My 100th Video!

I just uploaded a new video to Vimeo. I thought I'd do something a little different:

Drip Drip Drip

I've been trying to capture a water droplet colliding with another that has already hit the water. It's been challenging. Here's the closest I've gotten to matching both the timing and a really clear view of the event.

Water is wet - except when...

...it hits a water-repellant surface. In this case, compare what happens to a drop of water when it hits glass:


to water hitting a fabric that has been treated with a special nano-scale coating that causes the water to bead up:



The thin, spread-out film of water that forms on glass occurs because the water droplets "wet" the surface of the glass (through adhesion). The water molecules do not "stick" to the specially treated fabric and surface tension holds the water droplet together in little spheres. This is sometimes referred to as the Lotus Effect because the micro structures of the lotus leaf also cause water to form tiny spherical droplets instead of adhering to the surface.

Moar Mineral Mashing Madness: Muscovite

Here's a preview of a larger project that's in the works. I plan on bashing my way through Bowen's Reaction Series, but I thought I'd post one of the shots to get some feedback. Mainly, is the depth of field sufficient? I'm limited in how small I can make the camera's aperture and still get decent results, so I can't get more depth of field without buying more lights. And the pair of 500W tungsten lights I'm using right now are really, really hot. Like over 200°C near the bulb hot.

So, in what what will become a more "continuous" series (heh) of clips for the silicate minerals:


I'm not sure I like the hammer used in this shot - the 3lb sledge was too heavy to quickly pull away, so it kind of dominates the scene and covers up the mineral, so I adjusted the playback speed in a few places to minimize the time the hammer occupies the frame. The well-developed single plane cleavage of muscovite presented some additional challenges. In order to produce deformation (separation along that cleavage plane), I needed the direction of maximum stress (the hammer blow) to be perpendicular to the cleavage plane. I was worried that a smaller hammer would simply slip off or something and leave me without much visible deformation. But this kind of hammer wouldn't produce good results with smaller, more brittle samples.

They say a watched boil never pots... or something

At standard atmospheric pressure, water boils at 212°F (100°C). But at lower atmospheric pressures, water boils at lower temperatures. Here's a short clip of some boiling water:


Some of you might remember the formula for converting temperature: [Temp(F)] = (9/5) * [Temp(C)] + 32
This isn't all that easy to remember - there are some odd fractions in there and to be honest - it's time consuming to multiply things by weird fractions. Here's a quick way to convert (roughly) from Fahrenheit to Celsius that I use:

A few reference figures:
•Water Boils at 212F, 100C
•"Standard" body temp is 98.6F, 37C
•Water Freezes at 32F, 0C
•"REALLY COLD" is -40F, -40C

Let's say you're on vacation and the weather report says it's a cool 10C outside. Well, you can estimate that 100F is about equivalent to 40C (close enough, plus we're simplifying the math) and 30F is about 0C. Now you have the range of temps in C and F. Think of it as the total length of the ruler - if we know how long each ruler is and know that one measurement is some percent of the total, that same percent of the other ruler is our target. The length of our ruler (or change in temp) from our estimate is 70 for fahrenheit, and the total change in C is 40. 10C is about 25% of that the "length" of our celsius ruler (10/40, 1/4th or 25%). So 25% (1/4th) of 70 is (half of a half, so half of 70 is 35, half of 35 is 17.5). Since our celsius temp is above freezing, we add that 17.5 to 32F and get 49.5 - rounded up to 50. Checking the calculator, that ends up being spot-on (10C = 50F).

We could use the boiling and freezing points of water - since not everyone can remember 37C as the body temp. Water's liquid range is 100 degrees for celsius, and 180 for fahrenheit. 10C is 10% of liquid water's celsius range (10/100, 1/10th, or 10%), so 10% of the fahrenheit range is 18. SInce it's above freezing, 18+32 = 50 degrees fahrenheit. Not bad, eh?

Oh, and be very, very careful when the TV weather personality says it's absolute zero outside. That's cold - this refers to an object with zero heat energy (simplistically speaking). That's -273.16°C. BRRR! What about fahrenheit? Okay, so we know 0C and 32F are equivalent and (interestingly) -40 is the same in F and C. So the range here is 40 degrees celsius and 72 degrees fahrenheit. Well, -273 is a little less than 7 times our range of 40. So for our range in fahrenheit, 7 x 70 (again, rounding down to nearest 10 to simplify the math in our heads) is 490. Since we're below freezing, we subtract 490 from 32 to get -458°F.

Wouldn't you know it, -273.15°C is -459.67°F. My mental conversion must be a little low because I rounded down in order to keep the math quick and easy. At those temperatures, are you going to worry about being less than two degrees off? Well, sure, if you're trying to form a Bose-Einstein condensate - but then you're not going to be rounding numbers to the nearest degree - or even worrying about english imperial units at all.

But in everyday life, you don't need a calculator all the time. Estimation is a powerful tool. If you need to be precise, use a machine. If you just need to get an idea, use your head. You always have that with you and it doesn't need batteries.

It's a Crystallographic Abattoir...

The result of two days of mineral cleaving...

Mineral Mashing: Halite

Less "mashing" and more of a "love tap" on a crystal of halite:

Moar Mineral Mashing: Calcite

Okay, let's try something that shows cleavage in some non-orthogonal orientations. Calcite is a good one:

Mineral Mashing: Galena

This one turned out pretty nicely. I shot it at 10,000 frames per second, so the resolution is a little reduced. But the tendency of galena to break into tiny cubic cleavage fragments is pretty clear. And I just love the glitter effect, too.

Moar Mineral Mashing Massacres

I've been busy. Classes have started again, which means lectures and syllabi and course stuff. Since we have this fancy camera, I'm going to try and integrate some of the mineral footage into the rocks and minerals part of the class. Don't know how much mineral mashing I'm going to do "in-class," but I figure the high speed video will help show off the difference between cleavage and fracture. More video insanity to come...

Mineral Mashing: Fluorite

Fluorite is also cool. WIth the added characteristic of cleaving along specific planes of weakness within the crystal:

Moar Mineral Mashing: Instant Glitter

Just smack some iron pyrite with a hammer:

Water is wet

The reason water forms wonderful droplets? Because it is "wet." But not too wet...

A Demo Reel of sorts

I threw together a "demo reel" to highlight some of the things we can do with our department's new high speed camera.



It's not perfect, but it gives people an idea of what we can do. I also think I've used up all the decent royalty-free music that comes with iMovie...

Amphibole-slo-mo

Smacking a mineral with a hammer. Simple enough. I've got some pyroxene lying around that I'm going to have to try next...

Thurs-Demo: The one with a Slinky

Today's demo: P and S-wave propagation using a slinky. When talking about earthquakes, it's often hard for students to "see" the relative motion of energy through rocks. We often use a slinky or a large spring to demonstrate the behavior of waves moving through a solid material. Trouble is, the movement of the wave is so fast, it's sometimes hard to see. What better way to slow things down than with the high-speed camera?

I haven't done any motion tracking, but I don't think the pressure wave is traveling any faster than the transverse (shear) wave in the spring - I think the spring is too "springy" so there's no discernible difference in velocity between the two.

Froude!

Something else that demonstrates an interesting conceptual overlap - the design of battleships and fluid forces exerted on an object. Geology in Motion has a fun little tale about how the "Froude Number" (another wonderful word) came to be.

on the intersection of muppets and continental sedimentology

I've always been a fan of the Muppets. More so the muppets under the direction of Jim Henson than most of the newer offerings. Well, if one were to draw a Venn diagram of "things that interest me" you would notice a new spot where two fields overlapped. It seems that Jim Henson wrote a screenplay called "A Tale of Sand" that is getting some renewed attention.

Everything Old is New Again

NOVA is touting a new special, the "3D Spies of WWII." While the actual technique they used is still amazing, calling it "3D" is kind of silly. The technique places two pictures taken from slightly different angles next to each other. When viewed close up, the brain interprets the image from one picture (going to one eye) and the image from the other picture as a sort of three dimensional image. It's something that field geologists have used for decades to get a better idea of what the landscape is like. Particularly because hills and depressions show up more easily. But the title is simply a re-branding of a centuries-old technology. It kind of annoys me, but at the same time I understand that "stereoscope" and "3D" make use of the same visual illusion, "3D" has more cultural relevance today. It's one of those connotation versus denotation issues. While they mean the same basic thing in fairly specific terms, they convey a fairly different sense of relative meaning.

One could do some interesting optics analysis to demonstrate how a British intelligence service person could estimate the height of a V2 rocket based on a simple pair of photographs.

Drip Drip

Just Another Day

I don't know how many of you have ever dunked a tuning fork in water, but the results are definitely worth a wet tuning fork.

One of those days

Today was the kind of day where you do lots of cool stuff and the time just seems to fly by. My colleague and pal, Todd and I were trying our hands at high speed filming of popping water balloons. Todd also blogs about his physics teaching here. It was also a little strange in that my computer (a MacBook) spent most of the day booted in Windows 7, because that's what the video processing software for the camera uses. I also don't have as many internet thingies set up with my Windows partition, so I was intermittently aware of what was going on in the interwebs while I was filming.

Here was the general setup:



And here's the finished project (I tossed in some "pop" music for good measure):

This doesn't get old.

The high speed camera just doesn't get old. It's an amazing piece of equipment. One of our department goals with the camera is to produce a library of videos that can become part of a laboratory activity or lecture demo (and available to anyone).



Now if you'll excuse me, I've got some water balloons to break...

Thurs-Demo: The one with Warts

Although I mainly teach introductory geology, I have taught other upper-level geology courses. One of my favorite topics is bedding structures (ripples graded beds, mudcracks, etc). The differences in those bedding structures formed by moving water compared to those formed on land by moving air are particularly helpful when interpreting the environment of formation of a particular unit of sedimentary rock. Combine a stack of these units into a stratigraphic column and you have a record of environmental change over time. Compare one stratigraphic unit to an adjacent unit of the same age and you have environmental change over spatial scales. Combine the vertical analysis of time with the spatial analysis and you have a four-dimensional study of an area. Time and space. All from a set of lovely sediments all piled up together (more or less depending on your field area).




Here's a lovely example of some bedding structures from the Chinle Formation (Triassic) of Utah. There are some interesting drag marks and some other traces that my ichnologists might be able to tell more about. But the lumpy ridges are what struck me. They aren't normal ripples where you might see some distinct cross laminations to give you a sense of fluid flow direction. They're also kind of "smooshed" at their crest, suggestive of some kind of soft-sediment deformation after they formed.

My current thought is that these are adhesion structures. These are ripples, ridges and bumps (wonderfully called "warts") that form when wind blows loose sand across a wet surface. If you live near the beach, or - for those of us in colder climes - walk across a parking lot on a windy winter day, you may see little bumps as the snow bounces across and then sticks to the wet pavement.


Here are some "nivean adhesion warts" that formed as snow blew loose snow across a wet sidewalk last winter. The orange BB is 6mm in diameter.

You can make your own adhesion warts - all you need is a wet paper towel and some fine sand. Here's a quick video:



Oh, and since my department has a fancy new camera, it would be cruel of me not to show you some of these sand grains bouncing across a wet surface in slow motion, here you go (I suggest going full-screen for this one)


Adhesion warts are probably my favorite bedform. In part it's got a great name. But also, they are clear indicators of terrestrial sedimentation. You really can't form these things underwater because there's no surface tension to allow the sediment grains to "stick" to each other underneath the water.

Stupid Human Tricks

Here's a fun little demonstration of inertia you can try next time you're at a bar or otherwise might find yourself with a stack of quarters. I used dollar coins in this version, but it works the same with quarters. My limit is about 20 coins - any more and they start getting pulled away as I rotate my arm and my hand doesn't catch them.

Merry New Year!

Wow, it's already the 3rd and I hadn't gotten a new post up yet? Crazy. Testing of the camera continues - I'm still working on how to balance the needs of light for the sensor - it's easy enough to dump 1000W of lights into a studio setup, but another question when outside. Here's some footage of me juggling to entertain you for the time being: