Loose Leaf For Explorations: Introduction To Astronomy
9th Edition
ISBN: 9781260432145
Author: Thomas T Arny, Stephen E Schneider Professor
Publisher: McGraw-Hill Education
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Chapter 18, Problem 2TY
To determine
The age of the Universe, if Hubble’s constant were half of the value we thick it is.
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The matter density in the Universe today is ?m=2.7×10−27kgm−3. What would be the value of the density parameter, Ω0, if the Hubble constant had the value H0 = 38 km/s/Mpc?
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?
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
Chapter 18 Solutions
Loose Leaf For Explorations: Introduction To Astronomy
Ch. 18 - Why do astronomers think that the Universe is...Ch. 18 - What is meant by the age of the Universe? How old...Ch. 18 - Prob. 3QFRCh. 18 - What is Olbers paradox?Ch. 18 - Prob. 5QFRCh. 18 - Prob. 6QFRCh. 18 - Prob. 7QFRCh. 18 - Prob. 8QFRCh. 18 - Prob. 9QFRCh. 18 - Prob. 10QFR
Ch. 18 - Prob. 11QFRCh. 18 - Prob. 12QFRCh. 18 - Prob. 13QFRCh. 18 - Prob. 14QFRCh. 18 - Prob. 15QFRCh. 18 - Prob. 16QFRCh. 18 - Prob. 17QFRCh. 18 - Prob. 18QFRCh. 18 - Prob. 19QFRCh. 18 - Prob. 20QFRCh. 18 - Prob. 1TQCh. 18 - Prob. 2TQCh. 18 - Prob. 3TQCh. 18 - Prob. 4TQCh. 18 - Prob. 5TQCh. 18 - Prob. 6TQCh. 18 - Prob. 7TQCh. 18 - Why are there points below the green line (instead...Ch. 18 - Prob. 9TQCh. 18 - Until recently, experimental results for the...Ch. 18 - The temperature of Universe at recombination was...Ch. 18 - Prob. 3PCh. 18 - Prob. 4PCh. 18 - The temperature of the Universe at recombination...Ch. 18 - One second after the Big Bang, the density of the...Ch. 18 - Prob. 7PCh. 18 - Prob. 8PCh. 18 - Prob. 1TYCh. 18 - Prob. 2TYCh. 18 - Prob. 3TYCh. 18 - Which of the following statements about the first...Ch. 18 - Prob. 5TYCh. 18 - Prob. 6TYCh. 18 - Prob. 7TYCh. 18 - Prob. 8TYCh. 18 - Prob. 9TYCh. 18 - Prob. 1EQFRCh. 18 - Prob. 2EQFRCh. 18 - Prob. 3EQFRCh. 18 - Prob. 4EQFRCh. 18 - Prob. 5EQFRCh. 18 - Prob. 6EQFRCh. 18 - Prob. 7EQFRCh. 18 - Prob. 8EQFRCh. 18 - Prob. 9EQFRCh. 18 - What is meant by the Gaia hypothesis?Ch. 18 - Prob. 11EQFRCh. 18 - Prob. 1ETQCh. 18 - Prob. 2ETQCh. 18 - Prob. 3ETQCh. 18 - Prob. 4ETQCh. 18 - Prob. 5ETQCh. 18 - Prob. 6ETQCh. 18 - Prob. 7ETQCh. 18 - Prob. 8ETQCh. 18 - Prob. 1EPCh. 18 - Prob. 2EPCh. 18 - Prob. 3EPCh. 18 - Prob. 4EPCh. 18 - Prob. 5EPCh. 18 - Prob. 6EPCh. 18 - Prob. 1ETYCh. 18 - Prob. 2ETYCh. 18 - Prob. 3ETYCh. 18 - Prob. 4ETYCh. 18 - Prob. 5ETYCh. 18 - Prob. 6ETYCh. 18 - Prob. 7ETY
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- What does the term Hubble time mean in cosmology, and what is the current best calculation for the Hubble time?arrow_forwardWhy couldnt atomic nuclei exist when the Universe was less than about 2 minutes old?arrow_forwardNow let’s determine when the universe “started its trip”. The distance is 800 Mpc, but first convert Mpcinto km because the rate, or velocity, is in km/sec.800 Mpc = _____________________kmUse equation (E) to determine how many seconds ago the universe started:_____________________secsarrow_forward
- 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_forwardAccording to the cosmological principle, our place in the universe does not appear to be particularly special compared to any other and it allows us to make predictions about the development of other galaxies and the evolution of the universe. The principle relies on Hubble's results that the universe appears to be the same in all directions (aka it is Question Blank 1 of 2) {hint: one word} and that any large region of space at a given distance from us appears like any other large region of space at a similar distance from us (aka it is Question Blank 2 of 2) {hint: one word}arrow_forwardExplain why the universe cannot be older than the Hubble time.arrow_forward
- Calculate the age of the universe for the following Hubble's constant, (b) 65 km/s/Mpcarrow_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_forwardIf a galaxy is 8.8 Mpc away from Earth and recedes at 498 km/s, what is H0 (in km/s/Mpc)? _______ km/s/Mpc What is the Hubble time (in yr)? _______ yr How would acceleration change your answer? A: If the expansion of the Universe has been accelerating, the Universe could be substantially younger than the value entered above. B: If the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.arrow_forward
- The 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_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_forwardWhat is the spatial radius of curvature for a hypothetical closed universe at a moment of time with given values below. Give the answer in units of Mpc, to the nearest integer (not in scientific notation - e.g., 1234). Values: H = 51 km s-1 Mpc-1 ρ = 2.9x10-26 kg m-3arrow_forward
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