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    MATERIAL FROM CLASS 12: Wednesday October 18

    Corrections: to fuse 4 protons (hydrogen) to make helium requires temperatures above 8 million K (not 108K). This process turns 0.7% (not 0.07%) of the mass into energy.

    Nuclear fusion in the Sun: 4 protons become one helium atom plus two positrons and two neutrinos. Gamma rays carry off the energy that is released. Each positron is attracted to an electron, and both disappear to create two gamma rays. The neutrinos escape from Sun and we detect them as they reach Earth.
    [fusion in the Sun: www.lancs.ac.uk/ug/bown/]

    About 1015 neutrinos from this process in the Sun's interior pass through each square meter of everything on Earth each second. John Updike found this sort of thing a little disturbing and wrote a poem, called Cosmic Gall:

    Neutrinos, they are very small.
    They have no charge and have no mass
    And do not interact at all.
    The earth is just a silly ball
    To them, through which they simply pass,
    Like dustmaids down a drafty hall
    Or photons through a sheet of glass.
    They snub the most exquisite gas,
    Ignore the most substantial wall,
    Cold-shoulder steel and sounding brass,
    Insult the stallion in his stall,
    And, scorning barriers of class,
    Infiltrate you and me! Like tall
    And painless guillotines, they fall
    Down through our heads into the grass.
    At night, they enter at Nepal
    And pierce the lover and his lass
    From underneath the bed -- you call
    It wonderful; I call it crass.

    They Might Be Giants' song "Why Does the Sun Shine?"

  • Listen to "Why Does the Sun Shine?"

    The sun is a mass of incandescent gas
    A gigantic nuclear furnace
    Where hydrogen is built into helium
    At a temperature of millions of degrees.

    Yo ho, it's hot
    The sun is not
    A place where we could live
    But here on Earth there'd be no life
    Without the light it gives.

    We need its light
    We need its heat
    We need its energy
    Without the sun,
    Without a doubt,
    There'd be no you and me.

    The sun is a mass of incandescent gas
    A gigantic nuclear furnace
    Where hydrogen is built into helium
    At a temperature of millions of degrees.

    The sun is hot
    It is so hot that everything on it is a gas.
    Iron, copper, aluminium, and many others.
    The sun is large.
    If the sun were hollow, a million Earths could fit inside,
    and yet, the sun is only a middle-sized star.
    The sun is far away
    About ninety-three million miles away! And that's why it looks so small.
    And even when it's out of sight, the sun shines night and day.

    The sun gives heat
    The sun gives light
    The sunlight that we see
    The sunlight comes from our own sun's atomic energy.

    Scientists have found that the sun is a huge atom-smashing machine.
    The heat and light of the sun come from the nuclear reactions of hydrogen, carbon, nitrogen, and helium.

    The sun is a mass of incandescent gas
    A gigantic nuclear furnace
    Where hydrogen is built into helium
    At a temperature of millions of degrees.