The model includes a single originating event, the " Big Bang ", which was not an explosion but the abrupt appearance of expanding spacetime containing radiation at temperatures of around 10 K. This was immediately (within 10 seconds) followed by an exponential expansion of space by a scale multiplier of 10 or more, known as cosmic inflation. The early universe remained hot (above 10 000 K) for several hundred thousand years, a state that is detectable as a residual cosmic microwave background, or CMB, a very low-energy radiation emanating from all parts of the sky. The "Big Bang" scenario, with cosmic inflation and standard particle physics, is the only cosmological model consistent with the observed continuing expansion of space, the observed distribution of lighter elements in the universe (hydrogen, helium, and lithium), and the spatial texture of minute irregularities (anisotropies) in the CMB radiation. Cosmic inflation also addresses the " horizon problem " in the CMB; indeed, it seems likely that the universe is larger than the observable particle horizon.