76 ACTIVITY 34 • Timing from the Big Bang to Today Now we are at the time when the temperature is 10 K and the density is 10 times that of water. We watch the universe shrink exponentially (reversing its 10" growth originally), sometime between 10 and 10-33 seconds after the Big Bang. It is now the Planck era, 10seconds after the Big Bang, and the temperature is 10" K and the density is 10% times that of water. The four fundamental forces are combined under the thcory of everything (TOE). We have arrived at a time when the conditions of the universe are unknown; our theories are unable to describe it. 1. At the stage where Big Bang nucleosynthesis was occurring, the temperature and density of the universe were about K and kg/m

76 ACTIVITY 34 • Timing from the Big Bang to Today Now we are at the time when the temperature is 10 K and the density is 10 times that of water. We watch the universe shrink exponentially (reversing its 10" growth originally), sometime between 10 and 10-33 seconds after the Big Bang. It is now the Planck era, 10seconds after the Big Bang, and the temperature is 10" K and the density is 10% times that of water. The four fundamental forces are combined under the thcory of everything (TOE). We have arrived at a time when the conditions of the universe are unknown; our theories are unable to describe it. 1. At the stage where Big Bang nucleosynthesis was occurring, the temperature and density of the universe were about K and kg/m