Much in the same way archeologists reconstruct past civilizations by looking at remains in the present, cosmologists reconstruct the universe’s past by looking at the constituents of the current universe. By doing so, they can infer how the universe began, how it evolved into its present state, and how it will continue to change over time. The study of the early universe is one of the most exciting fields in all of science. In fact, two of the last six Nobel prizes in physics have been awarded to scientists working to understand the conditions of the early universe.
As Many Questions as Answers
The current model asserts that the universe began expanding billions of years ago from a very dense, high-energy state, spreading out and cooling down in the process. But when compared with observations, this commonsense model presents as many questions as it does answers. For example, if the universe is cooling then why does its expansion continue to speed up rather than slow down? And why is the current acceleration rate so much smaller than the theoretical estimates projected by Albert Einstein in his cosmological constant?
Another key question involves the formation of the “stuff” of the universe, matter, and its opposing substance, antimatter. Why are the scales tipped so far toward antimatter and how did this asymmetry occur?
Theory of Inflation
And, finally, if we look into space, we will see that stars and galaxies surround us. But how did it all get here? The most widely accepted explanation is that the initial conditions of the early universe were quite different than those of the present. By observing small fluctuations in the cosmic microwave background, scientists have gained the first indirect evidence of this primordial phase and are now teasing out the specifics of the theory of inflation.
Early Universe and Particle Physics
In seeking to understand the cosmology of the early universe, scientists have been able to apply the current laws of physics to the extremely high-energy conditions of the primordial universe, allowing us to explore the laws of physics at energy scales far greater than what is achievable in manmade particle accelerators. This new application of physics shows the deep connections between the fundamentals of the early universe and the principles of theoretical particle physics.