) 07:03, 14 June 2014 (UTC)

one can get any amperage by connecting batteries in parallel. this lowers the internal resistance (which is the limiting factor) of the compound battery, for example two batteries in parallel and the resistance is halved, four, and it's quartered. one can measure the internal resistance of the battery by connecting a resistor of some 100 Ohms across it (the fewer, the better, accuracy-wise, but make sure you don't get an excessive current.) the resistance is then r=(ER-VR)/R, where R = your resistor, E= open-circuit voltage of the battery, V= voltage across the battery with the resistor connected. also, the internal resistance isn't a constant, it changes (grows?) as the battery approaches the end of its life. Asmrulz (talk) 08:10, 14 June 2014 (UTC)

Tardigrades

Why don't we use tardigrades to terraform Mars? They can survive the trip through space, and can live in a cold environment. KägeTorä - (^影_虎) (Chin Wag) 18:38, 13 June 2014 (UTC)

Wouldn't the lack of oxygen cause the tardigrades to enter cryptobiosis? Wouldn't the terraforming have to be done by extremophilic bacteria or plants? The Earth was terraformed by the cyanobacteria (not extremophiles, to be sure). Robert McClenon (talk) 19:15, 13 June 2014 (UTC)

It is definitely an interesting idea. The key thing to bear in mind is that there is the suggestion - the controversial suggestion - that dark slope streaks involved in Seasonal flows on warm Martian slopes are the result of the flow of a liquid brine. Tardigrades have a hyperosmotic body fluid even relative to marine environments. [6] I think that their ability to survive highly saline conditions may be crucial, though the presence of chlorate is not something that evolution has tested them with. Still --- chlorate is indeed a stand-in for actual oxygen, and so what we have there is nearly half a simple ecosystem. Throw in some lichens which can tolerate martian conditions and form an ideal environment to find tardigrades [7] and you are getting somewhere! Lichens are marine fungi that can survive on seashores, so they are a good candidate for the brine also. Both are known for being able to stand up to vacuum and extreme conditions. Wnt (talk) 20:17, 13 June 2014 (UTC)

The addition of the lichens, extremophilic composite organisms that have a photosynthetic component, may address my concern about the need of extremophilic animals for oxygen. Robert McClenon (talk) 20:22, 13 June 2014 (UTC)

Actually the photosynthesis is more important for food - animals are going to need some kind of reduced carbon and hydrogen containing compound to work with, not to mention some nutrients. I don't actually know how much chlorate if any is in these brines, if they even exist. (To be honest, while it's convenient here, when I look that the things I wonder if they could just be little jets of CO2 coming out from under the surface that send grains of sand flying to cause mini avalanches...) But I saw a figure of something like 0.5% for chlorate in the Martian surface soil, and if there's something like that in the water, then that would be hugely in excess of typical dissolved oxygen levels. Any animal living in water (when active) and capable of splitting that chlorate back into chloride and oxygen should have no need for another oxygen source. Wnt (talk) 20:47, 13 June 2014 (UTC)

Do you mean just sending a bunch of critters to Mars and hoping that somehow makes it more hospitable to humans? If so, "survival" isn't really even the important issue (scare quotes in reference cryptobiosis). Even if they survived the trip and the environment, what would they eat? On Earth, they eat bacteria and algae. Even if they had something to eat, how would that help in the goal of terraforming? Since they are heterotrophic, their respiration would act to deplete the Martian atmosphere of Oxygen. Sure, water bears might be an interesting ingredient in a terraforming recipe, but what you really need to get the process going is an autotroph, preferably xerophytic, with high primary production. Something that on Earth participates in primary succession might be a good place to start. Anyway, we can all come up with crazy ideas for terraforming. Here's some science articles on the topic if you want to see what kinds of ideas can make it through peer review. "A primitive cyanobacterium as pioneer microorganism for terraforming Mars" [8], and "The Biological Terraforming of Mars: Planetary Ecosynthesis as Ecological Succession on a Global Scale" [9]. SemanticMantis (talk) 20:48, 13 June 2014 (UTC)

Well, definitely the OP has the right to speculate and get answers about his speculation to the degree we can do so. Tardigrades have been called a model organism for space research. [10] Mostly though I think it's a matter of perspective. If we are envisioning a very powerful humanity remaking Mars in a few hundred years, then I see why getting high oxygen levels is our first priority. However, I would think the top interest should be working out an ecosystem that contains representatives of key top-level groupings of living organisms in order that life could be given an enduring foothold on Mars. That way if a runaway greenhouse effect or other disaster overtakes the Earth, these organisms could gradually adapt to a Mars that grows steadily warmer over the next billion years of the warming Sun until it has an ocean and atmosphere once more - I remember reading a claim it might even have a magnetic field then as its core cools, to keep the atmosphere it gains. But Mars is a small planet, with scant resources and little time, and it may never have the conditions to properly start life from scratch, so the issue is jumpstarting it with the condensed results of about 4 billion years of evolution and letting it figure out what to do with that over half a billion years or so. Wnt (talk) 21:08, 13 June 2014 (UTC)

That said, I think there is still quite a conversation to be had over whether it ought to be done. Some say that life is suffering, and if people believe that dogs and frogs and perhaps even a worm on a hook is suffering, do we have the right to inflict that on the denizens of another planet? If Earth destroys itself through stupidity, does its biota have the right to ruin any other world? I would like to see what a wise person could make of such issues. Wnt (talk) 21:10, 13 June 2014 (UTC)

The moral issues are complex. If we found rich ecology of life on Mars - then there would be both a scientific and moral issue about (most probably) destroying it with earthly lifeforms. If Mars is a sterile environment, then we have time to learn about it before a terraforming effort could be made - why would we have more moral concerns over populating that than we have with populating an antarctic ice station or building a new city in the deserts of Saudi Arabia? Why draw mankinds boundary at the edge of a continent, a planet, the solar system or the edge of the galaxy itself?

There is another moral question though - is it right to doom future generations of humans to an overcrowded planet that's running low on resources? Is it right to risk everything that humanity has ever achieved to the next dinosaur-extinction-sized catastrophy?

Humanity seems to have only three possible routes into the future:

1. Gradually wrecking the earth until we make ourselves extinct along with most of the other organisms living on it - and perhaps even consuming so many non-renewable resources that we effectively prevent future intelligent species from ever emerging again?
2. Downscaling our population so drastically in the name of indefinite sustainability (an impossible goal) - and thereby reducing human civilization to a mere shadow of it's former self?
3. Getting off this rock and spreading throughout the galaxy?

Whether one of these is more morally acceptable than the other is a tough one. Is it "right" to spread our species through the galaxy like an infecting plague? Is it "right" to consume resources now and thereby doom future generations to a more minimal existence? Is it "right" to run ourselves (and most other large animals and plants) into extinction?

None of those seems unambiguously morally correct - but one of them seems inevitable. If Mars is sterile, then (3) seems the least evil...if it's not, well, we have a choice - trash the Martian species, trash the other Earth species, trash the future of our own species. I don't know how to distinguish those outcomes from basic moral principles alone.

It seems to me though that we aren't going to make that decision. Each generation of humans will probably do exactly what we're doing - which is to make ourselves as comfortable and happy as we can, without much regard for the effect this will have on our grandchildren. Since continuing to consume and pollute and heading down route (1) is by far the easiest thing to do with a short-term view of (say) 100 years. Nobody will have the guts and the political power to tell the people of the world that they have to make the sacrifices necessary to make (2) or (3) happen in 200 years from now.

Terraforming Mars couldn't possibly be done in the lifespan of a single human. Who is going to stand up in front of the people of the USA, Europe or whatever and say "We need to spend X billion dollars to start the Mars terraforming process so that people in 200 years time will be able to live there." ... I just don't see that happening.

SteveBaker (talk) 14:28, 14 June 2014 (UTC)

Politically, no, but private companies are sending stuff into space now. KägeTorä - (^影_虎) (Chin Wag) 18:07, 14 June 2014 (UTC)

Yes, they are. But unless those companies are charities, they have to make money. You can't make money soon enough to satisfy investors by terraforming Mars - you have to put an ungodly amount of money into the project with no possible chance of getting any return on it for many hundreds of years. Basically, everyone wants a financial return within (at most) one human lifetime. Could a charity do it? Well, you'd need billions of dollars - probably more like trillions. People might donate to that cause - but again, asking people to donate to something without any chance of seeing any results within their own lifetime seems unlikely. The only organizations with the kind of money you'd need, and which don't necessarily need to see a return on that expenditure, is a major government. SteveBaker (talk) 16:52, 16 June 2014 (UTC)

People should understand that interstellar travels are impossible as a matter of principle, now, tomorrow, and a million years from now. --AboutFace 22 (talk) 02:56, 15 June 2014 (UTC)

That's what they said about flying, and traveling to the moon. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:05, 15 June 2014 (UTC)

Did you post this one to the wrong place? We're only talking about Mars here that I know of. Though sending a ship full of tardigrades to another system should be easier than sending humans - they're smaller, and they have the suspended animation thing nailed down pretty well. :) Wnt (talk) 06:21, 15 June 2014 (UTC)

I don't know what AboutFace 22 is talking about. Voyager has just left the solar system. Anyway, back to tardigrades. They are lighter than humans, so would be a smaller (and cheaper) payload. Humans themselves would not be able to terraform Mars just by being there, so we could send them first. Sooner or later we will have to leave this planet anyway. Why not set up shop next door? KägeTorä - (^影_虎) (Chin Wag) 09:43, 15 June 2014 (UTC)

It will take the Voyager million years to possibly arrive to any star. People cannot live that long. All the energy invested in Voyager has already been spent long, long time ago. Whoever said that people cannot go to the moon? Any quote? As far as the Mars is concerned, I still maintain that reaching it possible but establishing a viable long term colony is impossible. Going to even the closest stars is many, many orders of magnitude more complex and no amount of energy we can invest in the process will ever take us there. You are all impossible dreamers. Focus on what is real. --AboutFace 22 (talk) 18:08, 15 June 2014 (UTC)

That's what they said about flight and space travel at points in the past. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:30, 16 June 2014 (UTC)

Give me a couple of quotes, Baseball Bugs. Who said that? Following your logic anything is possible, anything. Your statement about flying is obviously false. Every reasonable person with some scientific background could point to the birds flying, hot air balloons flying, Greek legend about Icarus is another example of the dream. Everyone understood that flying is a matter of propulsion, nothing else. Flying to the moon was resolved mathematically long before the actual flight. Flying to the moon is a little bit more than a touchdown. You are talking about colonization of deep space and I am telling you, it is impossible. --AboutFace 22 (talk) 02:14, 16 June 2014 (UTC)

Google the expression "if man were meant to fly" and you'll find endless references. Looking at the moon thing, there's an amusing story about Joseph Fielding Smith who said space flight was impossible. Unlike the moon hoaxsters, he owned his statement and admitted he was wrong. Here's a quote for you, attributed to Henry Ford: "Whether you think you can, or you think you can't--you're right." ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:29, 16 June 2014 (UTC)

Mars is not in deep space. Why can't you get that into your head? KägeTorä - (^影_虎) (Chin Wag) 05:48, 16 June 2014 (UTC)

@AboutFace 22: What makes you say that deep space colonization is impossible? All it takes is a little imagination.

We can (and indeed have) built and launched spacecraft with enough delta-V to escape the solar system and EVENTUALLY reach another star. We didn't choose to aim Voyager at Alpha Centauri - but we certainly could have done that if this was its primary mission. We are also getting very much better at identifying exo-planets that might be viable colonization targets. So the only problem is how to keep humans alive through the bazillions of years it takes to get there. For that, we'd probably want to freeze sperm and eggs and put them into a heavily shielded box - then provide robots to handle the in-vitro fetrilization and synthetic womb needed turn them back into humans at the other end (with computers to teach the resulting children, robotic doctors to cure their boo-boos, robotic farmers to make them food, and so forth) .

The robotic and AI technology is the only thing we don't know how to do here...and given the rapid progress in that area, you'd be going out on a limb to tell us that we're not going to be able to do it within (say) 100 years. You'll probably only be able to ship one multi-purpose robot with the spacecraft - so initially, it's going to have to use locally available materials to make copies of itself before the new humans are created. Even if you don't know for sure which exo-planets are good enough, we have the capability to launch 10,000 Voyager-scale probes with genetic material + robot and send a handful of them off to each reasonable sub-100 lightyear target. Many of them will fail en-route or at their destination. Many colonies will suffer hardship and die off...but we could launch many of these systems every year...sooner or later, one will get someplace and then we have a route to colonize the entire galaxy. Colonization isn't going to be done with warp drives and giant colony ships full of people...but that doesn't mean that it can't be done. With DNA synthesis, we could easily store enough genetic variation to make an entire colony of humans from a small number of sperm and eggs without getting into problems with inbreeding in subsequent generations.

What makes this hard is that the cash expenditure to do it - given that the mission will take a few thousand years to complete. That's the same scale of problem as terraforming Mars - too much money - payback time too far into the future. The only fix for that is to do it gradually. First get a small colony on Mars, then make it bigger - then consider terraforming.

What you can't say is that this is impossible - that's a ridiculous assertion. I feel that there are plenty of other ways to do this too...although a lot depends on what is meant by "Human" in this context.

SteveBaker (talk) 17:12, 16 June 2014 (UTC)

Color-blind animals

It is my understanding that various animals are color-blind. How do scientists "know" that? Thanks. Joseph A. Spadaro (talk) 21:00, 13 June 2014 (UTC)

How do YOU know that? It's hard to respond to a question based on something like "It is my understanding that..." What is YOUR source that tells you that "various animals are color-blind". HiLo48 (talk) 21:19, 13 June 2014 (UTC)

Quite frankly, I believe it to be common knowledge. Joseph A. Spadaro (talk) 22:13, 13 June 2014 (UTC)

No need for confrontation - sources are close at hand. [11] Much is inferred from the photoreceptor pigments in the cones of the eye, under the assumption that humans and dogs have similar overall functioning. You can tell from the pigment what colors it absorbs. That said... there's always a remote possibility that there's some neat mechanism by which, say, a structural color you can't detect in your homogenized retina sample shields some of the receptors from certain frequencies, etc. So you'd really need behavioral studies or perhaps fMRI scans, etc. to clinch the case, and... there's often a way to argue with those. Bottom line: you need a lot of evidence. Wnt (talk) 21:28, 13 June 2014 (UTC)

I agree. But we have to be careful. Most people think that (for example) dogs can only see in shades of grey. That's really not true - they can distinguish some colors - but not as many as we can. SteveBaker (talk) 21:31, 13 June 2014 (UTC)

That is what the article says. Dogs have what would be red-green color blindness in humans, which is not total color blindness. So the statement that dogs are color-blind, if not qualified, is partly true but misleading. Robert McClenon (talk) 21:50, 13 June 2014 (UTC)

With relatively intelligent and cooperative animals such as dogs or horses, one can devise a test. Robert McClenon (talk) 21:46, 13 June 2014 (UTC)

Many birds and some reptiles have four receptor pigments. Mammals either always had two receptor pigments or lost two (going from four to two) during the K-T event. Subsequently, Old World monkeys, and great apes, which evolved from Old World monkeys, evolved three receptor pigments. (New World monkeys have a slightly different history.) We apes have more variety of color vision than many other mammals but less than birds. Robert McClenon (talk) 21:46, 13 June 2014 (UTC)

I understand that we can describe what we know about the receptors that different animals have, but I cannot see how anyone can be certain what any other creature, human/animal or bird can see. We cannot get inside their heads. But I would be interested in good sources describing good testing processes. HiLo48 (talk) 21:59, 13 June 2014 (UTC)

Researchers can use observable behavior. When I was working on the horse article, I found research studies where they did tests where a horse had to distinguish between colors in order to get a treat. Once they learned the basic concept and would almost always pick the right box or whatever to get their treat, the researchers started using different color combinations. Where the horses could not distinguish between colors, it was clear they were unable to to see certain colors (horses are highly motivated by food) Like dogs, they have what we informally call red-green color blindness. Montanabw^(talk) 22:20, 13 June 2014 (UTC)

All my life I've been seeing unsourced claims that animals are colour blind. And I've had my (seemingly well justified) doubts. Why is this a topic where people won't provide sources? HiLo48 (talk) 22:24, 13 June 2014 (UTC)

To be fair, we're pretty darned colorblind too. The Visible spectrum (those colors we can see) are a pretty tiny fragment of all of the electromagnetic spectrum. --Jayron32 00:39, 14 June 2014 (UTC)

There is no great conspiracy here. Books on animal colour vision are easily found with a google search, eg [12] or [13]. Likewise scholarly papers are easily found. This paper for instance, confirms that dogs have only two colour receptors by behavioural experiments (as opposed to physiological examination of the eye and infering it from the pigment colours). I think that the common misconception that dogs cannot see in colour dates to some early poorly controlled experiments that wrongly concluded this. See for instance pages 155-156 of the second book I linked. It has been endlessly repeated with those saying it not really having any idea where the information came from. Science currently does not believe that. SpinningSpark 01:12, 14 June 2014 (UTC)

See How Animals See Color.

—Wavelength (talk) 23:08, 13 June 2014 (UTC)

• Here is a solid reference on how we understand color vision in some non-human species: "Color vision and color choice behavior of the honey bee" [14].

“ A general introduction to color vision in honeybees has been presented. Documenting the current state of research in this field, the theory of color vision and color choice behavior of the honeybee has been reviewed. Several tests of the predictions of the theory for behavioral and electrophysiological experiments have been presented. The properties of color memory have been derived. A complete neuronal interpretation of the color theory has been given. The decision-making process has been discussed with respect to the fluctuations in the neuronal network. In specifically-designed experiments, the information provided by the color vision system has been combined with the information from other perceptual systems in color choice behavior. Respective extensions of the color theory for the bee have been discussed. ”

The gist of it is, we can scientifically and objectively make inferences on what colors and wavelengths of light bees can discern, based upon what sorts of signals they can use to e.g. remember and relocate food sources. --This is ultimately a behaviorist and dispassionate approach. Since bees are a great and historic model organism, this topic of color vision has been taken up by neurobiology and other related fields. The citation above contains many references that discuss the history of what scientists know, from a variety of sub-disciplines. This google scholar search has a lot of good additional references [15]. So, while it's true that there are many difficulties in objectively quantifying color perception in non-human animals, it is a very well studied topic in some cases. I'd think similar searches for /color perception/ + [the animal of interest] should be fruitful. SemanticMantis (talk) 01:33, 14 June 2014 (UTC)

Thanks, all. Joseph A. Spadaro (talk) 21:06, 18 June 2014 (UTC)