Story
This worksheet provides an introduction to the prevailing scientific model for the origin and evolution of our universe: the
Big Bang Theory. This foundational theory in modern cosmology estimates that the universe began approximately 13.8
billion years ago, rapidly expanding from an extremely hot, dense state to the vast cosmos we observe today. We will
explore the core concepts of this theory, delve into the compelling evidence that supports it, trace the major epochs of
cosmic evolution, and consider some of the profound questions that still challenge cosmologists.
, The Big Bang Theory: A Cosmic Evolution
The Big Bang Theory describes how the universe began from an incredibly hot and dense state, often referred to as a
singularity. It is crucial to understand that this was not an explosion in space, but rather an expansion of space itself.
Imagine a balloon being inflated; dots drawn on its surface move farther apart, but they are not "flying" through the air4the
surface itself is stretching. Similarly, galaxies are not moving through a pre-existing space but are carried along by the
expansion of space.
In its initial moments, the universe was unfathomably hot, reaching temperatures of around 10^32 Kelvin. As it expanded, it
cooled, allowing fundamental particles to form and eventually coalesce into the structures we see. A key concept of the Big
Bang Theory is that this expansion is still ongoing today, a phenomenon that continues to shape the cosmic landscape.