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?
Astronomers frequently say that “there are more stars in the universe than there are grains of sand on all the beaches on the earth”. Given that a typical grain of sand is about 0.5 – 1.0 mm in diameter, estimate the number of grains of sand on all the earth’s beaches. The diameter of the Earth is 12,742 km.
About 1011
About 1016
About 1021.
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.)
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 distance from the Sun to the nearest star is about 4 1016 m. The Milky Way galaxy (Fig. P1.31) is roughly a disk of diameter 1021 in and thickness 1019 m. Find the order of magnitude of the number of stars in the Milky Way. Assume the distance between the Sun and our nearest neighbor is typical. Figure P1.31 The Milky Way galaxy.arrow_forwardSuppose 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_forwardThe nearest neutron star (a collated star made primarily of neutrons) is about 3.00 1018 m away from Earth. Given that the Milky Way galaxy (Fig. P1.81) is roughly a disk of diameter 1021 m and thickness 1019 m, estimate the number of neutron stars in the Milky Way to the nearest order of magnitude. Figure P1.81arrow_forward
- 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.arrow_forwardThe 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_forward
- Using a single dimensional equation, estimate the number of steps it would take a person with a step length of 2.65 ft to walk from the Earth to Alpha Centauri a distance of 4.37 light-years. The speed of light is 1.86282 x 105 miles/s. Number of Steps = Enter your answer in accordance to the question statement x 1017arrow_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_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
- I 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_forwardSuppose 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_forward
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