Monthly Archives: September 2016

What Color is Lightning in a Beaker?

Thunderstorms can be incredible to experience. From the bright flash of lightning that is often almost to fast too see, to the immense crack of nearby thunder that can make your heart feel like it skips a beat, they truly are a demonstration of the power of nature.


Image Credit: NASA

They are also full of interesting science! For instance, lightning usually carries between 100 million and 1 billion volts of electricity! This allows it to jump all the way from clouds to the ground, and as it does so, some of that energy is transferred to the atoms in the air. This energy is released as light, which is how we see it. 

This means that it is the air itself which determines what the air looks like. On Earth, our air is made up of about 78% nitrogen, 21% oxygen, and a bunch of other gases like water vapor, carbon dioxide and argon. When we put electricity through it, it gives off a characteristic glow:


The Oudin Coil generates up to 50,000 volts of electricity–much much less than a thunderstorm. This allows the electricity to jump about an inch, rather than the miles between clouds or to the ground of an actual lightning strike. However, when it arcs through the air, this still produces a similar look and identical color1.

Lets see what it would look like in a different environment. The beaker in this gif has a bunch of dry ice–which is just solid carbon dioxide–at the bottom. Unlike regular ice, dry ice doesn’t turn into a liquid, but instead skips straight to carbon dioxide gas! This gas is more dense than air, so the beaker ends up full of just carbon dioxide, which is a much different composition than our atmosphere. Check out what happens to the lightning in there!


Unfortunately, we can’t try this particular method with every gas for several reasons. First of all, not all gases are heavier than air. This would make it hard to keep it in the beaker. In addition, other gases might explode, or worse, if exposed to electricity with oxygen around in this way. Still other gases can be very toxic. Fortunately, we have some tubes of gas and a machine that puts electricity through it in a similar way. In this gif, the gas tubes are viewed through a diffraction grating which breaks up the light into the different colors of the rainbow contained within. This is actually a whole different branch of science which is used to figure out what elements different things are made of just by seeing the light that comes from them! Learn more about that here.

Written By: Scott Alton
1People actually report lightning to be many different colors. In general, nearby lightning will have a purple glow due to the composition of the atmosphere, and the central part will look white simply because it is so overpoweringly bright and doesn’t give time for eyes to adjust. Most other colors that are reported are because the lightning is being viewed from a long ways off and the light has to travel through dust, rain, haze, pollution, or other things that can change its color.

The Easiest UV Detector Ever

Science is full of words to describe the glowing process. We use bioluminescence for the glimmer of plankton, phosphorescence for the slow, ghostly shine of glow-in-the-dark toys, and fluorescence for pigments that emit light while exposed to just the right energy source.


L to R: Fluorite sphere with phosphorescent coating, Don Mengason, Gemological Institute of America Inc.; bioluminescent phytoplankton on Vaadhoo Island in the Maldives, Kriss-Anne Gayle, Penn State University; mineral specimen fluorescing under UV light, James A. Van Fleet, Bucknell University.

Unless you live on a coastline rich with bioluminescence, fluorescence is the glow you’re most likely to encounter in everyday life. It’s present in white materials exposed to a blacklight and in the neon glare of highlighter ink. Tonic water appears colorless under visible light, but a distinct fluorescent glow appears when it’s bombarded with ultraviolet radiation!



Tonic water contains a fluorescent compound called quinine. Expose quinine molecules to UV rays and they get excited, or gain energy. Excited molecules modify the absorbed light and eventually re-release it. Unlike the invisible incident radiation, the emitted glow is apparent to the human eye.


Test this idea for yourself by taking tonic water outside on a sunny day! The blue glow is more obvious when compared to a glass of tap water– consider setting one up as a control. For more intense fluorescence, up the UV radiation by exposing your experiment to a blacklight.

Written By: Caela Barry

A Supernova For Breakfast (Almost)

Iron makes up less than one one-hundredth of one percent of the human body. Most adults contain just a few grams of this micronutrient. Despite its small presence in humans, it’s essential to our lives. Without it, oxygen can’t get from the lungs to the rest of the body. Iron also plays a key role in energy production and DNA synthesis.

The human body can’t produce all the materials it needs to function, so we get vitamins and minerals from food and supplements. We don’t often directly observe substances like iron, calcium, or vitamin A in our food because they’re present in such tiny amounts. Iron, however, has an unusual property. It’s magnetic, so it’s relatively easy to sort out from other ingredients!


Trace amounts of magnetic material in a whole food item aren’t strong enough to break free from the larger structure, even in the presence of a strong magnetic field, so it helps to start with something that can be broken down into small parts. Breakfast cereal is one food that’s commonly fortified with iron and is also easy to crush into a powder. Bring a powerful magnet near the powdered cereal, and iron-rich fragments jump out.

Supernova remnant 1E0102.2-7219

Supernova remnant 1E0102.2-7219, visible near nebula M76 in the Southern Hemisphere, is an approximately 1,000-year-old leftover from the explosion of a huge star. Credit: NASA/JPL/Spitzer Space Telescope

Iron plays an important part in the lives of stars, too, as the end product of stellar fusion. After lighter elements in a very massive star’s core have fused into iron, the core begins to cool and condense. Central cooling causes outer layers of plasma to fall violently inwards, collide with the iron core, and blast back out into space. This incredibly energetic explosion is where all elements heavier than iron come from, including calcium, which is also essential to human biological function. (Lighter elements, including oxygen, come from fusion inside smaller stars.) From hydrogen to carbon to iron and beyond, you are literally made of star-stuff!

Written By: Caela Barry

DIY Soap-Powered Boat

Ever filled a container with water, and then filled it some more? With a careful touch, you might have created a hill of liquid taller than the container itself. This works because of the surface tension, or cohesion, between water molecules. Place a small paper, plastic or cardboard “boat” on the water’s surface, and molecules will stick to it as well– that’s adhesion in action. Under normal conditions, adhesive forces on the boat pull it equally in all directions, so it doesn’t move on its own.


In this experiment, we use the chemical properties of soap to disturb the surface tension around the boat. Soap is made of polar molecules, which attract water. Introducing even a trace of detergent disturbs surface tension enough to unbalance the forces acting on a floating object. The boat appears to be propelled forward. In reality, the water behind it is no longer pulling against the water in front. The stronger pull ahead moves the boat forward!


This is a great project to try at home. All you need is a bowl of water, a small piece of paper or cardboard, (plastic bread bag tabs also work well), and liquid soap. Cutting a notch in the back of your boat can help to keep the soap where you want it. Dab a little soap onto the boat’s back edge with your finger, a toothpick, or a napkin, and watch your watercraft speed away!  Once surface tension has been chemically broken, adding more soap won’t cause a big enough difference to power your boat, so it’s a good idea to use a shallow pool of water and replace it each time you want to repeat the experiment.

Written By: Caela Barry

What is an Electromagnet?

Here at AstroCamp, one of our most popular classes is Electricity and Magnetism. At first glance, it might not be obvious how these things are related, but they are actually tied together through important physical principles.

To give you some evidence, let me introduce the electromagnet.


This is really just a metal rod wrapped with a bunch of wire. Without any electricity going through the wire, it doesn’t do anything special. Now, let’s press the button and let electricity flow through the coil!


What is going on? Well, to explain that we have to back up a bit. Let’s start by answering this question: What is electricity? It is the thing that runs our light bulbs, smart phones, computers, and air conditioning but what is it on a more fundamental level? What is happening?

asset-v1-pkuhighschoolph1019999_t1typeassetblockatom-light-640x360As you probably know, everything you have ever touched is made out of atoms, and these atoms have three parts: the positively charged proton, the negatively charged electron, and the neutral neutron. These charges determine how the particles interact; particles with identical charges push away while those with opposites attract.

Electricity, as you may have figured out by looking at the word, has to do with electrons. Electricity basically means moving electrons. However, physics has a bit of a surprise for us here. Whenever a charge is moving, it makes a magnetic field–if this word seems confusing, this is just what is produced by a magnet to push and pull on other magnets–around it in a circle. This happens every single time. You might be tempted to ask why, but I don’t have a great answer for you. This is just how nature is.

All we have done to make an electromagnet is sort of durn this trick on its head. By wrapping the wire into a coil, the circular magnetic field created every time an electron moves adds up in the middle. This kind of design is called a solenoid.


This awesome illustration shows how the circular magnetic fields around each wire add up in a solenoid to make a strong magnetic field inside. All credit goes to Paul Nylander.

This might seem like a simple lab trick to convince you about the mysterious but very real connection between electricity and magnetism, but it turns out to be an incredibly useful and important design. Outside the obvious purpose of picking things up like the giant electromagnets at junkyards, electromagnets are used in speakers, hard drives, MRI machines, motors, generators, and many other things you might not expect!


This is a view inside the Large Hadron Collider at CERN, the most powerful particle accelerator on the planet! This shoots tiny particles at very near the speed of light along a very precise track. While you might expect it to be the metal walls that keep the particles inside, the tiny particles would actually fly right out through the walls! So how do they keep those pesky particles in line? They steer them using incredible powerful superconducting ELECTROMAGNETS! Photo credit CERN.

Written By: Scott Alton

How do Geysers Erupt to Over 300 Feet?

Note: This experiment shoots boiling water into the air, and should not be attempted at home without proper training and safety equipment!

Geysers are one of nature’s most incredible spectacles. In the most powerful eruptions, water can be shot over 300 feet–or the length of a football field–into the air!


The Castle Geyser in Yellowstone National Park erupts. Water droplets in the air produce a picturesque rainbow against the blue sky. Photo credit: Brocken Inaglory

But just how do these things work? Geysers require some very specific conditions, which means that they only exist in certain locations. In fact, over half of the world’s geysers live in Yellowstone National Park. To find out why, let’s look at how one of these actually work!

When a geyser erupts, it is going through something known as a hydrothermal explosion, which sounds awesome, if a little complex. Luckily for us, the key to this is something familiar: boiling water. Even more fortunate, most of us have never seen a violent eruption of steam from the stovetop while cooking dinner.

The key to this is something called superheating. Most of us are familiar with the phases of matter. In everyday life, many of the things we see exist solely in a liquid, gaseous, or solid state. However, any material can be in any of these states depending on its heat and pressure. Below is the phase diagram for water. On the left is pressure which gets higher as we move up the diagram, and on the bottom is temperature, which increases as we move right.


Phase diagram for water. In geysers, high pressure can push water’s boiling temperature from 212℉ to almost 500℉, well above the temperature required to burn wood! Image from Pearson Education.

To make a geyser, we need to have superheated water, which simply means water that is boiling at higher than the normal boiling point. You can see on the diagram, increasing the pressure–moving up on the diagram from the normal boiling point–means that water stays in a liquid state until a higher temperature. Bingo! I think we just found out how geysers work!



There is one more piece of the puzzle: How do we increase the pressure? By capping the boiling vessel, we don’t allow the air out. Capping the flask doesn’t instantly increase the pressure. Instead, as the water boils at the original pressure, liquid water turns into water vapor, which takes up about 1500 times as much space as in ts normal form. To fit in the fixed volume available to it (thanks to the cap) it has to become more tightly packed, which increases the boiling point slightly. This process repeats, causing the pressure to continue to rise and pushing the boiling point higher and higher!

As soon as the flask is open to the air again, we get our hydrothermal explosion: all of the compressed water vapor expands to its normal size flinging the surrounding water into the air, and water above the boiling point follows suit!

Water geyser 2


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