Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 29, Problem 3E
What does the term Hubble time mean in cosmology, and what is the current best calculation for the Hubble time?
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The figure below is based on an assumed Hubble constant of 70 km/s/Mpc. How would you change the diagram to fit a Hubble constant of 50 km/s/Mpc?
If the evolution of the universe were
determined only by gravity, then its
fate would be linked to its geometry.
Open
Negligible normal matter
Flat
Closed
14
9.5
Past Future
Time
Billion years ago
Now
The slope of the "negligible normal matter" line would be ---Select---
C and cross the time axis ---Select---
O than 14 billion years ago. The curved line separating the open and closed
universe regions would cross the time axis
O than 9.5 billion years ago.
---Select---
Scale of the universe, R
© Cengage Learning 2013
What is the most likely range of values for Hubble’s constant? What are the uncertainties in its value?
If you find that the Hubble constant is double what we currently believe, how does this affect the calculated age of the universe?
Group of answer choices
It decreased it by a factor of four.
It cuts it in half.
It doubles it.
It increases it by a factor of four.
Chapter 29 Solutions
Astronomy
Ch. 29 - What are the basic observations about the universe...Ch. 29 - Describe some possible futures for the universe...Ch. 29 - What does the term Hubble time mean in cosmology,...Ch. 29 - Which formed first: hydrogen nuclei or hydrogen...Ch. 29 - Describe at least two characteristics of the...Ch. 29 - Describe two properties of the universe that are...Ch. 29 - Why do astronomers believe there must be dark...Ch. 29 - What is dark energy and what evidence do...Ch. 29 - Thinking about the ideas of space and time in...Ch. 29 - Astronomers have found that there is more helium...
Ch. 29 - Describe the anthropic principle. What are some...Ch. 29 - Describe the evidence that the expansion of the...Ch. 29 - What is the most useful probe of the early...Ch. 29 - What are the advantages and disadvantages of using...Ch. 29 - Would acceleration of the universe occur if it...Ch. 29 - Suppose the universe expands forever. Describe...Ch. 29 - Some theorists expected that observations would...Ch. 29 - There are a variety of ways of estimating the ages...Ch. 29 - Since the time of Copernicus, each revolution in...Ch. 29 - The anthropic principle suggests that in some...Ch. 29 - Penzias and Wilson’s discovery of the Cosmic...Ch. 29 - Construct a timeline for the universe and indicate...Ch. 29 - Suppose the Hubble constant were not 22 but 33...Ch. 29 - Assume that the average galaxy contains...Ch. 29 - The CMB contains roughly 400 million photons per...Ch. 29 - Following up on Exercise 29.27 calculate the...Ch. 29 - Continuing the thinking in Exercise 29.27 and...Ch. 29 - Continuing the thinking in the last three...Ch. 29 - There is still some uncertainty in the Hubble...Ch. 29 - It is possible to derive the age of the universe...
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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
- 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.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_forwardWhat would be the Hubble constant if the universe were 18 billion years old?arrow_forward
- What is the estimated age of the Universe (in years) if the Hubble constant is 80 km/s/Mpc?arrow_forwardPerhaps the most fundamental problem in all of astronomy is the determination of distance to the various objects in the cosmos. Which of the following seems least reasonable regarding the various measurement techniques: Group of answer choices The Hubble Law relates the recessional speed of distant objects (measured with the Doppler Effect) to distance. Hubble law is most useful for determining the distance to nearby objects, while parallax is most useful for the more distant objects. We can determine the position of a star on the H-R diagram through spectral analysis and then figure out the distance by comparing absolute luminosity (from H-R diagram) to apparent brightness. The distance to nearby stars can be determined by measuring parallax. The distance to the planets in our solar can be determined by measuring the time for a radar signal to reach a planet, bounce off, and return.arrow_forwardWhat is the difference between hot dark matter and cold dark matter? How does this difference affect cosmology?arrow_forward
- The best parallaxes obtained with Hipparcos have an accuracy of 0.001 arcsec. If you want to measure the distance to a star with an accuracy of 10%, its parallax must be 10 times larger than the typical error. How far away can you obtain a distance that is accurate to 10% with Hipparcos data? The disk of our Galaxy is 100,000 light-years in diameter. What fraction of the diameter of the Galaxy’s disk is the distance for which we can measure accurate parallaxes?arrow_forwardCan an elliptical galaxy evolve into a spiral? Explain your answer. Can a spiral turn into an elliptical? How?arrow_forwardThere is still some uncertainty in the Hubble constant. (a) Current estimates range from about 19.9 km/s per million light-years to 23 km/s per million light-years. Assume that the Hubble constant has been constant since the Big Bang. What is the possible range in the ages of the universe? Use the equation in the text, T0=1H , and make sure you use consistent units. (b) Twenty years ago, estimates for the Hubble constant ranged from 50 to 100 km/s per Mps. What are the possible ages for the universe from those values? Can you rule out some of these possibilities on the basis of other evidence?arrow_forward
- If the diameter of the Milky Way Galaxys visible disk, 80,000 ly, is represented in a model by a dinner plate with a diameter of 10 inches, what is the model distance to galaxy M31, 2.6 millionly away? What is the model distance to the Virgo galaxy cluster, 16 Mpc away? (Convert answers to feet.)arrow_forwardWhy is Hubble’s law considered one of the most important discoveries in the history of astronomy?arrow_forwardSuppose you were Hubble and Humason, working on the distances and Doppler shifts of the galaxies. What sorts of things would you have to do to convince yourself (and others) that the relationship you were seeing between the two quantities was a real feature of the behavior of the universe? (For example, would data from two galaxies be enough to demonstrate Hubble’s law? Would data from just the nearest galaxies-in what astronomers call “the Local Group”-suffice?)arrow_forward
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