Many mysteries remain in study of cosmos	This is an artist's impression, by Adolf Schaller, of how the very early universe, less than one billion years old, might have looked when it went through an onset of star formation.
Howard Burton
February 2, 2004

It is rather difficult to formally mark the beginning of an entire academic discipline, but there is widespread recognition that both physics and philosophy began at a clearly defined moment -- when Thales of Miletus was able to successfully predict the solar eclipse of 585 BC.

This event marked a sea change in humanity's perceived relation to the world around them. Before Thales, most physical phenomena were considered fundamentally beyond comprehension, the privy of the gods and other unknowable forces.

Thales' bold prediction did far more than merely advance our knowledge of astronomy; he rewrote the ground rules of human understanding, pushing away the fictitious barrier between science and mythology and triumphantly allowing unfettered rational inquiry to reign throughout the observable world.

After Thales, the Greeks coined the word cosmos to reflect this new belief that the universe could be understood as a coherent system of ideas run on underlying principles, and the field of cosmology was born.

In the intervening millennia, we have come a considerable distance in our understanding. We realized that Earth is not at the centre of the universe, that planets and comets revolve around the sun in elliptical, not circular orbits due to the gravitational attraction of the sun, while the moon revolves around Earth by the same force of gravity (this time due to Earth).

We have learned that our solar system is in a huge cluster of billions of other stars contained within a galaxy (the Milky Way) that is itself one of billions of clusters throughout space. We discovered that a fuller understanding of gravity transforms our very perception of space and time, and that massive objects actually affect space time, bending light around them.

Perhaps even more significantly, we found observational evidence that our universe was expanding in size, much like a balloon.

All of this progress in understanding was truly remarkable, but there seemed little hope to fully answer the deepest question: How did our universe begin?

Some believed that, notwithstanding its current expansion, the universe was fundamentally constant (with new matter being spontaneously created to fill in the gaps caused by the expansion): the so-called Steady State Model. Others believe the universe was created in one overwhelming cataclysmic event, dubbed (ironically at the time) the Big Bang.

The discussion, however fascinating, looked to be as solvable as counting the angels dancing on the head of a pin. After all, finding some sort of observational evidence of the possible origin of the universe 15 billion years earlier seemed rather hopeless.

Or was it? In the early 1960s, in one of the most remarkable discoveries of 20th century science, physicists Arno Penzias and Robert Wilson discovered pesky ambient microwave radiation throughout the sky was interfering with their satellite communication system and they couldn't get rid of it.

Unbeknownst to them, this exact microwave background radiation had been recently predicted by some Princeton astrophysicists as a necessary consequence of a Big Bang. Big Bang proponents had their smoking gun and suddenly, to everyone's delight, the field of "observational cosmology" was born.

Since that time, things have just become more interesting. Experiments have probed the microwave background in remarkable detail, providing a treasure trove of information about both the early and present universe.

Other experiments and analysis have indicated, in stark contrast to what we expected, that all of the matter-energy that we observe and experience makes up only four per cent of the universe! The other 96 per cent is a combination of a mysterious "dark energy" and an equally mysterious but distinct "dark matter."

Clearly, there are more things in heaven and Earth than are dreamed of in our current philosophy. To a modern cosmologist, these are heady times indeed, with almost as many mysteries as answers 2,589 years after Thales got us going.