The Cosmic Perspective Fundamentals (2nd Edition)
2nd Edition
ISBN: 9780133889567
Author: Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider, Mark Voit
Publisher: PEARSON
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Textbook Question
Chapter 1, Problem 5QQ
Could we see a galaxy that is 20 billion light-years away? (a) Yes, if we had a big enough telescope. (b) No, because it would be beyond the bounds of our observable universe (c) No, because a galaxy could not possible be that far away.
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Check out a sample textbook solutionStudents have asked these similar questions
Does 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.
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.
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?
Chapter 1 Solutions
The Cosmic Perspective Fundamentals (2nd Edition)
Ch. 1 - Choose the best answer to each of the following....Ch. 1 - Choose the best answer to each of the following....Ch. 1 - Choose the best answer to each of the following....Ch. 1 - Prob. 4QQCh. 1 - Could we see a galaxy that is 20 billion...Ch. 1 - Choose the best answer to each of the following....Ch. 1 - Choose the best answer to each of the following....Ch. 1 - When we say the universe is expanding, we mean...Ch. 1 - Choose the best answer to each of the following....Ch. 1 - Choose the best answer to each of the following....
Ch. 1 - Choose the best answer to each of the following....Ch. 1 - Choose the best answer to each of the following....Ch. 1 - Explain all answers clearly, using complete...Ch. 1 - Alien Technology, Some people believe that Earth...Ch. 1 - Explain all answers clearly, using complete...Ch. 1 - Explain all answers clearly, using complete...Ch. 1 - Explain all answers clearly, using complete...Ch. 1 - Prob. 18SEQCh. 1 - Explain all answers clearly, using complete...Ch. 1 - Explain all answers clearly, using complete...Ch. 1 - Explain all answers clearly, using complete...Ch. 1 - Explain all answers clearly, using complete...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- Suppose you want to observe every galaxy within some distance. Your enterprising assistant says that instead you can observe every galaxy within double the original distance. What is the ratio of the number of galaxies you can now observe as opposed to before? (For example, if you can observe twice as many: 2. If you can observe half as many: 0.5) Your answerarrow_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_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_forward
- When we observe the most distant galaxies what are we looking at? At galaxies with ages similar to that of the Milky Way, because light travels so quickly that there is no significant time delay. Because of the finite speed of light, we are observing how galaxies looked like in the past. Because of the finite speed of light, we have the opportunity to observe our own galaxy when it started forming in the past. Because of the long light travel time, we are observing old galaxies.arrow_forwardIf 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. Need Help? Read Itarrow_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_forward
- How long ago was that galaxy right next door to our own Galaxy if it has always been receding at its present rate? Express your answer in years. Since the universe began when all galaxies were very close together, this number is a rough estimate for the age of the universe.arrow_forwardIf a galaxy is 500 Mly away from us, how fast do we expect it to be moving and in what direction?arrow_forwardIf most galaxies are moving away from us, are we at the center of the universe? Why or why not?arrow_forward
- 1. 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_forwardUse the photo to answer the question. If an observer looked out from a planet near the center of this galaxy, what would it look like to that observer? O A broad band of stars forming a ring around the planet O A sphere of stars evenly spread in every direction O A spiral shape with arms reaching out from a center O A band of stars in one direction, with fewer stars in other directionsarrow_forwardAre the galaxies red-shifting or blue-shifting? Explain. (You may find the big-bang theory helpful). Andromeda galaxy is currently approaching our galaxy with a radial velocity of 266 km/sec. How far is our galaxy from Andromeda? (Hubble’s constant, H, is 73 km/sec/MParsec). When can the two galaxies be anticipated to collide?arrow_forward
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