SENSE OF SCALE module [Chris Barrington-Leigh, 2003]: The theme / philosophy of this is that the cosmos is huge in both space and time, and that life is very local in space and human civilization is very local in time. Inhabitants on earth are sharing something special. I never taught this module as described, but rather tended to use more of a discussio nformat about the night sky. ------------------------------------- Summary: - intro : home/scales/UAS - home -> size -> Earth - neighbours: solar system : Moon - sizes and distances, Moon and Sun - motion / orbit - earth/Moon/Sun orbits -> eclipses - volunteers sit down- nearest star? shrink Solar System further - Alpha Centauri. Different way to express - Light / time / lightning - volunteers -> sound/light -> time - light from Moon, from Sun, Alpha - lightning, see past. - stars, time. - looking back at Earth. - population - unprecedented global... - hold arms out... - other life out there? we don't know of any - in fact, thin film of life. - so we came... . - ------------------------------------- Home: You know where our homes are now. You know where your home is (ask someone to show on globe). I want to talk about home. I want us to talk about what home means, and to get a feeling for hw far away different things are from our homes. We call this a sense of scale. I also want to talk about a sense of time, because our home is very old. And I'm going to talk about who our neighbours are. Let's start with the concept of home. How big is your community? [answers] Home can be as big as what you're aware of and care for. The Cosmos Ed team is all here because we think our home is big and that all of us are close neighbours. Everyone you know, ..... Earth. [[How far can you walk in a day? How far is Capetown / Joburg. My home?]] If planet Earth is home, what's nearby to home? If we wanted to visit our cosmic neighbours, where would we go? Earth's nearest neighbour? Other neighbours? Scale of solar system: if we were to shrink the solar system so that the entire Earth was the size of this globe, and everything else was scaled down by the same amount... [Volunteer to hold Earth. Team member hold moon]. moon distance: "closer or further?" -> moon keeps moving Earth is 30 cm diameter globe Moon is 7.5 cm diameter (potato) Moon is 9 m away bn 80 Sun is 30 m diameter Sun is 250 km away Space shuttle is 0.7 cm above ground [know some nearby etc towns] Do the cosmic neighbours stay still? What MAKES the Moon go around the Earth? (Throwing moon/potato into orbit) Anyone heard of the space shuttle? How high are satellites above Earth? (0.7 cm) Talk about thin film of life on Earth. (Volunteer to hold Moon, walk around Earth. Period of Moon orbit) But Earth isn't still. Volunteer to hold laminated Sun card. Stop! Lunar eclipse. Stop! Solar eclipse. December 4, 2002 R.S.A. Is the Sun standing still? Volunteers sit down. If we could now shrink the cosmos even further so that the sun was only as big as this orange/mango, etc, then the Earth would be a small pebble ... So what's the nearest star to the Earth? That was a trick question. It's the Sun. What's the next nearest? Alpha Centauri would be 3000 km away (Nairobi from Capetown). Sun=orange/mango 10 cm diameter Earth is pebble 1 mm diameter AU is 7.5 m Alpha Centauri is 3000 km away (Nairobi to Capetown) [[Possible ending here: With telescopes, we see things even further away. Life is only known here... -> end.]] This distance is so hard to think about (so hard to get intuition) because the numbers are so big that scientists use a different way to express the distance. We need to talk a little about light, and this will lead us to talk about sense of scale of times. How many people have seen lightning or heard thunder? know how they are related? One is energy in the form of sound, one in the form of light. Light and sound travel at different speeds. (Get three volunteers, use three laminated cards. Lightning raises hands to start walking sound and running light.) When lightning happens, a flash of light and a burst of sound are given off at the same time, but they travel at different speeds so you sense one before the other. For lightning 1 km away, the light takes 1/30 of one thousandth of a second and the sound takes 3 seconds. Light is very fast (not instantaneous) Using the speed of light, we can talk about very large distances by telling how long it takes light travel them. 1/8 s to the Moon, 8 seconds to the Sun, 4.3 years to the nearest star. [how far away is the nearest star?] When you hear the sound of thunder, you are hearing what happened 3 seconds ago, and when you see the flash from a lightning stroke, you're seeing the flash at almost the same time as the lightning happened, but not quite. You are seeing what happened a small fraction of a second in the past. When looking at other stars, you are seeing light that has been travelling for (4.3) years since it was emitted, and you are therefore seeing what happened in the past. So looking at distance objects in the cosmos is a way of looking back in time. [Understand? Can you also see into the future?] (Is the Sun standing still? Other stars you see at night are in the Milky Way galaxy (center is 28 kly away), which is also our home. The solar system orbits the Milky Way every 200,000 years. [Skip discussion of age of cosmos] If we were sitting on a distant star and looking at Earth, we would be seeing the Earth as it was a long time ago. 42 M people in S.A. If we looked back 12000 years, we would see only 1 million humans on the entire planet. 12000 ya: 1 M 1000 BC: 50 M 0 A.D.: 100 M 700 A.D.: 200 M 1250 A.D.: 400 M 1800: AD: 800 M 1900 AD: 1.5 B 1955 AD: 3 B : 4 B : 5 B 1999 AD: 6 B If another civilization were looking at our planet now, they would see it undergoing incredibly rapid change unlike anthing that has happened in the last 10000 years. In fact science tells us that while the human population is booming, the Earth is undergoing the biggest mass extinction of species in at least 200 million years. Does anyone think there is life out there around other stars which might be watching our home? Do we have friends in these other next-door neighbourhoods? What is life? reproduce, evlolve, energy transf, enclosed. How do we look for life elsewhere? (oxygen, water, radio, light). Does anyone thin there is life on other planets? Other solar systems? We don't know. We can see millions of stars, but there's only one planet around one star that we KNOW has life. And as compared with the age of the Earth (4By), the entire history of human civilizataion is a brief instant... armspan / fingernail width Going back to our common home planet, all the life that has ever existed has existed in a tiny layer. The entire bioshere, from the deepest ocean to the top of the atmosphere's troposphere layer, is less than 1 mm thick on our globe. We have come from all over our planet to talk about how you can look after yourself, how you can look after your ocommunity, and how you can look after our common home, the Earth. -------------------------------------- ====================================== Community development module [Chris Barrington-Leigh, 2003] This is an introduction to some economic ideas, and went by the name "globalization module". Tell everyone that the class is going to get stranded on a small deserted island. We all stand up and pretend to swim to shore. The island has some limited resources like not enough trees for everyone's wants. How shall we decide how many trees to cut down and who gets them? - Offer a simpler dilemma of two people (volunteers) choosing how many trees (sweets) to cut. Each person can either cooperate (C) or be selfish (S). The payoff matrix for this "prisoners' dilemma" is: Other Me Other Me S C 5 0 S 2 2 C C 3 3 S 0 5 Once this is clear, give the pair 20 seconds to plan, then have them stand facing aparat, think for another second, and then on the count of three show the class their choice: open hand for C, fist for S. Pay them their earned sweets, debrief them, and have them sit down. Possibly point out that if the other person is S, you maximise your reward by being S; if the other person is C, you also maximise your reward by being S. But if both follow this strategy, the total reward is *minimized*! Point out that the problem for the whole island/class is even more complex, since there are many people making the decision. If each takes just a little extra beyond their share, the resource will be depleted/destroyed, and some will go without. Solicit examples of other things on the island or in the real world which suffer from this "Tragedy of the Commons" (named after Commons grazing areas in old England). Pick up on the suggestion of fresh water as one resource. On a small island, it will be quite limited. Each day, a stream containing water will provide a certain amount of water. How to divide it up? -> Quota: split it evenly between all people. Problems: Some people don't need all of their share. Some need more due to appetite, or maybe community-benefitting projects like organising a medical clinic for the island. -> Concensus: sit around for long meetings each day deciding who needs how much. -> Price system. (Ask how things work in their own society -- e.g. distribution of food). Distribution is according means as well as need. For a price system, we might create a currency on our island (shells) earnable through work for the group. Who is to set the price? - Public ownership: price chosen by meeting, or through selection of some government/representatives. (In order to avoid the tragedy of the commons, societies make social contracts.) - Private ownership: two students in the class approach the community with a lot of money, and wish to pay everyone a one-time fee in order to own (half each) the water supply, and thus they set the price. Which is better (public/private)? Which will lead to a lower price (e.g., private due to competition; public due to lack of profit and to efficiency of single infrastructure). Which will see more water resource used? (e.g., private, due to advertising to convince people that they want more water) One day someone from another island (if have chalk, draw a tiny island for us and a huge one (or mainland) for them) comes along and offers one of the owners much money to buy their share of the water. Same happens to the other half. Identify DOMESTIC and FOREIGN private ownership. Which is better? (e.g., Domestic: owners have ties to community. Foreigners may get a better price abroad, etc. Foreign: with what did the foreign owner buy the water? Foreign currency -- useless paper on our island, but the ex-owner can now choose some foreign luxury to buy -- e.g. a nice car). Identify idea of IMPORT. Now what happens when the car breaks down or others want one? Water is already sold -- cannot sell it again. Part of the community begins to put their resources and efforts towards making something that is not for our community -- e.g. seashell art. EXPORT. (Maybe food is easier to make in the foreign country, and we can buy food to feed those who are now specialising in making shell art.) Now what happens when another begins making carved shells, and sells them for less? Given that we are a small island trading with a large one, how much control do we have over the price of our exported shells or our imported food? What happens when the food becomes too expensive, and most of our people know only how to make shells? What kind of pressures (economic, political) might we be subject to from the big country? Open up for discussion, especially in the context of the local country's economy. Concluding items: 1) There can be a tradeoff between SELF-SUFFICIENCY / STABILITY of one's economy and RAPID DEVELOPMENT or increase of wealth -- i.e., acquisition of foreign goods quickly in exchange for control etc. 2) Fresh water ownership and control will be one of the biggest issues in international relations in next decades. Fresh water is running out almost everywhere; wars, wealth + poverty of nations will rest on it. Those who train in water science will have important careers. 3) Subject we treated today is part of economics. This field needs more scientific (critical, questioning) minds in it. It needs more African scientific minds because these questions we've dealt with don't have simple answers. The answers this country chooses must come from its own people. I am encouraging some of you who find this topic intersting to pursue economics, but with this (strange) warning: be skeptical of what you are told. There are people on the big island who think they already have the answers for the little island, and they might sell them as truth. (Lastly, history is the real place to look for how these decisions affect a country's future.) Vision - gray gradient disappearing; two gray squares same darkness: objective reality, and what we perceive. - science aims get at this objective reality. Does so by taking things apart and understanding hw the pieces work, and fit together. e.g.: vision... some processing in eye, some in visual cortex, some elsewhere. - electrical signals. - learn how to make things: lenses in eye -> glasses, telescopes. Neurons -> circuits, computers. Retina -> video cameras, computer vision. Also, RGB-> displays. Muscles --> motors, twitching fibres. - technology often works to take on human jobs. Sometimes mimics nature. So goals to build smarter robots / machines. - measure speed of neurons in a circle. - make a neural network: R, G, B cells: yellow with dendrites on both R and G... - colour wheel. new outlne: - RGB colours. - colour wheel - inverse colours - neurons, RGB network. - another layer of cells that deal with motion; explain waterfall. - do spiral wheel.