It's been a pretty non-snowy winter so far, and we know some of you are missing it.  To keep busy until school starts back up again, here are a couple of snow-related STEM activities (that don't require real snow) to give you that winter wonderland feeling.

Foaming fake snow
Materials:
Two large plastic or glass containers
Measuring cup
Baking soda
Teaspoon
Tablespoon
Sticky note
Pen or pencil
Dish soap
Vinegar

Process:
1. Write "soap" on a sticky note and stick it on one of the containers.
2. Scoop one cup of baking soda in the container without the sticky note.  Add three tablespoons of water and mix to make a dough.  (It should feel like modeling clay.)  Add water in small amounts if needed to get to the right consistency.
3. Play with your fake snow!  Make a snowman, polar bear, anything you want!  Keep your creation in the container.
4. In the container labeled "soap", add one cup of baking soda,  a teaspoon of dish soap, and three tablespoons of water.  Mix the ingredients to make a dough.  Again, you can add water in small amounts until the dough molds well.
5. Make another critter.  Try and keep it a similar height and size as the first one.  Keep it in the container.
6. Take one cup of vinegar and pour it over your first creation.
7. Take another cup of vinegar and pour it over your second creation.  How did they react differently?
8. Find out what happens if you pour water over what remains instead of vinegar.

What's going on here?
When vinegar touches baking soda, the two chemicals react with each other.  You end up getting gas bubbling up in a watery solution.  Dish soap allows soapy solutions to spread out, so instead of a watery solution, you get gas and foam.


Why are skis so long?
Materials:
Deep plate, glass baking tray, or baking pan
Flour
Action figure or doll that can stand upright (preferably a heavier one)
Cardboard
Scissors
School glue

Process:
1. Cut two identical rectangles out of cardboard.  The length should be a little shorter than the height of your action figure.  The width should be about double the width of the feet of the action figure.
2. Pour a layer of flour about 3/4 inch deep on the plate.  Use a piece of cardboard to smooth out the surface.
3. Imagine that the flour is snow.  Place your action figure on the flour.  Pick it back up and observe what kind of marks are left in the flour.
4. Put the action figure back on the flour, but this time, press it down.  Was it easy to make it sink?
5. Pick up your action figure and let it stand on the flour.  To to knock it over in various directions.
6. Glue the skis on to the feet of your action figure.  The feet should be about halfway along the length of the skis.  Let the glue dry.
7. Smooth the flour out again.
8. Stand the action figure up on the flour with the skis on and try and knock it over again. 

What's going on here?
Skis create a large contact area between the skier and the snow.  The weight of the skier is spread out over a larger area.  The skier presses less on each square inch of snow, so instead of sinking into it, they can glide over it.  The skis also make it harder to push the action figure over.  It's easier to keep balance when you have a bigger contact area.  It's much harder to fall backward or forward, but, since the skis barely extend past your feet on the sides, skiers still fall easily from side to side

To wrap up (see what we did there) the year in time for the holidays, here are some fun Christmas numbers that you can bring up at holiday parties.

Santa has 31 hours of Christmas, thanks to time zones and the rotation of the earth.  This works out to 822.6 visits per second.

His sleigh would have to travel at 650 miles per second, which is 3,000 times the speed of light!

If Santa was carrying just a medium-sized Lego set to every child he visits, his sleigh would be carrying 321,300 tons.

If he was to eat a cookie in each of the 112 million homes in the US, he would consume 3 billion calories in one night!

And finally, no matter how carefully you pack Christmas lights, they're almost certainly going to tangle.  For any cord longer than 2 meters, physicists have proven that knots are almost mathematically guaranteed.

Have a very merry Christmas!

Ho, ho, ho!  It's time to learn about Santa's big helpers: reindeer!  There are so many cool things to learn about these Christmas heroes.  

First of all, let's get one thing straight.  Reindeer are real.  They are also known as caribou.  They are large members of the deer family, and live in herds of up to a few hundred.  In the spring, they sometimes form giant herds of many thousands!

As land mammals, they don't actually live at the North Pole; the North Pole is in the middle of the ice-covered Arctic Ocean.  Instead, they live in the arctic and subarctic regions of Europe, Asia, and North America.  The largest herds of reindeer live in Russia.

Unfortunately, reindeer can't really fly.  They are mammals, and the only mammals that fly are bats.  They can float though!  One of their two coat layers is made up of hollow hairs that trap air.  These hairs hold in body heat and give them some buoyancy.

There are actually some reindeer that have red noses!  Some scientists think the red hue is caused by a lot of blood vessels packed into a tight space to help regulate their body temperature in cold climates.  Other scientists think the red-nosed reindeer might be suffering from a parasitic infection.

And finally, reindeer have really cool eyes.  They change color!  In the summer,  their eyes are gold.  In the winter, their eyes turn blue, which increases the scatter of reflected light and helps them to see better in the near constant darkness.  They are also the only mammals that can see ultraviolet light, which helps them to see objects in the dark arctic winter.

Happy December!  As everyone festoons their houses with holiday decorations, we thought we'd talk a little bit about electricity.  This might even help you fix your broken Christmas lights.

Let's talk about holiday lights.  In a simple circuit, electricity travels through a closed circuit, passing over a filament, which causes it to glow brightly.  The more current that passes over the filament, the brighter it will burn and the quicker it will burn out.  If the circuit is broken, the electricity will not be able to pass over the filament, it will not be able to light.  If the current is too high, the filament will blow out of melt, breaking the circuit.

A lot of us probably remember detangling a whole string of lights only for it to not light because one bulb has blown out.  Finding and replacing that broken bulb suddenly makes the whole string of lights work again.  When this happens, it means that the lights on the string have been attached in a series.  This means that the electricity passes from the power source to the first light, and then from light to light until it returns to the power source.  Any single blown bulb breaks the circuit, making it impossible for electricity to reach any of the lights.

Another way to wire lights is in parallel.  When lights are attached in parallel, each light is on its own circuit.  If one light burns out, the remaining lights continue to shine because they continue to be in a closed circuit with the power source.

Holiday lights nowadays tend to be several series of lights strung together in parallel.  This means that, if a light burns out, some of the lights on the string may go out because their circuit has been disrupted, but the rest of the lights continue to glow.  Of course, they might not, and that is because of something called a shunt.

A shunt is a device that allows current to continue flowing through a circuit by creating a path of lower resistance than the original path.  In incandescent holiday lights, shunts are small wires wrapped beneath the filament.   When the lights are constructed, the shunts are coated with a substance that makes them an insulator.  Electricity will not pass across the shunt while the filament exists, because the coating gives the shunt a higher resistance than the filament.  The electrical current will avoid the shut because electricity seeks the path of least resistance.

If the filament burns out, the high temperature created from the burnout melts the coating off of the shunt.  Now the shunt stops being an insulator and becomes a conductor.  Current passes along the shunt, keeping the circuit open, allowing the rest of the lights in the series to keep burning.

In this blog post, we've talked about the electricity science behind incandescent holiday lights.  If you want to learn more or read about LED lights, check out this post.