Stick your hand in water and pull it out. You can tell that it’s wet, it “looks” wet.
But then try this. Stick your hand underwater and look at it while it’s still underwater. It doesn’t really look wet.
And even more striking — Look at your wet hand in a mirror. Now plunge your hand underwater, and look at it in the mirror underwater. It not only doesn’t look wet, it looks bone dry!
It’s a pretty simple answer to a neat little experiment. But before I give you the answer, think a moment. How might you try to figure out the answer? What are some tools you could use to figure out why this is the way it is?
Well, when your hand is wet, your eye can tell that it’s wet because there’s a layer of water on the hand. Light reflects from that water more strongly than it does from your skin, so it looks “shiny” because of that extra reflectivity.
When your hand is entirely under water, though, there is no surface layer of water on the hand. The entire hand is under water, so the only shiny reflection is from the surface of the water itself.
But what about when the extra trick with the mirror is added? All I can think is that this tricks the mind a little bit. Instead of looking at the hand underwater, you see a reflection of the hand, and so it’s out of context. Your mind just sees the hand, and doesn’t compensate for the fact that it’s underwater. I’d love to hear a more rigorous explanation of this though!
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A while back I blogged about a cool opportunity to get anything (yes, anything!) scanned on a Scanning Electron Microscope. Posted from the ASPEX website, here is a toy bunny, macrosize, and microsize:
Though how anyone could give up that cute wittle bunny is beyond me.
You can still send them samples (which I just think is so cool, and would be a great class activity), and they’ve just started a Name that Sample contest. The first correct answer wins a USB stick. Here’s this week’s image:
They’ve already got a bunch of comments on there — go ahead, give it a shot! This could be a good exercise in size and scale. This is magnified 110X, and the whole thing is about 1000 micrometers across, or 1 millimeter. So, the first guess on the site of “a blade of grass” is waaay off in order of magnitude (a blade of grass is probably about 10 mm). Besides, it doesn’t even look like a blade of grass to me. It also says that “Carbonaceous phases would be represented in darker tones where as Metallic features would be displayed in brighter tones.” So perhaps this is metallic? Lots of people have guessed that it’s some sort of adhesive being pulled apart. But I’m not so sure that that “stretching” is actually dynamic. SEM requires time to take, so whatever it is, it has to be sitting still while the image is being taken. And the features are so regular…
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Have you ever had this unusual occurrence in your freezer? This one observant science teacher says:
We had a single stalagtite form from one cube in an ice cube tray. It rose about an inch, no more than an eighth of an inch in diameter, and tapering to a sharp point. How did that form?
Paul Doherty (physicist extraordinaire) answered that this is called an ice spike.
The water in an ice cube freezes from the outside in. Once the outside is sealed the water inside freezes and expands.
So the interior water is pressurized.
If it freezes at just the right rate the pressure can push the liquid water out of a hole in the top surface and freeze it.
It helps if the water is clean and free of nucleation sites i.e. distilled
See this website here for a bunch more information and great pictures.
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As usual, geekgirl is a little groggy on the uptake, so I’m posting this after all the cool kids already had their fun with it (ie, The Bad Astronomer, Richard Wiseman, Blog of Phyz and Buzzhunt). The trick? There is no blue in this pattern. It’s green. The same color as you see next to the orange spirals. The Bad Astronomer has a nice explanation.
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One of my favorite blogs, when I get a chance to actually read it, is Cognitive Daily. They give you all sorts of wonderfully written tidbits and tests from the world of cognitive science. Fascinating stuff.
A recent study highlighted on the blog — self-refilling soup bowls — concerned what happened to how much people ate when their soup bowls constantly refilled, versus having to wait for a server to refill them. They ate much more, and the idea is that when you don’t have a cue as to how much you’re eating, you eat more, because those perceptual cues tell us about our eating habits as much (more?) than our stomach does.
Check out the comments for some thoughtful and amusing discussion, such as:
I did see a similar study where they were providing hot wings to people watching a football game. They would continually clear away the dishes with bones from some people and not others. The people who had visual feedback from the bones nearby ate much less than the people who’s plates were kept clear.
or
I once got a friend drunk by swapping glasses with her every time hers contained less than mine did. Then when she noticed mine had less in, she’d drink to catch up… and then i’d wait til she wasn’t looking, and swap again. She didn’t stop drinking because she ‘wasn’t thirsty’ or because she was getting drunk, she was entirely basing her drinking on the visual cue from the amount left in the glasses..
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My friend and fellow science writer Jen Frazer has started a new blog (well, two actually, but let’s start with the first). I don’t know how she can spend a whole day at work writing copy, and then come home and spin out gorgeous and witty prose, but, hey, she didn’t win the AAAS Science Journalism Award for nothing! In the Artful Amoeba she explores charismatic microfauna, or the “weird wonderfulness of life on Earth.” By way of explanation, she says:
I say: it’s not the taxonomy that’s important. It’s the learning about the diversity of life on Earth. We don’t have to go to Mars to find living wonders, and though I respect those that want to, I wish the 100% real living organisms on Earth could get half the attention the putative creatures on a planet millions of miles away do. The curiosity cabinet is long gone, but the curiosities are still here, just waiting for us. All 10,000 ferns. All 70,000 known fungi. All untold millions of species on Earth. I want to show you. I’m passionate about this stuff, and I like to make it fun. Please join me.
Her other blog is Home Cooking Well - A blog about how your kitchen can enrich your life, your wallet, and your sense of humor.
As a teaser, here’s one of her recent posts on Moss That Swings Both (all?) Ways
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I’m sometimes greatly amused by the quality of press release science writing that is taking the place of professional science writing these days, since no one will pay for us to do it full time anymore (Science Daily, a major source of internet science news, is made almost entirely of press releases reprinted verbatim. And you’ll notice that this very blog is, so far, gratis).
At first glance, mosses and human beings have little in common.
Gee, ya think? I’m imagining myself at a coffee shop holding a cup of steaming tea and sitting across the table from a noticeably uncomfortable bryophyte.
Cough. *blink*
Me: So, read anything interesting lately?
Moss: No.
See? Not much in common. Strangely, this doesn’t differ greatly from most of my actual dates.
I don’t want to seem too hard on the author here, since 1. the release was probably first written in German, and 2. this is actually one of the clearer and more helpful press releases I’ve read. In any case . . .
Scientists from ETH Zurich and the University of Freiburg im Breisgau report that they were able to insert DNA from humans and bacteria into the moss Physcomitrella patens (sounds suspiciously close to “patent”) and the moss was able to manufacture human proteins without any further help. Yes, they basically cut and paste. And the moss said: OK! Cool!
The protonema of Physcomitrella patens. When the spore of this moss lands on a suitable spot, it starts growing into filaments like these. Given enough time, these little filaments will grow into a full-grown moss plant. You can see the chloroplasts, or light harvesting equipment, as little green circles.
For those of you unfamiliar with the Way of the Cell, DNA makes RNA (with the help of proteins called RNA polymerases), and RNA makes proteins (with the help of cell organelles called ribosomes). The reason this moss-cular feat is astounding is that doing the same thing with flowering plants will get you nada. The mammalian gene start and end sequences have evolved themselves right out of business when placed in a similarly much-modified flowering plant. Not that there’s much of a reason that that would *ever* happen in nature. Now in an evil mad plant scientist laboratory, on the other hand . . . Belgians + petunias = Brussels sprouts. Mwa ha ha ha ha ha . . . . .
How is it mosses can do what so-called “higher” plants cannot? It’s a mistake to think of mosses as “primitive” in the sense of “inferior”. Both mosses and flowering plants have ancestors that were alive at the same time. What mosses are is “less-derived”, in biologist-speak. The lineage that gave us mosses just didn’t change as much over time as the lineage that produced flowering plants, because they found they were well-adapted as-is to their particular niche (forests, rocks, sidewalk cracks, and the sets of “Lord of the Rings” adaptations). Like sharks, they found a sweet gig and they stuck with it.
According to Ralf Reski, botanist and co-author of the paper announcing this discovery, as part of this cozying into a niche relatively early on for multicellular life (moss seem to have sprouted out of the ocean and then pretty much called it a day) mosses have stayed genetic generalists. And this easy-going gene-set enables them to translate a wide range of DNA. In fact, hold on to your hats . . .
This cross-kingdom conservation of mammalian and moss protein production machineries is phylogenetically profound, and has several implications for basic and applied research. Comparative genomics, as well as functional studies, have recently established major differences in metabolic pathways and gene function between flowering plants and P. patens, and have suggested that a substantial moss gene pool is more closely related to mammals than to flowering plants (Frank et al., 2007; Rensing et al., 2008).
In the next post, we’ll take a look at what on Earth possessed these scientists to stuff human genes into a soft, green, cushiony object and at why biology is WAY cooler than nuclear physics. Stay tuned.
A friend just pointed out an interesting misconception that I hadn’t thought about. When you inhale helium, your voice sounds higher. It turns out that your voice isn’t actually higher-pitched! At least, not in the way that we think it is. The reasoning is a little convoluted…. read on.
Here’s the common misconception: The speed of sound is faster in helium because it’s lighter than air (thanks to the commenter for correcting me that it’s not the density but the molecular weight of gas that is important here… see Wikipedia on speed of sound). So, they say, since the speed is faster, that means that the frequency of your voice has to increase to compensate if the wavelength remains the same. [remember, the speed of sound (meters/sec) = frequency (waves/sec) * wavelength (meters/wave)].
Or, another popular misconception is that frequency remains constant, but the wavelength goes up. When this long wavelength hits the air, it then gets converted into a higher frequency. (But if you do the math, you’ll find this logic is flawed, because it actually results in a lower frequency).
Here’s what actually happens, as far as I can figure.
You make sound with your vocal cords… or, more accurately, “vocal flaps” — they look like two fleshy lips slapping against each other rhythmically. See some video of vocal flaps here – look especially at the last one on the right. When you sing middle C, the vocal flaps vibrate together to make a mess of frequencies around middle C, and you change the shape of your mouth and throat to emphasize “middle C” out of the mess of different notes your vocal flaps are making.
In other words, the sound from our vocal flaps doesn’t make it directly to our ears. It resonates in our vocal tract, which picks out certain notes. This is sort of how if you yell into a big tunnel, the echo sounds rather low. That big tunnel “picks out” the low notes. This is why male and female voices sound different — our vocal flaps make the same jumble of notes when we sing or talk, but the vocal tract, or chamber, emphasizes the lower notes for men and the higher notes for women. You can see this if you get a man and a woman and have them sing the same note into a frequency analyzer — you’ll see the same spikes on the analyzer, but the woman will have stronger spikes in the higher frequencies and vice versa for the guy.
So, when your vocal tract is filled with helium, your vocal flaps make that same set of messy frequencies around middle C, but the vocal tract picks it up as a higher frequency. So, in this way, the pitch of your voice doesn’t change (it’s still middle C that you’re singing), but the timbre of your voice does — which frequencies are picked up. Faster speed of sound = higher frequency. (The wavelength is fixed by the size and shape of your mouth and throat). So, it’s true that what you’re hearing is a higher frequency, but the difference is in what happens to air in the chamber of your mouth, after you’ve produced the sound.
Here’s what the March 1987 edition of Scientific American says in an article titled “Sopranos of the Skies”:
When a soprano sings a high C, her vocal cords actually produce a broad band of frequencies. . . . If [she] inhales helium, her voice seems to rise in pitch not because her vocal cords vibrate faster in the less dense atmosphere (they do, but only slightly); rather, because sound travels almost twice as fast through helium as it does through nitrogen, the acoustic properties of the vocal tract change so that it resonates with and amplifies higher-frequency tones.
For those of you who like math:When your lungs are filled with air, and you sing middle C, it has a frequency of 261 hertz and the speed of sound in air is 333 m/s (that’s 770 mph!), with a wavelength of about 1.27 meters (or about 4 feet, neato). When you inhale helium, the speed of sound is faster (972 meters/sec) because helium is lighter than air. Well, if the frequency created by your vocal flaps is the same, and the speed of sound goes up, then the wavelength must also go up. Using speed = frequency * wavelength again, you can calculate that the wavelength of the “middle C” that you try to sing on helium is actually about 3.7 meters long.
But here’s the real puzzler! What happens when the sound leaves your helium-filled mouth and hits your ears? Why doesn’t that long wavelength just get downshifted to a shorter wavelength when it leaves your mouth and hits the air (so that you hear the regular “middle C” that the soprano was trying to make)? It’s because frequency has to stay the same, or “frequency is conserved”. If 300 pushes of air leave your mouth every second, then 300 pushes of air have to travel through the air outside your mouth as well or else you’ll get a traffic jam of air leaving your mouth (this is the same argument, roughly, as to why water has to leave a pipe at the same volume per second as it enters the pipe). Below is from the New Scientist:
Once sound leaves the mouth its frequency is fixed, so the sound arrives to you at the same pitch as it left the speaker. Imagine a roller coaster ride. The car speeds up and slows down as it goes around the track, but all cars follow exactly the same pattern. If one sets out every 30 seconds, they will reach the end at the same rate, whatever happens in between.
In stringed instruments, the pitch depends on the length, thickness and tension of the string, so the instrument is unaffected by the composition of the air. Releasing helium in the middle of an orchestra would therefore create havoc. The wind and brass would rise in pitch, while the pitch of the strings and percussion would remain more or less the same
Note that you can have all sorts of crazy fun by breathing in sulfur hexafluoride. Well, actually, don’t do it, but instead watch it in the below YouTube video.Sulfur hexafluoride is heavier than air, so it has the opposite effect. A balloon filled with sulfur hexafluoride feels heavy, like it’s filled with water or foam. And that’s why you shouldn’t do this at home — since it’s heavier than air, it sits in your lungs and you can’t expell it. You have to turn yourself upside down or over a chair for a few moments to get it out of your lungs.
I’ve inhaled sulfur hexafluoride and I have to say, it was one of the strangest sensations! It felt like I was trying to talk through mud.
Here’s another video that shows a neat demo about how heavy sulfur hexafluoride is. At the end they “float” a little aluminum boat on a “sea” of sulfur hexafluoride (which sits, invisibly, in a container. It’s a gas but doesn’t float away because it’s heavier than air). They then scoop some of the gas into the aluminum boat and you can see it slowly sink as it’s filled with the invisible gas….
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If you spin around and around, why is it that you can feel a little sick? The answer lies in how we sense our balance, and an ancient disease of the gut. We get our sense of balance in large part from the vestibular system of the inner ear. A delicate little set of organs in there contain fluid, and having a good sense of balance requires that these “fluid spaces” be properly maintained. However, our balance is, of course, also determined by what we see (try standing on one leg with your eyes closed).
When you spin around, the fluid in your inner ear gets sloshed around, momentarily confusing that sense of balance. Your eyes tell you you’re standing still, but your inner ear tells you you’re still spinning. Your brain panics when it gets this disconnect between the messages from your inner ear and your eyes. That’s because this is one of the signs of botulism poisoning. Botulism affects the inner ear and can result in this kind of disorientation. So what does the body want to do? Vomit, to get out that nasty toxin.
You can get the same effect if your eyes tell you you’re moving (for instance, walk into a room where the walls appear to move) but your inner ear tells you you’re standing still.
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A recent post over at Working Knowledge (Measuring the Intangible) about how Barcelona plotted Flickr photos on a map of Spain to reveal favorite tourist locations reminded me about a really neat site at the Exploratorium. This is a great example of enhanced mapping – taking some interesting available public data to find out someone more about an area. There was a wonderful project at the Exploratorium called “Cabspotting” – http://cabspotting.org/ - that traced the routes that taxis took throughout San Francisco.
Cabspotting traces San Francisco’s taxi cabs as they travel throughout the Bay Area. The patterns traced by each cab create a living and always-changing map of city life. This map hints at economic, social, and cultural trends that are otherwise invisible. The Exploratorium has invited artists and researchers to use this information to reveal these “Invisible Dynamics.”
Check it out, it’s really interesting (especially if you’re familiar with the city). Or to quote a friend who quoted Lincoln, “For the kind of people who like that sort of thing, it’s the sort of thing they like.”
Here’s the image of the city when I wrote this post:
http://cabspotting.org/
Interestingly, the cab in the top left (which has a empty circle showing it has no passenger) is almost out to the Exploratorium. It then turned left, seemed to be out near Lucas Films.
This reminds me of the World at Night photos, where the very fact of where there is light outlines the major cities and the continents.
Gosh, I’m posting a pi day post just FOUR DAYS before pi day. Heavens. Well, any teachers reading this aren’t going to be preparing until the night before, right? Besides, pi day is, sadly, on a Saturday this year, so you can always cheat and do it on Monday if you need to!
So, yes, pi day is 3/14 at 1:59 pm (and I just found out that square root day was 3/3/09 and I missed it!). This is a wonderful chance for geekery in your classroom. And it was invented by a fellow Explorite (the Exploratorium’s cheerfully eccentric Larry Shaw). It also happens to be Einstein’s birthday.
The Exploratorium website has a nice page devoted to Pi Day, lots of history and limericks and some pi poetry (pi-ku).
The Year of Science has a nice resource website with a bunch of activities related to pi day, such as information about Einstein, Pi songs, and trivia.
The Exploratorium will be having a celebration (which I’ll miss, waah) in Second Life. Visit this SURL to teleport to that location in Second Life.
The original Pi guy is Larry Shaw, a physicist with streaming white hair, a white beard and a transcendent glow. It was 1987, and a cacophony of cultural references and relationships of the time intersected in San Francisco at the Exploratorium, to this day an internationally acclaimed museum of science, art and human perception. Shaw was thinking a lot about the concept of rotation into another dimension — the sorts of things he was actually paid to do. To recapture the time and the place, imagine Shaw mulling over the metaphor of the Hitchhiker’s Guide to the Galaxy, specifically the infinite improbability drive of the Heart of Gold Space Ship that is a major factor in the book. Turns out that the concept of rotation into another dimension is exactly what Pi describes. Pi represents the relationship between one dimension to another in the sense of the linear dimension and the plane; or the relation of the linear dimension and the sphere. Pi is key to these relationships. So for Shaw, Pi was in the air and definitely on his mind. He and his colleagues were talking about a Pi Shrine or a Pi Day, something to make the concept of rotation noteworthy. And so it all came together. For the first Pi Day, they installed a Pi Shrine (a small brass plate engraved with pi to a hundred digits) at the exact center of a circular Exploratorium classroom, a spot that also corresponds to the center-line of the museum’s building. And they walked around the shrine because as Shaw notes, “People go around things to show respect to them in many cultures and religions.” And they ate pie.
I am a science education and communications consultant -- view my website for my full range of services.
I am a physicist, writer, podcaster, and educator in Boulder, CO. On this blog I get to wax on about science stuff I think is cool (like weird science, or stuff we think is true but isn't), K-16 science education, hands-on science activities, teaching pedagogy, and how to communicate science. Geek on. 8-)
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