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  In the last two decades, the contribution of solar energy to the world's total energy supply has grown significantly. This video will show how solar cells or photovoltaic cells produce electricity.  Energy from the Sun is the most abundant and absolutely freely available energy on planet earth. In order to utilize this energy, we need help from the second most abundant element on earth, sand. The sand has to be converted to 99.999% pure silicon crystals to use in solar cells. To achieve this, the sand has to go through a complex purification process as shown. The raw silicon gets converted into a gaseous silicon compound form.  This is then mixed with hydrogen to get highly purified polycrystalline silicon. These silicon ingots are reshaped and converted into very thin slices called silicon wafers. The silicon wafer is the heart of a photovoltaic cell. When we analyze the structure of the silicon atoms you can see they are bonded together. When you are bonded with someone you los

  Lots of kids grow up singing that tune about little stars twinkling, but even as adults, many folks don’t know why stars seem to flicker and wiggle. Astronomers describe the twinkling of the stars as stellar scintillation. Technically, it refers to variations in apparent brightness or position of a distant, luminous object as its light travels through a medium. In other words, that twinkling isn’t caused by the stars which are super constant in their brightness -- it’s caused by the Earth's atmosphere. As the light from a star travels toward you through the atmosphere, it passes through many layers of air of varying temperatures and densities. Each of the boundaries between those layers of air refracts the light, bending it in a slightly different direction from the moment. So, the starlight zigs and zags as it passes through the air to your eye or to a telescope on the ground. From our perspective, this makes the star appear to shift ever so slightly.  Of course, we can get arou

 Here’s a scientific mystery for you:  Does hot water freeze faster than cold water? The answer is: We don’t know. You’re probably thinking, how can we not know? I mean, we’ve all got water. Most of us have a freezer.  This seems like a pretty simple experiment. Well, you’re right, it is. It also isn’t. The experiment has been performed by brilliant people all over the world. And in those experiments, sometimes hot water freezes faster than cold water. And sometimes it doesn’t. And either way, the results of the experiment are not reproducible. The observation that hot water will freeze faster than cold water is called the Mpemba Effect. It’s named after Erasto Mpemba, who noticed the effect in 1963 when he was just thirteen years old and making ice cream with his classmates.  He noticed that the ice cream mixture made with hot milk froze faster than the mixture made with cold milk. However, he wasn’t the first person to make this claim. Aristotle said the same thing in the year 4 BCE.

  If you look around your house, you will see many devices that have electric motors, such as kids' toys, table fans, toothbrushes, hairdryers, and this electric cutting knife. But how does the electric motor work? You turn it on and somehow it starts rotating. Why is that? In this blog, we'll cover the basics of electricity and magnets and then put it all together to understand how the motor works.  Let's start with something called a circuit. You have a battery, some wires, and a device that uses electricity, such as a light bulb. Electricity flows through the circuit. But as soon as there is a break in the wire, the electricity stops flowing and the light bulb goes off. The path must be complete for the circuit to work. This is best down through the use of a switch. Electricity is flowing down the wire. This is called conventional flow. If we take the battery out and flip it, then the current will flow the other way. The light bulb will still work in either case but ther

 The Nerf Guns an important part of every toy collection, good for target practice, Nerf battles, and reverse engineering them so we can see how they work. Let's get ready to have some fun. This specific Nerf Gun is called the Nerf Elite Disruptor. Six darts can be loaded in at one time, pull back on the cocking mechanism, aim, and pull that trigger.  You'll see on the left side of the gun, a bunch of holes for the screws. If we take them all out, we can get a good look at what's inside. Naturally, let's start with the trigger. You can see it's connected to a spring. You can pull the trigger back, but as soon as you let it go, it will spring back into its original position. You can see a bunch of extra plastic here. This connects with another piece that I'm gonna call the vertical slider. This is normally held up by a spring. When the trigger gets pulled, the vertical slider comes down. I'm gonna come back to this in a second. This is the piston. It fits ins