Monthly Archives: September 2015

Crush A Can Day…Recycle!

Each day, a typical person generates over 4 pounds of waste. Over half ends up at the dump. Future anthropologists will learn a lot about the millennial world from its landfills. In 500 years, disposable diapers will just be starting to decompose, and the remains of today’s plastic bags will still be present twice as far in the future! Long as it sounds, that’s a blink of an eye in trash history. Styrofoam and glass are projected to last for over a million years.


Besides preserving humanity’s leftovers for generations to come, landfills are sinks for valuable resources. Between 1993 and 2003, we scrapped over $12 billion in aluminum cans. Recycled, the average can is reusable within 6 weeks, but once it hits a landfill, it’s doomed to centuries of slow decay. Saving aluminum and other waste is an easy, satisfying way to make a significant contribution to our planet’s health. Before you send your used cans to their (hopefully not final) destination, give this fun, simple DIY experiment a try. All you need is an empty soda can, a stove or hot plate, tongs, and a container of cool water.


Add water to a soda can until it just barely covers the bottom, then bring it to a boil. As the water evaporates, the air in the can expands due to its high temperature. The gas expands so much that some is pushed out of the container along with steam from the boiling liquid. Carefully, using tongs, pick up the can and invert it into the second container. The cool water causes the temperature in the can to drop dramatically. Cooled gas molecules inside the can exert less pressure on its walls as they slow down and condense. Atmospheric pressure compensates for the partial vacuum by crushing the can! cancrush3

What is a Superconductor?

Lots of materials are conductors, meaning electricity can flow through them. However, even power lines, which have the sole job of transporting electricity, aren’t perfect. A little bit of the energy gets lost as the electricity flows. This loss of energy is called resistance. Resistance isn’t a bad thing. We use it for a lot of things. Conservation of energy tells us that energy can’t just disappear, so as the electricity dwindles it is transferred to heat. We use this to our advantage in a process called resistive heating, and it is the reason the incandescent light bulbs and electric stoves work.


However, some unusual materials have a strange property: they have zero resistance. They conduct electricity perfectly. We call these materials superconductors. So far, the only superconductors we have found require very cold temperatures. This isn’t particularly surprising as all conductors become more efficient at low temperatures. How cold though? To give some perspective, the one in the video is known as a high temperature superconductor, and it only starts working at -300 ℉! Fortunately, liquid nitrogen is about -320℉, so they work together nicely. Scientists would really like to develop room temperature superconductors, but have had no luck thus far.


Our superconductor is an unassuming small black disk. Most superconductors are some sort of metal oxide. Ours, Yttrium Barium Copper Oxide, is known as YBCO.

One strange property of superconductors is that they essentially reflect all magnetic fields. This is essentially because whenever electricity flows, it creates a magnetic field, and whenever there is a moving magnetic field, it causes electrons to move. For more about how electricity and magnetism interact, check here. By approaching a superconductor with a magnet, this causes the magnetic field to be bounced back by effectively creating an electromagnet, causing the magnet to float in the magnetic bed of the superconductor.


This process is actually even cooler than the video shows. It turns out the the magnet is not only floating, it is completely held in place above the superconductor. If the magnet is lifted, the superconductor is lifted too, and even if the superconductor is inverted, the magnet is held in its own magnetic pocket. This is unlike normal magnetic repulsion, where the magnets opposite poles only push apart. This is called quantum locking. It also allows for the very cool superconducting racetrack shown below!

quantum locking

This superconductor is on a magnetic track displaying quantum locking. The low temperature of the superconductor results in a very cool cloud effect. Credit: TED

The Pendulum Challenge

Think you could stand still with a bowling ball swinging towards your nose? It’s tough! This scary experiment is governed by the same principle that decides the dynamics of a car crash and guides trick shots on a pool table: a gigantically important physical law called conservation of energy. This law states that if a system is left alone, its total energy doesn’t change.


A system’s total energy is composed of two parts: kinetic energy (the system’s motion) and potential energy (stored energy determined by the system’s position). Let’s think about our bowling ball when it’s suspended at head height. It’s not moving, so its kinetic energy is zero. We know that if we stop holding it up, it will fall. This means it has potential energy! this case, the potential energy comes from Earth’s gravity pulling on the bowling ball.

When we release the bowling ball, it begins to move. In other words, its potential energy starts turning into kinetic energy. This happens bit by bit: when the bowling ball has fallen a few inches, it’s not going very fast yet, and it still has most of its original gravitational potential. As it falls farther, more of its gravitational energy is converted to kinetic energy, so the ball picks up speed. The tradeoff continues smoothly and proportionally until all potential energy has been converted to kinetic energy. The bowling ball moves fastest (has highest kinetic energy) when it’s closest to the ground (has lowest gravitational potential energy).


Credit: BBC


No physical system is perfectly efficient. Air resistance and stretch in the tether damp the swinging bowling ball’s momentum. A tiny bit of energy is dissipated with each turn of the pendulum until, finally, it comes to rest. Since each pass of the bowling ball carries less energy than the one before, the pendulum swings a little lower every time. As long as you drop the weight cleanly from your nose, it’s perfectly safe to stay put.


It’s one thing to know that the bowling ball can never swing back up to its original height and crash into your nose… it’s quite another to override your body’s instinct to flinch or step back!

Survival Skills: Pocket Firestarter

To start a fire, you need three ingredients: fuel, oxygen, and heat. Friction is a good source of heat (think striking a match, or rubbing two sticks together). Heat can also come from flowing electricity! Have you ever noticed that electronic devices get warm after they’ve been running for a while? This is the result of resistance.


Resistance acts like friction between electrons and the medium they move through. It keeps electricity from moving freely and infinitely, and generates heat as a byproduct. Some substances have lower resistance than others (these are called conductors), but all everyday materials have some resistance.

We can use household supplies to explore this property! On a fireproof surface, hold the business end of a 9v battery up to a pad of steel wool. When a strand of wire touches both terminals, it completes a circuit. Electrons flow through the loop created by the battery and the steel. The wire resists the electrons’ movement and warms up dramatically. We have our heat source, and there’s plenty of oxygen around– but what about fuel?



Steel is mostly made of iron. We know that iron interacts with oxygen. When water is involved, it rusts. When heat is applied, it has the potential to burn. Iron doesn’t catch fire under normal circumstances because its inner molecules are shielded from the surrounding oxygen, but the tiny filaments in steel wool have an enormous surface area per volume. So much iron is exposed to the air that a combustion reaction can start!

So, we have fuel. We have oxygen. We have a heat source. Electrical resistance can start a fire just as well as friction, and with less effort on our part! The spark is easy to create, and it travels quickly along the tiny wires.


An infrared camera shows heat propagating through the steel wool.

Kids And Their Robots

Rough terrain. Unsurpassable obstacles. Navigating the rocky unknown with little help from home. These are the challenges space robots face as they explore distant worlds and the engineering problems tackled by the teams that design the rovers. Grade school might be a little early for NASA recruiting, but it’s a great time to start playing with the endless possibilities of robotics! At AstroCamp, kids create LEGO rovers to surmount all kinds of space-like challenges. The rovers must handle uneven ground, avoid unclimbable walls and murderous drop-offs, and collect samples to bring back to home base. It’s not just a building challenge, either! Students program their robots to get the job done with minimal human interference.


In advanced classes, pairs of young engineers invent & build robots from scratch. Each step of the process requires teamwork, creativity, and plenty of persistence. Campers quickly discover that programming is rarely a one-shot deal. They learn that the best line-following robots take their time, and that adding a sensor or claw often means tweaking programs to account for the extra weight. Like grown-up rocket scientists, they must revise and re-test their design to develop it into a working system.


In space, the tactical difficulties of pushing the final frontier ever outward have led to some truly awesome machines. Curiosity was lowered to the Martian surface from a hovering sky-crane– and that’s after riding the thin local atmosphere to a screaming halt with the help of a giant supersonic parachute. Curiosity’s predecessor, Spirit, crashed into the red planet amidst a cluster of airbags, coming safely to rest after a series of bounces up to 5 stories tall. Philae, the lander Rosetta dropped onto a comet last year, wields harpoons inside its washing-machine-sized body, designed to help anchor the lander in a spot where its solar panels could charge. Unfortunately, the harpoons didn’t deploy on impact, but what an idea! Space inspires incredible robotic inventions.

At the middle and high school level, robotics lays the foundation for a lifetime of problem-solving on Earth and beyond. Students learn that failure provides valuable insights. They experience trial and error as necessary steps in the innovation process. They also gain practical knowledge as they’re exposed to the basics of design and programming, making them less likely to be intimidated by future engineering opportunities.



Five Great Google Surprises!

Googol is a really really big number. It is a one followed by 100 zeroes. As big as that number is, it seems appropriate for its named counterpart, Google, which celebrates its 17th birthday since its incorporation today!

googleWhile Google has exploded to the point where it is both a noun and a verb, it has retained its fun roots. The main headquarters of the Googleplex, a play on the googolplex, and every holiday or anniversary is covered by a doodle. Below are some of our favorite Google easter eggs.

  • Zerg Rush: An homage to the incredibly popular Starcraft franchise from Blizzard Entertainment. Simply typing this into the search bar will have you fighting for your life! GG!
    Zerg Rush2


  • Atari Breakout: Searching this seems mundane until moving over the the image search, at which point the screen morphs into the famous arcade game!Breakout2


  • Do A Barrel Roll! Straight out of Starfox!
    Barrell Roll2


  • Google Gravity! For a bunch of Physics people like us, this is oddly satisfying.
    Google Gravity2


  • My favorite one doesn’t involve the internet at all. Google Chrome users will recognize the image below as a symbol of broken internet. I always thought this was a play on the T-Rex and his short arms not being able to reach the internet.

Then I hit the spacebar!

DIY + Grapes + Microwave = PLASMA!

WARNING: Handle dishes with a potholder, and be aware that they may break if left in the microwave too long. Always keep a fire extinguisher on hand when experimenting with high-energy science. 

What do lightning, the aurora, neon signs, and grapes have in common? Plasma! It might be the least familiar of the four states of matter (solid, liquid, and gas are the other three), but it’s actually the most common form of matter in the universe. It’s what stars are made of!


This 2002 coronal mass ejection (CME) on our sun blasted plasma out into space at millions of kilometers per hour! During periods of high solar activity, it’s not uncommon for scientists to observe 2 or 3 CMEs per day. Image credit: NASA

Plasma is what we get when we apply enough energy to a gas to strip molecules of their electrons. This energy typically comes in the form of heat or a strong electromagnetic field like lightning. If you have access to a microwave, you have a great source of electromagnetic waves to work with! Normal microwave use doesn’t produce plasma, though– it takes an antenna to create a strong, steady field.

A microwave heats food by barraging it with electromagnetic waves, causing the molecules inside to vibrate (see previous post for more in-depth microwave science). In this experiment, we’re interested in the waves themselves. A typical microwave oven radiation wavelength is about 12cm, or just under five inches. A line of four grapes is about five inches long. Thanks to this ratio, a grape makes a great antenna for our DIY plasma project!


Here’s why it works: a half-wave dipole antenna is an antenna made of two matching parts, each about ¼ the length of the wave the antenna is supposed to receive. This style of antenna does its job so well that it’s the standard in radar technology and other fields. You may even have seen it in your living room as “rabbit ears”  on a television! Conveniently, grapes conduct electricity well, and a typical grape diameter is about ¼ the size of a microwave oven wavelength. This makes two grapes next to each other (or one halved grape) an ideal antenna for concentrating the waves inside the oven. The grape antenna creates a strong, uniform electromagnetic field… exactly what we need to strip gas molecules of their electrons. Give the field a little time to gain intensity, and BZZZT! Plasma! DIY style!


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