Why is the sky blue?

The sky is blue because of light passing through it. Light from the sun enters Earth's atmosphere, the the layer of gases (air) that surrounds Earth, and hits the atoms and molecules in the air. The light from the sun is made of many colors of light that, when we look at them together, look white. 

Source: Hyperphysics

This is called scattering. Light is an electromagnetic wave that can come in many colors (see What is Color?). What we call "color" refers to the wavelength (and frequency) of light. The concept of wavelength is described in What is Color?. Certain wavelengths, or colors, of light are scattered more often than others. Blue light (shorter wavelength) is scattered more frequently red light (longer wavelength). This scattered light goes in all directions, including into your eye. 

Consequently, during the day, the sky appears blue since the scattered blue light, when you look at the sky not around the sun, you are seeing this scattered blue light. At dawn and dusk, you are looking more directly in the direction of the sun. Much of the blue light that the sun sent to earth is scattered in other directions, so less of the blue light reaches you. The light that reaches you tends to be orange and red. Consequently, the sky looks red or orange.

What is an electron microscope?

A microscope is similar to a telescope or a pair of eye glasses. All microscopes, telescopes, and glasses have something in common, lenses. A lens is normally a curved piece of glass that bends the light that passes through it, think of a magnifying glass. Similar to how eye glasses makes things that are blurry and how telescopes make things that are far away seem close up, microscopes make things that are very small seem larger.
Below is an example of how light waves bend through different kinds of lenses:

Source: http://www.shokabo.co.jp/sp_e/optical/labo/lens/lens.htm

Light microscopes used in a number of areas such as medicine, science, and engineering. Microscopes that use light are powerful tools, but they cannot see the very small objects like atoms. For this, we can use an electron microscope, a microscope that uses electrons rather than light.

Source: http://www.microscopy.ethz.ch/lens.htm

Since electron microscopes do not use light, it also does not use typical lenses. Instead, it uses magnets. Just as lenses bend lights, magnets will make electrons bend. Since you cannot see electrons with your eyes, we use some other equipment to make a television signal that shows an image on a tv screen. The tv at your home uses electrons to produce an image as well. An electron microscope is kind of like a tv attached to some magnets!

What are scientists like?

On TV, scientists are often shown as extremely smart people separate from the rest of society who speak in terms that few people understand. Big Bang Theory allows the scientists on the show to at least be a part of the rest of society and humanizes them, although they still fall into most stereotypes of scientists(stereotypes are exaggerated characters often used to make fun of a group). These are just stereotypes. Scientists are a diverse bunch of people. What unites scientists is an interest in how at least one aspect of the world works. Scientists like to ask questions, come up with ideas about the answers to these questions, and test these possible answers, called hypotheses. A hypothesis must be testable. 

For example, my office mate enjoys photography, soccer, and watching MMA. Another person in my research group enjoys listening to smooth jazz and movies. I play the saxophone (alto and tenor), enjoy playing most sports, love science fiction (especially Stargate SG-1), and enjoy debating public policy. This is only a part of my research group. There is even more diversity in our larger collaboration and in science, in general. Scientists come from all races and are of all genders. Curiosity unites us.

What is Energy?

When you are running around, people call you energetic. You may have heard about energy. What does it mean to scientists? Who cares about energy?

This video (the song is from Tom Glazer and Dottie Evans from Singing Science Records) provides a good overview of what energy is.

Energy is the ability to do work. It can be used to predict the future! Something called potential energy is stored energy due to the position of things or their arrangement. For example, a ball at the top of a mountain has a lot of potential energy, since it has the potential to move down the hill and lower its energy. When the ball is moving, it has something called kinetic energy. The total energy in a grouping of objects that interacts (including all interactions) is always constant. This is called the Law of Conservation of Energy.

Imagine that you have $10. That $10 can be divided in many different ways among different people. It can also be traded between people. Similarly, the amount of energy in the universe is constant. That energy can be transformed between different forms, such as solar, wind, gravitational potential energy, kinetic energy, nuclear energy, or chemical energy. A field called thermodynamics uses the law of conservation of energy along with a few other laws (such as the fact that disorder, measured by entropy, is always increasing) to predict what will happen to materials under a variety of conditions. A few years ago, I made this song and video with some friends talking about the predictive powers of thermodynamics (unfortunately, I am having difficulty getting it to embed on this site, but it can be seen on YouTube: http://www.youtube.com/watch?v=uqAh5LcCZPA ).
Everyone cares about energy.The food that keeps us alive gives us energy. We use energy to heat our homes and give us light. The computer that you are currently using consumes energy. Energy is hot!

The "Magic" of Magnets

Have you ever played with magnets? If you spill a bunch of screws, a fast way to clean them up is to hold a magnet over them, attracting them toward the magnet. If you hold a magnet over another magnet, they either attract each other or repel each other. You may have heard that opposites attract. Magnets have things called poles. There is a north pole and a south pole, kind of like the locations on Earth. Earth is a giant magnet. This is why compasses work. No one has ever observed a north pole without a south pole nearby. North poles attract South poles and South poles attract North poles. However, two north poles repel each other. Also, two south poles repel each other.

Magnets have poles (North, N, and South, S). A north pole attracts a south pole and a south pole attracts a north pole. However, two north poles repel each other. Two south poles repel each other.

Superconductors are a special type of material that, at certain (low) temperatures conduct electricity really well and expel all magnetic and electric fields. Here is a pretty cool video from the Royal Institution of Great Britain describing superconducting magnets.

One fun activity is to take a magnet to the beach. In many areas (at least around the Great Lakes), if you wave a magnet over the sand at a beach, you will likely find that small gray flecks stick to the magnet. Most of that is likely ferrite, Fe2O3, a magnetic material. You can also find magnets in most amplifiers, including telephones. Be sure to ask your parents permission before taking anything apart!

What is color?

When you look at this page, what colors do you see? Blue? Orange? Yellow? What exactly are you seeing? What is "seeing"? What are you sensing?

You are sensing light from your computer screen. Your eyes respond in different ways to different colors of light. Your eyes do not respond to certain colors of light at all. All light is part of what is called the electromagnetic spectrum. Light is a wave (like a wave on a lake or ocean or a ripple in a pond). Only a small portion of the electromagnetic spectrum is visible. 

Photo Courtesy of NASA kids: http://science.hq.nasa.gov/kids/imagers/ems/index.html
Only a small amount of all the light out there we can actually see. Visit NASA's site to learn more.

What is an electron? What is charge?

During the winter, have you ever rubbed your feet on a carpet and touched a metal object--like a doorknob? What did you feel? What did you see? Most likely you felt a shock and you may have seen a bright spark. That shock occurred because you developed a charge. Like charges repel each other, while opposite charges attract each other.

Two negative (-) charges repel each other. Two positive (+) charges repel each other. A positive (+) and negative (-) charge attract each other.

This is where the phrase "opposites attract" comes from. For convenience sake, we call one type of charge positive (+) and the other negative (-) (Thank you Benjamin Franklin!). Electrons carry a negative charge. When you rubbed your feet on the carpet, electrons from the carpet stuck to you, leaving positive charge behind on the carpet. Charge cannot spread out well on the carpet (it's a material property--caused by what is in the carpet). The situation when unbalanced charge is stuck somewhere, is called static electricity.

Static electricity makes the positive charge on the carpet stay there. You also develop a charge that, when it isn't moving, is also static electricity. Electrons, which carry negative charge, are more easily removed from materials than positive charge.