LDEO NGSS Summer Institutes: “Teaching about Astronomy” (GED 7214)
Lesson 8: Cosmology and the “Big Bang”
Expect Time Required: 4 – 5 hr
Submitted by: Date: Time Needed:
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Selected NGSS Connections:
MS-ESS1.A: The Universe and Its Stars
MS-ESS1.B: Earth and the Solar System
- The solar system consists of the sun and a collection of objects, including planets, their moons, and asteroids that are held in orbit around the sun by its gravitational pull on them.
- The solar system appears to have formed from a disk of dust and gas, drawn together by gravity.
| MS-ESS1-2. | Develop and use a model to describe the role of gravity in the motions within galaxies and the solar system. [Clarification Statement: Emphasis for the model is on gravity as the force that holds together the solar system and Milky Way galaxy and controls orbital motions within them. Examples of models can be physical (such as the analogy of distance along a football field or computer visualizations of elliptical orbits) or conceptual (such as mathematical proportions relative to the size of familiar objects such as students’ school or state).] [Assessment Boundary: Assessment does not include Kepler’s Laws of orbital motion or the apparent retrograde motion of the planets as viewed from Earth.] |
HS-ESS1.A: The Universe and Its Stars
HS-PS4.B: Electromagnetic Radiation
| HS-ESS1-2. | Construct an explanation of the Big Bang theory based on astronomical evidence of light spectra, motion of distant galaxies, and composition of matter in the universe. [Clarification Statement: Emphasis is on the astronomical evidence of the red shift of light from galaxies as an indication that the universe is currently expanding, the cosmic microwave background as the remnant radiation from the Big Bang, and the observed composition of ordinary matter of the universe, primarily found in stars and interstellar gases (from the spectra of electromagnetic radiation from stars), which matches that predicted by the Big Bang theory (3/4 hydrogen and 1/4 helium).] |
| HS-ESS1-3. | Communicate scientific ideas about the way stars, over their life cycle, produce elements. [Clarification Statement: Emphasis is on the way nucleosynthesis, and therefore the different elements created, varies as a function of the mass of a star and the stage of its lifetime.] [Assessment Boundary: Details of the many different nucleosynthesis pathways for stars of differing masses are not assessed.] |
Selected PS/ES Core Curriculum Concepts:
1.2a The Universe is vast and estimated to be over 10 billion years old. The current theory is that the Universe was created from an explosion called the Big Bang. Evidence for this theory includes:
> cosmic background radiation
> a red-shift (Doppler effect) in light from very distant galaxies
1.2b Stars form when gravity causes clouds of molecules to contract until nuclear fusion of light elements into heavier elements occurs. Fusion releases great amounts of energy over millions of years.
> The stars differ from each other in size, temperature, and age.
> Our Sun is a medium-sized star within a spiral galaxy known as the Milky Way. Our galaxy contains billions of stars, and the Universe contains billions of galaxies.
Introduction
On a clear night where there is no artificial lighting, you can look up and see a band of stars crossing the sky. People saw its whitish appearance and so it became known as the “Milky Way.” Over centuries, we realized our solar system is but one of many in the Milky Way Galaxy. (The word derives from the Greek for ‘milk.’) Our understanding of the organization of the Universe—“Cosmology”— is relatively recent and relies on complex observations from many kinds of technology and intricate calculations. Many useful resources are available in the AMNH “Science Bulletins.”
In this Lesson, you will consider some evidence that supports current scientific theories, along with some questions that preclude our reaching definitive answers.
Structure of the Universe
The taxonomic (hierarchical levels) approach taken by Linnaeus in the 18th Century provided a simple way to understand relationships among all living organisms, although it did not explain why things were related. So it is helpful to attempt a similar hierarchical approach to understanding the organization of the Universe. Examine this example of how we can represent levels of organization from atoms to the Universe to help students gain better understanding of this important concept. .
Response: Examine the model of a “Taxonomy from the Universe to Atoms” and describe how you would use this in your class?
Discovering that there are other galaxies
Until less than a century ago, people thought that the Milky Way composed the entire Universe. But many troubling questions among astronomers resulted in a public discussion called “The Great Debate” between astronomers Harlow Shapley and Heber Curtis. Critical to the argument was the true nature of a faint object first described in the 964 by the Persian astronomer Abd al-Rahman al-Sufi. We now know he described the most distant object visible to the unaided eye, the Andromeda Galaxy. Simon Marius, a contemporary and rival of Galileo, was the first to observe this object with a telescope. He called it a “nebula.” Charles Messier created the first “catalog” of celestial objects, and named this “M31,” a designation still in use for this object. http://www.space.com/15590-andromeda-galaxy-m31.html.
Why was this so critical in the Great Debate between Shapley and Curtis? Shapley held that everything is within our galaxy, but Curtis argued that novae within Andromeda proved it was a separate galaxy beyond the Milky Way. Shapley had determined that that the Milky Way is 100,000 light years across. Fred Hubble sought to settle the debate, and used a Cepheid Variable star within the Andromeda nebula to calculate its distance from Earth. It proved to be 2.5 million light years away, too far away to be within our Galaxy. The Universe was a lot larger than we had known.
Response: Briefly explain how astronomers can measure the distance to Cepheid variables and other celestial objects.
Observing distant objects from Earth’s surface, even from mountain peaks, poses problems because the light must pass through the atmosphere. In the 1990s, NASA placed the Hubble Space Telescope in orbit and overcame this problem. Since then, the HST has provided some of the most amazing images of ‘Deep, Deep Space.’
Response: Examine the HST website and describe 3 notable achievements.
Remarkable as the HST has been, new advances in technology are leading to what was originally called the Next generation Space Telescope, but has been renamed the James Webb Space Telescope. After its launch in 2018, the JWST will become the premier observatory of the next decade. It is designed to study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.
Response: Examine the JWST website and explain how you might have your students follow the preparations and launch of this observatory.
The Big Bang Theory
The question, “Where do we come from?” is one of the oldest, most compelling, and most controversial. The Bible begins with one explanation of the Origin of Everything. For centuries, people were content with such religious explanations, sure that theirs is correct and others wrong. As our scientific understanding developed, many astronomers accepted a “stable Universe,” one with “No Beginning and No End.” Hubble’s research using Doppler shifts opened new doors. Using spectroscope observations of distant galaxies, Hubble found that the expected patterns were shifted toward the red side, meaning that the objects were moving away from us. The greater the shift, the further away were the objects. In other words, Hubble found that the Universe is expanding.
Response: Explain the “Red Shift” and two examples of how you could teach about this in your classroom.
Astrophysicists wrestled with the implications of this theory for decades until confirmation came from an accidental discovery made by two Bell Lab scientists, Arno Penzias and Robert Wilson, and a team at Princeton led by Robert Dicke. They found evidence for Cosmic Microwave Background (CMB) radiation that had been predicted to remain after the formation of the universe. This energy resulted from a period in the early formation of the Universe when electrons and protons combined to form hydrogen atoms, releasing photons.
Observations made by many astrophysicists using a wide range of instruments and platforms on Earth and in orbit have led to the modern “Big Bang Theory.” Critical to developing this explanation was determining the age of the Universe. Read one description of how we calculate how old is the Universe. Basically, the idea is that everything in the Universe started a one dense object that began to expand some 13.8 billion years ago. View one description of the steps that scientists theorize occurred in the process.
Response: Design a way to show these steps, such as a chart, diagram, slideshow, etc.
To complicate the whole situation further, astrophysicists now think that everything we know of—galaxies, stars, planets, etc.—may comprise only about 5% of the Universe. Most of the Cosmos consists of dark matter and dark energy. These cannot be sensed by conventional instruments, but subtle indications of their existence have been identified. At this time, these are not included in what should be taught, but for your own knowledge, so should read about them and be ready to answers questions that students may ask.
Response: Briefly explain why astrophysicists think dark matter and dark energy exist.
Formation and Future of Our Solar System
One final idea to consider in the Lesson is, “How and when did our solar system form?” Related to this is another question that always stuns students when they learn the answer: “Where did the atoms in my body and everything around me come from?” The final “ultimate question” is, “What will happen to Earth and our solar system?”
The driving force behind the formation of the solar system is, of course, Gravity. Evidence of the formation of the solar system can be found in observations of objects in interstellar Deep Space, such as nebulae; spectroscopic studies of planets and other celestial objects; and examination of meteorites and lunar samples returned by the Apollo astronauts.
Based on these lines of evidence, we have been able to construct a reasonable story of the early history of the solar system. One summary can be found in that Fount-of-All-Knowledge, Wikipedia: https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System.
Response: Use this or other sources to design a visual display suitable for your classroom or hallway wall depicting significant events in the formation of the solar system and theories about what will happen in the far distant future to end it.
Note: Because there may be limited time during the summer course, you are not expected to make such a display, but only to create an outline of what you would do and include n your display.