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A WALK THROUGH THE SOLAR SYSTEM or SPACE IS FAR OUT by Mike Roach This material has been written by Mike Roach with reference to information from various astronomical sites and Educational material available from NASA and ESA. These days we are surrounded by knowledge via the internet. Only a few years ago students looked at text book versions of the Solar System which gave a distorted picture of the enormous distances between planets. Lately they can visit Video Clips from You Tube, watch TV programs and simulations to take them on a more exciting journey. Many modern computer simulations and videos allow us to capture a glimpse of what it would be like to travel in our Solar System, and even further, within our Galaxy the Milky Way, to other stars, just like our sun, but none have the capacity to show the gigantic scale of our Universe. This simple activity will do more to impress on your students the remarkable engineering and scientific progress that has taken place over recent years than any other I have seen. Taking these small steps will enable your students to cope with the flood of information available and lead them on a path to understanding Our Place in Space. As you walk your students through the Solar System, many questions will be forthcoming, but as this should be an introductory activity, you will not need to answer all of the questions now. They can form the basis of a learning programme which will generate wonder and amazement within your students as they try to satisfy their genuine thirst for knowledge in this fascinating topic area. Even the most knowledgeable of astronomers and astrophysicists do not have all the answers, so this puts the humble science teacher in very good company. LESSON FOCUS Teachers should pace out distances (only approximately) prior to the lesson and paste up planets to at least include Saturn although I have provided the rest. Although the students will have many questions the teacher should not attempt to answer all of them, and it is important that the walk is completed with plenty of time to hand out the Worksheet for students. The table should be photocopied and handed out to students. Suggested year levels: 6 - 10 TO THE TEACHER: PREPARATION: The lesson is most successful if you prepare your walk in advance by pasting the planets at the appropriate distances on the insides of windows somewhere in your building complex. Note that you can stop after Saturn, and simply double, triple and quadruple the distance you have walked. This is effective enough, but you may have the time and inclination to take your class the whole way. If you can leave the planets up for some time, you will observe many students looking at the information contained and those who are not in your class puzzling at why the planet is on show at this particular place. You may also have posters of the various planets, and spacecraft that have visited them, or flown by, which you could post near each planet station. INSTRUCTIONS TO SET UP "THE WALK" 1. The cards are in a separate document called Walk the Planets. Display the SUN at one end of a long corridor or on a window at the start of your walk. 2. Draw in box provided the diameters of the planets\ 3. Pace out the distances (no need for too much accuracy on this scale) 4. When you look at the distances involved you will probably want to stop at SATURN. This is fine since (very approximately) you can say that Uranus is twice as far from this point, Neptune three times and Pluto four times. 5. There is a complete set of these stations available in the attachments. A WALK THROUGH THE SOLAR SYSTEM Compare the size of the planet and it's distance away to our Sun. The Sun is 109 mm in diameter. HERE IS THE PLANET ......................................... DISTANCE from Sun OBJECT DIAMETER (Size) Sun 109mm Mercury 0.33 mm 5m Venus 1 mm 8.5 m Earth 1 mm 12 m Mars 0.5 mm 18 m Jupiter 11 mm 62 m Saturn 9 mm 114 m Uranus 4.0 mm 230 m Neptune 3.9 mm 360 m Pluto (at maximum orbit) 0.25 mm 480 m Proxima Centauri (pointer) 120 mm 3,200 kilometres Sirius (the brightest star) 20 mm 6,500 kilometres ADDITIONAL NOTES FOR THE TEACHER Once the students have some idea of the immense scale of our own Solar System, it seems appropriate to mention the hundreds of billions of stars that make up our Galaxy, the Milky Way, and then the hundreds of thousands of Galaxies that exist in our Universe. After the students have completed the "Walk" (you may be at Saturn or even Pluto, if you are adventurous) ask them to guess where the closest star (sun) is to our own Sun on the scale that we have been walking. Guesses come in thick and fast, but few believe that you would have to walk across Australia to reach Proxima Centauri, actually a part of a three sun solar system, which appears conveniently each night as one of the pointers to the Southern Cross. Now it is time to move to the scale of light years, as the students begin to appreciate the gigantic scale we will be operating in. I normally start back on Earth, and tell the students that light travels very fast, in fact nothing travels faster, at 300,000 km/sec. If I was to go to the moon and flash a torch back towards Earth it would take 1.3 seconds for the light to reach us. If I was to go to the Sun (which I really could not without burning up) and flash my torch, the light would take 8.5 minutes to get back. e would still have to wait three months to see the explosion! Now you have their attention, a poster of the Southern Cross against a background of stars, and a composite picture of a Galaxy like ours (as was published in Sky & Space Magazine in 1994) is useful, as you talk about the other pointer being 120 light years away, and our sun being just one of the billions in our Milky Way Galaxy, about two thirds of the way out from the centre, on one of the spiral arms. Light takes 100,000 years to cross our Galaxy. Paul Davies once stated in a lecture a useful observation that impressed me, and which fits in here quite well, regarding the chance of E.T. encounters. On Earth we have only been putting out radio signals for 100 years since Marconi started us off. Even if there were ET beings, they would have to be within 100 light years to detect us, and that does not take in much of our Galaxy, let alone the Universe. If the students are not feeling insignificant on the grand scale by now, they will once you begin to talk about our neighbouring galaxies, the Small Magellanic Cloud about 100,000 light years away) and the Large Magellanic Cloud (about 300,000 light years away), each containing billions of stars just like our own Milky Way. Both of these neighbouring galaxies are conveniently visible in our night skies, near the Southern Cross. And these are just two of an estimated 200 billion galaxies in our expanding Universe! A WALK THROUGH THE SOLAR SYSTEM or SPACE IS FAR OUT! INTRODUCTION FOR STUDENTS Ancient astronomers observed points of light that appeared to move among the stars, and they called these objects planets, meaning wanderers. They were named after Roman legends. Jupiter was the king of the gods, Mars the god of war, Mercury was messenger of the gods, Venus was the god of beauty, and Saturn (father of Jupiter), was the god of agriculture. They also observed comets with brilliant tails, and meteors or shooting stars falling from the sky. Science moved ahead slowly, and in 1610 Galileo studied and reported on the moons of Jupiter, with his telescope fashioned for this purpose. Your binoculars are as powerful as Galileo's telescope was back then, and you will easily be able to see the four major moons of Jupiter on a clear night when Jupiter is in the sky. In 1684 Sir Isaac Newton framed the Law of Universal Gravitation which explained very simply all of Kepler's observations of planetary motion. Astronomers continued to look to the skies with better optical telescopes, but it was not until about 1959 when advancements in rocketry after World War II allowed us to break free of the Earth's gravity and travel to the Moon and other planets that we entered the golden age of exploration of our Solar System. The U.S.A. and Russia sent automated spacecraft to the Moon, and eventually in July 1969 man set foot on the Moon. Automated spacecraft have orbited and landed on Venus and Mars, explored the Sun's environment, observed comets, and made close surveys while flying by Mercury, Jupiter, Saturn, Uranus and Neptune. These marvels of engineering have enabled us to better understand the Solar system. Through electronic sensors automated spacecraft have bought colour and complexion to planets that for centuries were observed from Earth as fuzzy points of light. With the launch of the Hubble Space Telescope (HST) in 1990,( and the subsequent repairs necessary to correct the lenses in 1993) scientists are now able to gaze way out into our Solar System and beyond without having to peer through the Earth's atmosphere. The Hubble Space Telescope is now able to be turned to look at any major event in the Solar System, or the Universe, to give us a first hand, uninterrupted view. The Shoemaker-Levy 9 comet impact with Jupiter was one such event that awarded scientists views not dreamt of ten years ago. Not only was the HST able to be pointed towards Jupiter for a look at the impact, but Galileo was also on its way to Jupiter and took some spectacular pictures. The knowledge gained from our journeys through the Solar System has redefined traditional Earth sciences like geology and meteorology, and given rise to new disciplines like comparative planetology. By studying the geology of planets, asteroids and comets, and comparing differences and similarities, we will learn more about the origin and history of these bodies, and the solar system as a whole. ANSWER THESE QUESTIONS 1.(a) The Earth is approximately 12, 800 km in diameter. The size (diameter) of the Moon ( approx 3,200 km in diameter) compared to the Earth. How large in diameter on our scale? (b) The Moon is approximately 400,000 km away from the Earth. Our Solar Scale has the Earth as 1mm diameter, and this represents 12,800 km. How far away is the Moon from Earth on our scale? 2.It took three days for Apollo 11 to reach the Moon in 1969. If we still had the technology available, how long would it take to reach Mars? 3.We wouldn't like Venus, and in fact many craft have already been sacrificed to this awful planet, so where else might we travel in the Solar System? (a) Mercury? Discuss (b) Jupiter? Discuss (c) Others? 4. It takes light 8.5 minutes to reach Earth from the Sun, even though light travels at 300,000 Km per second. We call this distance 8.5 light minutes. (a)How many light minutes is Jupiter from the Sun? (b)Pluto is at the outer most part of our Solar System. How many light minutes is Pluto from the Sun? (c)Now use the scale to work out how far away in light years is our nearest neighbouring solar system containing Proxima Centauri. (This Solar System contains three suns Proxima Centauri and Alpha Centauri A and B. From Earth this system looks like one star and is one of the Pointers to the Southern Cross.) 5. Some people remember the planets by using this saying: MY VERY ENERGETIC MONKEY JUST SHOWED US NINE PLANETS List the planets in order from the Sun. Special Note: Pluto is no longer considered a planet so the acronym is no longer valid. However it does open up a whole new discussion as to why that decision was made. A GUIDE FOR TEACHERS ON THE WORKSHEET FOR STUDENTS: "A WALK THROUGH THE SOLAR SYSTEM......FURTHER EXCURSIONS" The accuracy of the mathematics here should not be the most important feature. Approximations can readily be made on this gigantic scale! The students will find these distances and times impressive, and all the questions are intended to emphasise this. Teachers might point out the amazing achievements that humans have made since the Wright Brothers first took to the sky less than 100 years ago (1903). What might the next hundred years bring?? (The real distances are: Diameter of Earth 12,760 km. Moon Diameter is 3,476 km and the distance of the Earth to the Moon is 384,000 km. but approximates will be easier) We have more questions and answers if required, but these should keep the class busy. ANSWERS TO QUESTIONS 1.(a) The Earth is approximately 12, 800 km in diameter. The size (diameter) of the Moon ( approx 3,200 km in diameter) compared to the Earth. How large in diameter on our scale? Using these approximate diameters we need to divide 12,800 by 3200 . This gives 0.25 and since the Earth is 1mm on our scale then the moon will be 0.25 mm. (b) The Moon is approximately 400,000 km away from the Earth. Our Solar Scale has the Earth as 1mm diameter, and this represents 12,800 km. How far away is the Moon from Earth on our scale? If each 1 mm (Earth diameter) is really 12,800 km, then we simply need to find out how many lots of 12,800 divide into 400,000. Answer is approx. 31. So it is 31 mm away. 2.It took three days for Apollo 11 to reach the Moon in 1969. If we still had the technology available, how long would it take to reach Mars? We worked out in question 1 (b) that the moon is approx 31 mm away from Earth, and since 31 mm is close to 33 mm ( about one thirtieth of a metre), then it would have taken 3 days to travel about one thirtieth of a metre. That means each metre takes 30x3=90 days to cover. Now on the scale Mars is 6 metres further from the Sun than Earth, so there are 6 times 90 days of travel which comes to 540 days, or approximately 1.5 years. Of course lighter craft can achieve higher speeds and the spacecraft can reach Mars in less than a year. We need to wait for the 365 day orbit of Earth to line up with the 687 day orbit of Mars, so that we cover the least possible distance in space. This opportunity occurs about every 26 months. 3.We wouldn't like Venus, and in fact many craft have already been sacrificed to this awful planet, so where else might we travel in the Solar System? (a) Mercury? Discuss (b) Jupiter? Discuss (c) Others? Students should consider things like size, distance from the Earth (and from the Sun), temperatures, atmospheres, whether the planet has a solid surface etc. All of this can be researched readily through Computer Software, the Internet or the library. 4.It takes light 8.5 minutes to reach Earth from the Sun, even though light travels at 300,000 Km per second. We call this distance 8.5 light minutes. (a)How many light minutes is Jupiter from the Sun? If light reaches us in 8.5 minutes from the Sun, ( we are 12m away on our Scale of the Solar System) and Jupiter is about 60 metres (really 62m) then since Jupiter is 5 lots of 12(=60) then 5 times 8.5 minutes =42.5 minutes. That is 42.5 light minutes. (b)Pluto is at the outer most part of our Solar System. How many light minutes is Pluto from the Sun? 480 divided by 12 gives 40 times the Earth's orbit. Multiply 40 by 8.5 minutes equals 340 light minutes, or 5 hours and 40 minutes. (c)Now use the scale to work out how far away in light years is our nearest neighbouring solar system containing Proxima Centauri. (This Solar System contains three suns Proxima Centauri and Alpha Centauri A and B. From Earth this system looks like one star and is one of the Pointers to the Southern Cross.) Divide 3200 by 12 to find out the number of lots of 8.5 minutes we have to multiply by. This comes to approximately 4.3 light years. Now think about that! Light leaves our Sun and passes Earth 8.5 minutes later, leaves the Solar System at Pluto after only 5.5 hours, but will not encounter another thing for another 4.3 years. Wouldn't that be a boring trip?? 5. Some people remember the planets by using this saying: MY VERY ENERGETIC MONKEY JUST SHOWED US NINE PLANETS List the planets in order from the Sun. EXTENSION QUESTION Use the Internet, library or other sources to find out which spacecraft have visited other planets, from which country they came, how many have landed and what each mission found out!