A Sky Full of Ghosts
Study Guide for Episode 5
Note: Episode numbers in Study Guides and in the Netflix Streaming edition of "Cosmos" do not always agree with those of the disk set we use in class. Let the episode titles, not the numbers, be your guide to reading about or watching the episode shown in class.
Episode 5: A Sky Full of Ghosts
People
• John Michell was the first person known to propose the existence of black holes in publication, the first to suggest that earthquakes travel in waves, the first to explain how to manufacture artificial magnets, and the first to apply statistics to the study of the cosmos, recognizing that double stars were a product of mutual gravitation. As Neil DeGrasse Tyson says, he's the greatest scientist you've never heard of.
• John Herschel continued his father William's work in astrophysics, and also made contributions to photography and to the understanding color blindness. He was an early and strong advocate of the inductive method in science (reasoning from the specific to the general -- as from data to laws, and from laws to theories).
Ideas
• Referring again to our previous class on Episode 4, "Hiding in the Light", what are other kinds of radiation besides electromagnetic radiation? Where do they come from? Which ones can be harmful?
• We can see only a small portion of the electromagnetic spectrum, but in a way, scientists can see all of it; that is, they can detect all of it with various instruments. What can they learn from various parts of the spectrum, and how can they use them?
• The laws of the universe do not change, but we can only infer them from observations, so our awareness, knowledge, and understanding of them does change. Science's top job is to discover them, and ask what they mean.
• If the universe were only six or seven thousand years old, as James Ussher reasoned by interpretation of biblical passages, light from distant galaxies would not have had time to reach us, and we would see only a small nearby portion of our own galaxy, the Milky Way.
• Imagine that, at noon, you begin traveling away from a clock at the speed of light. Assuming that you can continue to make out the clock's face, what will you see?
• Vectors, symbols that indicate an object's direction and speed (together called its velocity), provide a way to show how time is affected for an object traveling near the speed of light. If you are not familiar with vectors, see what you can find out about them online.
Updates
• A recent discovery might lead to a way to unify gravity with quantum mechanics, which is the true Holy Grail of physics. It turns out that the same mathematical equations describe 1) a pair of entangled quantum particles (such a two photons), and 2) a pair of black holes joined by a wormhole. Shared underlying mathematical forms have often led to the unification of things previously thought to be unrelated. Read more HERE.
• The notion of early rapid inflation of the universe is being attacked on several fronts. According to an article in the February 2017 Scientific American, the theory has at least two shortcomings. 1) It predicts gravitational waves that have not been detected, although gravitational waves from smaller events are now detectable. 2) Its predictions of variation in the Cosmic Microwave Background does not agree with observed variations. Patched versions of early inflation can fit just about any patterns of variation, so these versions are not testable with current data. If you do not have access to Scientific American and want to read this article, you can purchase the online edition of the issue for $6.99 HERE.
• More planets out there around other stars. A new record (as of February, 2017) for terrestrial-type planets detected about a single star. The planet Trappist-1, an ultra-cool award star located 40 light-years away in the constellation Aquarius, has seven rocky planets, three of which lie "firmly" within its habitable zone (where a planet could could host liquid water). Read more HERE, and much more HERE.
Readings
• Poem: Howard Nemerov, "Figures of Thought". Read the poem HERE.
• John Michell was the first person known to propose the existence of black holes in publication, the first to suggest that earthquakes travel in waves, the first to explain how to manufacture artificial magnets, and the first to apply statistics to the study of the cosmos, recognizing that double stars were a product of mutual gravitation. As Neil DeGrasse Tyson says, he's the greatest scientist you've never heard of.
• John Herschel continued his father William's work in astrophysics, and also made contributions to photography and to the understanding color blindness. He was an early and strong advocate of the inductive method in science (reasoning from the specific to the general -- as from data to laws, and from laws to theories).
Ideas
• Referring again to our previous class on Episode 4, "Hiding in the Light", what are other kinds of radiation besides electromagnetic radiation? Where do they come from? Which ones can be harmful?
• We can see only a small portion of the electromagnetic spectrum, but in a way, scientists can see all of it; that is, they can detect all of it with various instruments. What can they learn from various parts of the spectrum, and how can they use them?
• The laws of the universe do not change, but we can only infer them from observations, so our awareness, knowledge, and understanding of them does change. Science's top job is to discover them, and ask what they mean.
• If the universe were only six or seven thousand years old, as James Ussher reasoned by interpretation of biblical passages, light from distant galaxies would not have had time to reach us, and we would see only a small nearby portion of our own galaxy, the Milky Way.
• Imagine that, at noon, you begin traveling away from a clock at the speed of light. Assuming that you can continue to make out the clock's face, what will you see?
• Vectors, symbols that indicate an object's direction and speed (together called its velocity), provide a way to show how time is affected for an object traveling near the speed of light. If you are not familiar with vectors, see what you can find out about them online.
Updates
• A recent discovery might lead to a way to unify gravity with quantum mechanics, which is the true Holy Grail of physics. It turns out that the same mathematical equations describe 1) a pair of entangled quantum particles (such a two photons), and 2) a pair of black holes joined by a wormhole. Shared underlying mathematical forms have often led to the unification of things previously thought to be unrelated. Read more HERE.
• The notion of early rapid inflation of the universe is being attacked on several fronts. According to an article in the February 2017 Scientific American, the theory has at least two shortcomings. 1) It predicts gravitational waves that have not been detected, although gravitational waves from smaller events are now detectable. 2) Its predictions of variation in the Cosmic Microwave Background does not agree with observed variations. Patched versions of early inflation can fit just about any patterns of variation, so these versions are not testable with current data. If you do not have access to Scientific American and want to read this article, you can purchase the online edition of the issue for $6.99 HERE.
• More planets out there around other stars. A new record (as of February, 2017) for terrestrial-type planets detected about a single star. The planet Trappist-1, an ultra-cool award star located 40 light-years away in the constellation Aquarius, has seven rocky planets, three of which lie "firmly" within its habitable zone (where a planet could could host liquid water). Read more HERE, and much more HERE.
Readings
• Poem: Howard Nemerov, "Figures of Thought". Read the poem HERE.
