Concept explainers
(a)
(a)
Answer to Problem 33Q
Solution:
Explanation of Solution
Given data:
The temperature is increased by a factor of 100.
The temperature is increased from 2.725 K to 272.5 K.
Formula used:
The expression for mass density of radiation is:
Here,
Explanation:
Recall the formula for mass density of radiation:
Substitute 272.5 K for T,
Conclusion:
Therefore, the density of the radiation,
(b)
Whether it would be more accurate to describe our universe as matter-dominated or radiation-dominated. If the average density of matter,
(b)
Answer to Problem 33Q
Solution:
Radiation-dominated.
Explanation of Solution
Given data:
The temperature is increased by a factor of 100 from 2.725 K to 272.5 K.
Formula used:
The expression for mass density of radiation is:
Here,
Explanation:
Recall the expression for mass density of radiation.
Substitute 272.5 K for T,
From the calculation,
Conclusion:
Therefore, the universe would be radiation-dominated.
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Chapter 25 Solutions
Universe
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- Suppose a hypothetical universe is expanding (at some moment in time) at a rate of H. At this same moment the density of this Universe is ρ. (a) Confirm for yourself that this is a closed universe, given the values below. (b) Determine, and enter below, the spatial radius of curvature for this closed universe (at the same moment in time at which the values above are given). Values: H = 90 km s-1 Mpc-1 ρ = 4.2x10-26 kg m-3 Please show work because I have trouble following alongarrow_forwardSuppose a hypothetical universe is expanding (at some moment in time) at a rate of H. At this same moment the density of this Universe is ρ. (a) Confirm for yourself that this is a closed universe, given the values below. (b) Determine, and enter below, the spatial radius of curvature for this closed universe (at the same moment in time at which the values above are given). Values: H = 56 km s-1 Mpc-1 ρ = 4.9x10-25 kg m-3 Give your answer for (b) in units of Mpc, to the nearest integer (not in scientific notation - e.g., 1234).arrow_forwardUse Wien’s law to answer the following questions: (a) The cosmic background radiation peaks in intensity at a wavelength of 1.1 mm. To what temperature does this correspond? (b) About 379 000 y after the big bang, the universe became transparent to electromagnetic radiation. Its temperature then was 2970 K.What was the wavelength at which the background radiation was then most intense?arrow_forward
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- Modern PhysicsPhysicsISBN:9781111794378Author:Raymond A. Serway, Clement J. Moses, Curt A. MoyerPublisher:Cengage Learning