HOW AND WHY DO INDIVIDUALS CHANGE THEIR MINDS? 2 THE BIG BANG HOW AND WHY DO INDIVIDUALS CHANGE THEIR MINDS?

THE BIG BANG UNIT 2 UNIT 2 BASICS Unit 2 Overview 4 Unit 2 Learning Outcomes Unit 2 Lessons Unit 2 Key Concepts LOOKING BACK 8 What Happened in Unit 1? KEY CONTENT 10 How Did Our View of the Universe Change? 11 Ptolemy, Brahe, Copernicus, and Galileo 12 Newton, Leavitt, and Hubble 13 A Big History of Everything Threshold 1: The Big Bang Threshold 1 Card Questions About the Big Bang Electromagnetism Approaches to Knowledge How Do We Decide What to Believe? LOOKING AHEAD 22 What’s Next in Unit 3? BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

UNIT 2 OVERVIEW Key Disciplines: Astrophysics and cosmology Timespan: Roughly 13.8 – 13.4 billion years ago Driving Question: How and why do individuals change their minds? Threshold for this Unit: Threshold 1: The Big Bang BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

UNIT 2 LEARNING OUTCOMES By the end of Unit 2, students should be able to: Explain the basics of the Big Bang theory and the primary evidence that supports this theory. Using evidence from texts, explain why views of the Universe have changed over time and the roles that scientists played in shaping our understanding of the origin of the Universe. Understand how to use claim testing to evaluate a claim or resource. BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

UNIT 2 LESSONS 2.0 How Did Our View of the Universe Change? How did our ideas that all the planets in our solar system revolve around the sun and the Universe is expanding develop? Scientific theories change as better observations and new experiments provide new insights into accepted beliefs. 2.1 The Big Bang The Big Bang is where Big History begins. Everything that’s ever existed – including you – traces back to this unimaginably profound event. 2.2 Claim Testing How do you know what to believe? If you read it on the Internet, does it have to be true? How about something your doctor tells you? Claim testing helps us assess the trustworthiness of information. BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

UNIT 2 KEY CONCEPTS astronomy helium atom hydrogen authority inflation Big Bang intuition Cepheid light-year claim logic claim testing matter collective learning nucleus (atomic) Cosmic Microwave Background (CMB) neutron parallax cosmology proton Doppler effect redshift electromagnetism scientific method electron space-time energy telescope evidence thermodynamics (first law of) gravity BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

LOOKING BACK

WHAT HAPPENED IN UNIT 1? Unit 1 introduced the Big History course and shared four main themes: Big History, scale, origin stories, and thresholds of increasing complexity. Big History tells the 13.8-billion-year story of the Universe. Big History is so big that in order to talk about it, we need to use measurements on an entirely different scale from the ones we use everyday. All communities have created origin stories to answer important questions about life and the Universe. Big History is a modern, scientific origin story told by a global community. Thresholds of complexity are a foundation of Big History: they’re fragile, diverse, precise, and they led to entirely new things in the Universe. BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

KEY CONTENT

HOW DID OUR VIEW OF THE UNIVERSE CHANGE? Video Talk / David Christian The ancient Greek thinker Ptolemy proposed a view of the Universe which was dominant in Europe for more than 1,000 years. Ptolemy’s Universe consisted of six planets, the Moon, and the Sun that moved in circular orbits around the Earth. Over time, human observations of the planets and stars became more precise and led some scientists to suggest alternative theories. Copernicus, Kepler, and Galileo contributed to a new view that put the Sun at the center of the Universe, with the Earth moving around it in an elliptical (rather than a circular) orbit. In the twentieth century, Hubble measured the distance and speed of many galaxies and found that most were moving away from Earth. He determined that the Universe was extremely large and was still expanding. BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

PTOLEMY, BRAHE, COPERNICUS, AND GALILEO Articles / Cynthia Stokes Brown In this set of articles, Cynthia Stokes Brown provides biographies of key figures who contributed to our changing view of the Universe. Ptolemy created the view of the Universe that dominated European thought for over 1,000 years. Copernicus was troubled by inconsistencies in Ptolemy’s work and believed that putting the Sun at the center of the Universe resolved many of these problems. Tyco Brahe is considered the last great naked-eye astronomer. His observations were used by other astronomers to make important contributions to Copernicus’s new view of the Universe. Galileo used a telescope to observe the surface of the Moon, the moons of Jupiter, the phases of Venus, and sunspots. His observations provided important evidence for Copernicus’s idea of a sun-centered Universe. BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

NEWTON, LEAVITT AND HUBBLE Articles / Cynthia Stokes Brown Isaac Newton was one of the inventors of calculus and did important work in many areas. His view that the Universe was both infinitely big and infinitely old was very influential. Henrietta Leavitt found a way to use Cepheid variable stars to measure the distance to distant galaxies, which Hubble and others to measure the distance to objects in space farther from the Earth than ever before. Edwin Hubble discovered a relationship between the distance of galaxies from the Earth and the speed at which they were moving. His work led directly to the ideas of an expanding Universe and the Big Bang theory. BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

A BIG HISTORY OF EVERYTHING Video Big History begins with the Big Bang, a moment scientists are currently unable to describe with any degree of certainty. The Universe appears to emerge from nothing, but scientists cannot describe the moments before the Big Bang or the moment of the Big Bang itself. Major questions surround the origin of the Universe. While four fundamental forces were created by the Big Bang, gravity has played the most influential role in the history of the Universe because it can operate over the largest scales. The nature of gravity helped define the future development of the Universe. If gravity had been stronger, everything would have collapsed on itself. If gravity had been weaker, stars, planets, and other complex combinations of matter could not have formed. The Big Bang set the history of the Universe in motion. BIG HISTORY PROJECT / UNIT 9 / ACCELERATION

THRESHOLD 1— THE BIG BANG Video This video states that the Big Bang happened 13.7 billion years ago. Recent observations (announced after after this video was made) show that the Big Bang happened before that– about 13.82 million years ago! The initial moments after the Big Bang saw the creation of time, space, matter, and energy, so we know a lot about what happened a few moments after the Big Bang. What is not clear are the moments immediately before or immediately after the Big Bang. What made the Big Bang possible and why it happened remain mysteries to scientists. Just after the Big Bang, the temperature and pressure in the Universe were so high that matter and energy were an interchangeable blur. As the Universe cooled and became less dense, the basic forms of matter and the four fundamental forces also appeared. This developments occurred incredibly quickly, probably within a billionth of a second after the Big Bang! The matter and energy that formed after the Big Bang took a variety of forms. Among the four forms of energy, gravity and electromagnetism were the most important.   BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

QUESTIONS ABOUT THE BIG BANG Video Talk Janna Levin is an astrophysicist at Barnard College. For Levin, the first really profound question that she thought was answerable in principle using math and scientific observation, and the one that got her interested in astrophysics, concerned the nature of the Big Bang. Other important questions about the Big Band include: What happened in the very first moment of the Big Bang? Did nothing really turn into something in an instant? Why did the Universe suddenly appear? One other important question about the Big Bang concerns whether or not we might be totally wrong in our perception of the Big Bang. Did the Universe really appear from nothing or did it already exist? Could what we think of as the Big Bang really just be the evolution of a small portion of a larger multiverse or megaverse. The challenge of this question is that we do not know how to ask for evidence to answer it. BIG HISTORY PROJECT / UNIT 9 / ACCELERATION

ELECTROMAGNETISM Video Electromagnetism is one of the four forces created during the Big Bang. Electromagnetism plays an important role in atoms, binding electrons, which are negatively charged, to the protons and neutrons in the nuclei, which is positively charged. Electromagnetism also plays an important role in the transmission of radio waves. Simple sound waves, like those produced in human speech, can travel about 600 feet. The vibration of electric and magnetic fields allows radio waves to travel over vast distances. Electromagnetism, for example, allows humans to talk on cell phones. BIG HISTORY PROJECT / UNIT 9 / ACCELERATION

APPROACHES TO KNOWLEDGE Article / Bob Bain Each discipline has a unique approach to investigating reality. The questions that drive each discipline and the types of evidence gathered to answer those questions differs from discipline to discipline. The quest for knowledge has not always required the separation of the disciplines into distinct spheres. Socrates, for example, emphasized questions and did not strictly separate the different disciplines and their questions. Today, scholars tend to emphasize the need for separation. An important question in the Big History course will be how scholars discover or create the ideas in each discipline. Textbooks tend to put questions last, after presenting evidence. Scholars tend to put questions first, before gathering evidence. The more general process of inquiry tends to be uniform across all disciplines. First, ask a question about something you’re curious about. Second, make a conjecture, guess, or hypothesis. Third, gather evidence to help you think about that question. Fourth, make a claim based on what you’ve found. Fifth, share your idea so others can critique it, and continue to look for additional evidence.   BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

HOW DO WE DECIDE WHAT TO BELIEVE? Video Talk / Bob Bain When you hear someone make a claim, you’re likely to have one of three responses: “I can trust this claim,” “I can ignore this claim,” or “I should investigate this claim.” The Big History Project emphasizes the importance of claims in each unit. You will need to decide whether to believe them or if you would like to investigate further. Four “claim testers” will help you evaluate claims made throughout the course: Intuition is your gut instinct. Does the claim feel right to you, or does it feel a bit off? Logic involves reasoning. Does the claim make sense? Is there a good argument for it? Authority requires you to think about who is making the claim. Do you trust the source? Does the source have specific knowledge or expertise that gives you confidence? Evidence is something you can investigate and verify. If you or another person looked at the same evidence, would you arrive at the same findings? BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG

LOOKING AHEAD

WHAT’S NEXT? In Unit 3, the first stars will appear. We will learn: How stars formed About the life (and death) of a star About the origin of heavy chemical elements in aging and dying stars How views of chemical elements changed over time BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG