Understanding Our Universe
3rd Edition
ISBN: 9780393614428
Author: PALEN, Stacy, Kay, Laura, Blumenthal, George (george Ray)
Publisher: W.w. Norton & Company,
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Chapter 17, Problem 18QAP
To determine
Reason why dark matter does not collapse.
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Students have asked these similar questions
What is the total energy of all the radiation in the current Hubble Radius?
H0 = 70 km/s/Mps
omega(radation) 0 = 9.0 x 10^-5
What can change the expansion rate of the Universe over time?
Gravity: Attractive forces increase the expansion rate by pulling mass together making gravity stronger.
Gravity decreases the expansion rate, while electromagnetic forces are always repulsive and speed-up expansion.
Attractive forces such as gravity decrease the expansion rate. Repulsive forces would speed-up expansion by pushing spacetime apart.
Nothing, since the expansion rate remains always constant, and it is measured from Hubble's law.
Give examples of baryonic matter.
Chapter 17 Solutions
Understanding Our Universe
Ch. 17.1 - Prob. 17.1CYUCh. 17.2 - Prob. 17.2CYUCh. 17.3 - Prob. 17.3CYUCh. 17.4 - Prob. 17.4CYUCh. 17.5 - Prob. 17.5CYUCh. 17 - Prob. 1QAPCh. 17 - Prob. 2QAPCh. 17 - Prob. 3QAPCh. 17 - Prob. 4QAPCh. 17 - Prob. 5QAP
Ch. 17 - Prob. 6QAPCh. 17 - Prob. 7QAPCh. 17 - Prob. 8QAPCh. 17 - Prob. 9QAPCh. 17 - Prob. 10QAPCh. 17 - Prob. 11QAPCh. 17 - Prob. 12QAPCh. 17 - Prob. 13QAPCh. 17 - Prob. 14QAPCh. 17 - Prob. 15QAPCh. 17 - Prob. 16QAPCh. 17 - Prob. 17QAPCh. 17 - Prob. 18QAPCh. 17 - Prob. 19QAPCh. 17 - Prob. 20QAPCh. 17 - Prob. 21QAPCh. 17 - Prob. 22QAPCh. 17 - Prob. 23QAPCh. 17 - Prob. 24QAPCh. 17 - Prob. 25QAPCh. 17 - Prob. 26QAPCh. 17 - Prob. 27QAPCh. 17 - Prob. 28QAPCh. 17 - Prob. 29QAPCh. 17 - Prob. 30QAPCh. 17 - Prob. 31QAPCh. 17 - Prob. 32QAPCh. 17 - Prob. 33QAPCh. 17 - Prob. 34QAPCh. 17 - Prob. 35QAPCh. 17 - Prob. 36QAPCh. 17 - Prob. 37QAPCh. 17 - Prob. 38QAPCh. 17 - Prob. 39QAPCh. 17 - Prob. 40QAPCh. 17 - Prob. 41QAPCh. 17 - Prob. 42QAPCh. 17 - Prob. 43QAPCh. 17 - Prob. 44QAPCh. 17 - Prob. 45QAP
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- What do the results from the Wilkinson Microwave Anisotropy Probe (WMAP) observations tell cosmologists?arrow_forwardWhat is the reason behind the creation of the lhc?arrow_forwardIn the early universe, the formation of л* or лº was through thermal interactions. What is the difference in mean temperatures for their thresholds of formation?arrow_forward
- Give examples of nonbaryonic matter.arrow_forwardWith a Hubble constant of 70 km/sec/Mpc, the critical density would be 1.4 g/cc. 9 × 10-27 kg/m3. 6.23 × 10-23 g/mole. 4 × 10-36 g/cc. 3 × 10-31 g/cc.arrow_forwardThe CMB contains roughly 400 million photons per m3. The energy of each photon depends on its wavelength. Calculate the typical wavelength of a CMB photon. Hint: The CMB is blackbody radiation at a temperature of 2.73 K. According to Wien’s law, the peak wave length in nanometers is given by max=3106T . Calculate the wavelength at which the CMB is a maximum and, to make the units consistent, convert this wavelength from nanometers to meters.arrow_forward
- The peak intensity of the CMBR occurs at a wavelength of 1.1 mm. (a) What is the energy in eV at a 1.1mm photon? (b) There are approximately 109 photons for each massive particle in deep space. Calculate the energy of 109 such photons. (c) If the average massive particle in space has a mass half that of a proton, what energy would be created by convening its mass to enemy? (d) Does this imply that space is “matter dominated”? Explain briefly.arrow_forwardNeutron stars are extremely dense objects that are formed from the remnants of supernova explosions. Many rotate very rapidly. Suppose the mass of a certain spherical neutron star is twice the mass of the Sun and its radius is 10.0 km. Determine the greatest possible angular speed the neutron star can have so that the matter at its surface on the equator is just held in orbit by the gravitational force.arrow_forwardExplain what is meant by the term cosmological redshift, and contrast it with the Doppler shift that is observed when a luminous object recedes from an observer. From the defi- nition of redshift in terms of the observed and emitted wavelengths of photons, obtain an expression that relates redshift to the expansion factor of the Universe. Hence calculate the expansion factor of the Universe while a photon travels from a galaxy with redshift z = 1.arrow_forward
- 2. Consider a neutron star of radius of 10 km and a mass of 1.4 M⊙ that has a surface layer of pure 1H. (a) For the given parameters, compute the luminosity and wavelength of peak emission of a neutron star shining at Eddington Luminosity in the rest frame of the neutron star. Assume black body emission. (b) What is the impact of a) the gravitational redshift and b) the time delay, both caused by general relativity, on the observed wavelength? (c) What is the wavelength and luminosity seen by an observer at large distance (much larger than neutron star radius)?arrow_forwardI understand how we got 1.485*10^19, but where did 1.6*10^-19 come from? Also what does that symbol before the E mean?arrow_forwardWhat is Hubble constant?arrow_forward
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