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 20, Problem 54EAP
To determine
The value of
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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
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.
Values: n = 1*10^80
Chapter 20 Solutions
The Cosmic Perspective (9th Edition)
Ch. 20 - Prob. 1VSCCh. 20 - Prob. 2VSCCh. 20 - Prob. 3VSCCh. 20 - Prob. 4VSCCh. 20 - Use the following questions to check your...Ch. 20 - Prob. 6VSCCh. 20 - Why do we need to understand the evolution of the...Ch. 20 - Prob. 2EAPCh. 20 - Prob. 3EAPCh. 20 - Prob. 4EAP
Ch. 20 - Prob. 9EAPCh. 20 - Prob. 10EAPCh. 20 - Prob. 11EAPCh. 20 - Prob. 12EAPCh. 20 - Prob. 13EAPCh. 20 - What is the cosmological horizon, and what...Ch. 20 - Prob. 15EAPCh. 20 - Prob. 16EAPCh. 20 - Prob. 17EAPCh. 20 - Prob. 18EAPCh. 20 - Prob. 19EAPCh. 20 - Decide whether the statement makes sense (or is...Ch. 20 - Prob. 21EAPCh. 20 - Prob. 22EAPCh. 20 - Prob. 23EAPCh. 20 - Prob. 24EAPCh. 20 - Prob. 25EAPCh. 20 - Choose the best answer to each of the following....Ch. 20 - Prob. 27EAPCh. 20 - Choose the best answer to each of the following....Ch. 20 - Prob. 29EAPCh. 20 - Prob. 30EAPCh. 20 - Prob. 31EAPCh. 20 - Choose the best answer to each of the following....Ch. 20 - Choose the best answer to each of the following....Ch. 20 - Choose the best answer to each of the following....Ch. 20 - Prob. 35EAPCh. 20 - Prob. 38EAPCh. 20 - Prob. 41EAPCh. 20 - Prob. 42EAPCh. 20 - Prob. 43EAPCh. 20 - Prob. 45EAPCh. 20 - Prob. 46EAPCh. 20 - Prob. 47EAPCh. 20 - Prob. 48EAPCh. 20 - Prob. 51EAPCh. 20 - Prob. 52EAPCh. 20 - Prob. 53EAPCh. 20 - Prob. 54EAPCh. 20 - Extremely Distant Galaxies. The most distant...Ch. 20 - Stretching of the Universe. The most distant white...
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- What does the term Hubble time mean in cosmology, and what is the current best calculation for the Hubble time?arrow_forwardAn astronomer observed the motions of some galaxies. Based on his observations, he made the following statements. Which one of them is most likely to be false? Take Hubble's constant to be 67 km/s/Mpc. A. A galaxy observed to be moving away from us at a speed of 70 km/s is at a distance of about 1 Mpc from us. B. A galaxy observed to be moving away from us at a speed of 700 km/s is at a distance of about 10 Mpc from us. C. A galaxy observed to be moving away from us at a speed of 7000 km/s is at a distance of about 100 Mpc from us. D. A galaxy observed to be moving away from us at a speed of 70000 km/s is at a distance of about 1 Gpc from us. Is the answer D? Thank you!arrow_forward1. If a galaxy is 9.1 Mpc away from Earth and recedes at 511 km/s, what is H0 (in km/s/Mpc)? 2. What is the Hubble time (in yr)? 3. How old (in yr) would the universe be, assuming space-time is flat and the expansion of the universe has not been accelerating?arrow_forward
- 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_forward1. The current (critical) density of our universe is pe = 10-26kg/m³. Assume the universe is filled with cubes with equal size that each contain one person of m = 100kg. What would the length of the side of such a cube have to be in order to give the correct critical density? How many hydrogen atoms would you need in a box of 1 m³ to reach the critical density? The matter we know, which consists mostly of hydrogen, constitutes only 4.8% of the current critical energy density of our universe. So how many hydrogen atoms are actually in a box of 1 m3 in our universe? Deep space is very empty and a much better vacuum than we can obtain on earth in a laboratory.arrow_forwardExplain how the Hubble constant, H0, can be used to make an estimate for the age of the Universe. Use the value of H0 = 0.07×103 kms-1/Mpc to estimate the Universe’s age. Comment on the significance of your answer.arrow_forward
- If a galaxy is 9.0 Mpc away from Earth and recedes at 488 km/s, what is H0 (in km/s/Mpc)? km/s/Mpc What is the Hubble time (in yr)? years How old (in yr) would the universe be, assuming space-time is flat and the expansion of the universe has not been accelerating? How would acceleration change your answer? A.If the expansion of the Universe has been accelerating, the Universe could be substantially younger than the value entered above. BIf the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.arrow_forwardUsing our example from the previous unit, let's try to determine the Hubble time for this example universe. You were given that a good representative galaxy receded at a speed of 4000 km/s and was found to be 20 Mpc away. With that in mind, what would the age of that universe be in years (aka what is that universe's Hubble time)? Go ahead and take the number of kilometers per Mpc to be approximately 3.1*10^19 km/Mpc. While this problem may look scary at first, this is really just bringing you full circle to one of the unit conversion problems you encountered at the beginning of this course.arrow_forwardIn the reading, you were told that there were roughly 10,000 galaxies in the image of the Hubble Ultra Deep Field alone. The image is roughly 10 square arcminutes and there are roughly 1.5*10^8 square arcminutes composing the entire sky. With that in mind and assuming that the Hubble Ultra Deep Field represents an average part of the sky, roughly how many galaxies may exist in the observable universe? (Please include commas for every factor of 1,000; for example 2,343,567,890)arrow_forward
- Astronomers 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_forwardWhat is the estimated age of the Universe (in years) if the Hubble constant is 70 km/s/Mpc?arrow_forwardStuck on homework, especially the significant part. If the value of the Hubble constant is 70 kilometers per second per Mpc, then what is the Hubble time – that is, the amount of time the universe has been expanding since the Big Bang? Give your answer first in units of seconds, and then in units of billions of years. Your answer is significant to two digits.arrow_forward
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