B Barber
Science Coordinator

Science

"Space Science Show" (Senior)
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Program: Christine Bellert & Kate Lorkin (St Anne's), Andrew Shelton (St Jude's).

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Our Solar System

The Sun

The Sun is by far the largest object in our Solar System. The next closest star is about 4 light years away. Light can travel around our Earth 7 times in a second. If it was travelling in a straight line into outer space for 4 years (!) it will finally reach the next closest sun! The core temperature of 15,000,000 degrees celcius produce nuclear reactions with hydrogen constantly changing into helium. All the heat it produces keeps life on Earth surviving. The sun also produces an electrically solar wind that can interupt radio communication on Earth and can produce huge solar storms and auroras. It is about 45 years old in human years and will live to an old age of 10,000,000,000 years! It will eventually use up all the gas it has and turn into a white, dwarf star. Radius: 700,000km Day length: 25 Earth days Length of year: 88 Earth days Surface temperature: 6,000 deg celsius

Mercury (Messenger of the Gods)	Venus (Roman Goddess of Love)	Earth
Mars has the largest range of surface temperatures of all the planets with a maximum temperature of 870 degrees celsius! On the sunny side of Mars, zinc metal can melt but can be far below freezing on the dark side of Mars. It has no atmosphere like the Earth to protect it from the elements and being so close to the Sun makes it impossible for life to live there. The surface of Mars looks very much like our moon and the lack of an atmosphere leaves it open for numerous meteorite collisions. Distance from Sun: 58,000,000km Radius: 2450km Day length: 59 Earth days Length of year: 88 Earth days Gravity: 0.38 times Earth Surface temperature: -180 to 420 deg celsius	Venus is the brightest planet in the night sky. It can often be seen at dawn as the Morning Star or the evening as the Evening Star. The Earth and Venus are very similar in size and density. It is surrounded by a thick layer of clouds made mainly of carbon dioxide and sulphuric acid. Very dangerous! It is extremely hot on the surface and creates a huge "greenhouse" effect. The surface is also full of active volcanoes and craters. Distance from Sun: 108,000,000km Radius: 6050km Day length: 243 Earth days Length of year: 225 Earth days Gravity: 0.91 times Earth Surface temperature: above 450 deg celsius	The only habitable planet in our Solar System. Our atmosphere of nitrogen and oxygen provides a protective layer necessary to sustain life, serving as a buffer between us and the extreme temperatures, the bitter effects of the Sun's ultraviolet radiation and all but the largest meteors. Moon: Galileo first discovered the moon back in the early 17th century and found the surface covered in craters, valleys and mountains.
Mars (God of War)	Jupiter (King of the Roman Gods)	Saturn (God of agriculture)
This red planet has similar temperatures to the Earth. Polar ice caps exist on Mars and it is thought that the planet may have once had water and microscopic fossils. Mars also has 2 moons: Phobos and Deimos. Distance from Sun: 228,000,000km Radius: 3400km Day length: 24.5 Earth days Length of year: 687 Earth days Gravity: 0.38 times Earth Surface temperature: -120 to -30 deg celsius	This gas giant is the largest of planets in our Solar System. If Jupiter were only 80 times larger it would turn itself into a new sun and nuclear reactions would happen in its centre! It has huge clouds layers around it and has a Great Red Spot on it which scientists think is a vast cyclone storm that has lived for 400 years and is itself larger than the Earth! There are 16 moons: Metis, Adrastea, Amalthea, Thebe, Io, Europa, Ganymede, Callisto, Leda, Himalia, Lysithea, Elara, Ananke, Carme, Pasiphae and Sinope. Distance from Sun: 778,000,000km Radius: 71,350km Day length: 10 hours Length of year: 12 Earth years Gravity: 2.9 times Earth Surface temperature: average about -140 deg celsius	Saturn is the ringed planet. The rings are largely frozen water snowballs orbitting around the equator. The rings are so thin you can see through them. The planet is largely gas and light enough to float in water! The 18 moons are Pan, Atlas, Prometheus, Pandora, Epimetheus, Janus, Mimas, Enceladus, Tethys, Telesto, Calypso, Dione, Helene, Rhea, Titan, Hyperion, Lapetus and Phoebe. Distance from Sun: 1,425,000,000km Radius: 60,000km Day length: 10.7 Earth hours Length of year: 29.5 Earth years Gravity: 1.3 times Earth Surface temperature: average about -170 deg celsius
Uranus (Father of the Gods Saturn)	Neptune (God of the Sea)	Pluto
This planet is invisible to the naked eye. It was first discovered in 1781 and it rotates in a strange way: it is laying down on its side! The atmosphere is made of methane which absorbs red light and produces the green-blue colour to us. It also has faint rings similar to Saturn. It has 15 moons: Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck, Miranda, Ariel, Umbriel, Titania and Oberon. Distance from Sun: 2,867,000,000km Radius: 25,400km Day length: 16 Earth hours Length of year: 84 Earth years Gravity: 0.93 times Earth Surface temperature: average about -210 deg celsius	Neptune was discovered in 1846 based on mathematical predictions that a planet should exist at this location. Wispy methane clouds form its atmosphere. It also has a Great Dark Spot which is a huge storm that has exists for a very long time. It has 8 moons: Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Triton and Nereid. Distance from Sun: 4,486,000,000km Radius: 24,300km Day length: 16 Earth hours Length of year: 165 Earth years Gravity: 1.2 times Earth Surface temperature: average about -220 deg celsius	This planet was discovered in 1930 and it explained why Neptune went out of orbit occasionally. It is almost 6,000,000,000 km from the Sun. It is the only planet yet to be visited by a satellite fitted with a camera. It's only moon is Charon.

Celestial Sphere: The stars at night seem to revolve around us endlessly. You can see many patterns within them and we call them constellations. Many people in the past looked to the stars for guidance and to fortell the future ... they were where the Gods live. Planets differ from stars in that they cannot give off their own light but simply reflect it. Stars are the ones that "twinkle". Planets in the old Greek language means "wanderer". This celestial sphere model of the planetary system was first proposed by the Greek astronomer Ptolemy in 150 AD suggesting that all the planets and stars we see at night are all placed on the surface of a huge sphere above us that rotates around us. The apparent circular motion we observe is due to the fact that we are revolving on an axis.

Galaxies: When the modern telescope was first invented by Leonardo de Vinci we were first able to see beyond the heavens. We started to notice groups of stars with planets in orbit around them and we called the galaxies. In 1817, Edmond Halley not only discovered Halley's comet (naming it after himself) but also discovered that the stars are not all fixed in position on the celestial sphere ... they were moving.He noticed the position of the stars change very slightly relative to each other as we orbit the sun.

How did the universe begin? The most popular opinion of how our universe began was by the "Big Bang Theory". It is found that the amount of matter in outer space is spread out very thinly. There is only one atom per 2 cubic centimetres compared with 30,000,000,000,000,000,000 atoms in the air we breathe. Like other stars, our sun was formed by a cloud of collapsing gas and dust. Its core temperature eventually rose high enough for atoms to begin to join together in nuclear fussion. These constant nuclear reactions are what keeps the sun burning today. In the beginning of time it is proposed that all matter in the universe started at one spot. It then exploded in a huge exsplosion which propelled matter to all ends of the universe. Some of this matter formed the sun and planets of our solar system. The sun releases 22,000,000,000,000,000,000,000,000 Joule of energy each minute which is huge! This is enough energy to keep a light bulb burning for 100,000,000,000,000 centuries! Some stars in the universe are red shifted (they have a red tinge to them). This suggests that these stars are travelling away from us at incredible speeds ... also demonstrating proof of the Big Bang Theory.

How is a star formed? Dust and gas exist in interstellar space. When clouds of gas and dust come together due to gravity there is a point when they begin to collapse in upon themselves to form a star. They continue to collapse and get bigger and start to form a nebula as the pressure and temperatures increase. The great nebula in the constellation of Orion is a nebula big enough to be seen with a naked eye. They are like nurseries for stars!

How do stars die? After forming a star they continually use up all of their hydrogen in forming helium. This allows them to burn and stay hot and sunny like our sun. But towards the endof their life there comes a time when the amount of hydrogen runs out and there is too much helium. The size of the star at this point increases to 200 or 300 times its original size cooling as it does and forms a red giant. Our sun will do this one day expanding so large that it will swallow up our Earth! The first red giant to be discovered was Mira in the constellation Cetus (the whale). Eventually all red giant go into pulsating motion and will lead to the destruction of the star. Within a few hours the outer layers explode producing a nova (meaning "new" star). It will last a week or two before turning into a white dwarf the size of Jupiter, very dense and with a surface temperature of about 1200 degrees celsius. They eventually simply disappear from view. Much rarer and 1000 times more violent is a supernova due to the collapse of massive stars. They are seen only every 200 years from Earth.

The Milky Way: We live in the Milky Way, a galaxy of immense proportions for which we live on the edge. At night you may be able to see and hazy line across the sky which is our side on view of the Milky Way galaxy.

Space & Time Travel: Can we ever get to time travel? Einstein first looked at this in his "Special Theory of Relativity" early in 1905. This relationship gives some really strange results (for each c = 300,000,000m/s). We can only observe something happen and measure when it happened by using our eyes, ears or other senses. We can see a cricket ball being hit and say it happened exactly at this time; we could see a runner go through the finishing posts in a race and time her. But this only happens because we observe it (ie. light reflects off the batter and strikes our eye). The signal goes to the brain and we register the action of a ball being hit. We can then start our stopwatch.

But since it requires light to strike our eye ... what would happen if we were running away from the field at the speed of light? The light will never actually reach our eye! We would never actually see the event occurring! This produces a paradox called the "Twin Paradox". On the earth there are twins of identical age. If one of them got into a space ship travelled around the earth for one hour at 98% the speed of light and then returned their ages would be different according to Einstein. The twin on earth will be 5 years older than the twin on the space ship! Trips in the space shuttle have proven this to actually happen!!

It is also found that travelling close to the speed of light allows you to shrink the distance you are travelling. You can warp space and travel millions of kilometres without even knowing it.

Radius of our planets: The following table summarises the sizes of each of the planets in our Solar System:

Make a sphere of radius 1m to represent the Sun. Each of the dimensions of the other planets are above. Make circles to represent these and compare the sizes.

Rocket Science: When most people think about motors or engines, they think about rotation. For example, a reciprocating gasoline engine in a car produces rotational energy to drive the wheels. An electric motor produces rotational energy to drive a fan or spin a disk. A steam engine is used to do the same thing, as is a steam turbine and most gas turbines. Rocket engines are fundamentally different. Rocket engines are reaction engines. The basic principle driving a rocket engine is the famous Newtonian principle that "to every action there is an equal and opposite reaction." A rocket engine is throwing mass in one direction and benefiting from the reaction that occurs in the other direction as a result.

This concept of "throwing mass and benefiting from the reaction" can be hard to grasp at first, because that does not seem to be what is happening. Rocket engines seem to be about flames and noise and pressure, not "throwing things." If you have ever shot a shotgun, especially a big 12-gauge shot gun, then you know that it has a lot of "kick." That is, when you shoot the gun it "kicks" your shoulder back with a great deal of force. That kick is a reaction. A shotgun is shooting about an ounce of metal in one direction at about 700 miles per hour, and your shoulder gets hit with the reaction. If you were wearing roller skates or standing on a skateboard when you shot the gun, then the gun would be acting like a rocket engine and you would react by rolling in the opposite direction.

If you have ever seen a big fire hose spraying water, you may have noticed that it takes a lot of strength to hold the hose (sometimes you will see two or three firefighters holding the hose). The hose is acting like a rocket engine. The hose is throwing water in one direction, and the firefighters are using their strength and weight to counteract the reaction. If they were to let go of the hose, it would thrash around with tremendous force. If the firefighters were all standing on skateboards, the hose would propel them backwards at great speed!

When you blow up a balloon and let it go so that it flies all over the room before running out of air, you have created a rocket engine. In this case, what is being thrown is the air molecules inside the balloon. Many people believe that air molecules don't weigh anything, but they do (see the page on helium to get a better picture of the weight of air). When you throw them out the nozzle of a balloon, the rest of the balloon reacts in the opposite direction. Imagine the following situation: You are wearing a spacesuit and you are floating in space beside the space shuttle; you happen to have a baseball in your hand. If you throw the baseball, your body will react by moving in the opposite direction of the ball. The thing that controls the speed at which your body moves away is the weight of the baseball that you throw and the amount of acceleration that you apply to it. Mass multiplied by acceleration is force (f = m * a). Whatever force you apply to the baseball will be equalized by an identical reaction force applied to your body (m * a = m * a). So let's say that the baseball weighs 1 pound, and your body plus the space suit weighs 100 pounds. You throw the baseball away at a speed of 32 feet per second (21 mph). That is to say, you accelerate the 1-pound baseball with your arm so that it obtains a velocity of 21 mph. Your body reacts, but it weighs 100 times more than the baseball. Therefore, it moves away at one-hundredth the velocity of the baseball, or 0.32 feet per second (0.21 mph).

If you want to generate more thrust from your baseball, you have two options: increase the mass or increase the acceleration. You can throw a heavier baseball or throw a number of baseballs one after another (increasing the mass), or you can throw the baseball faster (increasing the acceleration on it). But that is all that you can do.

A rocket engine is generally throwing mass in the form of a high-pressure gas. The engine throws the mass of gas out in one direction in order to get a reaction in the opposite direction. The mass comes from the weight of the fuel that the rocket engine burns. The burning process accelerates the mass of fuel so that it comes out of the rocket nozzle at high speed. The fact that the fuel turns from a solid or liquid into a gas when it burns does not change its mass. If you burn a pound of rocket fuel, a pound of exhaust comes out the nozzle in the form of a high-temperature, high-velocity gas. The form changes, but the mass does not. The burning process accelerates the mass.

Let's learn more about thrust. Go to the website: Rockets