Concept explainers
The number of joules of energy in each liter of space and the number of
Answer to Problem 8P
The number of joules of energy in each liter of space is
Explanation of Solution
The critical density of the Universe is
Therefore, the dark energy is
Convert
The mass of dark energy contains in
Write the formula to find the value of energy
Write the expression to find the energy of photon
Here,
Substitute
The dark energy present in
Substitute
The energy of
The
Conclusion:
The number of joules of energy in each liter of space is
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Chapter 18 Solutions
Loose Leaf For Explorations: Introduction To Astronomy
- Use 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_forwardThe geometry of spacetime in the Universe on large scales is determined by the mean energy density of the matter in the Universe, ρ. The critical density of the Universe is denoted by ρ0 and can be used to define the parameter Ω0 = ρ/ρ0. Describe the geometry of space when: (i) Ω0 < 1; (ii) Ω0 = 1; (iii) Ω0 > 1. Explain how measurements of the angular sizes of the hot- and cold-spots in the CMB projected on the sky can inform us about the geometry of spacetime in our Universe. What do measurements of these angular sizes by the WMAP and PLANCK satellites tell us about the value of Ω0?arrow_forward1. The current (critical) density of our universe is pe = 10-26kg/m³. Assume the universe is filled with cubes with equal size that each contain one person of m = 100kg. What would the length of the side of such a cube have to be in order to give the correct critical density? How many hydrogen atoms would you need in a box of 1 m³ to reach the critical density? The matter we know, which consists mostly of hydrogen, constitutes only 4.8% of the current critical energy density of our universe. So how many hydrogen atoms are actually in a box of 1 m3 in our universe? Deep space is very empty and a much better vacuum than we can obtain on earth in a laboratory.arrow_forward
- 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 = 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_forwardChoose the correct statements from the following list. (Give ALL correct answers, i.e., B, AC, BCD...) A) The inflationary model of the universe solves both the flatness and the horizon problems. B) The critical density is the density needed to cause the Big Bang. C) The horizon problem in cosmology is that regions of the universe that should not have ever had thermal contact with one another have the same temperature. D) A major difference between dark matter and dark energy is that one causes the univserse's expansion to slow down, the other to make it expand faster. E) Observations show us that the geometry of our universe must be very close to flat. F) Assuming no dark energy, if the matter density of the universe is less than critical, the universe is closed. G) Assuming no dark energy, if the matter density of the universe is greater than critical, the universe is will expand forever.arrow_forward(a) Estimate the mass of the luminous matter in the known universe, given there are 1011 galaxies, each containing 1011 stars of average mass 1.5 times that of our Sun. (b) How many protons (the most abundant nuclide) are there in this mass? (c) Estimate the total number of particles in the observable universe by multiplying the answer to (b) by two, since there is an electron for each proton, and then by 109 , since there are far more particles (such as photons and neutrinos) in space than in luminous matter.arrow_forward
- A space based observatory collects light emitted by a given galaxy. The light was initially emitted with a frequency of 600*10^12Hz but the detected signal is red shifted by 40*10^12Hz How fast is the galaxy moving and in what direction? Show the algebraic form of any equation(s) that you apply and report your calculation in the correct units and with the correct number of significant figures.arrow_forwardThe time before which we don’t know what happened in the universe (10-43 s) is called the Planck time. The theory needed is a quantum theory of gravity and concerns the three fundamental constants h, G, and c. (a) Use dimensional analysis to determine the exponents m, n, l if the Planck time tP = hmGncl . (b) Calculate the Planck time using the expression you found in (a).arrow_forwardIn the deep space between galaxies, the number density of atoms is as low as 106 atoms/m3, and the temperature is a frigid 2.7 K. a)What is the pressure, in pascals, in the region between galaxies? b)What volume, in cubic meters, is occupied by 1.5 mol of gas? c)If this volume is a cube, what is the length of one of its edges, in kilometers?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_forwardConsider the case where an electron and a positron annihilate each other and produce photons. Assume that these two particles collide head-on with equal, but slow, speeds. Is it possible that only one photon to is produced? If yes, how? If not, is it possible that only two photons are produced? If yes, how? Explain your reasoning.arrow_forward2.90 x 106 nm : K Find the wavelength (in mm) of maximum intensity of the cosmic microwave background radiation observed today. ( Hint: Use Wien's law, Amay mm What band of the electromagnetic spectrum is that in? (Examine the figure.) Visible light Short wavelengths Long wavelengths 4 x 107 5x 107 6x 107 7x 10meters (400 nm) (500 nm) (600 nm) /(700 nm) Wavelength (meters) 10 12 10 10 10 104 102 1 102 104 Gamma- Micro- Ultra- violet X-ray Infrared Radio ray wave UHF VHF FM AM Opaque Visual window Radio window Transparent Short Wavelength Long b O microwave O gamma ray O ultraviolet o o o Opacity of Earth's atmospherearrow_forward
- Stars and Galaxies (MindTap Course List)PhysicsISBN:9781337399944Author:Michael A. SeedsPublisher:Cengage LearningFoundations of Astronomy (MindTap Course List)PhysicsISBN:9781337399920Author:Michael A. Seeds, Dana BackmanPublisher:Cengage Learning