The Cosmic Perspective (9th Edition)
9th Edition
ISBN: 9780134874364
Author: Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider, Mark Voit
Publisher: PEARSON
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Chapter 22, Problem 55EAP
Daytime at “Night.” According to Olbers’ paradox, the entire sky would be as bright as the surface of a typical star if the universe were infinite in space, unchanging in time, and the same everywhere. However, conditions would not need to be quite that extreme for the “nighttime” sky to be as bright as the daytime sky.
- Using the inverse square law for light from Mathematical Insight 15.1, determine the apparent brightness of the Sun in our sky.
- Using the inverse square law for light, determine the apparent brightness our Sun would have if it were at a distance of 10 billion light-years.
- From your answers to parts a and b, estimate how many stars like the Sun would need to exist at a distance of 10 billion light-years for their total apparent brightness to equal that of our Sun.
- Compare your answer to part c with the estimate of the total number of stars in our observable universe from Mathematical Insight 1.3. Use your answer to explain why the night sky is much darker than the daytime sky. How much larger would the total number of stars need to be for “night” to be as bright as day?
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Your friends are talking about Olber's Paradox:
Friend 1: When the universe was quite young, it was also quite small, and therefore light
was trapped inside the universe. This is why we don't see light from the edge of the
universe in every direction.
Friend 2: No, Olber's Paradox describes only light from stars, not from galaxies, and why
you can't use light from distant stars to see at night.
Friend 3: You're both right and you're both wrong. The paradox concerns itself with the
expansion of the universe, and explains why light from the early universe was able to be
released.
Are any of them right, in part or in whole?
Hubble's First Attempt. Edwin Hubble's first attempt to measure the universe's expansion rate was flawed because the standard candles he was using were not properly calibrated. Look at (Figure 1)
a.Estimate the value of Ho corresponding to the solid line in the figure. Express your answer kilometers per second per million light-years to two significant figures.
b.What is the approximate age of the universe indicated by that erroneous value of Ho? Express your answer in years to one significant figure.
Assume the observable Universe is charge neutral, and that it contains n nuclei (hydrogen plus helium nuclei, ignoring other elements). Take the helium mass fraction as 1/4. How many electrons are there in the observable Universe? Enter your answer in scientific notation with one decimal place.
Value: n = 4*1080
Chapter 22 Solutions
The Cosmic Perspective (9th Edition)
Ch. 22 - Prob. 1VSCCh. 22 - Prob. 2VSCCh. 22 - Prob. 3VSCCh. 22 - Explain what we mean by the Big Bang theory.Ch. 22 - Prob. 2EAPCh. 22 - Prob. 3EAPCh. 22 - Prob. 4EAPCh. 22 - Prob. 5EAPCh. 22 - Prob. 6EAPCh. 22 - Prob. 7EAP
Ch. 22 - 8. Why do we think there was slightly more matter...Ch. 22 - 9. How long did the era of nucleosynthesis last?...Ch. 22 - 10. When we observe the cosmic microwave...Ch. 22 - 11. Briefly describe how the cosmic microwave...Ch. 22 - 12. How does the chemical abundance of helium in...Ch. 22 - Prob. 13EAPCh. 22 - Prob. 14EAPCh. 22 - Prob. 15EAPCh. 22 - Prob. 16EAPCh. 22 - Prob. 17EAPCh. 22 - Decide whether the statement makes sense (or is...Ch. 22 - Prob. 19EAPCh. 22 - Prob. 20EAPCh. 22 - Prob. 21EAPCh. 22 - Prob. 22EAPCh. 22 - Prob. 23EAPCh. 22 - Prob. 24EAPCh. 22 - Decide whether the statement makes sense (or is...Ch. 22 - Choose the best answer to each of the following....Ch. 22 - Prob. 27EAPCh. 22 - Prob. 28EAPCh. 22 - Prob. 29EAPCh. 22 - Prob. 30EAPCh. 22 - Prob. 31EAPCh. 22 - Prob. 32EAPCh. 22 - Prob. 33EAPCh. 22 - Prob. 34EAPCh. 22 - Prob. 35EAPCh. 22 - Prob. 37EAPCh. 22 - Prob. 38EAPCh. 22 - Prob. 41EAPCh. 22 - Prob. 42EAPCh. 22 - Prob. 43EAPCh. 22 - Prob. 44EAPCh. 22 - Prob. 45EAPCh. 22 - Prob. 46EAPCh. 22 - Prob. 47EAPCh. 22 - Prob. 48EAPCh. 22 - Prob. 49EAPCh. 22 - Gravity vs. the Electromagnetic Force. The amount...Ch. 22 - Prob. 51EAPCh. 22 - Prob. 52EAPCh. 22 - Prob. 53EAPCh. 22 - Prob. 54EAPCh. 22 - Daytime at “Night.” According to Olbers’ paradox,...
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- Assume the observable Universe is charge neutral, and that it contains n nuclei (hydrogen plus helium nuclei, ignoring other elements). Take the helium mass fraction as 1/4. How many electrons are there in the observable Universe? Enter your answer in scientific notation with one decimal place.arrow_forwardFor the graph shown above, a) what quantity would you label the y-axis with if the distance is between galaxies and the Earth? Explain your answer. Think through what we know is happening, motion-wise, out there in the galaxy. b) Also explain why you think there are dots and a solid line, on the graph.arrow_forwardAstronomers frequently say that "there are more stars in the universe than there are grains of sand on all the beaches on the earth". Given that a typical grain of sand is about 0.5 – 1.0 mm in diameter, estimate the number of grains of sand on all the earth's beaches. The diameter of the Earth is 12,742 km. a) About 1011 b) About 1016 c) About 1021. 6. Assume that a typical galaxy contains about 200 billion stars and that there are more than 150 billion galaxies in the known universe. Estimate the total number of stars in the universe. b) About 1022 a) About 1010 c) About 1016. 7. Compare the values of the number of grains of sand in all earth's beaches (from problem 5) with the number of stars in the universe (from problem 6) – which is greater? a) Number of sand grains b) number of stars c) they are about the same.arrow_forward
- State three pieces of evidence that support the idea that the Universe began in a hot Big Bang, and explain how each piece of evidence supports the hot Big Bang model. Describe the ob- servational evidence that supports the idea that the Universe is pervaded by Dark Energy, and explain why each piece of evidence you cite supports the Dark Energy model.arrow_forwardWith the aid of one or more diagram, explain how observations of the CMB can be used to determine whether or not space is flat, positively curved or negatively curved. Describe two pieces of evidence that have led to the suggestion that the Universe contains Dark Energy.arrow_forwardWhy cant an open universe have a center? How can a closed universe not have a center?arrow_forward
- What is the difference between hot dark matter and cold dark matter? How does this difference affect cosmology?arrow_forwardWhat does the term Hubble time mean in cosmology, and what is the current best calculation for the Hubble time?arrow_forwardWhat evidence shows that the Universe is expanding? What evidence shows that the Universe began with a Big Bang?arrow_forward
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