Space is hard to explore, because it’s really, really big. Most things in space are so far away that people we build special equipment just to see them. We use telescopes to magnify far-away solar systems, planets, and stars. Rockets send astronauts past the Earth’s atmosphere. Space probes with special cameras send back pictures of planets for scientists to study. Astronauts perform experiments in orbit around the Earth. We do all these things and more to learn more about our universe.

How do noses work? Objects give off tiny amounts of tiny molecules into the air. When just a few of these molecules get up your nose, they dissolve in the mucus up there. Some molecules come into contact with special receptors on what’s called your “olfactory membranes.” Each nostril has a membrane, and each membrane is only about the size of a postage stamp. The membranes hold millions of receptor cells, each of which are ready to send messages to the brain about the molecules that go up your nose.

Music is the art and science of expressing ideas and feelings through sound. A sad song can say more about how someone feels than most words, and a familiar song can make crowds clap together and feel like one happy family. Whatever the emotion, music seems to have a way to communicate it. The music we listen to today is the result of years of experimentation with sounds. As people figured out what they liked best, they invented instruments that could play their favorite tones and developed popular rhythms, or patterns of beats. Each note of music, and every tone of each instrument is a sound wave. Some sound waves sound great together. Some not so good. Getting the exact soundwaves in the pattern you want – now that’s science.

Fluids are cool; they ooze and swoosh. Whatever container you put a fluid in, that fluid will take the same shape. Milk poured into a pitcher forms to the shape of the pitcher. If you pour it into a glass, it takes the shape of the glass. You just can’t do that with a boulder. But with the right container, you could pour liquid rock from below the Earth’s crust. Fluids still act like fluids, even halfway to the center of the Earth.

Outer space is full of stuff. We’re not just talking about planets and moons. There are some bits and pieces, too small to be noticed most of the time that float around and occasionally run into all those planets and moons. Comets and meteors are the big bits of dirt, rock and ice that inhabit our Universe. More than just high-speed space chunks, comets and meteors carry important information about the history of our Universe.

Dirty water, land, and air are a result of pollution. People are the only animals on Earth that make pollution. Garbage, burning fuel, chemicals, sewage, oil, and pesticides are all human-made things that make the Earth’s atmosphere, water, and soil unclean. Humans are even leaving trash in space, such as broken satellites, pieces of metal, paint from rocket skin, and even cameras and toothbrushes. Much of the junk people make and leave behind hurts plants, animals, you and me.

Volcanoes are mountains made from molten rock. The Earth’s crust is divided into big slabs, called plates, which are slowly moving all the time. The plates are floating on the Earth’s mantle, a layer of gooey hot rock that flows like maple syrup. Some places in the mantle, the rock gets very hot and nearly liquid. It’s called magma. Sometimes the magma reaches the Earth’s surface and forms a volcano.

Dirt, sand, and rock from the Earth’s surface gets blown, sliced, torn, swallowed and distributed all over the world. What was yesterday’s hill is tomorrow’s flat plain. The planet looks a lot different than it did when it formed four and a half billion years ago. The force of erosion, the slow wearing away of the land, has never ceased.

Most dead animals and plants break up, get decomposed, and become part of the soil, but some turn into fossils. A fossil forms when a plant or animal dies, and gets buried. If conditions are right, water gets into the fossil bed, and chemical reactions preserve the impressions for thousands or millions of years. There are different types of fossils — imprints of animals, black carbon outlines, hardened bones, or actual animals and plants that have been trapped in ice or hardened tree sap.

Atoms are reeeeally small. They are so small that you can’t see them with just your eye. It takes as many as 10 million of them side-by-side to measure a single millimeter. In fact, atoms are the smallest pieces of “stuff” that are still considered “stuff.” If you take something and break it into tiny pieces, and then break it into tinier pieces, and keep going, the smallest part you’d be left with (and still have the same substance that you started with) is an atom. Atoms are the building blocks of all matter. Everything is made of only 109 different kinds of atoms, called elements. 92 of these elements occur naturally, but the rest of them – ones like Technetium and Promethium have only been found in distant stars and Californium and Einsteinium – are only made in laboratories. A molecule is born any time two or more atoms combine together. English

Bill Nye looks at how the brain controls the body and stores information

Flowers are an important part of many plants. Plants use flowers to make other plants – to reproduce. Flowers have special parts, called stamens and pistils. When pollen from the stamen finds its way down through the pistil, the flower is pollinated, and seeds start to grow. The seeds eventually find their way to the ground, the seeds sprout, and more plants are born.

Time affects every living thing on Earth. Trees shed their leaves. Some animals only come out at night. There are even insects that only emerge every 17 years. Days, hours, minutes, and seconds – all of these were invented by humans. Humans came up with these units of time to organize their lives and to study the world. One of the first ways humans told time was by noticing the difference between daytime and nighttime. Humans use the Earth revolving around the Sun to divide time into years and seasons. Months are based on the movement of the Moon around the Earth. A day is when the Earth spins completely around its own axis.

Each planet is different. They are all different sizes – Pluto’s the smallest, and Jupiter’s the biggest. They come in a variety of colors – Mars is covered with rust, so it looks red; the methane (cold natural gas) in the atmosphere of Uranus makes it look blue; and Saturn’s colorful rings are made of icy rock. As far as we know now, Earth is the only planet in our solar system that is home to living things.

Storms are big, loud, and often accompanied by rain, snow, sleet, or hail. Where do these wild, dangerous, and necessary tornadoes, hurricanes, and thunderstorms come from? Storms happen when huge different air masses collide. Along the border of these air masses, water vapor condenses into clouds, strong winds form, and the clouds rub against each other with the ground often becoming electrically charged waiting to send lightning bolts across the sky. What starts out as a placid summer day turns into two air masses boxing it out 10,000 meters up.

In Bill Nye the Science Guy: Forests, Nye shows students the levels of a forest, which include the canopy, the under story, and the floor. His special guest is Nalini Nadkarni, who has no qualms about going high up in the canopy to check out the wildlife and other happenings there

There are lots of different climates all over the world. Deserts are warm and dry. Temperate forests are cold and wet. Tropical rain forests are warm and wet. Animals and plants live in climates that are good places for them to live. Cacti wouldn’t grow too well in the Arctic, just like polar bears would over heat in the desert.

Mammals - They're (sometimes) big, they're hairy, and they're warm-blooded. From human being to moose and from cats to rats, Bill Nye explains what it takes to be in the mammal family.

Do-it-yourself science involves a question, observations, a hypothesis, and experimentation. You have probably come up with questions after you noticed something unusual. For instance, why do fingers get all pruny and wrinkled when I sit in the tub? The observation – shriveled fingertips – is the first step. Do-it-yourself science requires an eye for details surrounding your observations. Collecting related information helps you get to the next step, what scientists call a hypothesis, or “educated” guess. After weighing all the evidence, you hypothesize that your fingers get pruny because of the hot water in the tub. Once you have a hypothesis, it’s time for the fun part – testing it out.

Friction is a force that slows moving things down and turns the moving energy into heat energy. When two things rub together, like your bike tires and the road, friction between them slows you down. There’s also friction in the metal parts of the wheel’s hub – at the center. There’s even friction between the fibers and rubber of the tires themselves as they flex and roll. That’s why you eventually stop rolling when you stop pedaling. Rough things make more friction than smooth things. Rubber shoes on a clean wooden basketball floor create more friction than do hard metal skate blades on smooth ice.

Things can appear to be moving, when they really aren’t. Sometimes an object might seem to be at rest, even when it is in motion. It’s all relative. Relative motion, that is. How things appear to move depends on how you, or any observer, happens to be moving. So, if you’re on a bus looking out a window into another bus, and your bus begins to back up slowly, you may think the other bus is moving forward, when really it’s not moving at all. That’s motion in motion. It happens all around us all the time.

The relationship between the Earth, the sun, the wind and the weather. Guest: "Today" weather reporter Willard Scott.

When you push something, you’re using pressure. Pressure depends on two things – the power of the push and the area that’s being pushed on. A push on a small area makes more pressure than the same size push on a big area. Pushing hard on something creates more pressure than a little nudge, naturally.

About 70% of the Earth’s surface is covered in water, and almost all of that water has been around since the Earth formed billions and billions of years ago. That means a glass of water you drink today could be water that a dinosaur once sipped. Water is constantly recycled on Earth as rain, snow, sleet and hail. It makes its way in and out of oceans, lakes, streams, hail, and glaciers. Scientists call the recycling of water the water cycle (not that bad, huh?).

There’s an amazing amount of living things in the ocean. There are fish, sharks, flowers, whales, squid, sea plants, sea anemones, sea otters, and all sorts of other things living in the water. But most of the living things in the ocean are so small we can’t even see them. These tiny plants and animals are called plankton – the “drifters”.