Mastering Physics with Pearson eText -- Standalone Access Card -- for Essential University Physics (3rd Edition)
3rd Edition
ISBN: 9780133857955
Author: Richard Wolfson
Publisher: PEARSON
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Chapter 39, Problem 48P
To determine
The critical density of the universe.
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Assume the average density of the Universe is equal to the critical density. (a) Prove that the age of the Universe is given by 2/(3H). (b) Calculate 2/(3H) and express it in years.
The critical mass density needed to just halt the expansion of the universe is approximately 10-26 kg/m3. Convert this to eV/c2.m3 .
If the average density of the Universe is small compared with the critical density, the expansion of the Universe described by Hubble's law proceeds with speeds that are nearly constant over time.
Calculate t since the big bang, assuming H = 22.0 km/s/Mly.
Chapter 39 Solutions
Mastering Physics with Pearson eText -- Standalone Access Card -- for Essential University Physics (3rd Edition)
Ch. 39 - Prob. 1FTDCh. 39 - Prob. 2FTDCh. 39 - Prob. 3FTDCh. 39 - Prob. 4FTDCh. 39 - Prob. 5FTDCh. 39 - Prob. 6FTDCh. 39 - Prob. 7FTDCh. 39 - Prob. 8FTDCh. 39 - Name the fundamental force involved in (a) binding...Ch. 39 - Prob. 10FTD
Ch. 39 - Prob. 11FTDCh. 39 - Prob. 12FTDCh. 39 - Prob. 13FTDCh. 39 - Prob. 14FTDCh. 39 - Describe the origin of the cosmic microwave...Ch. 39 - Prob. 16FTDCh. 39 - Prob. 17FTDCh. 39 - The radiation that we observe as the cosmic...Ch. 39 - Prob. 19FTDCh. 39 - Prob. 20FTDCh. 39 - Prob. 21ECh. 39 - Prob. 22ECh. 39 - Prob. 23ECh. 39 - Prob. 24ECh. 39 - Prob. 25ECh. 39 - Prob. 26ECh. 39 - Prob. 27ECh. 39 - Prob. 28ECh. 39 - Prob. 29ECh. 39 - Prob. 30ECh. 39 - Prob. 31ECh. 39 - Prob. 32ECh. 39 - Prob. 33ECh. 39 - Prob. 34ECh. 39 - Prob. 35ECh. 39 - Prob. 36ECh. 39 - Prob. 37ECh. 39 - Prob. 38PCh. 39 - Prob. 39PCh. 39 - Prob. 40PCh. 39 - Prob. 41PCh. 39 - Prob. 42PCh. 39 - Prob. 43PCh. 39 - Prob. 44PCh. 39 - Prob. 45PCh. 39 - Prob. 46PCh. 39 - Prob. 47PCh. 39 - Prob. 48PCh. 39 - Prob. 49PCh. 39 - Prob. 50PCh. 39 - Prob. 51PCh. 39 - Prob. 52PCh. 39 - Prob. 53PCh. 39 - Prob. 54PCh. 39 - Prob. 55PCh. 39 - Prob. 56PCh. 39 - Prob. 57PCh. 39 - Prob. 58PCh. 39 - Prob. 59PCh. 39 - Prob. 60PCh. 39 - Prob. 61PPCh. 39 - Prob. 62PPCh. 39 - Prob. 63PPCh. 39 - Prob. 64PP
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- Some theorists expected that observations would show that the density of matter in the universe is just equal to the critical density. Do the current observations support this hypothesis?arrow_forwardThe critical mass density needed to just halt the expansion of the universe is approximately (a) Convert this to (b) Find the number of neutrinos per cubic meter needed to close the universe if their average mass is and they have negligible kinetic energies.arrow_forwardWhat is the evidence that a large fraction of the matter in the universe is invisible?arrow_forward
- Find the size and age of an Einstein–de Sitter Universe probed by Z = 5 quasars.arrow_forwardWhat are the basic observations about the universe that any theory of cosmology must explain?arrow_forwardDescribe at least two characteristics of the universe that are explained by the standard Big Bang model.arrow_forward
- Suppose that the universe were full of spherical objects, each of mass m and radius r, with the objects distributed uniformly throughout the universe as in the previous problem. (Assume nonrelativistic objects.) Given the density of these spherical objects (as you would have found in the previous problem), how far would you be able to see in meters, on average, before your line of sight intersected one of them? Values (note, different from the above problem): m = 3 kg r = 0.03 m Answer must be in scientific notation and include zero decimal places (1 sig fig).arrow_forwardWhat mechanism can simultaneously solve both the flatness and horizon problems in cosmology?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_forward
- What effect does increasing the interaction strength of a massive particle species haveon its thermal relic abundance if it was in thermal equilibrium in the early universe(assuming no initial asymmetry)? a. relic abundance increases b. relic abundance decreases c. relic abundance essentially unchanged d. not enough informationarrow_forwardBy what factor would the critical density of the universe today change if the Hubble constant today measured at 5 times greater than what we previously thought?arrow_forwardWhich particles are not present in the universe at t=300s after the big bang ? select one : a. Electons b. photons c. neutrons d. Positronsarrow_forward
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