It all started with the Science in Society This resource is part of the Forward Thinking project. For more information visit: www.ulster.ac.uk/scienceinsociety/ BIG BANG 13.7 BILLION YEARS AGO Space and time began when the infinitely small, dense universe began to expand. The universe has been getting larger and cooler ever since. How will it end? With a big crunch or expansion and cooling forever? No-one knows. OBJECTIVES To describe the characteristics of a good theory; To explain the evidence that supports the Big Bang theory; and To generate questions for enquiry. STARTER Bring a helium balloon to class and show that it will float when you let go of the string. Present the class with several theories that claim to explain why the helium balloon floats (see supporting floor cards, page 2). Read the theories together and ask students to discuss in pairs which they think is the best theory, and explain to each other their reason why. Stress STIMULUS The stimulus for this discussion is The Big Bang Theory theme tune by The Barenaked Ladies (available on iTunes, lyrics provided on page 2). A supporting video can be made in iMovie, to include information on three pieces of evidence that are used to support the Big Bang theory: the redshift of distant galaxies, the cosmic microwave background radiation, and the composition of the universe. Further ideas for demonstrations and models that may be incorporated in the video are found on page 3. REFLECTING ON THE ENQUIRY KSU: ask students to reflect on the Hydrogen: the most abundant element in the universe. that we are interested in what makes it a good knowledge they have gained, the skills they theory, rather than which is “correct”. Ask have used to gain it, and what they now everyone to stand next to the card that they understand better. Write these on an exit think is the best theory, and try to convince ticket to be handed in as they leave the others to move. Ideas that may be drawn out classroom (see page 2). universe. More able students can be asked are that theories help to explain the world, are NEXT STEPS to scale this to an Earth year. supported by observations, are generalizable, useful and don’t involve contradictions. They may be asked to refer back to these characteristics when they understand the Big Bang theory This lesson can be followed up by: a) Asking students to find out what the Large Hadron Collider at CERN is doing to help us understand the universe. The Forward Thinking project is funded by the Wellcome Trust [1] b) Creating a cartoon timeline for our c) Exploring the similarities and differences between the Big Bang theory and other theories, e.g. evolution. Focus on their qualities as theories. www.ulster.ac.uk/scienceinsociety/ Print the cards below, or copy them on to A4 pages. Place them on the floor and ask students to stand beside the card that represents the best theory. Some bir thday balloons float in the air. Here are six theories to explain why they float. Which is the best theory and why? It does not matter if you do not know which theory is correct! The foil on these balloons is a metal. This metal is magnetically attracted to the sun. The balloons are less dense than air. Less dense objects float in more dense fluids. These balloons are special. There is a force produced in the ribbon that acts to push the balloon up. These balloons have a property called levity. Anything that contains “levity” floats. The balloons are sprinkled with magic dust. Exit Ticket Knowledge I have gained Skills I have used What I understand better Something I still want to know... The Forward Thinking project is funded by the Wellcome Trust [2] BIG BANG THEORY Barenaked Ladies Our whole universe was in a hot dense state, Then nearly fourteen billion years ago expansion started. Wait... The Earth began to cool, The autotrophs began to drool, Neanderthals developed tools, We built a wall (we built the pyramids), Math, science, history, unraveling the mysteries, That all started with the big bang! Since the dawn of man is really not that long, As every galaxy was formed in less time than it takes to sing this song. A fraction of a second and the elements were made. The bipeds stood up straight, The dinosaurs all met their fate, They tried to leap but they were late and they all died (they froze their asses off) The oceans and pangea See ya, wouldn't wanna be ya Set in motion by the same big bang! It all started with the big bang! It's expanding ever outward but one day It will cause the stars to go the other way, Collapsing ever inward, we won't be here, it wont be hurt Our best and brightest figure that it'll make an even bigger bang! Australopithecus would really have been sick of us Debating out while here they're catching deer (we're catching viruses) Religion or astronomy, Encarta, Deuteronomy It all started with the big bang! Music and mythology, Einstein and astrology It all started with the big bang! It all started with the big BANG! www.ulster.ac.uk/scienceinsociety/ EVIDENCE FOR THE BIG BANG 1 2 Red shift of light from distant galaxies The Cosmic Microwave Background Radiation The composition of the universe 3 Visit the online Big Bang Time Machine at http://resources.schoolscience.co.uk/PPARC/bang/bang.htm 1 When we look at all the colours of light coming from space), students can see that the waves get longer, i.e. are red stars like the sun, we notice that some colours are shifted. Students can then identify the limitations of the model. missing, and in their place are dark “absorption lines.” These colours are missing because atoms in the star are absorbing these colours. Atoms of different elements 2 absorb different colours (or wavelengths of light), so we can tell The cosmic microwave background radiation was discovered when two scientists (Penzias and Wilson) were trying to get rid of interference to satellite which elements are present in a star from the position of the broadcasts. They detected microwaves from all areas of lines. They look a bit like a bar code. However, when we look at these “bar codes” of distant the sky, with a temperature of 2.7K (we can see this interference galaxies, we see the same pattern of lines, but shifted towards as the snow pattern on untuned televisions). This discovery the red end of the spectrum. This is an example of the Doppler supported the theory of the Big Bang, which could account for shift (the same effect that causes ambulance sirens to change these microwaves as energy left over from the Big Bang. pitch as they pass). This can be modeled by drawing Red light ➙ longer waves a wave on a long, thick 3 elastic band or length represent an Blue light ➙ shorter waves absorption lines from distant star: red-shifted observer on Earth (holding one end of the band) and another to represent a distant galaxy. As they move apart (to demonstrate the expansion of The Forward Thinking project is funded by the Wellcome Trust theory is the composition of the universe. The Big Bang theory predicts that in the first few minutes of of latex and asking one student to A third piece of evidence to support the Big Bang the universe, only the lightest elements, hydrogen and helium, were formed. This is consistent with what we observe today: the universe is mainly hydrogen (about 73%) and helium (25%), with heavier elements created in stars and in supernova explosions since the Big Bang. However, a mystery remains. Between 90 - 99% of the universe is unknown but scientists are currently looking for this “dark matter” and “dark energy”. [3] www.ulster.ac.uk/scienceinsociety/