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A few years ago, I had my mind blown by the Blackbird land yacht, which was able to "sail" directly downwind faster than the wind using only wind power. At first glance it appears to violate some law of physics, but in the end it turns out that it doesn't; energy is ultimately being provided by the wind, just in a way that you wouldn't expect it to be able to. I have now encountered a new aerodynamics brain twister. Artemis Racing, a perennial America's Cup contender, have said that it is possible to build a sailboat which can sail upstream in a river even if there's no wind, using the "apparent wind" created by the... uh... by the river water pushing the boat downstream, I guess? Maybe? Could someone explain how this might work in a way that I might be able to understand?
posted by clawsoon at 9:10 AM - 21 answers

I'm interested both in explorations of problems like climate change and mass extinction, and solutions like renewable energy. Longform articles welcome.
posted by pinochiette at 7:35 AM - 6 answers

I live in Charlotte, NC next to a creek and I am, essentially, at the bottom of a narrow valley carved out by the creek. The antenna I have now pulls in three, sometimes four local TV channels. I should be able to get several more in Charlotte but, I think, I have bad reception due to being at the bottom of this narrow valley. So, other than building a tall antenna tower, any suggestions for getting around this issue?
posted by zzazazz at 7:59 AM - 6 answers

A few years ago I read a wonderful deep dive article about the wild apple forests of Kazakhstan, but can't find it now that I need it. The article included a bit on apple genetics, why apples couldn't just be grown commercially from seed, and varieties under development. [more inside]
posted by Soliloquy at 1:43 AM - 9 answers

...from an academic perspective? [more inside]
posted by lesser weasel at 5:54 PM - 4 answers

Under what circumstances would contact with the work lead clamp of a TIG welder cause an electrical shock? I know a person who received a pretty significant shock this way, enough that he needed medical treatment; I've been told that it's an inevitable in TIG welding environments. Is this correct? Is there a way to eliminate the risk? Can someone explain to me why the electricity would even pass through a person who touches the work lead? That doesn't make sense to me at all.
posted by jwhite1979 at 1:53 PM - 8 answers

Evolutionary psychology has often been criticised for producing "just-so stories" that explain a particular result, where an equally compelling story could have been constructed if the opposite result had been found. Does anyone have any good examples of a compelling evolutionary psychology explanation that seems less compelling once you see that there is an equally compelling explanation for a contradictory theory?
posted by casebash at 8:38 AM - 5 answers

If catalytic converters convert CO to CO2 and CO isn't a greenhouse gas then is releasing CO actually the lesser of two evils? I know very little about why CO is so bad other than the suffocating in closed spaces without knowing it bit so explain it to me nicely :)
posted by zeoslap at 11:53 AM - 14 answers

When I peel carrots, I've noticed it almost invariantly takes nine swipes of the peeler to completely peel the carrot. Counter-intuitively, this number doesn't change according to the size (diameter) of the carrot. Is this some known constant property of the geometry of circles and cylinders and how they intersect with planes? [more inside]
posted by Rumple at 10:56 AM - 24 answers

My teenage niece needs to learn the basics of electricity in a hopefully entertaining format. Do you have any resources you can point me to? [more inside]
posted by M. at 12:38 PM - 7 answers

Why is it that every species isn't 33% smaller or 25% bigger? Why are people on average the height that they are, and cats the size that they are? Why isn't every form of life 10% smaller? [more inside]
posted by prefpara at 6:58 AM - 18 answers

I frequently wash the floor in the dog's washroom (yes, yes, that's not the point) with oxi-clean powder. This tends to leave some white residue. I wanted to wash with bleach, because it's been a while and it needed a thorough cleaning. I know you can't mix, so I washed floor with tonnes of water (no oxiclean) a few hours ago. Waited. Then dumped some bleach and then water on it. There was fizzing. Now I'm worried about deadly fumes. Should I be? [more inside]
posted by If only I had a penguin... at 7:19 PM - 8 answers

I am interested in finding this, but for Seattle. "fwd" in the URL stands for Dallas-Fort Worth. The equivalent string for Seattle is "sew", but alas, the days of transparent URL hackery are gone. [more inside]
posted by mwhybark at 8:36 AM - 8 answers

What type of wood is this? It has the color of redwood and looks very much like some kind of burl. But there’s no such thing as a burl plank. It’s very soft wood; you can easily scratch it with a thumbnail. The board is 3/4×12×80.
posted by not_the_water at 11:59 AM - 4 answers

Can I make something (telescope, microscope, whatever) from the two 4-1/2" x 9" planoconvex lenses in this old Q4M spotlight? [more inside]
posted by wenestvedt at 1:27 PM - 6 answers

So I learned recently that kangaroos are one of those species with indeterminate growth; they keep growing, slowly, their entire lives. Obviously there must be some kind of body/mass/energy ratio calculation that will eventually mean they are too big to survive. How big could a kangaroo get before this happens? [more inside]
posted by The otter lady at 9:15 AM - 6 answers

I am looking for a heavy-duty Pyrex (or similar sturdy borosilicate) straight-walled beaker, so that I can use it with my hand blender for making mayonnaise and aioli. For this purpose, the beaker needs to be just barely larger than the head of the hand blender, which is 3" in diameter. All of the specs I see list the outer diameter, but I don't know how thick the walls are, or if that counts the beaded rim. Can any of you scientists help me out?
posted by mboszko at 11:21 AM - 9 answers

Scientists of Metafilter: Please explain to me how molecular mass affects gas behavior. Do heavier gases pool in low-lying areas at ambient pressure, and do lighter gases rise higher, or is this a myth? What about inside canisters, at higher pressures? Why do they or don't they? [more inside]
posted by cnidaria at 4:28 PM - 8 answers

Mosquito A bites you and injects a nasty virus into your system. After the acute infectious period subsides, you are left with antigens which (hooray!) confer immunity upon you for that particular virus in the future. Is this the end of the matter? [more inside]
posted by alonsoquijano at 4:39 PM - 6 answers

I want to understand some acoustic theory to design solutions for outdoor noise (or at least communicate better with acoustic engineers). I know of software for this but want to know just enough of the nuts and bolts. There's lots of info available but I don't want all of it and don't know where to start. [more inside]
posted by unearthed at 12:20 PM - 7 answers