--- title: "How did the universe begin?" subtitle: "Year 10 Earth and space · The big bang · Lesson 1" --- # How did the universe begin? **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** The hydrogen nuclei in the water you drink were made in the first minutes of the universe. The carbon in you was made inside stars. :::teacher-note **In one sentence:** Students describe the big bang as the origin of space, time and matter about 13.8 billion years ago and outline the main stages as the universe expanded and cooled (AC9S10U03, node 2, a hinge node). **Students should be able to say:** I can describe what the big bang theory says. I can outline at least three stages from the big bang to galaxies. I can explain that the universe has been expanding and cooling. **Width:** the unmarked parts are the floor every student does (Engage, Explore, Explain, Evaluate). Typical and Wider sections add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Engage :::keep-together **What does the big bang theory say happened?** ☐ A huge explosion at one point in empty space, throwing matter outwards ☐ Stars collided to make the universe ☐ Space, time and matter began together in a hot, dense state, and space itself has been expanding ever since ☐ The universe has always looked the way it does now My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** Space, time and matter began together, extremely hot and dense, and space itself has been expanding and cooling ever since. There was no empty space for it to explode into, and there is no centre. ::: ## Explore Try it on the board in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Explain: the model :::keep-together ### Order **Put the stages of the universe in order.** A. `The first stars` B. `Protons and neutrons form` C. `The first atoms; light set free` D. `The sun and Earth form` E. `The first nuclei (hydrogen and helium)` F. `The big bang: space and time begin` G. `Galaxies` H. `Inflation` Correct order (letters): {{field-24}} ::: :::teacher-note **Answer:** see the program below ```science The big bang: space and time begin Inflation Protons and neutrons form The first nuclei (hydrogen and helium) The first atoms; light set free The first stars Galaxies The sun and Earth form ``` ::: :::keep-together ### Atoms **Why could atoms only form after about 380 000 years?** ☐ Gravity was too weak ☐ There were no electrons ☐ Stars hadn't made them yet ☐ Before then the universe was too hot: electrons moved too fast to stay attached to nuclei ::: :::teacher-note **Answer:** Before then the universe was too hot: electrons moved too fast to stay attached to nuclei ::: :::keep-together ### Your atoms **Where did the carbon and oxygen in your body come from?** ☐ Made on Earth ☐ Made inside stars and spread by supernovae, long after the big bang ☐ Made in the first three minutes ☐ They have always existed ::: :::teacher-note **Answer:** Made inside stars and spread by supernovae, long after the big bang ::: :::keep-together ### Expanding and cooling **About how long ago did the big bang happen, and what has the universe been doing since?** ☐ About 13.8 billion years ago; it has been expanding and heating up ☐ About 13.8 billion years ago; it expanded at first and has stayed the same size since the galaxies formed ☐ About 4.6 billion years ago; it has been expanding and cooling ever since ☐ About 13.8 billion years ago; it has been expanding and cooling ever since ::: :::teacher-note **Answer:** About 13.8 billion years ago; it has been expanding and cooling ever since ::: :::typical ## Elaborate: stars as element factories :::keep-together **The very first stars were made of hydrogen and helium only. The sun also contains carbon, oxygen and iron. What does that tell us?** ☐ The sun is older than the first stars ☐ Carbon was made in the big bang ☐ The sun formed from material that earlier stars had made and spread out ☐ The sun has already made its own carbon, oxygen and iron by fusion ::: :::teacher-note **Answer:** The sun formed from material that earlier stars had made and spread out ::: ::: :::wider ## Elaborate: open questions :::keep-together **Measurements show the universe's expansion is speeding up, and galaxies hold far more mass than we can see. How do scientists treat these findings?** ☐ They throw out the big bang theory ☐ They prove the universe is shrinking ☐ They add new ideas (dark energy, dark matter) to the model and test them with new observations, from telescopes such as ASKAP in Western Australia ☐ They ignore them ::: :::teacher-note **Answer:** They add new ideas (dark energy, dark matter) to the model and test them with new observations, from telescopes such as ASKAP in Western Australia ::: ::: ## Evaluate: look back Write one sentence: "At first I thought… Now I think… because…" **Revision summary** - The **big bang theory**: space, time, matter and energy began about **13.8 billion years ago**, extremely hot and dense; the universe has been **expanding and cooling** ever since. - Stages: inflation → protons and neutrons → hydrogen and helium nuclei (3 min) → atoms and free light (380 000 years) → first stars (about 200 million years) → galaxies → the sun and Earth (9.2 billion years). - Heavier elements were made **in stars**. ## Exit ticket :::keep-together **Outline three stages of the universe after the big bang.** {{lines-3}} ::: :::teacher-note **Answer:** For example: the first nuclei of hydrogen and helium (3 minutes), atoms forming and light set free (380 000 years), the first stars (about 200 million years), galaxies (about 1 billion years). :::