Aug 31

Last Person to Know Everything

Has anyone grasped all human knowledge? Aristotle, two millennia before the printing press? The lesser-known Thomas Young, who published on tides, light, bridges, languages, and Egyptian hieroglyphics? Will our technological progeny ride an exponential growth curve to catch up with all human-computer knowledge? Or does the shoreline of the unknown inevitably expand with the island of knowledge?

My aim, less ambitious than knowing everything, is knowing where my knowledge fits into the totality, the context of my knowledge. Start with science: a map could show us how concepts connect. Any science demonstration or experiment could be located–Your phenomenon is here 👉🏽 and it connects to related phenomena. Students could start anywhere, with the most recent experience provoking their curiosity. With persistence to follow their curiosity, they could reach all of science, or at least know where their interests fit in a big picture.  That would give them a sense of place and a seed for future research.

Science Concept Map

Science Concept Map

The map here is a draft–perhaps it will always be a work in process because of the nature of knowledge. One of my students is interested in quarks, so the science concept map frames and guides our discussions, clarifying what we don’t know. And then the map grows from those discussions. Other students will add their own areas to the map.

Some students may go “meta” by reorganizing the map or porting it to virtual reality so that detail can be intelligently hidden, keeping the map uncluttered but progressively revealing what interests individual viewers. Or dynamically-generating the map from meta-tags on Wikipedia or Google Graph.

Conversations with professors and grad students from nearby universities have resulted in interest in the map, but no recognition of it already having been developed. Perhaps specialization makes those familiar with the details that would go into this map too busy with their field or sub-field to develop such a general map.

If this map already exists elsewhere, please comment on this post. But even if it does, my students and I learn from creating it, so we would learn from those parallel efforts, not abandon our own.

Jul 30

Who or what pulls the trigger?

A landmine is autonomous. However indiscriminate its selection of a target, a landmine does not require intervention by a human. Deadly weapons that do not require human intervention date back to pits with spikes, but something new is on the horizon: weapons that are selective in their targets. Concern that artificial intelligence will facilitate a new arms race has mobilized prominent scientists to publish an open letter warning of the dangers.

What are autonomous weapons? Technology that selects its own targets to destroy. This goes beyond the proximity fuse of World War II, kept as important an Ally secret as the atomic bomb. That caused an anti-aircraft shell to detonate when close to an airplane, but was aimed and launched by humans. In 2015, the U.S. Army developed guided bullets. The so-called “smart bullets” would follow the target at which they were shot. But they were still aimed and launched by humans. Weaponized drones that can independently identify targets and attack them are, perhaps, the first manifestation of autonomous weapons. The category, however, could stretch our imagination.

Why would we use autonomous weapons? For many of the same reasons that we automate anything: accuracy, speed, economy, scale. While humans are still better and often faster at recognizing patterns, for instance an appropriate target, technology is rapidly catching up. Technology has long been cheaper and easier to replicate than humans. Train a robot to do something, and then make copies.

One driver of autonomous technology is space exploration. Sending humans to other planets is both expensive and dangerous. But the distances mean that even speed-of-light communication is slow: Mars is minutes away and Saturn is over an hour. So some decisions have to be made by the technology. Imagine driving a car and feeling the lane-separating bumps only an hour after your tires touch them.

How could autonomous weapons change us? As imagined in the Open Letter, they could make it easier for dictators to control their populace, for warlords to murder by ethnicity, or for terrorists to target their attacks. Terrorists already deploy a poor-man’s autonomous weapon: suicide bombers. Someone clad in explosives can enter an area to choose the time and place of detonation. Autonomous weapons could bring economy and scale to this threat.

How can we change autonomous weapons? Thinking critically, we can understand and evaluate them. This essay has applied some of KnowledgeContext’s ICE-9 questions. Once we understand and evaluate, one possible act is the Open Letter. Another would be a treaty similar to the Ottawa Treaty or Anti-Personnel Mine Ban Convention. Civilization can choose its direction.

Jun 18

Why do rattlesnake egg magnets rattle?

rattlesnake egg magnet questions resizedHold two dark, egg-shaped magnets in your hand, separate them with your thumb, and throw them in the air.  As they arc in the air, they crash together and rattle.  How? Why?

We played with them, watched them in the air, watched them on a carpet, listened to them, recorded 120 FPS video, and noted questions and observations to guide our exploration.

Video of magnets colliding freely:

Video of magnets colliding with one held in place:

Video of magnets rocking together:

We observed that one type of sound coincides with the collision and bouncing of magnets against each other.  A second sound coincides with the magnets in constant contact, but rocking rapidly against each other.  While we are tempted to say “caused by” instead of “coincides with” we have yet to devise experiments to distinguish these.

One magnet was too weak to hold another in the air, but still produced the familiar rattling when allowed to collide.

I had thought that the rattling came entirely from collision and bouncing, so the slow-motion video showing that most of it came from rocking surprised me.  We have only just begun exploring how this works.

May 12

Ring of magnets cool hand?

IMG_4237Phoenix and Maverick thought they sensed a cooling of their hands when placed within a ring of magnets, so they created an experiment to see if their impressions were accurate and what the pattern might be.  They hypothesized that the magnets could exert a pull on the iron in the blood of the hand, causing a cooling sensation.

They used “rattlesnake egg” magnets as a test and a glass bowl as a control. IMG_4239They measured the bowl and then used enough magnets to create the same diameter, 25. Then they used an IR thermometer to measure the bowl, the ring of magnets and the hand.  Ten times they placed a hand in the magnets and remeasured temperature. Ten times they placed a hand in the bowl and remeasured temperature.

IMG_4238Their results show no decrease in hand temperature in either magnets or bowl.  This does not rule out the sensation of cooling, which could also come from the magnets serving as heat sink if they are cooler than the ambient air. We might have continued this investigation in class, but time was running out to play with a Van de Graaf generator…

May 07

Wind Tunnel and Wiffle Balls

Maverick drops wiffle ball in wind tunnelMaverick’s interest in flying saucers led us to studying fundamentals of aerodynamics.  We dropped wiffle balls into a vertical wind tunnel made from a shop vac and sliced 3-liter soda bottles.  The balls behave differently, usually hovering at one of two heights, so we took 3 balls, weighed them, inspected their surface (noticing some had smooth seams and others a lip), and noted their color.  We then dropped each into the wind tunnel (already blowing) 10 times, noting the hover height.weight of wiffle ball

The 15.6 gram blue ball hovered at 6″ four times, 26″ once, and 27″ five times.  The 15.8 g green ball hovered at 6″ six times and 27″ four times.  The 13.7 g orange ball hovered at 22″ once and 27″ nine times.  We looked for patterns, noticing that lighter balls tended to hover higher, exposed seams might cause balls to drop to a lower hove, and color was not controlled.  So we took another 3 balls of the same colors and weighed and inspected them.  We dropped each of those 10 times into the wind tunnel.

wiffle ball seamsThe 15.2 g blue ball hovered at 6″ twice, 26:” once, and 27″ six times.  The 15.9 g green ball hovered at 6″ nine times and 27″ once.  The 13.4 g orange ball hovered at 6″ once, 15″ once, 20″ once, 26″ once, and 27″ six times.  Between the two sets of balls color and weights correlate, so we can’t yet separate those even though we strongly believe that color should not affect aerodynamics.  To distinguish color and weight, we could attach weights, such as pieces of masking tape, to equalize weights, but we’d have to be careful to not impact aerodynamics with the tape.  Although weight appears to affect hover height, the lightest ball (Orange run 2) averaged lower hover heights than the 2nd lightest ball (Orange run 1).

data of wiffle ball height in tunnelThis is prelude to testing the impact of covering holes on the wiffle balls and measuring aerodynamic impact.  Most encouraging for me is that Maverick had the patience and tenacity to run 60 tests. Judging science fairs and teaching science, I see few students eager to persist after a few runs…but that just gives impressions, not supporting data.  I look forward to continuing this exploration of aerodynamics!

solar animation and chaotic pendulumBefore we started with the wind tunnel, we played with animated solar toys: dancing flower, swinging bear, flapping turkey, and fluttering butterfly.  We compared the fluttering butterfly with a chaotic pendulum when Maverick thought the obvious magnet stuck to the thorax of the butterfly might be interacting with a similarly fixed magnet hidden in the flower.  The differing behavior of the chaotic pendulum, which we configured with a repelling magnet directly under the magnetic pendulum suggested something different going on with the butterfly.

Since its motion was most interesting and its case easiest to pry apart, we opened the dancing flower to find the solar panel powering an integrated circuit, which controlled an electromagnet.  We opened the swinging bear, too, to find an voltage from solar flowerintegrated circuit setup the same in appearance, possibly identical.  We suspected that the integrated circuit turns the electromagnet on and off, so we tried to measure that with a multimeter.  While we did get a 1.6 volt reading from the solar panel, the wires to the electromagnet were very, very small, making it hard to maintain electrical connection with the multimeter probes long enough to measure.  Our make and break contact, due to hand shake, hid any periodicity we might measure of the integrated circuit’s output.  Since we wanted to get to the wind tunnel, we did not take the time to figure out how to make reliable electrical connections.  Once we get that, we could also use an oscilloscope to better measure periodicity (or its inverse, frequency) and even see the wave form.


May 05

Electrolysis and camp towels

Max brought a 12V battery and a jar with two tufts of steel wool separated by a sock.  He used baking powder as an electrolyte in the water.  Wiring the jar to the battery worked well, creating enough hydrogen and oxygen to ignite with a match to create the pop you can see and hear in this video:

Max explains how this works:

separating hydrogen and oxygen

When we poured the solution into a jar that separates hydrogen from oxygen (see photo at left), we got little activity.  We suspect that’s because it uses pencils as electrodes, so the surface area is much less than with the steel wool.  Though the graphite cores of pencils are reputed to resist breaking down during the electrolytic reaction, there’s not enough reaction for us, so we may figure out how to connect the pencil cores with steel wool or something similarly rich in surface area.

draining camp towel We experimented with camp towels for a lightweight backpacking trip I plan for late June.  Though we do not have a high-tech towel like Cascade Design’s ultralite camp towel, we tested two candidates from Dollar Tree: microfiber and shammy (reminiscent of chamois).  We measured them and then weighed them dry, soaked in water and dripped for a minute, wrung out, hang dried for an hour in an 80F garage, and hang dried overnight.

While we used a digital scale to weigh the towels initially and after hanging dry (1 hour and overnight), we inferred the intermediate weights, soaked and wrung, by capturing all the water back into the source beaker. Each beaker started with 300 mL before dunking each towel in.  We noted the water height after removing the towel, letting it drip for one minute, and also after wringing. With each mL of water weighing one gram, the math was easy.measuring water left by camp towel Our results are shown in the photo, with the last bit of data missing: overnight drying brought both towels back to their original weight of 29 grams.

Starting and ending weights were the same.  Shammy had more area (260 vs 224 inches squared), but the microfiber was half the price (2 for $1).  Shammy soaked up more water (171 vs 131 g), but both released the same amount of water on wringing (100 g).  An hour hanging got the microfiber a bit drier (down to 44 vs 61 g), which was no surprise because it held less water both soaked and wrung.

camp towel dataThe verdict? Each should soak up the same amount of water (100 g) after each wringing cycle, so that’s a wash.  Shammy soaks up more initially and microfiber releases more.  Unless I had a lot of water to soak up at once and then left the cloth to dry on my pack while hiking, I slightly favor the microfiber because it will be less wet and less weight while drying on my hike. If there’s a lot of water to soak up (perhaps condensation in my bivy sack), then I may need one additional wring-soak cycle with the microfiber to catch up with the shammy’s greater initial absorbence.  The lesser area and the lower price are not significant to me.

The hope? That someone with high-tech camp towels will repeat this experiment and share their results in a comment here.  At $24 for a “large” (and discounts from that), this experiment would be overkill just to avoid cost.  It is justified for the experience of science and for the possibility that additional data from high-tech camp towels will give the public the knowledge to make their own choices between performance and price. If you know any scientifically-playful ultralight backpackers, send them to this blog on the chance they replicate the experiment.

Apr 22

Newton’s Cradle completed

Newtons cradle 1Maverick built a giant cradle with five 15-pound bowling balls.  The saw horse rocked, so we could use stabilization, perhaps with guy wires/strings extending from each end, similar to tent strings attached to ground spikes.  Balls slipped out of line after a few collisions, so we could use a 2nd sawhorse and string balls between the two, keeping balls lined up. With one ball pulled up, we could get 4 or 5 collisions (back and forth) before failing alignment dispersed energy.

Pictured: Maverick using a level to adjust height of bowling balls during assembly. Videos below show various tests, including spinning, which would not be possible with a 2nd saw horse keeping balls in line.

Lava lamps temp check diagramming lava lamps lava lamp temp diagramUsing an infrared thermometer to measure temperature at 3 different levels of 5 different lava lamps at 2 different times.  Dry erase board diagrams 1st (red) and 2nd (blue) measurements. Maverick developed 3 hypotheses for patterns in temperature.  Hottest being in the middle was a tempting hypothesis, but the lava lamps near the middle did not support it.

magnet game 1 magnet game 2

Game of sliding magnet scout past magnet mines into goal.  Tested various patterns of 4 mines guarding 12″ goal with magnetic goalposts.  Used “rattlesnake eggs” for all magnets. Experimented with speed and angles of shot, as well as pattern of mines.

Apr 14

Falling through the earth and black hole math

Falling through the worldBlack hole mathDave Francis was our guest today.  He apologized for the state of the earth that our generation is leaving for the generation of students.  He then challenged them to devise solutions.  Max, Rhys, and Maverick tackled population, thinking up solutions that Dave and I critiqued and also helped with. Ideas ranged from sending old people to war to sending old people to space. Incentives to have fewer children seemed gentler and more effective. While improved health and education appears to reduce fertility rates, it also lengthens lifespan, which increases population.

In our last class, we talked about falling through the earth and emerging in the Indian Ocean.  This time, we considered conservation of energy to help us predict how fast we might shoot out the other side.  We listed our assumptions of no friction slowing us down, no weight loss (or death) from the heat, no air pressure related problems (like the bends), and no Coriolis effect slamming us against the side of the tunnel as our speed at the surface of a spinning earth differs from the speed closer to the center of the earth.  We also assumed that changes in the gravitational force as we drop beneath much of the earth’s mass would cancel out on our exit.  “Based on conservation of energy, we concluded that if we simply stepped off the edge of the tunnel on our side of the earth, we would be similarly motionless when we reached the other end of the tunnel.

Gravity got us thinking about black holes, so we showed how the force of gravity tends toward infinity as the radius of the mass tends toward zero. We talked about how black holes might not exist, that is the radius of the mass contained might not reach zero, a singularity.  Perhaps, denser than neutron stars are quark stars, prion stars, and Planck stars, ever denser but never reaching a singularity.

Cheryls birthdayThen we tried to solve a logic puzzle Miguel found in the BBC News.  Singapore parents complained that a question on a test was so hard it was stressing their kids.  We made progress toward answering the question before a sunny day called us outside to battle with pool noodles and then race solar cars in upside-down frisbees.  Our tiny racetrack was perfect to keep a train of solar-powered cars zooming in circles.  We also raced the cars on the edge of pool noodles and elsewhere.

Apr 09

Oscilloscope and oscillators



Ohms Lawresistors in series and parallelmass and weight and 555Guest Keith Gudger brought his digital storage oscilloscope to demonstrate. Max brought his State Science Fair-bound project to the be first subject of the oscilloscope.  Max has improved his energy-gathering soccer ball since we last saw it, now using 5 piezoelectric transducers, each with its own bridge rectifier to charge a single capacitor.  The scope showed a positive spike followed by a negative swing and no ringing after each flex of a transducer.

We introduced Ohm’s Law for new students and reviewed it for old.  While Max and Keith analyzed the soccer ball, Carlin, Rhys, and Maverick wired 555 chips to flash an LED.  Keith then connected his oscilloscope to one of the circuits (between the LED dropping resistor and the LED) to reveal a sharp square wave.  I gave students a 22 microfarad capacitor to incorporate into their output circuit, and each chose a different location: A) from cathode of LED to ground, B) across the LED, and C) between the anode of the LED and +5V.  Circuits A and B both continued to blink, but showed attack and decay (like a shark fin) on the oscilloscope.  Circuit C stopped blinking and showed no activity on the oscilloscope.  We speculated that circuit C charged the capacitor but did not discharge it, as A and B did, so it blocked all further current flow through the LED.

555 oscillator with 3 capacitor placementsoscilloscope traces

Electronics was hard work, so we adjourned to the front yard to run around with pool noodles.  After working off some energy, we watched the first 15 minutes of Wonders of Life episode 1, pausing frequently to discuss topics sparked by the video.  This led to energy, potential gravitational energy, and what would happen if we could drill a tunnel through the earth. We concluded that in the absence of friction or physical damage to extreme temperatures in the core, we would emerge in the Indian Ocean, moving about as fast as when we stepped off the edge here.  Conservation of energy brought us to that conclusion after we talked about E=mc² to account for matter + energy being conserved.

Jan 31

Vertical wind tunnel and patterns in ping pong balls

Carlin used a shop vacuum exhaust and concatenated translucent 3-liter soft drink bottles to form vertical wind tunnel to illustrate balance between aerodynamics and mass.  Videos show patterns in floating ping pong balls using high speed capture.  First video is with 3 ping pong balls and second with 15.  Balls were striped in different colors and patterns to aid in identifying how balls move in airstream, spin, and change places.  Carlin conducted tests, not shown here, on how layers form when additional balls are added.  Fluid dynamics are complicated (the mathematics is advanced), so Carlin is starting with observations of patterns.



Jan 31

Energy harvesting from soccer ball

Max is using piezo-electric transducers to convert the energy from kicking a soccer ball into electricity, potentially useful for lighting or cellphone charging. Piezos produce high voltage and low current in one polarity when flexed and then in the reverse when the flex is reversed to return the piezo crystal to a neutral position.  To capture this energy, Max runs the electricity from the piezo through a full-wave bridge rectifier and to a polarized electrolytic capacitor.  The bridge prevents reverse-voltaging the capacitor as well as the capacitor discharging through the piezo.

Photos show Max wiring and testing the circuit, soldering and testing it, and then mounting it in a soccer ball.  He placed the piezo just under a ball flap he cut away, where a kick would flex it.  He drilled a hole to the center of the ball for wires to attach to the bridge and capacitor.  Max hollowed out a cave in the ball center to hold this electronics.  Two more wires run from the capacitor out of the ball for testing and, eventually, energy recovery.

Testing showed progressively higher voltages across the capacitor with each flex of the piezo, which he flexed by thumb.  Next steps: testing efficiency of mechanical to electrical energy capture and how much energy can be captured.

working outdoorswiring circuitsolderingpeeling panel from ballclosing panel inserting piezo behind paneltaping leads energy storage inside ballIMG_3641 (1)flexing piezo in ballflexing piezo under panel


measuring voltage from flex
voltage from piezo

Jan 25

Build an earthquake-safe structure

2015 April 26ready for judges

Day of the competition! Team 476 Gravity Rex gathered at the Tech Museum of Innovation with our building and engineering journal to compete with thousands of other kids and face a panel of judges. Our engineering journal was pronounced “good” as we could back up everything we claimed about our building and the process we followed to create it.  Our building, too, was good, leaning very little as the shake table tried to take it down.  Here are videos of our team’s introduction and three runs on the shake table.

Coteam staging areangratulations, team! Click on the photo to the right to see a panorama of the team staging area:

Our Thursday class is done, but we can look forward to the 2016 Tech Challenge on “flight”.  The Tech Museum may take a few months to figure out the details and guidelines for the competition, then test and revise them before public release.


2015 April 23

checking stability final building measuring floor separation Noting bulding specsIn our final class before the competition, we added a roof and the laser-reflecting paper.  Maverick had worked on the agenda and calculationsbuilding in between classes, adding metallic footing at the base of each of the four vertical dowels, and screwing these to a wooden baseplate replacing the earlier cardboard baseplate.

Nathanael documented the weight and height of the building.  He also measured spacing between floors and estimated usable floorspace.  Maverick diagrammed the final building on a 2-page foldout for our engineering journal.  He also wrote up an acknowledgement of help received from his father. Documenting sources of assistance and information is important in science and engineering.

To calculate floorspace, we reviewed the mathematics of linear and area measures. The vertical supporting posts are nearly half an inch thick, occupying almost 1/4 square inch.  With one at each corner, we lose one square inch of usable floorspace on each floor.  Diagonal bracing costs us even more.

We added an opening page to the engineering journal with our team number 476, name Gravity Rex, grade 7-8, and roster.  Maverick took the engineering journal home with the building and may do some homework on them.

We cleaned up our unused materials from the shed, recycling cardboard and taking home usable cardboard and dowels.  Sunday is our competition at the Tech Museum.  We will meet at 10:00 AM at

180 Park Avenue
San Jose, CA 95113
(Between Market Street and Almaden Boulevard)

.  More information is at


2015 April 9

setting the 2nd floorteam namesWe began our fieldtrip with the discovery that our building had been damaged in storage.  Undaunted, we took the parts plus duct tape, string, and utility knife to the Tech Museum of Innovation.  There, we joined dozens of other teams working on their buildings.  Here are photos of the team names and of us working on our building.

There were wonderful varieties of buildings at the trials.  One, pictured, slide back and forth atop a foundation that insulated it from the shaketable almost entirely.  The judges kept increasing the energy of the shaketable, but the building hardly seemed to notice.competitor that rolls with quake  Some buildings were very tall, reaching toward the 7′ height limit (check the rules for 7′). Some had a central core that appeared to test the limit of 5″x3″ cylinders in the rules.  One building looked very light, with clear plastic floors and fishing line or dental floss as cross-bracing.  Some buildings were short and ungainly.  Others used bolts and springs to space floors.  Some were worked on by families, including adults well beyond the age categories. I find it hard sometimes to keep my ideas to myself and simply guide students to find their own answers and create their own building.judge meaures floor

Holes around our octagon are not symmetric, so we tested and rotated each floor until the supporting dowels were vertical.  This time, we labeled one side of each floor to ease alignment in the future, if our building is taken apart.  Using string as diagonal bracing proved difficult.  Unless taught, the string helps little, and getting it taught took persistence in choosing different anchor points and styles of knots.  Eventually, we got our building to stand upright, unlike the Leaning Tower of Pisa.

Called up for inspection by judges, we were surprised to find that our floors are less than 5″ apart.  That’s an area we had been careful to assure, by cutting oversize (and hard to find) straws to 5″ and using them to space the floors.  Something went wrong, which we will investigate in our next class.  Good news is that we are very light, so we can add much structure without violating the weight limit.  We know that we need at least one more floor to carry load bolts plus a roof with a card to reflect a laser beam (Nathanael will bring the cardstock).viewing shaketable from safety area

leaning tower of PisaOn the shaketable, our twine cross-bracing could not prevent the return of the Leaning Tower of Pisa, shown in one photo alone and one next to our team posed. Yes, our team is standing vertically so our building’s skew is no optical illusion. On the drive home, there was talk of a whole new approach, returning to a square floor.  With just 2 classes left before the April 26 competition, a fresh start may not be possible.  Nor may it be possible to go after the bonus points that the judges displayed in one of our photos.bonus points

posing by shaketableSince students have been haphazard at keeping an engineering journal, its creation will have to fit into one of those two classes or as a homework assignment.  Students may use this blog to jog their memory in that process and also print photos from here include in their journal, which must be on paper.


2015 April 2

Brennan wiring magnetic support Maverick spaces floors with straw sleeves over sticksMaverick and Brennan raise floors of the octagon Maverick measuring baseplate to within a quarter inchstring crisscrosses supports to strengthen against sway

Maverick sleeved the vertical wood columns with large straws (for which he and his father had to search many stores) to space floors the minimum of 5″ apart.  Since holes in the cardboard floors are just large enough to allow the wooden sticks through, the straws prevent each floor from collapsing onto the floor below.  While straws can bend, the wooden stick prevents their buckling, giving the straws apparent strength.  For our April 9 or 16 class, Maverick will try to bring more straws plus clear tape (e.g. scotch tape) to combine short straws.

Maverick also brought twine to create a crisscross pattern across vertical columns.  He tested this on one face, showing that it did provide good stability in one direction.  Crisscrossing every face should provide stability in all horizontal directions.

Brennan crafted magnetic supports, insulating the building from horizontal motion of the baseplate.  He wired a pair of repelling modules together in an attempt to keep the 4 pairs of repelling magnets from moving so far that they attract. The first length of wires he used did, however, allow sufficient shift to turn repulsion to attraction.  Bending the wires hurt his hands, discouraging him from testing shorter lengths in class.  He took the materials home to continue experiments.

Without functional motion isolators (magnetic or sliders, as Brennan developed earlier), Maverick duct-taped the octagon building directly to the 20″x20″ cardboard baseplate he fashioned in this class. The building has 3 floors, which we started populating with load bolts.  For the competition, we will need at least 4 floors, excluding 1st floor and roof, to accommodate all 20 load bolts.  We will also need to mount the cardstock that Nathanael will bring (he was away this class) and string all the open faces.  For next week’s test trial, we have enough of a building to test, so the fieldtrip is on.

Next week, please meet at Iris at 3:00 for a 3:15 departure time.  At the event, each student needs a helmet and safety goggles.  While a hardhat would look cool, a bicycling helmet would do.  I have safety glasses and a few old bicycle helmets (that fit me well, but may not students), so please let me know by Wednesday if you would like me to bring either for anyone.  I anticipate our return by 6:15, but cannot predict how much time students will want on the shake table or how slow traffic will be over the mountain.  If I can anticipate an earlier or later arrival time before starting to drive back from San Jose, I will text parents. Once driving, I will not text.

The inspiration of seeing other student groups testing their varied designs may be as valuable as testing our own and seeing more clearly what remains for us to accomplish.


2015 March 26

Maverick tests paper towel tubes to space floors Nathanael explores geometry for floors

Maverick continued development of an octagon building, while Nathanael came up with a geometry he has kept secret (we could only guess by looking at his building).  We had hoped to have straws to space floors in the octagon building, but nobody visited Jamba Juice since the previous class.  Cutting paper towel cores did not work well, as they were too large in diameter, though they would have satisfied the rule restricting size to 5″ long and 3″ in diameter or less.  Since floors must be separated by at least 5″, spacers thicker than 1/2″ must be exactly 5″.

Brennan brought a magnetic support he’d built since the last class.  It is a prototype that he prefers to the sliders he fabricated earlier.  We need at least 4 supports per floor, so Brennan will make at least 3 more, if not sets of 4, before our next class. He designed these supports on his iPad.

Maverick brought sticks and will bring straws and string next time.  Nathanael will bring sticks and the official cardstock for next class.  We have just one class before our fieldtrip to the Tech Museum for testing one or more buildings.


2015 March 19

Maverick drills octagon floorBrennan models twisting triangular floor Magnet concept, algegra, geometryMaverick is interested in octagonal  floors and Brennan in triangular floors. Both recognize that floorspace will be lost because the rules specify a maximum of 16″x16″ for lower floors, which is a square.  Other shapes fitting within those dimensions will have less area than the square.  Maverick thinks octagons will be more stable and look cooler. Brennan thinks triangles will be more stable because they have fewer directions in which they can fall, fewer axes of freedom.

Octagons and triangles gave us reason to explore geometry and algebra.  To calculate the size of an octagon inscribed in a square, we used the Pythagorean Theorem and Quadratic Formula, as shown in our very crowded dry erase board.  Each side of the octagon will be about 6.6 inches (metric would be easier, but the Tech Museum uses Imperial units).  That means we measure about 4.7 inches (just shy of 4 3/4 inches) in from each corner of a 16″x16″ square to identify the triangles to cut off in order to form an octagon. Maverick had multiple cardboard floors and punctured holes in each for supporting sticks.

To create right triangles from 16″x16″ squares, we could cut the diagonal, but Brennan wanted the symmetry of equilateral triangles.  He used geometry and a stick marked at 16 inches to sweep out arcs from two ends of a 16 inch line drawn on our giant cardboard sheets.  Those arcs intersect at one point, the 3rd vertex of the equilateral triangle. Brennan made multiple cardboard floors and modeled a building.

Brennan brought updated sliders, disc-within-in-a-circle, that are deeper and use Gorilla Glue (the hot glue on the previous shallow version failed).  He also proposed a magnetic flotation system with two magnets for each corner of our building.  In a square building, that would mean 8 magnets per floor.  With 5 floors, that would require 40 magnets.  He will test this concept with just 2 magnets to make sure it is worth scaling up.

For next class, please bring the following:

  • Brennan will bring magnets (or an assembled mag-lev pair with wood) and large straws (possibly from Jamba Juice) to slide over sticks for Maverick’s floor supports
  • Maverick will bring sticks and string (any might do, but he prefers twine)
  • Nathanael will bring sticks and one sheet of card stock (8.5×11″ 110 pound white)

We have 2 more classes before our April 9 fieldtrip to the Tech Museum.  If we do not have at least 1 building to test on the official shake table by the end of our April 2 class, we will cancel the fieldtrip to spend that time in class to develop buildings.  Today’s progress suggest that we might have 2 buildings, octagon and triangle, to test.  The fieldtrip would be 3:15 – 6:15 (approximate return time, I will text updates from the Tech Museum), replacing our regular class.


2015 March 5

Brennan and Nathanael test cross-bracingMaverick makes our first multifloor modelBrennans suspension idea

Brennan assisted Nathanael in testing cross-bracing on a building.  Components were longer than allowed in Tech Challenge, so this was proof of concept, so it was taken apart after the diagonal bracing proved resilient.  Maverick created our first multi-floor building, following component length restrictions.  We retained this model to build upon in our next class.

Brennan described a disc-within-a-circle system to isolate our building from the shaking ground.  I sketched from his description.  He committed to fabricating this before the next class because he did not have the tools or materials to do so in class.



2015 Feb 26

Maverick tests load bolts in cardboard flooringBrennans model of shock absorberNathanael drawing lines to cutagenda and mathMaverick tested load bolts on the cardboard that we plan to use as flooring.  He found no visible flexing, suggesting that placement near or distant from supports won’t affect flooring.  Placement may, however, affect building resonance and stability.

Brennan mocked up a horizontal shock absorber that he imagined.  It comprises a horizontal disc that can slide wihtiin alarger circle.  The disc would support the building and the circle would be mounted on the foundation. He has more modeling to do before we can test how well it might work.

Nathanael cut cardboard for structural elements within the size restrictions of the Tech Challenge rules, mocking up new building designs.  We all cut squares out of a giant cardboard box that Maverick brought to class. We will figure out how to attach these to structural elements for our building.

Discussion of a Science & Engineering Fair project about capturing energy from kicking a soccer ball led to the very useful technique of “dimensional analysis”.  We used it to figure out the total number of kicks a soccer ball sustains in a game if each of 20 players kicks an average of 12 times per game. Our dry erase board shows how the units of measure cancel when multiplying kicks/player x players. We implied the units of “game”.


2015 Feb 19

Nathanael building slow motion recording of impact 1 Tslow motion recording of impact 2he team tested resonance of a building design by striking the building with a toy sword while recording in slow-motion with an iPad.  Outside of class, students will seek parental permission to use YouTube so they can share this video.  Next up: analyzing the video to guide our designs.

The team considered splitting into two, with one focusing on taking the building apart and reassembling it for the competition and the other team focusing on making the building resist falling down when shaken.  Discussion included the difficulty / inefficiency of splitting design constraints between different teams and the competition rules apparently not requiring disassembly. The team concluded that they should maintain a single team.

Maverick brought cardboard and foam corners.  Nathanael brought duct tape.  We used all but the foam corners, as we concluded that they violate competition rules.  They are too large for either the 20″ x 0.5″ x 0.5″ envelope or the 5″ tall x 3″ diameter tube for structural elements.  Flooring need not fit within these dimensions.


2015 Jan 29

materials building models notes ready to shake shaking table

The team brought balsa wood, measured it, and discussed sizing factors (practicing addition of fractions with different denominators).  The competition shake table will move in only one axis, so we discussed axes: x, y, z.  We even introduced the 4th dimension of time, and how it is both similar and different to the physical dimensions.

They came up with three candidates for team name so that Maverick, out sick, could pick one: Nitro Banana, Ow Son of Cow, or Gravity Rex.

We watched a PBS Nova documentary on earthquakes, providing background to our project and emphasizing that resilient buildings may be the best defense against earthquakes.  Quote from the documentary: “Earthquakes don’t kill people; falling buildings do.”

We built test structures with mini-marshmallows and toothpicks.  Then we tested them on a shake table fashioned from a skateboard, peg board, and clamps.  Mini-marshmallows and toothpicks will unlikely be our building materials, so this was to test building geometry.  We were pleasantly surprised how long our structures stood up.  Testing will be harsher once we incorporate the “load” bolts into floors.  For next class, we want cardboard and load bolts so models can be closer to our competition model.


2015 Jan 22

We have a team competing in the Tech Challenge at the Tech Museum of Innovation in San Jose, CA (  This year’s challenge is to design and build an earthquake-safe structure.  Lots of rules make for an interesting design challenge.  On April 26, our team’s building will be shaken on a motorized table through three simulated earthquakes.  Points for a team journal documenting our process and for a building that does not fall down (or sway too much or have little floor space).

Here are some of our notes on open questions, evaluating design ideas, and formulas for mechanics of motion:

open questions open questions 2feature evaluation matrix mechanics and machines

Updates on our progress will appear in this posting.

Jan 13

Winding our own electromagnet

Max brought several electromagnets he made himself as well as wire and cores to make another.  His project to capture energy from soccer balls being kicked will use an electromagnet as part of the kick-testing jig, so he wanted to make a more powerful one.

We measured voltage, current, and pull strength for an existing electromagnet using first batteries and then a computer power supply.  In our excitement to measure, our recordings were disorganized.  Instead of an orderly table showing which electromagnet we were testing, the voltage, current and pull strength, we jotted down numbers haphazardly.  We will do better next time.

The results we got were, not surprisingly, contradictory.  With the first electromagnet, the batteries (two 6-volt lantern) provided 11.9V, 4.8A, and pull strength of 0.3 kg.  With the first electromagnet, the PC power supply (rated 12V, 15A) provided 11.6V, 10.8A, and 1.0 kg of pull.  We suspect our voltage measurement for the batteries because they provided less than half the current of the PC supply, so their voltage should have dropped to about half.  Could we have measured voltage before attaching the load? Early in the process, we introduced a second multimeter with higher current range (20A, not 10A), allowing us to measure voltage and current simultaneously.

Eager to wind a new electromagnet, we practiced poor science by not returning to explore the anomaly.  We used a power drill to wind 20 gauge wire onto an iron nail.  We did not measure or note the length of wire.  Photos show the crude mass we created.  Testing the new electromagnet with the PC power supply showed 11.1V, 1.43A, and 0.32kg of pull strength.  The new electromagnet had much more wire than the first, possibly explaining why less current flowed through and why, in spite of many more turns of wire, we got a third of the pull strength.  Not explained, however, is why the voltage would be lower (11.1V) than the first, high current, test (11.6V).

We ran out of time trying to unwind the electromagnet back onto the original spindle.  Excited to build something, we were careless with our data logging and did not make time to investigate anomalies.  It was a fun class, but we have plenty to learn from and not repeat.

IMG_3556 IMG_3557 IMG_3558 IMG_3560 IMG_3561

Jan 09

Newtons Cradle spin

IMG_3526 IMG_3528Our Newton’s Cradle nears completion.  We are discussing how to secure the cords suspending bowling balls to the saw horse.  In the time we had, we spun the bowling balls.  See the balls behave like gears and also climb up their suspension cords:

We inverted a honey jar and observed the speed of air bubbles, large and small.  Our dry erase board shows our discussion with formulas of the bubbles’ volume (encouraging fast rise because surrounding honey is denser than air) and surface area (discouraging fast rise because of friction).  This assumes spherical bubbles, but seems a good approximation.  Also on the board are notes for Max’s soccer ball energy recovery project, showing how he might arrange peizo-electric cells in series, parallel, or both.IMG_3532

We also watched behavior of 5 different lava lamps:

Jeanette is considering a project to build an electric lava lamp.  She has previously brought in an Alka-Seltzer–powered version.


Dec 09

Hunting polarized lenses in an old TV






Inspired by an Exploratorium exhibit called Watching Water Freeze, we placed very thin mica between two polarized lenses to get a similar effect of rainbows.  See the video I took of the Exploratorium exhibit created by Charles Sowers.

Disassembling TV 1

Disassembling TV 2Disassembling TV 3Since we have just two small polarizer sheets, we disassembled a broken LCD TV to harvest its polarizer sheet.  Photos show the the breakdown process.  We used nail polish remover to separate the plastic polarizer sheet from the cracking glass, with some success, but the sheets came off in pieces and cloudy.  Soap and water cleared some of the cloudiness, but we will try other cleaners. See the video we took of the liquid inside the LCD (Liquid Crystal Display).

We experimented with melting a crayon in hot water, hoping to find an ingredient for a DIY lava lamp.  Crayons from OfficeMax floated, which would not work for us since we want them to sink when solid and float when liquid.  Crayons from Dollar Tree did sink, so we placed one in a beaker of water and that into a pot of water on a gas flame (double boiler).  Water in the pot boiled, but in the beaker did not exceed 74 C, which was insufficient to melt the crayon.  After half an hour, we abandoned the proof-of-concept because we would want our DIY lava lamp to run from an incandescent light, much cooler than a stovetop flame. I bought a Lava Lite but it arrived with broken bulb, so am waiting for replacement bulbs to arrive.

Trying to melt a crayon in hot water

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