r of 34 degrees Kelvin. Being that hot, naturally it expanded. For an extremely brief and short period, billionths of billionths of a second, it inflated. At the end of the period of inflation, the universe may have a diameter of a few centimetres. The temperature had cooled enough for particles of matter and antimatter to form, and they instantly destroy each other, producing fire and a thin haze of matter-apparently because slightly more matter than antimatter was formed. 5 The fireball, and the smoke of its burning, was the universe at an age of trillionth of a second. The temperature of the expanding fireball dropped rapidly, cooling to a few billion degrees in few minutes. Matter continued to condense out of energy, first protons and neutrons, then electrons, and finally neutrinos. After about an hour, the temperature had dropped below a billion degrees, and protons and neutrons combined and formed hydrogen, deuterium, helium. In a billion years, this cloud of energy, atoms, and neutrinos had cooled enough for galaxies to form. The expanding cloud cooledstill further until today, its temperature is a couple of degrees above absolute zero. In the future, the universe may end up in two possible situations. From the initial Big Bang, the universe attained a speed of expansion. If that speed is greater than the universe's own escape velocity, then the universe will not stop its expansion. Such a universe is said to be open. If the velocity of expansion is slower than the escape velocity, the universe will eventually reach the limit of its outward thrust, just likea ball thrown in the air comes to the top of its arc, slows, stops, and starts to fall. The crash of the long fall may be the Big Bang to the beginning of another universe, as the fireball formed at the end of the contraction leaps outward in another great expansion.6 Such a universe is said to be closed, and pulsating. If the universe has achieved es...
