Physics The Big Bang: New light on an old theory This lesson explores the evidence for the Big Bang theory of the origin of the Universe. In it, you will learn about the following: • Using the electromagnetic spectrum (EMS) to define radiation. • The Big Bang origin of the Universe theory. • What is the cosmic microwave background and how does this support the Big Bang theory? • Universe or Multiverse? Get ready for extragalactic time travel as we squeeze and bend our way through this space-time lesson. This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmosforschools.com Introduction: The Big Bang (P1) Scientists say they have just made a discovery that will help explain how our Universe began. If they are right, it could be the biggest, most exciting event in physics ever. Looking through a telescope into the clear skies over the South Pole, scientists spotted what they say is evidence of gravitational waves, or ripples in space-time, from the split second after the birth of the Universe – what scientists call the Big Bang. What’s got everyone so excited by this is that Albert Einstein predicted the existence of gravitational waves when he described how space and time were related and could be bent by huge forces of gravity. What the scientists at the South Pole think they saw was not gravitational waves – they would be invisible – but the effect of the waves on the light left over from the Big Bang. The gravitational waves make some patches of space a little warmer than others, which polarises light waves that pass through. Polarisation is when light waves vibrate in one direction more than others and that has made a pattern detected in the cosmic microwave background. It’s like looking back 13.7 billion years into the past when the baby universe was like a “hot seething soup”. For the first 380,000 years no light could escape but finally the universe expanded enough so it could. Paul Davies, the famous physicist who wrote the Cosmos magazine story, says that if the discovery is proven it will give us a new way of looking at our universe. He says it might also help to explain whether there was something before the Big Bang or just nothing. Even more excitingly, he says it could explain whether our universe is the only one or if there are many other universes out there. Read or listen to the full Cosmos magazine article here. Left: The Ancient Greek astronomer Hipparchus was very much a star gazer. Right: German-born theoretical physicist Albert Einstein (1879 - 1955) at home in Princeton, New Jersey, 1944. Credits: Ann Ronan Pictures / Print Collector / Getty Images and Popperfoto / Getty Images. Question 1 Imagine: You are from an ancient civilisation. When you look up at the night sky, what is the story your tribe uses to explain the stars and the origin of the Universe? Question 2 Construct: Use the table below to organise your thoughts about the Big Bang theory, cosmic microwave background radiation, gravitational waves and inflation. At this stage of the lesson, use the first two columns: 'K' What I already know, 'W' What I want to know and leave the 'L' column - what I learned - until the end of the lesson. This is quite a complicated topic, yet one that many of you may have a fascination with and quite a store of knowledge about; so don't worry if you know a lot or nothing at all, this table helps identify that and therefore help personalise future tasks. K W L What I know What I want to know What I learned Write what you already know about this topic in In this column what you would like to After completing the lesson, write this column now before starting the lesson. know about this topic. down what you learned in this column. Gather: The Big Bang (P1) Loading Credit: MinutePhysics / YouTube. Question 1 Question 2 Light detected now as cosmic microwave background originated Remember: CMB is the acronym used by scientists for Cosmic from the Big Bang when the Universe was only around 380 000 Microwave Background. years old. True True False False Light-years is a unit of measurement used to express immense distances, such as those between stars and galaxies. It is often mistaken for a measurement of time. By definition, one light-year is the distance that light travels in a vacuum in one year. (Space is considered to be a vacuum.) Question 3 Calculate: ​Both the video and the Cosmos article explain how light from the cosmic microwave background (CMB) originated from the first light escaping the thick, dense, early Universe. In space, light travels at 3.00 x 108 m.s -1. Use this speed to calculate the distance travelled by light (in metres) in one year. Question 4 You may optionally upload a photo of your working out for Question 3 ​below. Drag and drop file here Question 5 Extrapolate: The tiny fluctuations in temperature between hotter and cooler spots in the CMB were only different by 0.001%. So if the mean temperature of the CMB was 2.725000 K, or -270.425 oC, what were the maximum and minimum observed temperatures? Give your answer in both Kelvin and degrees Celsius. Hint: You will need to use more significant figures than appropriate to answer this question. Unit of measurement Mean temperature of CMB Minimum temperature of Maximum temperature of CMB CMB Kelvin (K) 2.72500 Degrees Celsius (o C) 270.425 Question 6 Recall: Cosmic Background Radiation has been used to date our Universe to approximately: 6 thousand years old 13.7 million years old 13.7 billion years old cannot be concluded Question 7 Recall: The Cosmos article describes the baby universe as a "hot, seething soup". In the first 380 000 years from the beginning of the Universe light was unable to escape the extremely hot, very dense, smooth environment that existed. However, as the young Universe expanded, eventually light was able to escape this environment and the Universe became transparent because of which of the following? The concentration of energy within regions of the Universe was dispersing. Electrons and protons had insufficient energy to resist their electrostatic attraction and formed hydrogen atoms. There were fewer free electrons to interact and scatter the light. All of the above. Light from the Big Bang originally had the frequency and colour of white sunlight, but after years of travel has stretched (or been red shifted) to microwaves measured on the cosmic microwave background. Look at the electromagnetic spectrum below. Question 8 Identify: Use the electromagnetic spectrum (EMS) above to identify the frequency and wavelength of light as it was over 13.7 billion years ago (when it was in the visible light section of the EMS) and of cosmic microwave background. Hint: Remember to include appropriate units in your answers. Light as it was 13.7 billion years ago Cosmic microwave background Frequency Wavelength Question 9 List: The tiny temperature fluctuations evident in the CMB coalesced over time through the process of gravitational attraction to form the massive structures in the Universe today. Using the information in the MinutePhysics clip and any knowledge you already have, list the types of 'massive structures' contained within our Universe in order of ascending size, so from smallest to largest. Process: The Big Bang (P1) Loading Question 1 Hypothesise: In the MinutePhysics clip in Gather (dated June 7, 2012) the estimated age of the Universe was 13.7 billion years. In the Cosmos article (31 March 2014) and this clip (19 March 2014), the estimated age of the Universe has now 'increased' by 100 million years to 13.8 billion years. Can you think of reasons why there has been a change? BICEP2 operated from January 2010 until December 2012. The Keck Array of telescopes took over from BICEP2 in January 2013. The original data was received by BICEP2 and confirmed from the KECK Array data. The telescopes are located in Antarctica where the atmosphere is thin and dry. The first evidence of gravitational waves was discovered two years before the announcement in March 2014. Question 2 Infer: Can you infer why Antarctica was chosen as the best site for locating these telescopes and also suggest reasons why there was a two year delay in making such a significant scientific announcement? Question 3 Design: Create a mind map below to organise the concepts from the Cosmos article and the two MinutePhysics clips. Your mind map should encompass the Big Bang theory of origin of the Universe, the evidence to support it (cosmic microwave background and gravitational waves) and tools used in the interpretation (polarisation of light, the electromagnetic spectrum). You should add any other links or concepts of which you are aware that were also referenced in the Cosmos article, (Einstein's theory of General Relativity, Guth's theory of inflation and the acceleration of expansion of the Universe). Big Bang Apply: The Big Bang (P2) Research task: Choose your own cosmic adventure Getting your head around the history of the Universe can leave you in a spin. Let's explore some of the fun facts of this epic story. Fun fact #1 – At the time of the Big Bang, 13.8 billion years ago, the Universe (that is, everything) was infinitesimally small. Fun fact #2 – After the period known as inflation, the most rapid expansion that the Universe has undergone, the Universe was just 10 cm wide, roughly the size of a grapefruit.