Monthly Archives: May 2016

DIY Wave Machine

Waves are everywhere! Electromagnetic waves traverse the vacuum of space. Gravitational waves ripple spacetime itself. Mechanical waves propagate energy through air, water, and other media.

Sound is a great example of a mechanical wave. Vibrating molecules disturb their neighbors, which disturb their neighbors, and so on. The individual units don’t move far, but the energy they transfer spreads widely. When the molecules closest to your ear jiggle back and forth, you perceive sound.

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Propagation of a sound wave in air. Image credit: HyperPhysics/Georgia State University

It’s easy to make your own mechanical wave machine at home. Center wooden skewers at approximately equal intervals (an inch or two apart works well) along a length of wide tape. Lay another strip of tape across the top of the skewers to hold them in place. Tension the system by attaching the ends of the tape to secure holding points. You’re ready to make waves! Lift and drop a single skewer end to generate a pulse. What happens?

Oscillate one skewer, and its neighbors move, too. The domino effect continues down the line even as the skewers themselves stay in their taped positions. Matter isn’t propagated along the machine, but energy is!

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For slower waves & easier observation, add mass to the ends of the skewers. We used modeling clay to weigh down each point.

Written By: Caela Barry

Small but Mighty: Eggshell Architecture

In West Virginia’s New River Gorge, an 88-million-pound bridge spans a chasm eight tenths of a mile wide. Before its construction, drivers detoured for the better part of an hour to navigate the Gorge’s steep, water-carved walls. Today, the crossing takes less than a minute at highway driving speed. (Image credit: Louise McLaughlin.)

NewRiverGorge2

For most of history, a crossing of this magnitude was architecturally impractical at best. It takes a combination of age-old engineering and lightweight, strong, flexible modern materials to make massive suspension structures a reality.

An arch is a way to redirect force. Imagine two pillars supporting a heavy crossbeam. The crossbeam sags like a hammock, even if the beam is made of relatively rigid material. Its weight squishes the pillars downward– and also pushes them outward. An arch does two useful things: it transforms the tension (the sagging, stretching force on the crossbeam) into compression, and it aims the outward push of the roof more directly down through the support pillars. Check out this quick, fun, interactive piece to really get a feel for the forces involved.

A dome is essentially an extension of an arch– instead of directing force along a single dimension, it spreads weight out radially from a central point.

EggshellGif

These three raw eggs hold up a stack of books weighing about thirty pounds.

Human-made arches and domes date back to ancient Mesopotamia, but nature has been on board with this kind of construction for even longer! The phrase “walking on eggshells” evokes a common misconception: that eggshells are weak. The calcium carbonate they’re made of may not stand up to impact very well, but its dome-shaped structure is surprisingly tough under static stress. Hard to believe? Try it yourself! We placed a paper ring on each end of our test eggs, creating a stable surface to stack books on top of. What other methods can you come up with for testing the strength of these natural domes?

Written By: Caela Barry

DIY Tumblewing Glider

To build a tumblewing glider, start with a long, thin rectangle of paper. We experimented with gliders ranging from about three to eight inches in length and had good results with rectangles roughly 4-6 times as long as they were wide. The lighter and thinner the building material you use, the easier your glider will be to fly. Printer paper, craft tissue, and phone book pages all work well.

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First, fold the short ends of the rectangle straight up away from your work surface, forming 90 degree angles with the middle of the glider, as shown in the center picture. The long edges of the glider body, between the two folded-up ends, will need to point in opposite directions, as in the picture on the right. Fold a long, thin flap towards you on one side and away from you on the other (it doesn’t matter which edge points up and which points down).

TumbleGif

Next, check out how your glider moves through the air. Hold it by one of the long, thin folded edges and drop it with a gentle flick of the wrist. It might take a few tries to get a feel for what’s going on… don’t worry if it doesn’t seem to work right away! Ultimately, the tumblewing should rotate smoothly and quickly as it floats to the ground.

Once you’ve mastered dropping your tumblewing into a stable spin, try piloting it with a large, flat object, like a piece of cardboard. When you push a flat object through the air, air molecules move up and over it, creating a swell. The swell pushes the glider along a little bit like the water wave behind a surfer in the ocean!

TumbleWave

Image courtesy of Science World British Columbia

For a more challenging (and portable) piloting experience, try using smaller and smaller surfaces to push the tumblewing through the air. With enough practice, it’s possible to control a phone book paper glider using just your hands.

Our tumblewings were inspired by Science Toy Maker. Check out their site for even more glider ideas!

Written By: Caela Barry

Is it a Microwave or a Shrink Ray?

I’ll be honest: This one blew me away the first time I saw it! What is going on here? It all has to do with polymers, which are basically long chains of repeated molecules, which you can learn more about here.

Just to re-iterate: This is not dangerous to you, but it is dangerous to the microwave!

Microwave Magic

These polymers have some interesting properties that we need to understand, and then this will become much simpler. As we have seen before, temperature can be an important part of chemistry. That is also important here! Let’s start by talking about something a more familiar polymer: protein!

We all have lots of protein in our bodies which perform many different functions. These functions are determined by their shapes, which are in turn determined by the specific molecules that make them up. However, if proteins are exposed to high temperatures or acidic conditions, they lose their shape and just uncoil into a big mess. This is called denaturation, is actually a good thing for us. Human stomachs are highly acidic, and when you eat food with protein in it, this allows the protein to be broken down so that it can be used.

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A similar thing happens with the polymers in the bag*. When these huge chains are hot, they become very flexible. Left to their own devices, they will tangle up and clump into a polymer mess. Alternatively, in this flexible state they can be easily manipulated a different shape. When they are cooled down, they maintain this shape.

This gives us all the tools we need to understand the behavior of these bags in the microwave. These bags contain a polymer skeleton surrounded with foil and paint. When the bags are manufactured, they are heated up and stretched out before being cooled off. The result is that the long polymers in the bag are locked into long straight lines forming the structure of the bag.

In the microwave, they get HOT. Without anything to hold them in position, they collapse into their natural shape: a big clump. As the bag’s polymer skeleton collapses, the bag itself shrinks dramatically. The results are astounding!

Written By: Scott Alton

Microwave Magic Display

*Note: If you are reading carefully, it may seem like this is the exact opposite of the protein. This is because proteins are heated up to the point where they collapse to the appropriate shape at body temperature, whereas for these polymers that temperature is much higher. If these polymers were to get even hotter, they would exhibit similar denaturation behavior. Similarly, cooling the protein well below body temperature would lock them into their current shape. The same thing is happening, it is just on different temperature scales.

Why Do Water Glasses Sing?

TacomaNarrowsImagine pushing a child on a swing set. When, exactly, do you push? Intuitively, most of us wait for the swing to be at its closest, then give it a shove as it starts to fall away. At any other time we’d either be inviting a collision or chasing after the child.  Amplifying the swinging motion is easiest at a specific, recurring point. This is called resonance.

On a swing set, resonance provides an efficient way to move someone higher and higher. In other contexts, it’s a major safety threat. The Tacoma Narrows bridge, shown at left, famously collapsed in 1940 when gusting winds pushed it at its resonant frequency. The bridge thrashed up and down so violently that it eventually disintegrated. (Image credit: Barney Elliott.)

Musical instruments resonate, too, although this is harder to see. We hear oscillations of different speeds as individual pitches. Press a piano key, and a hammer strikes a wire, which vibrates at its characteristic frequency, producing the same note every time. Trapping a guitar string against a fretboard changes its resonant frequency, so the same string can generate many pitches.  

We can use this science to make a wine glass sing! A wet finger run along the edge of the glass alternates sticking and slipping as it slides across the surface. Under just the right pressure, the stick-slip pattern matches the glass’s resonant frequency. This periodic push oscillates the glass, which in turn vibrates the air nearby, creating a sound wave. The faster the glass moves back and forth, the higher the pitch we hear.

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Adding water to the glass is a bit like applying a brake to the vibration. In order to move, the glass has to push the water out of the way. This slows down the oscillation, resulting in a lower pitch.

Line up several glasses filled with different levels of water for a glass harp with easily repeatable notes. Pick one up and tilt it as you play to change its pitch like a trombone! Alternately, try partially submerging an empty glass in a large container of water, and see what happens when you adjust its depth. Can you think of any other ways to tune a musical glass?

Written By: Caela Barry

Fluorescent Flowers

Transpiration Water enters a plant at the root system and moves upwards through specialized tissue called xylem. Xylem carries water all the way to the plant’s extremities, where some escapes into the air through minute openings in the outer surface. This loss of moisture is called transpiration. In hot conditions, large trees can lose huge volumes of water, on the order of hundreds of gallons per day! (Image: UC Irvine.)

At the molecular level, water is “sticky”. It’s attracted to many surfaces, including paper, glass, and human skin. This is called adhesion. Molecules within a body of water tend to stick together, too– that’s cohesion. Tube-shaped cells in xylem tissue take advantage of a combination of adhesion and cohesion to overcome gravity and drag water upwards.

MeniscusPour water into a glass and you may notice that the liquid’s surface angles up slightly around the edges. That’s the effect of adhesion between glass and water! Thanks to cohesion, the molecules closest to the exposed glass drag their neighbors along, and the liquid climbs noticeably. Farther along the molecular chain, gravity wins out over adhesive pull, which is why water doesn’t crawl all the way up and out of most containers. (Image: East Stroudsburg University).

When the exposed surface is small enough, though, adhesion and cohesion actually beat gravity. Water naturally climbs up very tiny tubes. This is called capillary action, and it’s how water gets from roots to treetops.

See capillary action at work by sending different liquids through the xylem of a white flower. Food coloring mixed with water works well. Give this a try and see where the color ends up! For an extra-bright twist, place cut white carnations or daisies in water colored with highlighter ink. Neon pigment glows under a blacklight, so you can make fluorescent flowers!

Written By: Caela Barry

You Are Here: Our Place In Space

Spend a clear night outside and you might notice something strange about the sky: the stars migrate from horizon to horizon. It’s not quite as obvious as the sun’s motion, but it’s true. Our home star isn’t the only one that appears to rise in the east and set in the west.

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Image credit: Pearson Prentice Hall, Inc. 2005.

The illusion that everything outside our atmosphere orbits around us results from our planet’s own spin. Only the points along our axis of rotation, the imaginary skewer Earth spins on, seem to stand still. It just so happens that a star lies on this line! Polaris gets its name because of its strange behavior. Unlike other lights in the sky, the North Star can always be found in the same place. As for other stars, the closer they are to our axis of rotation, the smaller the circles they seem to trace.

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Polaris appears to stand still because it’s located along Earth’s axis of rotation. The farther a star is from that axis, the larger the circular path it appears to take from our perspective. Image credit: Peter Michaud (Gemini Observatory), AURA, NSF

Stargazing cultures throughout history have noticed this hierarchy of motion and canonized it along with the constellations themselves. One Greek myth places self-centered queen Cassiopeia in the sky near Polaris, where she’s doomed to dip her head in the ocean year after year, never fully disappearing below the horizon. She’s a circumpolar constellation, one that circles Polaris closely. Farther from Earth’s axis of the rotation, tracing more generous loops in the sky, Cygnus the swan dives in and out of sight with the seasons, nobly trying to rescue a drowned friend.

NightSky3

Dark summer skies treat stargazers to one of the most striking sights to slice through the night: the main belt of the Milky Way Galaxy itself.

It’s a grand cosmic coincidence that there’s anything visible along our rotational axis at all. The night sky is mostly empty space. A typical star apparent to the naked eye has an angular diameter in the ballpark of 0.01 arc-seconds. In the whole world, the average human eye can detect 9,096 individual stars. This means that resolvable stars take up less than one millionth of one percent of our view of the universe. It’s astonishing that a stellar signpost happens to hang out in one of the two spots that don’t seem to move. What’s more, the North Star hasn’t always held its convenient position, and it won’t stay there forever. Our axis of rotation moves slowly over time. As it moves, it points to different patches of sky. Luckily for humanity in the Northern hemisphere, the axis has pointed to a guiding star through the time in history when we’ve learned to navigate.

Written By: Caela Barry

Meet Your Teachers

How does a person end up teaching at AstroCamp? Most instructors study physics as undergraduates. Mathematicians and biologists are represented on staff, too! All share a passion for communicating science to children.

Screen Shot 2016-05-03 at 11.38.56 AM L: Caity helps a student look for micrometeorites. During summer camp, she teaches rock climbing on Idyllwild’s iconic granite. R: Christian debriefs students as part of their wind turbine engineering process. He plans to move to Europe for graduate study this fall.

Some pursue advanced degrees before coming to camp. This season’s teaching pool includes experts in fusion plasma dynamics and group theory.


DanJpg1 Dan, Ph.D. (physics, UW Madison) and extreme endurance athlete, guides students through an interactive exploration of electromagnetism.

AstroCamp balances hands-on lab time, science outreach, and outdoor recreation. This unusual combination draws a unique applicant pool from all over the country. Before they get here, they’re students, teachers, Scouts, park rangers, band members, and more. Some arrive straight from school, while others wrap up long-term adventures at camp, happy to find a haven of STEM education and like-minded scientists in a mountain playground.

Screen Shot 2016-05-03 at 11.39.12 AM L: Britta takes in the view from Tahquitz Peak, five miles’ hike from AstroCamp. R: Kyle catches sunset on the mountainside. During summer camp, Britta and Kyle lead trail running classes.

The people who find themselves at home here are kids at heart. Instructors are drawn to AstroCamp by a desire to share their perspective and excitement about science: it’s all around us, it’s fun, and the best way to “get it” is by getting your hands dirty!

EvaColleenjpg Eva (L) and Colleen (R) are all smiles after the spring color throw. Eva and Colleen both worked as planetarium presenters before coming to AstroCamp.

WELCOME TO OUR ASTROCAMP BLOG

We would like to thank you for visiting our blog. AstroCamp is a hands-on physical science program with an emphasis on astronomy and space exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and astronomical happenings. This blog has been created by our staff who have at least a Bachelors Degree in Physics or Astronomy, however it is not uncommon for them to have a Masters Degree or PhD. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science, space and astronomy information. Feel free to leave comments, questions, or share our blog with others. Please visit www.astrocampschool.org for additional information. Happy Reading!

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