2
THE BIG BANG
HOW AND WHY DO INDIVIDUALS
CHANGE THEIR MINDS?
UNIT 2
THE BIG BANG
CONTENTS
UNIT 2 BASICS
3 Unit 2 Overview
4 Unit 2 Learning Outcomes
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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
14 Threshold 1: The Big Bang
15 Threshold 1 Card
17 Questions About the Big Bang
18 Electromagnetism
19 Approaches to Knowledge
20 How Do We Decide What to Believe?
LOOKING AHEAD
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BIG HISTORY PROJECT / UNIT 2 / THE BIG BANG
What’s Next in Unit 3?
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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
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UNIT 2
LEARNING OUTCOMES
By the end of Unit 2, students should be able to:
1.
Explain the basics of the Big Bang theory and the primary evidence that supports this theory.
2.
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.
3.
Understand how to use claim testing to evaluate a claim or resource.
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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.
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UNIT 2
KEY CONCEPTS
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astronomy
atom
authority
Big Bang
Cepheid
claim
claim testing
collective learning
Cosmic Microwave Background
(CMB)
cosmology
Doppler effect
electromagnetism
electron
energy
evidence
gravity
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helium
hydrogen
inflation
intuition
light-year
logic
matter
nucleus (atomic)
neutron
parallax
proton
redshift
scientific method
space-time
telescope
thermodynamics (first law of)
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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?
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LOOKING AHEAD
WHAT’S NEXT?
In Unit 3, the first stars will appear. We will learn:
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How stars formed
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About the life (and death) of a star
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About the origin of heavy chemical elements in aging and dying stars
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How views of chemical elements changed over time
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