Foundations of Astronomy (MindTap Course List)
14th Edition
ISBN: 9781337399920
Author: Michael A. Seeds, Dana Backman
Publisher: Cengage Learning
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Chapter 17, Problem 5P
To determine
The Hubble constant, Hubble time, the age of the flat Universe without acceleration and effect of acceleration.
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Students have asked these similar questions
If a galaxy is 8.9 Mpc away from Earth and recedes at 497 km/s, what is H. (in km/s/Mpc)?
km/s/Mрс
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?
years
How would acceleration change your answer?
If the expansion of the Universe has been accelerating, the Universe could be substantially younger than the value entered above.
If the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.
Using 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.
If a galaxy is 9.0 Mpc away from Earth and recedes at 488 km/s, what is H, (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?
years
How would acceleration change your answer?
O If the expansion of the Universe has been accelerating, the Universe could be substantially younger than the value entered above.
O If the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.
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Chapter 17 Solutions
Foundations of Astronomy (MindTap Course List)
Ch. 17 - Is cosmology the study of the Universe, the...Ch. 17 - Is a cosmologist an astronomer? Is an astronomer a...Ch. 17 - How does the darkness of the night sky tell you...Ch. 17 - Explain the differences among the observable...Ch. 17 - Prob. 5RQCh. 17 - Prob. 6RQCh. 17 - Prob. 7RQCh. 17 - Prob. 8RQCh. 17 - Prob. 9RQCh. 17 - Prob. 10RQ
Ch. 17 - Prob. 11RQCh. 17 - If you accept the cosmological principle, how can...Ch. 17 - Why cant an open universe have a center? How can a...Ch. 17 - In which type of model universe is space-time...Ch. 17 - In which type of model universe is space-time...Ch. 17 - What is the fate of a closed universe? In what...Ch. 17 - In which model universe does the average density...Ch. 17 - Prob. 18RQCh. 17 - What evidence shows that the Universe is...Ch. 17 - Why couldnt atomic nuclei exist when the Universe...Ch. 17 - Why are measurements of the current density of the...Ch. 17 - What percentage of matter is ordinary matter? What...Ch. 17 - How does the inflationary universe hypothesis...Ch. 17 - Prob. 24RQCh. 17 - What is the evidence that the Universe was...Ch. 17 - Prob. 26RQCh. 17 - If the Universe is negatively curved, and dark...Ch. 17 - What is the difference between hot dark matter and...Ch. 17 - Prob. 29RQCh. 17 - What evidence can you cite that the Universe's...Ch. 17 - Prob. 31RQCh. 17 - Reasoning by analogy often helps make complicated...Ch. 17 - Prob. 33RQCh. 17 - In science, wishing something to be true does not...Ch. 17 - Prob. 1PCh. 17 - Prob. 2PCh. 17 - Prob. 3PCh. 17 - Measure the lengths of the two arrows in the left...Ch. 17 - Prob. 5PCh. 17 - Prob. 6PCh. 17 - Find the wavelength of maximum intensity of the...Ch. 17 - Prob. 8PCh. 17 - Prob. 9PCh. 17 - Prob. 10PCh. 17 - Prob. 11PCh. 17 - Prob. 12PCh. 17 - Prob. 1SOPCh. 17 - Prob. 2SOPCh. 17 - Prob. 1LTLCh. 17 - Prob. 2LTLCh. 17 - Prob. 3LTLCh. 17 - Prob. 4LTLCh. 17 - Prob. 5LTLCh. 17 - Prob. 6LTL
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- 1. 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_forwardAssume 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*10^80arrow_forwardThe Andromeda Galaxy is a member of the Local Group of galaxies. It is approaching us. Does this mean that the Hubble Law is wrong? Why or why not? Explain.arrow_forward
- Assuming that the Hubble constant is, in fact, constant over the age of the universe, what is the Hubble look-back time (effectively the age of the universe in this case) if the Hubble constant is measured to be 50 km/s/Mpc (Please give your answer in units of billions of years; i.e. 10 billion years should be answered as 10)? Keep in mind that this is not the observed measurement of the Hubble constant (70 km/s/Mpc) and is only a value given for this problem. That said, it is not incredibly different so you should expect your answer to still be on the scale of billions of years.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_forwardIf a galaxy is 8.8 Mpc away from Earth and recedes at 498 km/s, what is H0 (in km/s/Mpc)? _______ km/s/Mpc What is the Hubble time (in yr)? _______ yr 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. B: If the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.arrow_forward
- Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In this case, A. Galaxy 1 must be twice as big as Galaxy 2. B. we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2. C. we are seeing Galaxy 1 as it looked at a later time in the history of the universe than Galaxy 2. D. Galaxy 2 must be twice as old as Galaxy 1.arrow_forwardDoes Hubble's Law work well for galaxies in the Local Group (such as Andromeda)? No, because dark energy is accelerating the universe's expansion over those distances. No, because we do not know the precise value of Ho. No, because Hubble did not know the Local Group existed when he discovered his law. Yes, it works well for all galaxies. No, because galaxies in the Local Group are bound gravitationally together.arrow_forwardAssume 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*1080arrow_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_forwardYour 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?arrow_forwardHubble'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.arrow_forward
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