Early Universe

Computer simulation of one of the earliest stars in the Universe. (Credit: Abel, et al.)

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 man-made 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.


KIPAC researchers are heavily focused on understanding the origin of the early Universe, a period in which very different rules of physics were at play in the cosmos than those that govern it now. It is believed that the Universe began with very high energies. To tease apart the forces that touched off the Universe’s expansion—some 14 billion years ago—KIPAC scientists are using an array of instruments such as telescopes and satellites to look as far away and as far back in time as possible.

Among the most important observational tools in KIPAC’s exploration of the early Universe are instruments that measure irregularities in the cosmic microwave background radiation (CMB), such as the WMAP and Planck satellites. By looking at the distribution of the irregularities in the CMB, for example, KIPAC researchers are attempting to reconstruct the quantum conditions of the early Universe and understand the laws governing its dynamics at the beginning. By looking back, scientists may also deduce the existence of new particles, forces or dimensions in existence during the Universe’s first moments and, in turn, gain a more comprehensive understanding of the laws of the present Universe.