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Science can be seen everywhere, and it can be a lot of fun. Just take a look at today's video or another EepyBird Diet Coke® and Mentos® experiment. That's really cool! And scientific. Today's Wonder of the Day is also about science, but it won't create such a big mess!

What happens when it's hot outside? You just finished your chores for the day. You mowed the lawn, raked leaves, and then picked up branches in the yard for almost two hours. You're tired...and thirsty! What better way to rest on a hot day than with a tall, cool of on the front porch.

You slowly sip your and relish its sweet and tangy flavor. The cold cools you from the inside out. You set your aside and close your eyes for a few moments.

When you reach for your again, you notice that it's wet on the outside. Tiny drops of have formed on the outside of the . They slowly bead and drip down like the on your forehead. You knew it was hot out, but is your really sweating?

Not quite! It may look like , but that's on the outside of your of . But how did it get there? Did it just magically appear out of thin ?

Actually, it DID come right out of the , but there's nothing about it. It's all science! In fact, there's a scientific name for what happened. It's called condensation .

If you wear glasses, you may have noticed condensation in another form. If you've been wearing your glasses inside where it's cool and suddenly walk outside where it's warm, you may have noticed your glasses fog up. This is the result of the in the hot outside suddenly condensing on your cooler glasses.

Particularly during fall and spring, when temperatures vary more than at other times of the year, you may notice condensation on the walls or windows of your house. You can also see it on the windows of your car. These are all examples of the same scientific process of condensation .

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Science can be seen everywhere, and it can be a lot of fun. Just take a look at today's video or another EepyBird Diet Coke® and Mentos® experiment. That's really cool! And scientific. Today's Wonder of the Day is also about science, but it won't create such a big mess!

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Can you imagine on Earth without the Sun? It might be fun for about an hour. You could play an awesome game of flashlight tag with your friends and then tell stories around a fire.

Before long, though, it wouldn't be so fun. You'd soon need to keep a fire going around the clock, because Earth would become a much colder place without the Sun's . In addition, food would become scarce over time, since plants wouldn't grow without the sunlight they need for photosynthesis .

The Sun's also powers Earth's and, through evaporation , the water . What Earth would be like without these processes working properly is anyone's guess. It's safe to say that on Earth wouldn't exist very long if the Sun went out.

Scientists have long known that the Sun makes on Earth possible. We use the Sun's in many different ways. But just how does the Sun produce all that ? To find out, we need to get to the heart of the matter and travel all the way to the Sun's .

Unlike Earth, which is made up mostly of , rock, water, and many other elements, the Sun is made up primarily of hydrogen gas. The Sun is similar to Earth in one way, however: its is by far its hottest part.

In addition to intense , there is an incredible amount of at the Sun's . In fact, the vast amounts of hydrogen atoms in the Sun's are compressed and heated so much that they fuse together.

This reaction, known as , converts hydrogen atoms into helium. The by-product of in the Sun's is a massive volume of that gets released and radiates outward toward the surface of the Sun and then into the solar system beyond it.

The reaction that occurs in the Sun's is similar to the reaction that produces the mighty explosion in a hydrogen bomb. Of course, the reactions that occur in the Sun's are almost-infinitely more powerful than a hydrogen bomb. So why doesn't the Sun explode?

The outward created by the reactions in the Sun's are balanced by the inward created by the gravitational force of all the gases that surround the . Stars can and do collapse or explode if the reactions at their cores become too weak or too strong.

Fortunately for those of us living on Earth, the Sun's outward and inward pressures are nicely balanced, resulting in a stream of coming our way. Of all the that the Sun produces, scientists estimate that Earth receives only about two billionths of it.

Of that amount, about a third is reflected back into space by clouds and snow. A little over 40% warms Earth, while about 25% is used by the water . Winds and ocean currents absorb about 1%, while all the plants on Earth use only about 0.023% for photosynthesis !

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Can you imagine on Earth without the Sun? It might be fun for about an hour. You could play an awesome game of flashlight tag with your friends and then tell stories around a fire. Before long, though, it wouldn't be so fun.

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Do you have a green thumb? If someone asks you that, they're not wondering if your thumb is actually the color green. They're wondering if you're good with plants. Can you make "green" things like plants ?

In today's world, the color green is often associated with the Earth and its environment. So many of Earth's living things - from plants to trees to the grass in your front lawn - are green. That's why the movement to protect our environment - called environmentalism - is often referred to as the "green" movement or "going green."

The overall goal of environmentalism is to protect and conserve the Earth's environment. Everything we do has an impact on the environment - either good or bad. The environmentalists encourage us to pursue actions that will help rather than harm the environment.

Environmentalism can take many forms and concentrate on numerous issues. For example, attempts to reduce and strategies to increase of materials are just two common forms of environmentalism in action.

As more and more people are made aware of the effects of their actions on the environment, they seek ways to reduce the negative effects of these actions. "Going green" has become a popular saying as people take steps to help preserve the Earth for future generations.

These actions may be as simple as using a grocery bag instead of paper or plastic bags. Or they may be more complex, such as purchasing a car to reduce the burning of fuels.

"Going green" takes on new importance each year on Earth Day. As we celebrate the Earth and its natural resources, it's appropriate to think about what choices we can make to have a positive impact on the environment and reduce the negative impacts.

If you need some encouragement to "go green," consider some of these interesting facts:

The size of the world's tropical rainforests decline by 1.5 acres every second because of land development.

This reduction in the size of rainforests leads to the destruction of over 130 plant, animal and insect species every day - that's about 50,000 species per year that become extinct!

Approximately 36 of the 50 United States expect some type of water shortage by 2013.

saves energy: experts say 20 cans can be made out of recycled material with the same amount of energy it takes to make one can from new material.

A television set can run for about 3 hours on the energy saved by just one aluminum can.

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Do you have a green thumb? If someone asks you that, they're not wondering if your thumb is actually the color green. They're wondering if you're good with plants. Can you make "green" things like plants ? In today's world, the color green is often associated with the Earth and its environment.

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You may have noticed that there are many different types of lights surrounding you every day. In your table lamp at home, there may be a regular - what scientists call an incandescent . There are many other types of lights, though, that contain LEDs.

LEDs - or -emitting diodes - are found in all sorts of things. For example, the numbers on your clock are formed by LEDs. Your television remote control probably uses LEDs to send signals. LEDs can up wristwatches and traffic lights. Your television might also be powered by LEDs!

But what exactly are LEDs? The science behind LEDs can get really complicated, but basically they're like bulbs that are part of a electrical . They're different from regular bulbs, though, because they don't get very hot and they don't have a that will burn out. These features make LEDs very popular for many products.

LEDs are illuminated by the movement of electrons across a semiconductor material, such as -- (AlGaAs). The movement of the electrons causes the release of , which can then be directed outward by the shape of the .

Regular bulbs often burn out after a few hundred hours of use (or less), but LEDs can last for thousands of hours. In fact, some LEDs can last 50,000 hours or more!

LEDs can also be very . Their small size has helped television makers replace bulky tubes with LEDs, so that modern televisions can be nearly flat and very thin.

LEDs have many other advantages. For example, LEDs tend to be more than regular incandescent bulbs. They also fit more easily into electric circuits. LEDs are much more than regular bulbs, since a higher percentage of the electrical power goes to generate rather than heat.

The cost of semiconductor material can make LEDs more expensive than regular incandescent bulbs. However, their efficiency, durability and extended life usually make them a much better bargain in the long run.

Although LEDs are all the rage these days, they've actually been around for a while. American Nick Holonyak, Jr., created the first in 1962.

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You may have noticed that there are many different types of lights surrounding you every day. In your table lamp at home, there may be a regular - what scientists call an incandescent . There are many other types of lights, though, that contain LEDs.

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Today's Wonder of the Day was inspired by Sue from , . Sue Wonders, " How do lightbulbs work? " Thanks for WONDERing with us, Sue!

Imagine you're back in the Middle Ages. It's almost dusk and you head into the house to get cleaned up after a hard day of work in the fields. After a quick bath and a hearty supper, you want to relax and enjoy the evening for a bit. As it gets dark, what do you do for lighting?

Back before the invention of modern lighting, you probably would've reached for a candle or an oil lamp. If you lived in a big house, you probably needed several candles or lamps. Lighting all these devices - and keeping them lit - could be quite a chore. They could also produce a lot of and soot that weren't necessarily very pleasant.

It's no WONDER that inventors of the past yearned for a simple solution to lighting their way in the dark. In the late 1800s, two inventors - American Thomas Edison and Englishman Sir Joseph Swan - came up with the same invention independently around the same time: the bulb.

Looking back across time, it's interesting to note that it took so long for such a simple invention to come about. The traditional bulb, also called an incandescent bulb, is an elegantly simple device made up of only a few basic parts. In fact, it hasn't changed much since Edison's day. It was, however, a technological revolution that forever changed history.

bulbs consist of only a few basic parts. The metal base has two metal contacts that connect to the ends of an electrical circuit. The metal contacts attach to two stiff wires, which themselves are connected by a thin metal filament. The is the thin wire you see in the middle of the bulb, held up by a glass mount. All of this exists within a glass filled with an gas, such as argon.

When a connects to an electrical power supply, an electrical flows from one metal to the other. As the travels through the wires and the filament, the heats up to the point where it begins to emit photons, which are small packets of visible light.

In a typical 60-watt bulb, the is made of a long, thin length of metal. Although the inside the looks like it's only about an inch long, it's actually over six feet long and rolled into a tight coil. This is possible because it's only about one-hundredth of an inch thick!

Not all metals will emit visible when heated to extreme temperatures. In fact, most will melt before reaching such temperatures. Tungsten, however, has an extremely high melting temperature, making it the perfect metal for filaments.

To keep the from catching on fire at such a high temperature, bulbs are made with all the oxygen sucked out to create a near vacuum. To prevent evaporation of atoms, an gas, such as argon, is inserted into the to extend its life.

Although incandescent bulbs are cheap, effective, and very easy to use, they aren't very efficient. They generate a lot of heat. More advanced technologies, including fluorescent lights and light-emitting diodes (LEDs), are much more efficient, generating more and less heat. These newer technologies use less energy and are well on their way to replacing regular bulbs.

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Today's Wonder of the Day was inspired by Sue from , . Sue Wonders, " How do lightbulbs work? " Thanks for WONDERing with us, Sue! Imagine you're back in the Middle Ages. It's almost dusk and you head into the house to get cleaned up after a hard day of work in the fields.

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Have you ever noticed how many things we tend to take for ? When we wake up in the morning and head to the bathroom to get ready for school, we don't give much thought to how we'll see in the dark. We just take it for that we'll flip the light switch and, like magic, the lights will come on!

But have you ever thought about how many things have to happen for those lights to come on when you flip that switch? For starters, you have to have to the outlets and switches in your house.

Where does the electricity you use come from? There are many different ways to produce electricity . Some people have electricity generated by plants that burn . Others might get their electricity from.

Still others who live near rivers may get their electricity from an entirely different source. What are we talking about? Hydroelectricity, of course!

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Have you ever noticed how many things we tend to take for ? When we wake up in the morning and head to the bathroom to get ready for school, we don't give much thought to how we'll see in the dark.

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Many years ago, the thought of powering lights by harnessing the power of the Sun sounded like science fiction. Today, though, you can see panels dotting the rooftops of buildings and houses, as well as street lights in some cities.

What was once a dream has become reality, In fact, you might even have power at your fingertips in the form of a -powered calculator. If you have a garden or landscaping at home, you might even have -powered lights guiding your at night.

Have you ever stopped to WONDER exactly how these affordable lights convert the Sun's rays into electricity to power lights that shine for hours after the Sun goes down? Is it magic? Nope! It's science!

A consists of multiple layers of crystalline silicone and chemicals that create layers of negatively-charged electrons and positively -charged spaces. As sunlight passes through the , it excites the negatively-charged electrons and pushes them into the positively -charged spaces.

The positively -charged spaces then transfer the stream as a direct of electricity through wires into the to a where the electricity is stored until it's needed. The charges throughout the day as sunlight continues to be converted to electricity.

When evening approaches, the stops converting sunlight as it weakens and eventually disappears. A photoreceptor on the detects when it's and turns on the , which is usually made up of several -emitting diodes ( LEDs). The then supplies electricity to the throughout the night.

This process repeats on a daily cycle. During the day, sunlight is converted to electricity and stored in the . At night, the supplies the electricity to the until it is all used up or the photoreceptor shuts off the as daylight reappears.

Of course, adequate sunlight is necessary to charge the fully. During the summer, this shouldn't be a problem as long as the is placed where it can receive direct sunlight for most of the day. If possible, make sure no trees or bushes create shade that could affect the charging of the .

During the winter, however, a might not be able to receive enough sunlight to charge the sufficiently to stay all night. This occurs because in winter nights are longer and days are shorter, resulting in fewer hours of sunlight to charge the . In addition, wintertime often brings snow, which can block the and prevent charging during the day.

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Many years ago, the thought of powering lights by harnessing the power of the Sun sounded like science fiction. Today, though, you can see panels dotting the rooftops of buildings and houses, as well as street lights in some cities.

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Today's Wonder of the Day was inspired by sohail from , . sohail Wonders, " How Solar Panel works " Thanks for WONDERing with us, sohail!

Do you look forward to the weekend? If you're like most kids, Saturday with the call of free time to do all sorts of things you don't have time to do during the week. You can sleep in, ride your bike, go for a hike, play games with your friends outside, and stay up later than on weeknights.

All those hopes can be shattered, though, when you wake up on a Saturday to cloudy skies that promise rain. At those times, you may wish that you could head to the and grab a of sunshine off the shelf. Wouldn't that be great? All you'd need to do is take your of sunshine outside, open it, and let the sunshine fill the skies.

It's too bad that the world doesn't really work that way. We might not be able to bottle rays of sunshine, but scientists have found a way of collecting sunlight and storing its energy to use as electricity . Do they use glass jars? Nope! They use solar panels and batteries.

Solar power has become an increasingly popular alternative energy over the last couple of decades. You can see solar panels on residential homes, schools, office buildings, and even road signs and traffic lights. Solar panels can also power everything from simple calculators to the International Space Station.

A solar panel consists of a group of photovoltaic cells linked together. As their name suggests, these cells convert light ("photo") into electricity ("voltaic").

Each photovoltaic cell is like a sandwich made with two slices of semiconducting material, which is usually silicon. In its crystalline form, silicon is not a good conductor of electricity . That's why the silicon layers in a photovoltaic cell have impurities added to them to give each a different charge.

Phosphorus gets added to the top of silicon to give it a charge. Likewise, gets added to the bottom to give it a positive charge. These opposing charges create an electric between the layers of silicon.

When arranged together in a solar panel, the photovoltaic cells just need sunlight to work. As small particles of light, known as photons, hit the photovoltaic cells, they knock electrons free, creating a flow of electricity .

Metal plates attached to the sides of the photovoltaic cells transfer the flowing electrons to wires, which direct the flow of electricity like any other of power. For example, those wires can be connected to a machine that will use the electricity . Alternatively, the wires could be connected to a battery that will store the electricity for use at a later time.

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Today's Wonder of the Day was inspired by sohail from , . sohail Wonders, " How Solar Panel works " Thanks for WONDERing with us, sohail! Do you look forward to the weekend? If you're like most kids, Saturday with the call of free time to do all sorts of things you don't have time to do during the week.

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Isn't electricity ? Just think about how life would be if you couldn't turn on the lights to read before bed. How would you all your electronic devices? Could you live without a computer and television?

If you can't life without electricity, then you might have a hard time if we didn't have electrical power. Can you reading by candlelight ? How about cooking all your food over an open ?

As as electricity is, generating all the power we need takes a on Earth. Mining enough coal to power electric plants, for example, requires tremendous natural resources, and many people are affected by and other by-products of the processes we use to generate electricity.

That's why many scientists are searching diligently for alternative ways to generate power with resources, such as water and wind. If you think about hydroelectric dams and windmills that generate electricity, you realize it's the of these natural resources that is the key.

As water and wind move turbines, they create mechanical energy. This mechanical energy can then be converted by a generator into electricity. Scientists looking for other alternative sources of energy naturally look for other resources that move.

Wait, YOU move! Could you be a source of alternative energy? Some scientists think so, and some have even created new machines to harness the power of humans to create their own electricity.

For example, an organization called Billions in Change has developed a "Free Electric" stationary bike that it claims can turn one hour of human pedaling into a day's worth of electricity. As a person pedals, the bike's wheels drive a flywheel.

The flywheel, in turn, drives a generator. The generator charges a battery that can store enough electricity for an entire day with just one hour of human pedaling. The bike's creators believe it's a cost-effective solution to provide electricity, especially in places that don't otherwise have electric power.

While this might seem like a new idea, people have actually been attaching generators to exercise equipment for several decades. Some of the first to try it were owners of gyms who retrofitted exercise equipment with generators to help offset the cost of the gym's electric bill. Some schools have even installed stationary bikes with generators in classrooms, so that students can exercise, read, and generate power all at once!

The idea of converting human exercise to electricity hasn't taken off as a mainstream source of alternative energy yet, especially in modern areas already connected to the electric grid. On average, commercial power in the United States costs approximately 10 cents per kilowatt-hour.

A person exercising on a stationary bike for an hour might generate 100-200 watts of power during that time. If a piece of exercise equipment was used for five hours each day every day for an entire year, it would still probably generate less than $20 worth of electricity.

Given the costs to retrofit exercise equipment with generators, it could take many years to justify the cost of doing so. Hopefully, technology will continue to improve in the future, allowing exercise equipment to generate larger amounts of power at cheaper rates, making humans a good alternative source of electric power!

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Isn't electricity ? Just think about how life would be if you couldn't turn on the lights to read before bed. How would you all your electronic devices? Could you live without a computer and television? If you can't life without electricity, then you might have a hard time if we didn't have electrical power.

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What do you think of when you hear the word ""? Animals? Vegetables? Tractors? Farmers? Would you believe there are farms without any of those things? It's true! What are we talking about? farms!

farms are areas where many large turbines have been grouped together to "" the power of the . These large turbines look a bit like super-tall, futuristic windmills.

A large can contain hundreds of turbines spread out over hundreds of miles. The land in between the turbines may be used for other purposes, such as regular agricultural farming. Some farms are also located to take advantage of winds that blow across lakes or oceans.

Did you realize that energy is actually another form of energy? Winds are created by the combination of the rotation of the Earth, the irregular shape of the Earth's surface and the uneven heating of the atmosphere by the Sun's rays.

farms are built in areas known to be especially windy on a regular basis. As the winds turn the blades of the turbines, the turbines the energy of the into mechanical power. Generators then the mechanical power into electricity that can be used to power homes just like other forms of energy.

If you're wondering why scientists looked to the as an energy source, there are plenty of good reasons. energy is free and and, unlike conventional power plants, farms don't emit pollutants or greenhouse gases.

On the negative side, farms can cost a lot of money to set up. Over time, though, their cost is competitive with other types of generating systems. Unfortunately, you can't make the blow whenever you want it to, so farms can't always meet electricity needs on demand.

Over time, scientists believe new technologies, such as using batteries to store power for peak demand times, will make power even more popular. power already accounts for about 3% of the United States' electricity . Experts believe power will account for 20% of the nation's electricity by 2030.

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What do you think of when you hear the word ""? Animals? Vegetables? Tractors? Farmers? Would you believe there are farms without any of those things? It's true! What are we talking about? farms! farms are areas where many large turbines have been grouped together to "" the power of the .

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What do you think is the greatest scientific discovery or invention of all time? For some, Benjamin Franklin's discovery of electricity would probably rank near the top of the list. After all, without electricity , our lives would be drastically different than they are today.

Have you ever given much thought to how electricity gets from the power plant to your house? Simply plugging an electronic device into the nearest is a convenience we often take for granted. However, electricity 's to those little plugs in the wall is a fascinating journey.

If you've ever seen objects hanging from the top of poles or large boxes sitting near buildings, then you're familiar with some of the most important pieces of machinery in the system that delivers energy to your home. These machines are called transformers. No, they don't change into superhero vehicles when you're not looking, but they are all about change!

Most transformers, however, are step-down transformers. They take electricity at a high and change it to a lower . This is a critical step in the energy-delivery process, since the electricity that comes from a power plant is at an extremely-high , which is much too high for use in your home.

For example, a power plant transmission might carry electricity at 400,000 to 750,000 volts. Electricity is sent out at such high voltages because it often has to travel great distances. Using higher voltages helps to minimize energy loss as it travels.

In certain areas, called electrical substations, huge transformers reduce those high voltages to lower voltages to send out to specific areas. Have you ever seen an electrical substation near your home? You can usually identify by them by the presence of lots of electrical lines and equipment, including numerous transformers.

Step-down transformers in substations reduce high voltages to lower voltages in the range of 7,200 volts. When the electricity reaches your neighborhood, transformers on top of poles or ground boxes connected to underground wires reduce the of the electricity to 220-240 volts to use in your home. Some major electrical appliances, such as water heaters, stoves, and air conditioners, will use the 220-240 volts, while most other smaller electrical appliances will use 110-120 volts.

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What do you think is the greatest scientific discovery or invention of all time? For some, Benjamin Franklin's discovery of electricity would probably rank near the top of the list. After all, without electricity , our lives would be drastically different than they are today.

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Can you imagine living without electricity? How much would you enjoy a house without a stove? Do you think you could go back to the days before gasoline-powered automobiles? We take all of these modern conveniences for granted...and they all have something in common.

Most electricity is produced from burning . Many stoves run on natural gas. And those automobiles? They run on gasoline made from (what we call ). All of these things - , natural gas, and - are fuels.

So what is a ? It sounds like it's something made out of dinosaur bones, right? Well, that's not exactly true, but fuels date back a long, long time...even before the dinosaurs!

Way back when, fuels, including , , and natural gas, formed during an age known as the Carboniferous Period, which was during the Paleozoic Era. How long ago was that? Try between 286 and 360 million years ago!

At that time, before the dinosaurs came along, Earth was very different than it is today. Humid swamps covered Earth's surface, full of all sorts of strange animals and huge leafy plants and trees. The oceans also contained large amounts of algae, as well as prehistoric fish.

As all these plants and animals died over the years, they decomposed and collected on the bottoms of the swamps and oceans. Layer after layer of dead plant material eventually formed a spongy material called .

Over thousands and thousands of years, the layers of were covered by various minerals, clays, muds, and sands. These heavy materials slowly formed layers of sedimentary rock. As time passed, additional layers of rock formed.

All that rock pressed down on the layers of with unbelievable weight. Over millions and millions of years, the layers of rock squeezed all of the water out of the layers of , leaving behind only the carbon-rich material that would eventually turn into , , or natural gas.

Because it took millions of years to create the fuels we use today, that means that we can't simply make more when they run out. The fuels that are in existence today aren't . When they're gone, they're gone! How long will they last? No one can say for sure. However, many scientists believe that, within the next century, the cost of locating and harvesting the remaining fuels will become too expensive to justify their continued use.

That's why so many scientists dedicate their time today to finding alternative , sources of . Their goal is to develop technologies that will allow us to create sources of that won't run out. Such alternative sources could include technologies such as , , , and hydroelectric .

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Can you imagine living without electricity? How much would you enjoy a house without a stove? Do you think you could go back to the days before gasoline-powered automobiles? We take all of these modern conveniences for granted...and they all have something in common. Most electricity is produced from burning .