Astronomy Today (9th Edition)
9th Edition
ISBN: 9780134450278
Author: Eric Chaisson, Steve McMillan
Publisher: PEARSON
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Chapter 1, Problem 9P
To determine
The number of grains of sand in all the beaches of the world, and then to compare it with the number of stars in the observable universe.
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Check out a sample textbook solutionStudents have asked these similar questions
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?
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.)
What would be your estimate for the age of the universe if you measured Hubbleʹs constant to be 33 km/s/Mly? You can assume that the expansion rate has remained unchanged during the history of the universe.
Chapter 1 Solutions
Astronomy Today (9th Edition)
Ch. 1 - Prob. 1DCh. 1 - Prob. 2DCh. 1 - Prob. 3DCh. 1 - Prob. 4DCh. 1 - Prob. 5DCh. 1 - Prob. 6DCh. 1 - Prob. 7DCh. 1 - Prob. 8DCh. 1 - Prob. 9DCh. 1 - Prob. 10D
Ch. 1 - Prob. 11DCh. 1 - Prob. 12DCh. 1 - Prob. 13DCh. 1 - Prob. 14DCh. 1 - Prob. 15DCh. 1 - Prob. 1MCCh. 1 - Prob. 2MCCh. 1 - Prob. 3MCCh. 1 - Prob. 4MCCh. 1 - Prob. 5MCCh. 1 - Prob. 6MCCh. 1 - Prob. 7MCCh. 1 - Prob. 8MCCh. 1 - Prob. 9MCCh. 1 - Prob. 10MCCh. 1 - Prob. 1PCh. 1 - Prob. 2PCh. 1 - Prob. 3PCh. 1 - Prob. 4PCh. 1 - Prob. 5PCh. 1 - Prob. 6PCh. 1 - Prob. 7PCh. 1 - Prob. 9P
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- The Universe is approximately 13.8 Billion years old. What is the volume of the visible universe in m3?arrow_forwardOur galaxy is approximately 100,000 light years in diameter and 2,000 light years thick through the plane of the galaxy. If we were to compare the ratio of the diameter galaxy and its thickness to the ratio of the diameter of a CD and its thickness (CD has a diameter of 12 cm and thickness of 0.6 mm), what would be the factor differentiating those ratios? Put differently, if the galaxy were scaled down to the diameter of a CD, how many times thicker or thinner would the galaxy be than the CD? (For example if it would be twice as thick, you would answer 2 and if it were twice as thin you would answer 0.5 (aka 1/2))arrow_forwardi paste a screenshot herearrow_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. 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_forwardConvert 3,000 grades/century to Mega Hertz (MHz)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_forwardMeasure the length of the meter stick using your ruler. How many ‘rulers’ is equal to the length of the meter stick?arrow_forwardUsing the data in the table below and the appropriate conversion factors, find the mean distance to the moon, in feet. Approximate Values of Some Measured Lengths Length (m) Distance from Earth to most remote known quasar 1 ✕ 1026 Distance from Earth to most remote known galaxies 4 ✕ 1025 Distance from Earth to nearest large galaxy (M31 in Andromeda) 2 ✕ 1022 Distance from Earth to nearest star (Proxima Centauri) 4 ✕ 1016 One lightyear 9 ✕ 1015 Mean orbit radius of the Earth about the Sun 2 ✕ 1011 Mean distance from the Earth to the Moon 4 ✕ 108 Mean radius of the Earth 6 ✕ 106 Typical altitude of a satellite orbiting Earth 2 ✕ 105 Length of a football field 9 ✕ 101 Length of a housefly 5 ✕ 10-3 Size of the smallest dust particles 1 ✕ 10-4 Size of the cells of most living organisms 1 ✕ 10-5 Diameter of a hydrogen atom 1 ✕ 10-10 Diameter of an atomic nucleus 1 ✕ 10-14 Diameter of a proton 1 ✕ 10-15arrow_forward
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