Fraser Spiral Illusion

Photo name: Fraser Spiral Illusion Picture category: Illusions Image size: 104 KB Dimensions: 620 x 623 Photo description: This optical illusion image is known as a Fraser spiral illusion, or false spiral. The black arcs appear to form a spiral when in fact they are a series of concentric circles.

Peripheral Drift Illusion

Photo name: Peripheral Drift Illusion Picture category: Illusions Image size: 127 KB Dimensions: 640 x 480 Photo description: This peripheral drift illusion gives the impression of motion despite the fact that the image is motionless. This is a common type of optical illusion and there are numerous other examples of it in action.

Hypnosis Illusion

Photo name: Hypnosis Illusion Picture category: Illusions Image size: 45 KB Dimensions: 500 x 500 Photo description: This hypnosis illusion makes the person looking at it feel disoriented, as if they are traveling down a moving spiral to the center of the image. The hypnotic optical illusion appears to be moving when in fact it is staying still. It’s the kind of image that brings thoughts of a hypnotist making their patient sleepy to mind.

Delboeuf Illusion

Photo name: Delboeuf Illusion Picture category: Illusions Image size: 15 KB Dimensions: 740 x 452 Photo description: This image is an example of the Delboeuf illusion that relates to relative size perception. The black circle on the right appears bigger than the black circle on the left because of the distance to the rings that surround them. A distant surrounding ring makes the inner circle look smaller relative to an inner circle with a closer surrounding ring. This optical illusion is similar to theEbbinghaus illusion.

Balcony Facade Illusion

Photo name: Balcony Facade Illusion Picture category: Illusions Image size: 43 KB Dimensions: 450 x 600 Photo description: This photo shows a unique balcony facade illusion. A man and a woman appear to be standing outside on the balcony when in fact they are just drawn onto the wall of the building. There are also a number of vases that appear to be sitting on the window frames but they too are just drawn illusions.

Parallel Lines Cafe Wall Illusion

Photo name: Parallel Lines Cafe Wall Illusion Picture category: Illusions Image size: 33 KB Dimensions: 800 x 514 Photo description: This famous optical illusion makes the parallel horizontal lines appear to be bent when in fact they are straight. It was originally noticed amongst the tiles of a cafe wall and can now be seen in architecture such as on a large building in Melbourne, Australia.

Big as a Tree Illusion

Photo name: Big as a Tree Illusion Picture category: Illusions Image size: 72 KB Dimensions: 586 x 600 Photo description: This depth perception illusion makes the load the woman is carrying on her head appear as large as the small tree in the background when in fact it is not.

Face & Vase Illusion

Photo name: Face & Vase Illusion Picture category: Illusions Image size: 10 KB Dimensions: 501 x 482 Photo description: This face and vase picture is a very common optical illusion. Do you a white vase or two identical black faces looking at each other?

Scintillating Grid Illusion

Photo name: Scintillating Grid Illusion Picture category: Illusions Image size: 34 KB Dimensions: 343 x 349 Photo description: This picture is an example of a scintillating grid illusion. Discovered in 1994 by E. Lingelbach, it is similar to the Hermann grid illusion. When looking at the grid, dark dots seem to appear and disappear at random.

Afterimage

Photo name: Afterimage Picture category: Illusions Image size: 23 KB Dimensions: 542 x 485 Photo description: The following picture is an example of an afterimage, a type of optical illusion that continues to appear in one's vision even after you finish looking at the original image.

Whales are singing?!

Mother Earth

We know more today than ever before about our planet Earth and what’s going on around us.

Science is always continuing to connect the dots through Earth research, study, and experimentation.

As technology advances, we continue to learn and find more out about our planet Earth.

Here are some facts about our Earth.

Age: 4.6 billion years old.

Position: 3rd planet from the sun.

Size: 5th largest planet in our solar system.

Surface Area: 197 million square miles, about 70 percent of the Earth's surface is covered with water..

Diameter: The Earth has an average diameter of 12,742 kilometers. (7,926 miles)

Average Temperature: The temperature at the Earth's core is estimated to be between 5000 and 7000 degrees Celsius.

Length of Year: 365.25 days

Inclination of Axis: The Earth's axis has a tilt of about 23 ½ degrees. It is this tilt which causes the seasons.

Chemical Composition: The Earth is made mostly of iron, oxygen, silicon, magnesium, nickel and sulfur: 34.6% Iron, 29.5% Oxygen, 15.2% Silicon, 12.7% Magnesium, 2.4% Nickel, 1.9% Sulfur, 0.05% Titanium

Planets >> Pluto

Don't forget Pluto! Sure it may not be officially recognized as a planet anymore but it's still there and offers a lot of interesting facts and cool information. Check out these fun Pluto facts for kids.

Pluto was the smallest and furtherest planet from the Sun in our solar system, now it is not even officially recognized as a planet! In 2006 Pluto was demoted to the status of dwarf planet. Because it is so far away from the sun it is very cold with temperatures ranging form -235 Degrees Celsius to -210 Degrees Celsius. Pluto consists of rock with a very thick coating of ice. The atmosphere of Pluto consists of nitrogen with some carbon monoxide and methane.

Planets >> Neptune

Neptune is a large planet that experiences extreme atmospheric weather conditions. After the demotion of Pluto, it now holds the distinction of being further away from the sun than any other planet in our solar system.

Neptune is a large planet, nearly four times the size of Earth. Neptune suffers the most violent weather in our Solar System. Storms have been spotted swirling around its surface and freezing winds that blow about ten times faster than hurricanes on Earth make it the windiest planet. Neptune is a large, water planet with a blue hydrogen-methane atmosphere and faint rings. Neptune is covered in thin wispy white clouds which stretch out around the planet.

Planets >> Uranus

Uranus likes to be a bit different from other planets in our solar system. In rolls like a barrel rather than spinning like Earth and other planets, it also shows off a majestic blue/green haze due to its high levels of Methane gas.

Uranus spins lying on its side (like a barrel), this is perhaps due to a large collision early in its formation. Uranus was the first planet discovered by telescope. Since Uranus takes 84 Earth years to go around the sun, this means that each of its poles is in daylight for 42 years and in darkness for the next 42. Uranus’s atmosphere is mostly hydrogen but it also contains large amounts of a gas called methane. Methane absorbs red light and scatters blue light so a blue-green methane haze hides the interior of the planet from view. Uranus hides its interior but scientists guess that under the hydrogen-methane atmosphere is a hot, slushy ocean of water, ammonia and methane thousands of miles deep wrapped around a rocky core.

Planets >> Saturn

Perhaps the most beautiful planet in our solar system (other than earth of course) due to its spectacular ring system, Saturn is a gas giant that features many extreme physical features and atmospheric conditions.

Saturn is the second largest planet in our solar system and is another gas giant. Saturn has a small rocky core covered with liquid gas. It is surrounded by a system of rings that stretch out into space for thousands of kilometres. The rings are made up of millions of ice crystals, some as big as houses and others as small as specks of dust. Saturn is very light as it is made up of more hydrogen than helium so it is less dense. If we could fit Saturn into a bathtub it would float (but that would have to be one big bathtub!) Like Jupiter, Saturn has many moons which surround it. Saturn is not a peaceful planet. Storm winds race around the atmosphere at 800kmp/h. Saturn has a very strong magnetic field which traps energy particles resulting in high levels of radiation.

Planets >> Jupiter

Jupiter is the largest planet in our solar system. Its famous 'Red Spot' and raging gas storms give it an impressive if not intimidating appearance. As well as having many moons, Jupiter also has a number of rings similar to that of Saturn but much less noticeable.

Jupiter is the largest planet in our Solar system. It is so big that more than 1300 Earth's could fit inside it. Thick, colorful clouds of deadly poisonous gases surround Jupiter. The quick spinning of the planet whips up the atmosphere, creating the bands around the planet. If you were to descend into Jupiter, the thin, cold atmosphere becomes thicker and hotter, gradually turning into a thick, dark fog. In the blackness about 1000km down the pressure squeezes the atmosphere so hard that it becomes like liquid. At the centre of Jupiter is a rocky core, slightly bigger than Earth but weighing about 20 times more. Surrounding the core is an ocean of liquid hydrogen, about 1,000 kilometres deep. Jupiter has many storms raging on the surface, most notably the big red spot which is the largest hurricane in our Solar System. It's been raging for over three hundred years. Jupiter has a very strong magnetic field, you would weigh two and a half times as much as you would on earth. Jupiter has many moons circling around it. Four of these moons are bigger than Pluto.

Planets >> Mars

Mars is nicknamed the red planet because it is covered with rust-like dust. Even the atmosphere is a pinkish red, colored by tiny particles of dust thrown up from the surface. Mars experiences violent dust storms which continually change its surface. Mars has many massive volcanoes and is home to Olympus Mons, the largest volcano in our solar system, it stands 21km high and is 600km across the base. Mars has a very thin atmosphere made mostly of carbon dioxide. It is not thick enough to trap the sun's heat like Venus, so the planet is very cold. Temperatures range from -120 Degrees Celsius on winter nights to 25 Degrees Celsius in the summer. Mars has many channels, plains and canyons on the surface which could have been caused by water erosion in the past. Mars has very weak gravity which cannot hold onto the atmosphere well. The polar ice caps consist of frozen Co2 (dry ice) which lies over a layer of ice.

Planets >> Venus

The atmosphere of Venus made up mainly of carbon dioxide. Its size is slightly smaller than Earth. It also features gravity similar to that of Earth. Venus is surrounded by clouds consisting of mercury, ferric chloride hydrocarbons and sulphuric acid. These clouds create the most corrosive acid rain found anywhere in our solar system. The clouds are so thick that little light even reaches the surface. The light that does reach the surface is converted to heat and can not escape the atmosphere making Venus the hottest planet at around 500 Degrees Celsius. The surface of Venus is often described as a "stormy desert" full of many craters and very active volcanoes. The surface is also likened to molten lead. Venus features no liquid water.

Planets >> Mercury

Mercury is a small planet which orbits closer to the sun than any other planet in our solar system. As well as being very hot, it features a barren, crater covered surface which looks similar to Earth's moon.

The surface of Mercury is very similar to our moon. It has a very barren, rocky surface covered with many craters. Being so close to the Sun, the daytime temperature on Mercury is scorching - reaching over 400 Degrees Celsius. At night however, without an atmosphere to hold the heat in, the temperatures plummet, dropping to -180 Degrees Celsius. Mercury has a very low surface gravity. Mercury has no atmosphere which means there is no wind or weather to speak of. There is also no water on the surface of Mercury, it is possible however that there could be water underneath the surface. Likewise, there is no air on the surface but it could be trapped underneath.

Froggy

A frog is an amphibian. They lay their eggs in water. The eggs hatch into a tadpole which lives in water until it metamorphoses into an adult frog. Tadpoles look more like fish than frogs, they have long finned tails and breathe through gills. An amphibian can live both on land and in water. Although frogs live on land their habitat must be near swamps, ponds or in a damp place. This is because they will die if their skin dries out. Instead of drinking water, frogs soak it into their body through their skin. Frogs breathe through their nostrils while also absorbing about half the air they need through their skin. Frogs use their sticky, muscular tongue to catch and swallow food. Unlike humans, their tongue is not attached to the back of its mouth. Instead it is attached to the front, enabling the frog to stick its tongue out much further. The common pond frog is ready to breed when it is only three years old. Frogs in the wild face many dangers and are lucky to survive several years. In captivity however, frogs can live for much longer. Frogs can see forwards, sideways and upwards all at the same time. They never close their eyes, even when they sleep. Remarkably, frogs actually use their eyes to help them swallow food. When the frog blinks, its eyeballs are pushed downwards creating a bulge in the roof of its mouth. This bulge squeezes the food inside the frog's mouth down the back of its throat.

Dolphinsss

Compared to most other animals, dolphins are believed to be very intelligent. Dolphins are carnivores (meat eaters). The Killer Whale (also known as Orca) is actually a type of dolphin. Bottlenose dolphins are the most common and well known type of dolphin. Female dolphins are called cows, males are called bulls and young dolphins are called calves. Dolphins live in schools or pods of up to 12 individuals. Dolphins often display a playful attitude which makes them popular in human culture. They can be seen jumping out of the water, riding waves, play fighting and occasionally interacting with humans swimming in the water. Dolphins use a blowhole on top of their heads to breathe. Dolphins have excellent eyesight and hearing as well as the ability to use echolocation for finding the exact location of objects. Dolphins communicate with each other by clicking, whistling and other sounds. Some dolphin species face the threat of extinction, often directly as a result of human behavior. The Yangtze River Dolphin is an example of a dolphin species which may have recently become extinct. Some fishing methods, such as the use of nets, kill a large number of dolphins every year.

Whales

Many whales are toothless. They use a plate of comb-like fibre called baleen to filter small crustaceans and other creatures from the water. There are 79 to 84 different species of whale. They came in many different shapes and sizes! A baby whale is called a calf. Whales form groups to look after calves and feed together. These groups are often made up of all female or all male whales. Whales that are found in both Northern and Southern hemisphere never meet or breed together. Their migration is timed so that they are never in breeding areas at the same time. The arched lower lip of a whale can often make it look like it is smiling! However, this isn’t a “real” smile as the blubber in the head of the whale prevents the muscles of the face from reaching the surface. You can tell the age of a whale by looking at the wax plug in its ear. This plug in the ear has a pattern of layers when cut lengthwise that scientists can count to estimate the age of the whale. Whales love to sing! They use this as a call to mates, a way to communicate and also just for fun! After a period of time they get bored of the same whale song and begin to sing a different tune. Sometimes whales make navigation mistakes during migrations. Although they may have made the mistake days before, they don’t realise it until they becoming stranded. Whales support many different types of life. Several creatures, such as barnacles and sea lice, attach themselves to the skin of whales and live there.

Sharks

Sharks do not have a single bone in their bodies. Instead they have a skeleton made up of cartilage; the same type of tough, flexible tissue that makes up human ears and noses. Some sharks remain on the move for their entire lives. This forces water over their gills, delivering oxygen to the blood stream. If the shark stops moving then it will suffocate and die. Sharks have outstanding hearing. They can hear a fish thrashing in the water from as far as 500 metres away! If a shark was put into a large swimming pool, it would be able to smell a single drop of blood in the water. Although most species of shark are less than one metre long, there are some species such as the whale shark, which can be 14 metres long. A pup (baby shark) is born ready to take care of itself. The mother shark leaves the pup to fend for itself and the pup usually makes a fast get away before the mother tries to eat it! Not all species of shark give birth to live pups. Some species lay the egg case on the ocean floor and the pup hatches later on its own. Great whites are the deadliest shark in the ocean. These powerful predators can race through the water at 30 km per hour. Unlike other species of shark, the great white is warm-blooded. Although the great white does not keep a constant body temperature, it needs to eat a lot of meat in order to be able to regulate its temperature. A shark always has a row of smaller teeth developing behind its front teeth. Eventually the smaller teeth move forward, like a conveyor belt, and the front teeth fall out.

Doggyyy

In total there is said to be around 400 million dogs in the world. The domestic dog has been one of the most popular working and companion animals throughout human history. Dogs perform many useful tasks for humans including hunting, farm work and security as well as assisting those with disabilities such as the blind. Although experts often disagree, there is scientific evidence which shows that the domestication of dogs could have occurred more than 15,000 years ago. There are hundreds of different breeds of dogs. Examples of these breeds include: Bulldog, German Shepherd, Collie, Golden Retriever, St Bernard, Greyhound, Bloodhound, Chihuahua, Labrador, Great Dane, Rottweiler, Boxer and Cocker Spaniel. The most popular breed of dog in the world by registered ownership is the Labrador. With their gentle nature, obedience, intelligence and near limitless energy, Labradors make for excellent family pets and reliable workers. They often assist police and are a common choice as guide dogs. Dogs have formed such a strong bond as pets, workers and companions to humans that they have earned the nickname "man's best friend". Humans help train various dog breeds to enter in competitions such as breed shows, agility and obedience contests, racing and sled pulling. Dog have superior hearing than humans, capable of hearing sounds at four times the distance. Dogs have a remarkable sense of smell, they are capable of differentiating odors in concentrations nearly 100 million times lower than humans can. The average life span for a dog is around 10 to 14 years. Those involved in dog breeding refer to males as ‘dogs’, females as ‘bitches’, dogs younger than a year old as ‘puppies’ and a group of offspring as a ‘litter’. Domestic dogs are omnivores, they feed on a variety of foods including grains, vegetables and meats.

Fast Food = Junk Food

Fast food (or junk food) is the name given to food that can be prepared and served quickly, often served at basic restaurants or in packaged form for convenient takeaway/takeout. It is typically inexpensive to buy but unhealthy to eat. Popular forms of fast food include burgers, fries, pizza, fish and chips, kebabs and fried chicken. Well known fast food franchises and restaurants include McDonalds, Kentucky Fried Chicken (KFC), Pizza Hut, Taco Bell and Burger King. As well as at restaurants, fast food is commonly sold at convenience stores and gas stations. Examples of this include hotdogs, meat pies and doughnuts. Fast food is often highly processed and produced on a large scale to decrease costs. Ingredients and various menu items are typically prepared at a different location before being sent to restaurants to be cooked, reheated or quickly put together for the customer’s convenience. While hamburgers, fries and pizza are seen as traditional fast foods, countries throughout the world sell all types of fast food that may not be so well known. Some examples of these include kebabs, Chinese takeaways (friend noodles, rice and meat dishes), sushi and bento type foods in Japan and fish and chips in the UK, New Zealand and Australia. Consumers in the USA spend over $100 billion on fast food every year. McDonald’s is arguably the worlds most well known fast food chain. There are McDonald’s restaurants found in over 100 countries around the world and they serve over 40 million customers every day. Due to increased awareness of public health and obesity levels, efforts have been made to improve fast food menus by lowering fat levels or at least offering healthier alternatives. While these health concerns are generating more attention, fast food is still linked to worldwide weight gain problems, increased diabetes risks and healthcare costs.

FOOD!!!

• McDonald’s fast food chains employ over 1.5 million people around the world. More fast food facts.

• Different parts of the world have their own local cuisine. The diets and general food habits of various cultures depend on social, religious, economic and safety factors as well as the availability of different foods.

• Examples of food and cuisine that are popular or famous in certain areas of the world include hummus in the Middle East, apple pie in the USA, raw fish in Japan, cheese in France, roast meat and vegetables in England, curry in India and tortillas in Mexico.

• There are around 2000 different plant types that humans use to cultivate food.

• Examples of popular vegetables include lettuce, carrots, asparagus, cauliflower, broccoli, spinach, potatoes and onions.

• Cutting onions releases a gas which causes a stinging sensation when it comes into contact with your eyes. Your body produces tears to dilute the irritant and remove it from your eyes.

• China is the largest producer of garlic, producing over 10 million tons in 2008 and accounting for over 75% of world output.

• Examples of popular fruits include apples, oranges, pears, strawberries, peaches, bananas, apricots and grapes.

• India is the world’s largest producer of bananas, producing nearly 22 million tons in 2007.

• Humans use many different methods for gathering food which include farming, hunting, gardening, foraging and fishing.

• Humans eat meat from a number of different animals, common examples include meat from chickens, cows, sheep and pigs. Other food products that come from animals include milk, eggs and honey.

• Although humans are omnivores (eating both plants and animals), many people choose not to eat meat and fish, they are known as vegetarians. Those who don’t eat or use any products made from animals (including eggs, dairy products and honey) are known as vegans.

• Food for human consumption is typically made from plants and animals but we also eat other products such as fermented foods and fungus (mushrooms, truffles etc).

• Cooking is an important part of food preparation that involves applying heat. In most cases this transforms the chemical make up of food, altering its texture, flavor, nutritional properties and appearance.

• Types of equipment used in the cooking process include ovens, microwaves, toasters, grills, pots and frying pans.

• Various cooking methods include boiling, simmering, steaming, sautéing, pan frying and deep-frying.

• Around 70 million people suffer from food poisoning every year with around 7 million of these cases being fatal. Careful food storage, temperature control and preparation is necessary to avoid potentially dangerous bacteria, toxins and viruses.

• Around 8% of children and 2% of adults have some kind of food allergy, this occurs when the body’s immune system incorrectly assumes a certain food protein is harmful and attacks it. Common examples of food allergies include reactions to peanuts, gluten and shellfish.

Chemistry facts

Hydrogen is the first element on the periodic table. It has an atomic number of 1. It is highly flammable and is the most common element found in our universe. More hydrogen facts. Liquid nitrogen boils at 77 kelvin (−196 °C, −321 °F). More nitrogen facts. Around 1% of the sun’s mass is oxygen. More oxygen facts. Helium is lighter than the air around us so it floats, that's why it is perfect for the balloons you get at parties. More helium facts. Carbon comes in a number of different forms (allotropes), these include diamond, graphite and impure forms such as coal. More carbon facts, diamond facts, and coal facts. Although it is still debated, it is largely recognized that the word 'chemistry' comes from an Egyptian word meaning 'earth'. The use of various forms of chemistry is believed to go back as long ago as the Ancient Egyptians. By 1000 BC civilizations were using more complex forms of chemistry such as using plants for medicine, extracting metal from ores, fermenting wine and making cosmetics. Things invisible to the human eye can often be seen under UV light, which comes in handy for both scientists and detectives. Humans breathe out carbon dioxide (CO2). Using energy from sunlight, plantsconvert carbon dioxide into food during a process called photosynthesis. Chemical reactions occur all the time, including through everyday activities such as cooking. Try adding an acid such as vinegar to a base such as baking soda and see what happens! Water expands as it drops in temperature, by the time it is frozen it takes up about 9% more space. Often formed under intense pressure over time, a crystal is made up of molecules or atoms that are repeated in a three dimensional repeating pattern. Quartz is a well known example of a crystal. Athletes at the Olympic Games have to be careful how much coffee they drink. The caffeine in coffee is a banned substance because it can enhance performance. One or two cups are fine but they can go over the limit with more than five. (update - as of 2004 caffeine has been taken back off the WADA banned list but its use will be closely monitored to prevent future abuse by athletes.)

What's the Difference?

Although there can sometimes be a blurry line between categories the following definitions should help you understand the difference between comets and asteroids, why Halley’s Comet is not a meteorite and more. Comet A comet is a relatively small solar system body that orbits the Sun. When close enough to the Sun they display a visible coma (a fuzzy outline or atmosphere due to solar radiation) and sometimes a tail. Asteroid Asteroids are small solar system bodies that orbit the Sun. Made of rock and metal, they can also contain organic compounds. Asteroids are similar to comets but do not have a visible coma (fuzzy outline and tail) like comets do. Meteoroid A meteoroid is a small rock or particle of debris in our solar system. They range in size from dust to around 10 metres in diameter (larger objects are usually referred to as asteroids). Meteor A meteoroid that burns up as it passes through the Earth’s atmosphere is known as a meteor. If you’ve ever looked up at the sky at night and seen a streak of light or ‘shooting star’ what you are actually seeing is a meteor. Meteorite A meteoroid that survives falling through the Earth’s atmosphere and colliding with the Earth’s surface is known as a meteorite.

Gravity

• Objects with mass are attracted to each other, this is known as gravity.

• Gravity keeps Earth and the other planets in our solar system in orbit around the Sun. It also keeps the Moon in orbit around Earth.

• Tides are caused by the rotation of the Earth and the gravitational effects of the Moon and Sun.

• Because Mars has a lower gravity than Earth, a person weighing 100kg (220 pounds) on Earth would only weigh 38kg (84 pounds) on Mars.

• It is thought that Isaac Newton’s theories on gravity were inspired by seeing an apple fall from a tree.

• While Newton’s older law of universal gravitation is accurate in most scenarios, modern physics uses Albert Einstein’s general theory of relativity to describe gravity.

• Acceleration of objects to due to the gravity on Earth is around 9.8 m/s2. If you ignore air resistance (drag) then the speed of an object falling to Earth increases by around 9.8 metres per second every second.

• The force of gravity 100 kilometres (62 miles) above Earth is just 3% less than at the Earth’s surface.

• The human body can handle increased g-forces as seen in activities such as dragster races, airplane acrobatics and space training. The highest known acceleration voluntarily experienced by a human is 46.2 g by g-force pioneer John Stapp.

• While formula one racing drivers may feel around 5 g’s under heavy braking, they can experience over 100 g’s if a crash causes them to decelerate extremely quickly over a very short distance.

• Some roller coasters have been known to include g-forces of around 4 to 6 g.

• The higher something is, the greater its gravitational potential energy. Back in the Middle Ages, weapons called trebuchets were used to take advantage of this principle, using mechanical advantage and the gravitational potential energy of a counterweight to hurl rocks and other projectiles at or over walls. In modern times we use the gravitational potential of water to create hydroelectricity.

THE Solar System

The solar system includes the Sun and all the objects that orbit around it due to its gravity. This includes things such asplanets, comets, asteroids, meteoroids and moons. The Solar System formed around 4.6 billion years ago. There are eight planets in the Solar System. The four inner planets are Mercury, Venus, Earth and Mars while the four outer planets are Jupiter, Saturn, Uranus and Neptune. The inner planets (also known as terrestrial planets) are smaller and made mostly of rock and metal. The outer planets (also known as gas giants) are much larger and made mostly of hydrogen, helium and other gases. As of 2008, there are also five dwarf planets: Pluto, Ceres, Eris, Makemake & Haumea. There is an asteroid belt which lies between the orbits or Mars and Jupiter, it features a large number of irregular shaped asteroids. For thousands of years humans were unaware of the Solar System and believed that Earth was at the center of the Universe. Astronomers such as Nicolaus Copernicus, Galileo Galilei, Johannes Kepler and Isaac Newton helped develop a new model that explained the movement of the planets with the Sun at the center of the Solar System. The Sun contains 99.86 percent of the Solar System's known mass, with Jupiter and Saturn making up making up most of the rest. The small inner planets which include Mercury, Venus, Earth and Mars make up a very small percentage of the Solar System’s mass.

Comets

Enjoy these fun comet facts for kids. Learn interesting info about Halley’s Comet, Shoemaker-Levy 9 (the comet that collided with Jupiter in 1994), what comets are made of, why they have tails and lots more.

A comet is a relatively small solar system body that orbits the Sun. When close enough to the Sun they display a visible coma (a fuzzy outline or atmosphere due to solar radiation) and sometimes a tail. The coma is created as the comet gets closer to the Sun, causing water, carbon dioxide and other compounds to sublime (quickly changing from solid to gas) from its surface. Comets are made of ice, dust and small rocky particles. The name comet comes from the Greek word meaning ‘hair of the head’, it came from the Greek philosopher Aristotle who observed comets as ‘stars with hair’. Short term comets (also known as periodic comets) have orbital periods of less than 200 years while long term comets have orbital periods of over 200 years. Halley's Comet Halley’s Comet (or Comet Halley as it is also known) is the most well known comet. It is known as a periodic comet (or short term comet) because the time it takes to orbit the Sun is less than 200 years. Records of humans observing Halley’s Comet go back thousands of years, with appearances noted by Babylonian, Chinese and European star gazers. It can be seen with the naked eye from Earth every 75 to 76 years (although the time period has between 74 and 79 years in the past). It last appeared in the inner Solar System in 1986 and will return again sometime in 2061 (start charging your camera battery). Halley’s Comet is named after English astronomer Edmond Halley who first determined its period of orbit. It was the first comet to be recognized as having a periodic orbit. Halley’s Comet appearance in 1986 allowed researchers to investigate its make up more closely using spacecraft. While some previous theories were proven correct, other models were altered with the new information. For example, while earlier models predicted the comet to feature many volatile ices, the actual amount was less than first expected. The tail and fuzzy glow you see around Halley’s Comet is known as a coma. It occurs when the comet gets close to the Sun and compounds such as frozen water and carbon dioxide sublime (rapidly change from solid to gas) from its surface. While the coma over Halley’s Comet can stretch up to 100,000 km across, the nucleus is actually small, only around 15km (9.3 miles) long, 8km (5 miles) wide and 8km (5 miles) thick. Comet Shoemaker-Levy 9 In July 1994, the Shoemaker-Levy 9 comet broke apart and collided with Jupiter. This event gave astronomers a unique opportunity to observe what happens when such a collision occurs. The largest fragments were 2 km (1.2 mi) in diameter and struck Jupiter at a speed of around 60 km/s (37 mi/s). The impact scars were clearly visible for months after the impact. Shoemaker-Levy 9 was originally located by astronomers Eugene M. and Carolyn Shoemaker and David Levy in March 1993.

The Sun

Enjoy these fun Sun facts for kids. Learn how hot the Sun is, how long it takes light from the Sun to reach Earth, what the Sun is made of and more. Read on for a range of interesting facts about the Sun.

The Sun is a star found at the center of the Solar System. It makes up around 99.86% of the Solar System’s mass. At around 1,392,000 kilometres (865,000 miles) wide, the Sun’s diameter is about 110 times wider than Earth’s. Around 74% of the Sun’s mass is made up of hydrogen. Helium makes up around 24% while heavier elements such as oxygen, carbon, iron and neon make up the remaining percentage. Light from the Sun reaches Earth in around 8 minutes. The Sun’s surface temperature is around 5500 degrees Celsius (9941 degrees Fahrenheit), so pack plenty of sunscreen if you plan on visiting (remembering that the average distance from the Sun to the Earth is around 150 million kilometers). The Sun’s core is around 13600000 degrees Celsius! The Sun generates huge amounts of energy by combining hydrogen nuclei into helium. This process is called nuclear fusion. Because of the Sun’s huge influence on Earth, many early cultures saw the Sun as a deity or god. For example, Ancient Egyptians had a sun god called Ra while in Aztec mythology there is a sun god named Tonatiuh. The Sun produces a solar wind which contains charged particles such as electrons and protons. They escape the Sun’s intense gravity because of their high kinetic energy and the high temperature of the Sun’s corona (a type of plasma atmosphere that extends into space). Planets with strong magnetic fields such as Earth manage to deflect most of these charged particles as they approach. A solar eclipse occurs when the Moon is between the Sun and the Earth.