Understanding Our Universe
3rd Edition
ISBN: 9780393614428
Author: PALEN, Stacy, Kay, Laura, Blumenthal, George (george Ray)
Publisher: W.w. Norton & Company,
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Chapter 1, Problem 13QAP
To determine
The statement of Occam’s razor.
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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
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.)
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.
Chapter 1 Solutions
Understanding Our Universe
Ch. 1.1 - Prob. 1.1CYUCh. 1.2 - Prob. 1.2CYUCh. 1.3 - Prob. 1.3CYUCh. 1 - Prob. 1QAPCh. 1 - Prob. 2QAPCh. 1 - Prob. 3QAPCh. 1 - Prob. 4QAPCh. 1 - Prob. 5QAPCh. 1 - Prob. 6QAPCh. 1 - Prob. 7QAP
Ch. 1 - Prob. 8QAPCh. 1 - Prob. 9QAPCh. 1 - Prob. 10QAPCh. 1 - Prob. 11QAPCh. 1 - Prob. 12QAPCh. 1 - Prob. 13QAPCh. 1 - Prob. 14QAPCh. 1 - Prob. 15QAPCh. 1 - Prob. 16QAPCh. 1 - Prob. 17QAPCh. 1 - Prob. 18QAPCh. 1 - Prob. 19QAPCh. 1 - Prob. 20QAPCh. 1 - Prob. 21QAPCh. 1 - Prob. 22QAPCh. 1 - Prob. 23QAPCh. 1 - Prob. 24QAPCh. 1 - Prob. 25QAPCh. 1 - Prob. 26QAPCh. 1 - Prob. 27QAPCh. 1 - Prob. 28QAPCh. 1 - Prob. 29QAPCh. 1 - Prob. 30QAPCh. 1 - Prob. 31QAPCh. 1 - Prob. 32QAPCh. 1 - Prob. 34QAPCh. 1 - Prob. 35QAPCh. 1 - Prob. 36QAPCh. 1 - Prob. 37QAPCh. 1 - Prob. 38QAPCh. 1 - Prob. 39QAPCh. 1 - Prob. 40QAPCh. 1 - Prob. 41QAPCh. 1 - Prob. 42QAPCh. 1 - Prob. 43QAPCh. 1 - Prob. 44QAPCh. 1 - Prob. 45QAP
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- Suppose you are standing in the center of a large, densely populated city that is exactly circular, surrounded by a ring of suburbs with lower-density population, surrounded in turn by a ring of farmland. From this specific location, would you say the population distribution is isotropic? Homogeneous?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_forwardI asked the following question and was given the attached solution: Suppose that the universe were full of spherical objects, each of mass m and radius r . If the objects were distributed uniformly throughout the universe, what number density (#/m3) of spherical objects would be required to make the density equal to the critical density of our Universe? Values: m = 4 kg r = 0.0407 m Answer must be in scientific notation and include zero decimal places (1 sig fig --- e.g., 1234 should be written as 1*10^3) I don't follow the work and I got the wrong answer, so please help and show your work as I do not follow along easily thanksarrow_forward
- mathematician Archimedes, responding to a claim that the number of grains of sand was infinite, calculated that the number of grains of sand needed to fill the universe was on the order of 1063. Our understanding of the size of the universe has changed since then, and we now know that the observable universe alone is a sphere with a radius of 1026 m. Estimating the size of a grain of sand, A) Approximately how many grains of sand would fill the observable universe? B) How many times larger or smaller is this number than Archimedes' result?arrow_forwardThe visible section of the Universe is a sphere centered on the bridge of your nose, with radius 13.7 billion light-years. (a) Explain why the visible Universe is getting larger, with its radius increasing by one light-year in every year. (b) Find the rate at which the volume of the visible section of the Universe is increasing.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.arrow_forward
- Suppose that the universe were full of spherical objects, each of mass m and radius r . If the objects were distributed uniformly throughout the universe, what number density (#/m3) of spherical objects would be required to make the density equal to the critical density of our Universe? Values: m = 10 kg r = 0.0399 m Answer must be in scientific notation and include zero decimal places (1 sig fig --- e.g., 1234 should be written as 1*10^3)arrow_forwardExplain the Higher-Order Systems?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_forward
- Please list 4 different forms of energy present in the universe?arrow_forwardI have submitted this question 4 times and the responses have all been wrong. Please put your best person on this. I have tried 19.9923, 20.6, and 20.69 for part 1 and those are all wrong and I have tried 14.1122, 14.80, 8.41781, and 14.87 for part 2 and those are all wrong too. Please help! I'm wasting questions!arrow_forwardAnother explanation for the Universe is the Steady State Hypothesis. The Steady State Hypothesis says that the Universe has always existed and is infinite in extent. Which of the following supports the Big Bang Theory and which supports the Steady State Model. (Select B-Big Bang Theory, S-Steady State Model, If the first is B and the rest S, enter BSSSSS). A) An observation that some globular clusters show M-type stars that have evolved off the main sequence. B) The measurement of redshifts that show galaxies appear to be moving away from each other and the Universe is expanding. C) A measurement that shows the density of the Universe is close to the critical density. D) The measurement of the microwave background radiation. E) Observing that galaxies at very large distances look identical to those in the nearby universe.arrow_forward
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