Astronomy

0% Complete
0 out of 65 Lessons
0% Complete
0 out of 4 Exams
Previous Lessons
Open Chapter Ch. 1: A Modern View of the Universe
Lesson #1 The Scale of the Universe
Incomplete Assignment Study Questions for Lesson 1
Lesson #2 The History of the Universe
Incomplete Assignment Study Questions for Lesson 2
Lesson #3 Spaceship Earth
Incomplete Assignment Study Questions for Lesson 3
Open Chapter Ch. 2: Discovering the Universe for Yourself
Lesson #4 Patterns in the Night Sky
Incomplete Assignment Study Questions for Lesson 4
Lesson #5 The Reason for Seasons
Incomplete Assignment Study Questions for Lesson 5
Lesson #6 The Moon, our Constant Companion
Incomplete Assignment Study Questions for Lesson 6
Lesson #7 Ancient Mystery of the Planets
Incomplete Assignment Study Questions for Lesson 7
Open Chapter Ch. 3: The Science of Astronomy
Lesson #8 The Ancient Roots of Science
Incomplete Assignment Study Questions for Lesson 8
Lesson #9 Ancient Greek Science
Incomplete Assignment Study Questions for Lesson 9
Lesson #10 The Copernican Revolution
Incomplete Assignment Study Questions for Lesson 10
Lesson #11 The Nature of Science
Incomplete Assignment Study Questions for Lesson 11
Open Chapter Ch. 4: Understanding Motion, Energy, and Gravity
Lesson #12 Describing Motion
Incomplete Assignment Study Questions for Lesson 12
Lesson #13 Newton's Laws of Motion
Incomplete Assignment Study Questions for Lesson 13
Lesson #14 Conservation Laws in Astronomy
Incomplete Assignment Study Questions for Lesson 14
Lesson #15 The Force of Gravity
Incomplete Assignment Study Questions for Lesson 15
Open Chapter Ch. 5: Light: The Cosmic Messenger
Lesson #16 Basic Properties of Light and Matter
Incomplete Assignment Study Questions for Lesson 16
Lesson #17 Learning from Light
Incomplete Assignment Study Questions for Lesson 17
Lesson #18 Collecting Light with Telescopes
Incomplete Assignment Study Questions for Lesson 18
Exam Exam 1
Open Chapter Ch. 6: Formation of the Solar System
Lesson #19 A Brief Tour of the Solar System
Incomplete Assignment Study Questions for Lesson 19
Lesson #20 The Nebular Theory of Solar System Formation
Incomplete Assignment Study Questions for Lesson 20
Lesson #21 Explaining the Major Features of the Solar System
Incomplete Assignment Study Questions for Lesson 21
Lesson #22 The Age of the Solar System
Incomplete Assignment Study Questions for Lesson 22
Open Chapter Ch. 7: Earth and the Terrestrial Worlds
Lesson #23 Earth as a Planet
Incomplete Assignment Study Questions for Lesson 23
Lesson #24 The Moon and Mercury: Geologically Dead
Incomplete Assignment Study Questions for Lesson 24
Lesson #25 Mars, a Victim of Planetary Freeze Drying
Incomplete Assignment Study Questions for Lesson 25
Lesson #26 Venus, a Hothouse World
Incomplete Assignment Study Questions for Lesson 26
Lesson #27 Earth as a living planet
Incomplete Assignment Study Questions for Lesson 27
Open Chapter Ch. 8: Jovian Planet Systems
Lesson #28 A Different Kind of Planet
Incomplete Assignment Study Questions for Lesson 28
Lesson #29 A Wealth of Worlds: Satellites of Ice and Rock
Incomplete Assignment Study Questions for Lesson 29
Open Chapter Ch. 9: Asteroids, Comets, and Dwarf Planets
Lesson #30 Classifying Small Bodies
Incomplete Assignment Study Questions for Lesson 30
Lesson #31 Asteroids
Incomplete Assignment Study Questions for Lesson 31
Lesson #32 Comets
Incomplete Assignment Study Questions for Lesson 32
Lesson #33 Pluto and the Kuiper Belt
Incomplete Assignment Study Questions for Lesson 33
Lesson #34 Cosmic Collisions - Small Bodies vs Planets
Incomplete Assignment Study Questions for Lesson 34
Open Chapter Ch. 10: Other Planetary Systems
Lesson #35 Detecting Planets Around Other Stars
Incomplete Assignment Study Questions for Lesson 35
Lesson #36 The Nature of Planets Around Other Stars
Incomplete Assignment Study Questions for Lesson 36
Lesson #37 The Formation of Other Planetary Systems
Incomplete Assignment Study Questions for Lesson 37
Exam Midterm Exam
Open Chapter Ch. 11: Our Star
Lesson #38 The Sun, Our Star
Incomplete Assignment Study Questions for Lesson 38
Lesson #39 Nuclear Fusion in the Sun
Incomplete Assignment Study Questions for Lesson 39
Lesson #40 Sun-Earth Connection
Incomplete Assignment Study Questions for Lesson 40
Open Chapter Ch. 12: Surveying the Stars
Lesson #41 Properties of Stars
Incomplete Assignment Study Questions for Lesson 41
Lesson #42 Patterns in the Stars
Incomplete Assignment Study Questions for Lesson 42
Lesson #43 Star Clusters
Incomplete Assignment Study Questions for Lesson 43
Open Chapter Ch. 13: Star Stuff
Lesson #44 Star Birth
Incomplete Assignment Study Questions for Lesson 44
Lesson #45 Life as a Low Mass Star
Incomplete Assignment Study Questions for Lesson 45
Lesson #46 Life as a High Mass Star
Incomplete Assignment Study Questions for Lesson 46
Open Chapter Ch. 14: The Bizarre Stellar Graveyard
Lesson #47 White Dwarfs
Incomplete Assignment Study Questions for Lesson 47
Lesson #48 Neutron Stars
Incomplete Assignment Study Questions for Lesson 48
Lesson #49 Black Holes: Gravity’s Ultimate Victory
Incomplete Assignment Study Questions for Lesson 49
Exam Exam 3
Open Chapter Ch. 15: Our Galaxy
Lesson #50 The Milky Way Revealed
Incomplete Assignment Study Questions for Lesson 50
Lesson #51 Galactic Recycling
Incomplete Assignment Study Questions for Lesson 51
Lesson #52 The History of the Milky Way
Incomplete Assignment Study Questions for Lesson 52
Open Chapter Ch. 16: A Universe of Galaxies
Lesson #53 Islands of Stars
Incomplete Assignment Study Questions for Lesson 53
Lesson #54 Distances of Galaxies
Incomplete Assignment Study Questions for Lesson 54
Lesson #55 Galaxy Evolution
Incomplete Assignment Study Questions for Lesson 55
Lesson #56 The Role of Supermassive Black Holes
Incomplete Assignment Study Questions for Lesson 56
Open Chapter Ch. 17: The Birth of the Universe
Lesson #57 The Big Bang Theory
Incomplete Assignment Study Questions for Lesson 57
Lesson #58 Evidence for the Big Bang
Incomplete Assignment Study Questions for Lesson 58
Lesson #59 The Big Bang and Inflation
Incomplete Assignment Study Questions for Lesson 59
Open Chapter Ch. 18: Dark Matter, Dark Energy, and the Fate of the Universe
Lesson #60 Unseen Influences in the Cosmos
Incomplete Assignment Study Questions for Lesson 60
Lesson #61 Structure Formation
Incomplete Assignment Study Questions for Lesson 61
Open Chapter Ch. 19: Life in the Universe
Lesson #62 Life on Earth
Incomplete Assignment Study Questions for Lesson 62
Lesson #63 Life in the Solar System
Incomplete Assignment Study Questions for Lesson 63
Lesson #64 The Search for Extraterrestrial Intelligence
Incomplete Assignment Study Questions for Lesson 64
Lesson #65 Interstellar Travel and Implications for Civilizations
Incomplete Assignment Study Questions for Lesson 65
Exam Final Exam

Assignments:

Unfinished Assignment Study Questions for Lesson 65

Lesson Objectives:

- Current spacecraft
- Challenges of interstellar travel
- Starship design
- Fermi's paradox



We have had five spacecraft leave our solar system. They are Pioneer 10, Pioneer 11, Voyager 1, Voyager 2 and New Horizons. Even though they are traveling through space at over 10,000 miles/hour, it would still take 100,000 years to reach the nearest star system - Alpha Centauri.



We would need to build starships that travel close to the speed of light to reach any other planet or star, but high speed interstellar travel would require vast amounts of energy. For example, a ship the size of Star Trek's Enterprise would require 2,000 times the amount of energy used by the entire Earth's population in a single year just to accelerate to half the speed of light.

We would also need to protect crew members from instant death because travel at such high speeds would cause ordinary atoms to hit the ship with the force of high-energy cosmic rays.

In addition, there is the time difference. According to Einstein's theory of relativity, time will run more slowly aboard a spaceship than on Earth. For example, if a space crew spent two years traveling close to the speed of light to the star Vega, 50 years would have passed on Earth. When the crew returned, life would be different; their skills would probably be obsolete and many of the people they knew would have passed away.



Building a starship that would be able to travel fast enough and survive the impacts of collisions is no easy task. Scientists and artists have been envisioning various ways to make this happen. One example is Project Orion, a concept for accelerating a starship with repeated detonations of hydrogen bombs. This would propel the starship forward and make it possible to reach Alpha Centuri within 50 years. However, this would be extremely expensive and currently, international treaties ban nuclear detonations in space.

Another idea is the interstellar ramjet, a massive spaceship that would collect interstellar hydrogen with a gigantic scoop using the collected gas as fuel for its nuclear engines. The problem is that since interstellar gas is so thin, it would take a scoop the size of a planet to collect enough hydrogen to make this idea work.

While high speed interstellar travel has not yet occurred and is beyond the capabilities of our current technology, there are people studying and experimenting with ways to make it possible some day.



In 1950, Nobel prize physicist Enrico Fermi asked, "So where is everybody?" in response to questions about alien life in the universe. He discussed the question further and proposed three possibilities, which came to be known as Fermi's paradox.

The 3 categories are:
- we are alone
- civilizations are common, but no one has colonized the galaxy
- there is a galactic civilization, but its existence has yet to be revealed

Each category has its own questions and concerns. Alien life has yet to be discovered or disproven.