Why is the Sky Blue?

Light travels in waves, similar to waves on the ocean. The science term for light waves is electromagnetic waves. Like waves on the ocean, electromagnetic waves can be measured by their wavelength. This is the length between two crests in the wave. A crest is the top part of the wave (the foamy white part). Light coming from the sun is made up of all the colors of the rainbow and is known as white light. All the colors in white light have different wavelengths. Red light has the longest wavelength of all the colors. This wavelength is larger than the oxygen atoms in the atmosphere. When red light passes through the atmosphere, its long wavelength causes it to pass through the oxygen atoms without being scattered or spread around. Blue light on the other hand has a much shorter wavelength than red light. The wavelength of blue light is smaller than the oxygen atoms and when blue lights passes through the atmosphere it collides with the oxygen atoms. These collisions cause the blue light to be scattered in all directions. This scattering of the blue light is what causes the sky to appear blue. All other colors, with longer wavelengths than blue, are scattered as well, but blue light's short wavelength causes it to be scattered the most. Actually violet light has the shortest wavelength of all the colors and is scattered even more than blue light, but our eyes our much more sensitive to blue light so we see the sky as blue.

During a sunset, the white light has to travel through much more atmosphere than when the sun is directly overhead. The blue light and other short wavelength colors are scattered around and diluted so much by this that only the longer wavelengths of light remain. This is why the sky appears red, orange, and yellow during sunsets.

Information to answer this question was found at http://www.why-is-the-sky-blue.org/

What Is A Virus And Why Are Viruses Worse Than Bacteria?

There are many different types of viruses. Some viruses cause diseases, and some do not. Viruses are all very small, and they are all made out of proteins and genes. Some viruses also have a membrane, like cells do. There is a debate about whether viruses are alive or not. They may be alive because they are able to copy themselves, and they are made of protein and nucleic acids, like all other life is; however, viruses cannot do anything by themselves. Because they are completely dependent on a host for everything, some people do not consider them to be alive.

In order to copy themselves, viruses must enter a cell. Once they are inside, they take over the machinery in the cell and use it to copy their DNA or RNA and to make virus proteins instead of the normal proteins a cell would make. Different kinds of viruses can grow in just about any kind of life. There are viruses that infect animals, plants, and even bacteria. Since viruses are so good at taking over cells, they make loads of virus copies that then go on to infect other cells. There are some viruses that make so many copies that there are a trillion (1,000,000,000) viruses in one milliliter of blood (about the size of a sugar cube). This is five times more viruses in a few drops of blood than there are stars in the galaxy! When viruses take over a cell, they kill it or disrupt it. This is what makes you sick. Your immune system fights the virus, and many of the things it does make you feel sick also. Your body gets fevers because sometimes viruses do not grow as well at higher temperatures. Because the viruses are inside your cells, your immune system has to kill the infected cells before they can make more viruses to prevent the virus from multiplying.

Viruses actually do not make us sicker than bacteria. In fact, you never even know you have many viral infections. We do not have as many problems with bacteria as we used to, because bacteria can usually be treated with antibiotics. Except in a few cases, such as HIV and herpes-viruses, there are no drugs to treat viral infections. We may feel worse with a viral infection than with a bacterial infection, because our only choice is to suffer through it. In major infections, however, bacteria are generally much more dangerous than viruses. There are bacteria that make the most deadly poisons on earth. Also, there are bacteria that are resistant to all known forms of antibiotics. There are only a very few viral diseases that are deadly, such as smallpox, Ebola, and Hantavirus. The biggest danger to viral infections is generally that they will weaken a person to the point that they cannot fight off bacterial infections.

Viruses are fascinating, teetering on the edge of living and nonliving, unable to do anything by themselves but able to completely take over cells they invade. Studying viruses has given us insights into how our own cells work. Because viruses can enter cells, they can potentially be used in gene therapy. There is even at least one virus that slows down cancer. Viruses can be dangerous, but exciting, tiny windows into our own bodies.

Sources:

Fundamental Virology, third edition. ed. B Fields, D Knipe and P Howley. Lippincott-Raven. Philadelphia 1996.

www.virology.net

How Does a Lightbulb Work?

A light bulb is made from a very thin piece of glass. The glass is heated up and blown into a shape of a bulb. Once cooled, the inside of the bulb is coated with a material that diffuses the light. The filament of a light bulb is made of tungsten. Tungsten is a metal like element that burns in the presence of oxygen. The tungsten wire that the filament is made from is very thin, on the order of 0.0017 inches thick! The filament is made of coiling the tungsten wire around itself, forming a double coil. The ends of the coil are then attached to power leads that are inside the glass base of the bulb. The glass top and bottom are then melted together, the bulb is sealed, and the oxygen is removed from the bulb. Various gases can then be introduced into the bulb. A metal base is added and the bulb is ready to use.

In a normal light bulb an electric current travels through a coiled tungsten wire. Current is carried in a wire by bumping electrons off of the atoms or molecules that make up the wire, like marbles. One electron is bumped which bumps another electron. Electrons do not collect within the wire, but rather one electron is bumped and replaced in the atom by the one that bumped it. This bumping creates energy. The energy is released as heat in the filament and can heat the filament to up to 2500 degrees Celsius! At 2500 degrees Celsius the light bulb emits about 12% of its energy as visible light. Energy is also given off from the bulb as invisible infrared light or heat.

Evidence exists that Thomas Edison was not actually the inventor of the light bulb. In 1878 British inventor Joseph Swan patented the carbon filament light bulb. That following year Edison patented the same carbon filament bulb. As a result of the law suit Swan flied against Edison, the Edison and Swan Electric Company was formed. In 1882 Swan sold his patent to Brush Electric Company. Edison owned Brush, later General Electric, and got the credit for the patents. The light bulb developed by Swan and Edison is based on the same principles as the ones we currently use today. Improvements in the make up of the filaments have been made to lengthen the life of the bulb.

In neon lights, similar concepts are used. Different gases and coatings can be added to the glass to induce different colors.

How Do Sun-Powered Homes Work?

Most existing buildings, including your home, are powered through an electrical grid.This grid connects all the homes in your neighborhood and all the buildings downtown through wires. At a power plant the wires all come together. A power plant generates the electricity that you use to light, heat, and cool your home. Power also allows you to turn on your hair dryer, your computer, and your microwave.The power that is produced at most of these power plants comes from fossil fuels.

There are three forms of fossil fuels: coal, oil, and natural gas. All three were formed several hundred million years ago, before the time of the dinosaurs. This time period is called the Carboniferous Period and occurred about 360 million years ago. The planet was covered with swamps, trees, and large leafy plants. As the plants died, they sunk to the bottom of the swamps. Over many, many years, these plants were covered with sand, rocks, and other minerals. Eventually, all the water within the plants was squeezed out. The remaining material became coal, oil, or natural gas.

Mining companies take these fossil fuels out of the earth and use them to generate electricity. In order to produce energy, power plants burn fossil fuels. These fuels give us the energy to run our cars and power our homes. However, fossil fuels take millions of years to make. Right now, we are using fossil fuels that were made over 300 million years ago. If we don't conserve the fossil fuels that we have, we may run out!

HAVE NO FEAR! There is an alternative to using fossil fuels. Any guesses?

The sun and the wind! Scientists are discovering more ways to use renewable energy sources such as the sun and wind. Renewable means that unlike fossil fuels, which are limited in energy, these sources will not run out. Another bonus to using renewable resources is that they don't pollute the environment the way fossil fuels do. When fossil fuels are burned, they release gases into the air. These gases can be harmful to the environment and may contribute to individuals' developing cancer or allergies. Renewable resources, like sun and wind, do not have bad side effects. Through science the sun may help us fuel more environmentally friendly homes, cars, and much more.

Little Lions Experiment:

For this month's experiment, you need to talk your parents or an adult family member into taking you to the Clean Energy Expo at Penn State. This event is free and will take place from April 2-3, 2004, at the Bryce Jordan Center. Check it out on the web at http://www.wppsef.org/cee/. Once you are at the expo, visit the Penn State Science Lions booth where you can do some actual hands-on energy experiments!

If you are not able to make it to the expo, search your home for ways to cut down on use of electricity and other resources. For example, figure out ways to conserve water while showering or washing your dishes. Or, research how to start a recycling program in your home, school, or neighborhood.

Resources:

Chapter 8: Fossil Fuels- Coal, Oil and Natural Gas; found at http://www.energyquest.ca.gov/story/index.html.

A Primer on Sustainable Building. Rocky Mountain Institute, 1998.

Dr. Riley with the Penn State American Indian Housing Initiative found at www.engr.psu.edu/greenbuild.

Author:

Science Lions wrote this article with the help of Amy Grommes, a graduate student in Architectural Engineering at Penn State. Amy studies architectural sustainability and works on using straw bales and other "green" (environmental friendly) materials to build homes for the Northern Cheyenne in Lame Deer, Montana. View Dr. Riley's website for more information on this project.

What is Love?

Valentine's Day is full with heart-shaped candy, cards, and decorations. But, is the heart the only thing involved in falling in love? No. People in love often feel what they describe as a love "high." Professor Semir Zeki and his team of researchers at the University College London wanted to find out what parts of the brain are involved in this "love high." The professor and his team tested 17 young men and women who had fallen in love in the previous six to twelve months. Each of these research participants had their brain scanned. The scans help measure changes in blood flow. These measures were taken as the research participants looked at a photo of their loved one. Measures were also taken when the participant looked at three other photos. These other photos were pictures of individuals of the same gender, but were only friends. The research team noted changes in the blood flow in the brain. There was heightened activity in four areas when the individual looked at the photo of his or her loved one.

The four hot spots were the anterior cingulate, the medial insula, the putamen and the caudate nucleus. The anterior cingluate is the section of the brain that is towards the bottom of the brain. The anterior cingluate is known to be involved with responding to drugs that induce feelings of relaxation. It is associated with happy states, attention to one's own emotional state, and especially social interactions. The second region is the medial insula. This section can be viewed from the top. The medial insula is related to a host of emotional functions. The third and fourth sections are the putamen and caudate nucleus. They are in the back of the brain. The putamen and caudate lie deep in the brain. Both are frequently stimulated when we experience both positive and negative emotions.

Professor Zeki was pretty excited about these findings as he explained: "...we have discovered that this overwhelming state of love--which mobilizes your whole life--is actually controlled by four small areas of the brain." The team also found out what is not activated in the brain by their lover's photos. Some of these regions have been found to be related to sadness and can be overactive when people are depressed.

Little Lion Experiment:

Psychologists are scientists who study the mind and behavior. Psychologists study a variety of parts of the human experience from the functions of the brain to the actions of nations. They study child development to the care of the aged. One tool psychologists use to study the mind and behavior is pictures and a notebook. They use the pictures to ask their patients questions about how they feel and what they are thinking about when they look at these pictures. Cut through the newspaper and some magazines (after people are done reading them) and then ask your friends and family about the pictures. Take notes of their answers and see if certain pictures made more people happy or sad, excited or scared, or any other terms that the participants come up with. Be creative and you will find the brain is creative too.

How Do Airplanes Stay in the Air?

Flying for the holidays? Or, did grandma fly in to visit you for Christmas? Have you ever wondered--while on a plane or watching one--how a heavy, metal plane flies through the air?

Whether you are scared of flying or not, the answer to this question is a little frightening. Physicists and aeronautical engineers continue to debate the basic mechanics of flight. This is even more suprising when you consider that the Wright brothers invented the plane over 100 years ago! In spite of the debate, everyone agrees that flight boils down to physics. Yes, this means that no invisible strings are hanging from space!

Most will go on to explain that a plane's ability to fly results from air traveling faster over the more curvaceous top surface of the wing than under the flatter bottom surface. The quicker a fluid like air moves, the less pressure it exerts. This phenomenon is known as Bernoulli's principle and was discovered by Daniel Bernoulli, an 18th century Swiss mathematician. The principle helps us to understand how slower moving air below the wing exerts more pressure on the wing than the faster moving air above it. This results in an upward force called lift. Lift pushes the aircraft upward against the downward pull of gravity.

This principle is well-accepted and accurate, but it does not help us to understand why the air flowing over the wing moves faster. This lack of explanation causes confusion among physicists and aeronautical engineers. One of the leaders in helping to explain this phenomenon, Jef Raskin, actually started his research by arguing with one of his middle school teachers. He argued that this principle didn't make sense because he had seen planes fly upside down. Raskin felt that Sir Isaac Newton's laws of motion were a better explanation, as "a wing is just a device for forcing air down." According to Newton's third law, for every action there is an equal and opposite reaction, so the downward force that the wing applies to the air produces an upward force of the air on the wing. The amount of air directed downward depends on the angle of the wing (the angle of attack) and not the shape of the wing. This would help explain why a plane can fly upside down.

Although Newton's law helps to explain how planes can fly upside down, most believe that both Bernoulli and Newton help to explain flight. They also recognize that curves on the top of the plane are important and without them an airplane may stall and fall.

Flight is a fascinating science, and many aspects of why we can fly are still under debate. Start asking your teacher questions and maybe you will help get some of the debate of flight mechanics off the ground!

Source: Chang K. "What Does Keep Them Up There?" New York Times. 9 December 2003.

Little Lion Experiment

An important concept in understanding how objects move is gravity. Gravity is the tendency of matter toward some attracting body, particularly towards the center of the earth. To understand the effect of gravity or a flying objects attraction to the ground, drop varies objects such as a piece of paper, a shoe, a book, and a feather from a table. Guess, watch, time, and test which object falls the fastest.

Gravity adds weight or force - an equal amount to each object. But, gravity increases the force or speed of motion on the heavier objects. Thus, the heavier objects such as a shoe or book would beat a piece of paper or feather. You can also feel this principle at work when you slip on ice with and without your book bag! Be careful this winter!