Throughout history people have been driven by their unabated curiosity to comprehend the Universe. This whole process of revelation spanned over several millennia, from prehistoric peoples creating mythologies on the origin of the Universe to explain all kinds of celestial phenomena, to scientists like Edwin Hubble and Albert Einstein in the 20th century, who made use of science and technology to obtain a more accurate picture of space and time.

We may imagine the expanding Universe as a loaf of raisin bread being baked: as it (space) expands, the distance among raisins (galaxies) increases. If you were an ant on the bread, you would see the raisins (galaxies) move further away from you. The further out the raisins (galaxies) the faster they rose out. Yet you are not at the centre of the expansion. Regardless of your location in the bread, you will see exactly the same thing.

We now know from observations that most of the galaxies in the Universe are moving away from us. Not only does this provide substantial evidence that our Universe is expanding, but also imply that it was smaller and hotter in the past. About 14 billion years ago, our Universe was created in a colossal explosion in which matter and energy were released. The explosion brought about the continual expansion of the Universe ever since. The resulting drop in temperature precipitated the eventual formation of stars and galaxies. Aptly coined "The Big Bang Model", this cosmology is by far the most widely accepted theory on the origin of our Universe and its subsequent evolution.

(Credit: Max Planck Institute for Astrophysics)

The Millennium Run is a computer simulation on the evolution of the Universe. By tracing 10 billion particles under the influence of gravity and dark matter in a cubic region 2 billion light-years on each side, a supercomputer simulates the distribution of matter in the Universe from several hundred thousand years after the Big Bang to the present. Through comparing the results of the project with observed data, scientists hope to grasp a better understanding on the formation of large-scale structures in the Universe.

(Credit: NASA/WMAP Science Team)

 The latest Sky Show "The Big Bang" will review changes in our cognition of the Universe and go back to the moment when matter, time and energy were born. Based on the prevalent Big Bang Model, we will discuss the process of formation from atoms to stars, and also the present and the fate of our Universe.

According to the Big Bang Cosmological Model, the Universe began from a colossal explosion at an extremely tiny point triggered by quantum fluctuation about 14 billion years ago. Soon after its birth, the Universe experienced an inflationary epoch during which its volume expanded exponentially within an extremely short period of time. The Universe remained in darkness until 400,000 years after the Big Bang, when photons became free roaming, bringing about the Cosmic Microwave Background Radiation. As the temperature of the Universe steadily dropped with its incessant expansion, galaxies and stars were eventually formed.

(Credit: NASA, ESA, S.Beckwith (STScl) and the HUDF Team)

Taken by the Hubble Space Telescope, the Hubble Ultra Deep Field, HUDF required a series of exposures that added up to nearly a million seconds. It is the deepest portrait of the visible universe ever seen by humankind. The image captures about 10,000 galaxies born around 13 billion years ago, when the Universe was just 5% of its current age.

Scientists deduce that 74% of the Universe is made up of dark energy. In comparison, dark matter takes up 22% whereas normal matter makes up the leftover 4%. Dark energy may accelerate the cosmic expansion while dark matter is invisible matter of unknown composition yet interacts gravitationally. Normal matter includes stars and interstellar materials.