21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Chapter 21, Problem 42QP
To determine
The number of hydrogen atom resent in each cubic meter in the universe.
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We are going to make a simple approximation of the number of atoms in the universe.
Assume all the atoms in the universe are hydrogen. (In actual practice, over 75% of the atoms in the universe are hydrogen.)
Assume the sun is a typical star (made of pure hydrogen) has a density of 1.4 g/cm3 and is a sphere with a radius of 7.0*108m
Assume that there are 100 billion stars in our Milky Way galaxy that are identical to our sun.
Assume that there are 10 billion galaxies in the universe identical to our Milky Way galaxy. How many atoms are there in the universe?
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
How many galaxies are there in the universe?
Chapter 21 Solutions
21st Century Astronomy
Ch. 21.1 - Prob. 21.1CYUCh. 21.2 - Prob. 21.2CYUCh. 21.3 - Prob. 21.3ACYUCh. 21.3 - Prob. 21.3BCYUCh. 21.4 - Prob. 21.4CYUCh. 21 - Prob. 1QPCh. 21 - Prob. 2QPCh. 21 - Prob. 3QPCh. 21 - Prob. 4QPCh. 21 - Prob. 5QP
Ch. 21 - Prob. 6QPCh. 21 - Prob. 7QPCh. 21 - Prob. 8QPCh. 21 - Prob. 9QPCh. 21 - Prob. 10QPCh. 21 - Prob. 11QPCh. 21 - Prob. 12QPCh. 21 - Prob. 13QPCh. 21 - Prob. 14QPCh. 21 - Prob. 15QPCh. 21 - Prob. 16QPCh. 21 - Prob. 17QPCh. 21 - Prob. 18QPCh. 21 - Prob. 19QPCh. 21 - Prob. 20QPCh. 21 - Prob. 21QPCh. 21 - Prob. 23QPCh. 21 - Prob. 24QPCh. 21 - Prob. 25QPCh. 21 - Prob. 26QPCh. 21 - Prob. 27QPCh. 21 - Prob. 28QPCh. 21 - Prob. 29QPCh. 21 - Prob. 30QPCh. 21 - Prob. 31QPCh. 21 - Prob. 32QPCh. 21 - Prob. 33QPCh. 21 - Prob. 34QPCh. 21 - Prob. 35QPCh. 21 - Prob. 36QPCh. 21 - Prob. 37QPCh. 21 - Prob. 38QPCh. 21 - Prob. 39QPCh. 21 - Prob. 40QPCh. 21 - Prob. 41QPCh. 21 - Prob. 42QPCh. 21 - Prob. 43QPCh. 21 - Prob. 44QPCh. 21 - Prob. 45QP
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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
- Recent findings in astrophysics suggest that the observable universe can be modeled as a sphere of radius R=13.7x109 light-years=13.0 x 1025m with an average total mass density of about 1x10-26 kg/m3 Only about 4% of total mass is due to “ordinary” matter (such as protons, neutrons, and electrons). Estimate how much ordinary matter (in kg) there is in the observable universe. (For the light-year, see Problem 19.)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_forwardWhen the universe was approximately one second old its size grew by a factor of 10 to the power of 30. true or false?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_forwardWe are going to make a simple approximation of the number of atoms in the universe. 1. Assume all the atoms in the universe are hydrogen. (In actual practice, over 75% of the atoms in the universe are hydrogen.) 2. Assume the sun is a typical star (made of pure hydrogen) has a density of 1.4 g/cm3 and is a sphere with a radius of 7.0*108m 3. Assume that there are 100 billion stars in our Milky Way galaxy that are identical to our sun. 4. Assume that there are 10 billion galaxies in the universe identical to our Milky Way galaxy.arrow_forwardIf we assume that the universe has been expanding at its current rate for its entire history, how old is the universe?arrow_forward
- What is the densest substance in the universe?arrow_forwardhow big is the universe in numbersarrow_forwardCurrent evidence suggests that the universe is a. flat, infinite, and neither expanding nor contracting. b. closed, finite, and slowing its expansion. c. open, infinite, and slowing its expansion. d. open, finite, and accelerating its expansion. e. flat, infinite, and accelerating its expansion.arrow_forward
- Most distances in the Galaxy are measured in light-years instead of meters. Why do you think this is the case?arrow_forwardConstruct a timeline for the universe and indicate when various significant events occurred, from the beginning of the expansion to the formation of the Sun to the appearance of humans on Earth.arrow_forwardSince the time of Copernicus, each revolution in astronomy has moved humans farther from the center of the universe. Now it appears that we may not even be made of the most common form of matter. Trace the changes in scientific thought about the central nature of Earth, the Sun, and our Galaxy on a cosmic scale. Explain how the notion that most of the universe is made of dark matter continues this “Copernican tradition.”arrow_forward
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