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+{
+ "metadata": {
+ "name": "",
+ "signature": "sha256:3790a3d51914dcd136e5ca3ce886512d33fbd8ae15c97de507356c2c79104f21"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+ {
+ "cells": [
+ {
+ "cell_type": "heading",
+ "level": 1,
+ "metadata": {},
+ "source": [
+ "Chapter 16: Cosmology and Modern Astrophysics - The Beginning and the End"
+ ]
+ },
+ {
+ "cell_type": "heading",
+ "level": 2,
+ "metadata": {},
+ "source": [
+ "Example 16.1, Page 581"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "import math\n",
+ "\n",
+ "#Variable declaration\n",
+ "H0 = 22; # Value of Hubble constant, km/s per million ly\n",
+ "parsec = 3.26; # The value of 1 parsec, light years\n",
+ "\n",
+ "#Calculations&Result\n",
+ "print \"The value of Hubble constant = %d km/s per Mpc\"%math.ceil(H0*parsec)"
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "The value of Hubble constant = 72 km/s per Mpc\n"
+ ]
+ }
+ ],
+ "prompt_number": 1
+ },
+ {
+ "cell_type": "heading",
+ "level": 2,
+ "metadata": {},
+ "source": [
+ "Example 16.2, Page 583"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "#Variable declaration\n",
+ "M = 1; # Let the current mass of the universe be unity\n",
+ "m_u = 1; # Mass equivalent of 1 amu, u\n",
+ "N_n = 2; # Number of neutrons in helium\n",
+ "N_p = 2; # Number of protons in helium\n",
+ "\n",
+ "#Calculations\n",
+ "M_p = 0.75*M*m_u; # Total mass of protons\n",
+ "M_He = 0.25*M*m_u; # Total mass of helium\n",
+ "N_fp = M_p/M_He*(N_n + N_p); # Total number of free protons for every He-4\n",
+ "N_P = N_fp + N_p; # Total number of protons per He-4\n",
+ "ratio = N_P/N_n; # Current ratio of protons to the neutrons in the universe\n",
+ "\n",
+ "#Result\n",
+ "print \"The current ratio of protons to the neutrons in the universe = %d\"%ratio"
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "The current ratio of protons to the neutrons in the universe = 7\n"
+ ]
+ }
+ ],
+ "prompt_number": 2
+ },
+ {
+ "cell_type": "heading",
+ "level": 2,
+ "metadata": {},
+ "source": [
+ "Example 16.3, Page 607"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "import math\n",
+ "\n",
+ "#Variable declaration\n",
+ "m_n = 939.566; # Rest mass of the neutron, MeV/c^2\n",
+ "m_p = 938.272; # Rest mass of the proton, MeV/c^2\n",
+ "e = 1.6e-019; # Energy equivalent of 1 eV, J\n",
+ "c = 1; # For simplicity assume speed of light of light to be unity\n",
+ "T = 1e+010; # Temperature of the universe, K\n",
+ "\n",
+ "#Calculations\n",
+ "delta_m = m_n - m_p; # Mass difference between a proton and a neutron, MeV/c^2\n",
+ "k = 1.38e-023; # Boltzmann constant, J/k\n",
+ "# As from Maxwell-Boltzmann distribution from thermodynamics, N = exp(-m*c^2/(k*T)), so\n",
+ "ratio = math.exp(delta_m*c**2*1e+006*e/(k*T)); # Ratio of protons to neutrons in the universe at 10 billion kelvin\n",
+ "\n",
+ "#Result\n",
+ "print \"The ratio of protons to neutrons in the universe at 10 billion kelvin = %3.1f\"%ratio"
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "The ratio of protons to neutrons in the universe at 10 billion kelvin = 4.5\n"
+ ]
+ }
+ ],
+ "prompt_number": 3
+ },
+ {
+ "cell_type": "heading",
+ "level": 2,
+ "metadata": {},
+ "source": [
+ "Example 16.4, Page 589"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "import math\n",
+ "\n",
+ "#Variable declaration\n",
+ "M = 1.99e+030; # Mass of the sun, kg\n",
+ "G = 6.67e-011; # Universal gravitational constant, N-Sq.m/kg^2\n",
+ "k = 1.38e-023; # Boltzmann constant, J/K\n",
+ "R = 6.96e+008; # Radius of the sun, m\n",
+ "m = 1.67e-027; # Rest mass of the proton, kg\n",
+ "\n",
+ "#Calculations\n",
+ "PE = 3./5*(G*M**2/R); # Self potential energy of the sun, J\n",
+ "# As KE = 1./3*(M/m_p)*m_p*v**2, solving for v\n",
+ "v = math.sqrt(2*PE/M); # Velocity of a proton inside the sun, m/s\n",
+ "# From kinetic theory of gases, v = sqrt(3*k*T/m), solving for T\n",
+ "T = m*v**2/(3*k); # The mean temperature of the sun, K\n",
+ "\n",
+ "#Result\n",
+ "print \"The mean temperature of the sun = %1.0e K\"%T"
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "The mean temperature of the sun = 9e+06 K\n"
+ ]
+ }
+ ],
+ "prompt_number": 4
+ },
+ {
+ "cell_type": "heading",
+ "level": 2,
+ "metadata": {},
+ "source": [
+ "Example 16.5, Page 590"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "import math\n",
+ "\n",
+ "#Variable declaration\n",
+ "M_sun = 1.99e+030; # Mass of the sun, kg\n",
+ "m_n = 1.675e-027; # Rest mass of the neutron, kg\n",
+ "h = 6.62e-034; # Planck's constant, Js\n",
+ "\n",
+ "#Calculations\n",
+ "h_bar = h/(2*math.pi); # Planck's constant, Js\n",
+ "G = 6.67e-011; # Universal gravitational constant, N-Sq.m/kg^2\n",
+ "N = 2*M_sun/m_n; # Number of neutrons in the neutron star\n",
+ "V = (6.5*h_bar**2/(N**(1./3)*m_n**3*G))**3; # Volume of the neutron star, metre cube\n",
+ "R = (3./(4*math.pi)*V)**(1./3); # The radius of neutron star, m\n",
+ "\n",
+ "#Result\n",
+ "print \"The radius of the neutron star of 2 solar masses = %d km\"%math.ceil(R/1e+003)"
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "The radius of the neutron star of 2 solar masses = 11 km\n"
+ ]
+ }
+ ],
+ "prompt_number": 5
+ },
+ {
+ "cell_type": "heading",
+ "level": 2,
+ "metadata": {},
+ "source": [
+ "Example 16.7, Page 598"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "#Variable declaration\n",
+ "c = 1; # For simplicity assume speed of light to be unity, m/s\n",
+ "d = 1.6e+005; # Distance of the supernova 1987A from the earth, ly\n",
+ "m = 16; # Mass of heavier neutrino, eV/c^2;\n",
+ "E = 20e+006; # Energy of the neutrino, eV\n",
+ "\n",
+ "#Calculations\n",
+ "delta_t = d/(2*c)*(m/E)**2; # Difference between the travel times of the lighter and the massive neutrinos, y\n",
+ "\n",
+ "#Result\n",
+ "print \"The difference between the travel times of the lighter and the massive neutrinos = %3.1f s\"%(delta_t*(365.25*24*60*60))"
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "The difference between the travel times of the lighter and the massive neutrinos = 1.6 s\n"
+ ]
+ }
+ ],
+ "prompt_number": 6
+ },
+ {
+ "cell_type": "heading",
+ "level": 2,
+ "metadata": {},
+ "source": [
+ "Example 16.8, Page 602"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "import math\n",
+ "\n",
+ "#Variable declaration\n",
+ "c = 3.00e+008; # Speed of light, m/s\n",
+ "H = 22; # Hubble constant, km/s per million ly\n",
+ "G = 6.67e-011; # Universal gravitational constant, N-Sq.m/kg^2\n",
+ "\n",
+ "#Calculations\n",
+ "rho_c = 3/(8*math.pi)*H**2/G*1e+003/(c*365.25*24*60*60*1e+006)**2; # The critical density of the universe, g/cc\n",
+ "\n",
+ "#Result\n",
+ "print \"The critical density of the universe = %3.1e g/cc\"%rho_c"
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "The critical density of the universe = 9.7e-30 g/cc\n"
+ ]
+ }
+ ],
+ "prompt_number": 7
+ },
+ {
+ "cell_type": "heading",
+ "level": 2,
+ "metadata": {},
+ "source": [
+ "Example 16.9, Page 604"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "collapsed": false,
+ "input": [
+ "#Variable declaration\n",
+ "H0 = 71; # Hubble constant, km/s per Mpc\n",
+ "\n",
+ "#Calculations\n",
+ "tau = 1./H0*1e+006*3.26*9.46e+012/3.16e+007; # The upper limit of the age of the universe, y\n",
+ "\n",
+ "#Result\n",
+ "print \"The upper limit of the age of the universe = %4.2e y\"%tau"
+ ],
+ "language": "python",
+ "metadata": {},
+ "outputs": [
+ {
+ "output_type": "stream",
+ "stream": "stdout",
+ "text": [
+ "The upper limit of the age of the universe = 1.37e+10 y\n"
+ ]
+ }
+ ],
+ "prompt_number": 8
+ }
+ ],
+ "metadata": {}
+ }
+ ]
+} \ No newline at end of file