EBK FOUNDATIONS OF ASTRONOMY
14th Edition
ISBN: 8220106820612
Author: Backman
Publisher: YUZU
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Textbook Question
Chapter 17, Problem 1RQ
Is cosmology the study of the Universe, the observable universe, or both? How do you know?
Expert Solution & Answer
To determine
Whether cosmology is the study of the universe or the observable universe or both.
Answer to Problem 1RQ
Cosmology is the study of both the universe and the observable universe.
Explanation of Solution
Cosmology deals with a reasonable and suspicious effort to understand and explain the evolution and construction of the whole universe.
It provides information about evolution and origin of the entire universe.
The study of the galaxy and other matter which is observable from the Earth is called an observable universe. It is a sphere with the center at the observer at the locations of universe.
Therefore, cosmology is the study of entire universe.
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Students have asked these similar questions
Question B3
Consider the following FLRW spacetime:
t2
ds² = -dt² +
(dx²
+ dy²+ dz²),
t2
where t is a constant.
a)
State whether this universe is spatially open, closed or flat.
[2 marks]
b) Determine the Hubble factor H(t), and represent it in a (roughly drawn) plot as a function
of time t, starting at t = 0.
[3 marks]
c) Taking galaxy A to be located at (x, y, z) = (0,0,0), determine the proper distance to galaxy
B located at (x, y, z) = (L, 0, 0). Determine the recessional velocity of galaxy B with respect
to galaxy A.
d) The Friedmann equations are
2
k
8πG
а
4πG
+
a²
(p+3p).
3
a
3
[5 marks]
Use these equations to determine the energy density p(t) and the pressure p(t) for the
FLRW spacetime specified at the top of the page.
[5 marks]
e) Given the result of question B3.d, state whether the FLRW universe in question is (i)
radiation-dominated, (ii) matter-dominated, (iii) cosmological-constant-dominated, or (iv)
none of the previous. Justify your answer.
f)
[5 marks]
A conformally…
SECTION B
Answer ONLY TWO questions in Section B
[Expect to use one single-sided A4 page for each Section-B sub question.]
Question B1
Consider the line element
where w is a constant.
ds²=-dt²+e2wt dx²,
a) Determine the components of the metric and of the inverse metric.
[2 marks]
b) Determine the Christoffel symbols. [See the Appendix of this document.]
[10 marks]
c)
Write down the geodesic equations.
[5 marks]
d) Show that e2wt it is a constant of geodesic motion.
[4 marks]
e)
Solve the geodesic equations for null geodesics.
[4 marks]
Page 2
SECTION A
Answer ALL questions in Section A
[Expect to use one single-sided A4 page for each Section-A sub question.]
Question A1
SPA6308 (2024)
Consider Minkowski spacetime in Cartesian coordinates th
=
(t, x, y, z), such that
ds² = dt² + dx² + dy² + dz².
(a) Consider the vector with components V" = (1,-1,0,0). Determine V and V. V.
(b) Consider now the coordinate system x' (u, v, y, z) such that
u =t-x,
v=t+x.
[2 marks]
Write down the line element, the metric, the Christoffel symbols and the Riemann curvature
tensor in the new coordinates. [See the Appendix of this document.]
[5 marks]
(c) Determine V", that is, write the object in question A1.a in the coordinate system x'. Verify
explicitly that V. V is invariant under the coordinate transformation.
Question A2
[5 marks]
Suppose that A, is a covector field, and consider the object
Fv=AAμ.
(a) Show explicitly that F is a tensor, that is, show that it transforms appropriately under a
coordinate transformation.
[5 marks]
(b)…
Chapter 17 Solutions
EBK FOUNDATIONS OF ASTRONOMY
Ch. 17 - Is cosmology the study of the Universe, the...Ch. 17 - Is a cosmologist an astronomer? Is an astronomer a...Ch. 17 - How does the darkness of the night sky tell you...Ch. 17 - Explain the differences among the observable...Ch. 17 - Prob. 5RQCh. 17 - Prob. 6RQCh. 17 - Prob. 7RQCh. 17 - Prob. 8RQCh. 17 - Prob. 9RQCh. 17 - Prob. 10RQ
Ch. 17 - Prob. 11RQCh. 17 - If you accept the cosmological principle, how can...Ch. 17 - Why cant an open universe have a center? How can a...Ch. 17 - In which type of model universe is space-time...Ch. 17 - In which type of model universe is space-time...Ch. 17 - What is the fate of a closed universe? In what...Ch. 17 - In which model universe does the average density...Ch. 17 - Prob. 18RQCh. 17 - What evidence shows that the Universe is...Ch. 17 - Why couldnt atomic nuclei exist when the Universe...Ch. 17 - Why are measurements of the current density of the...Ch. 17 - What percentage of matter is ordinary matter? What...Ch. 17 - How does the inflationary universe hypothesis...Ch. 17 - Prob. 24RQCh. 17 - What is the evidence that the Universe was...Ch. 17 - Prob. 26RQCh. 17 - If the Universe is negatively curved, and dark...Ch. 17 - What is the difference between hot dark matter and...Ch. 17 - Prob. 29RQCh. 17 - What evidence can you cite that the Universe's...Ch. 17 - Prob. 31RQCh. 17 - Reasoning by analogy often helps make complicated...Ch. 17 - Prob. 33RQCh. 17 - In science, wishing something to be true does not...Ch. 17 - Prob. 1PCh. 17 - Prob. 2PCh. 17 - Prob. 3PCh. 17 - Measure the lengths of the two arrows in the left...Ch. 17 - Prob. 5PCh. 17 - Prob. 6PCh. 17 - Find the wavelength of maximum intensity of the...Ch. 17 - Prob. 8PCh. 17 - Prob. 9PCh. 17 - Prob. 10PCh. 17 - Prob. 11PCh. 17 - Prob. 12PCh. 17 - Prob. 1SOPCh. 17 - Prob. 2SOPCh. 17 - Prob. 1LTLCh. 17 - Prob. 2LTLCh. 17 - Prob. 3LTLCh. 17 - Prob. 4LTLCh. 17 - Prob. 5LTLCh. 17 - Prob. 6LTL
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