In the beginning... 'first there was nothing, which exploded'

In one of his books, author Terry Pratchett summarized the beginning of the universe in a simple statement: "First there was nothing, which exploded."

On the basis of our current knowledge, that is a pretty good summary. What we are fairly sure of is that the universe began about 13.8 billion years ago. At that moment, everything we see in the universe today: all matter and the fabric of space-time, were all crunched together in something that might have been as small as the nucleus of an atom.

The first to propose this idea was Senior Jesuit Georges Lemaître. He took the data on the expansion of the universe and tracked it backward in time, and found that at a particular point in the past, it was all in one tiny lump. He called it the primaeval atom. Since it contained all the matter and energy in the current universe, it had to be so incredibly dense and hot that the physics we know today, learned from centuries of studying the universe we see around us, does not help us understand what that atom was like.

Then that atom started to expand, and as it did so it became less dense and less hot, and became more comprehensible to our science. During this phase it was filled with an incredibly hot, glowing fog of elementary particles. About 380,000 years after the beginning – the "Big Bang" – the temperature fell to the point when atoms could form and stay together. The glowing fog vanished and the universe became dark. There were no stars to illuminate it. This era in the history of the universe is now known as the "Dark Age".

We know the universe is not like that now. It is illuminated by countless billions of stars. So there must have been a moment when the first stars formed, lighting up the young universe. One of the big questions is exactly when that happened. Thanks to a detailed study using ground and space-based telescopes, we now have an answer.

A UK-led research team has examined six of the most distant known galaxies. This project involved using both orbiting and ground-based telescopes. The objective was to place those galaxies in the history of the universe and to estimate their ages.

Investigating the remote past of the universe might seem out of the question. However, there is a something that makes this possible; the universe is very big. As we look further out into space, we are looking further back in time. It is just a matter of having large enough telescopes to see the extremely faint objects far enough out in the extreme depths of space.

Light travels at about 300,000 kilometres a second. Even so, it takes over four years for light from the nearest star after the sun to reach us. The recent study has provided observations of galaxies some 13.25 billion light years away, when the universe was only 550 million years old. All these galaxies were busily forming new stars. However the objective of the study was to seek the signatures of the oldest stars and to deduce their ages. They turned out to be 200-300 million years old. This means that galaxies existed and stars were being born only 250-350 million years after the Big Bang. This does not rule out stars existing earlier in the youth of the universe than this.

The stars in the young universe were bright, blue and short-lived. In addition to ending the Dark Age, they provided another important service. During their lives the stars produced energy by turning hydrogen into all the other elements. These were blasted off into space when the stars exploded at the end of their lives, seeding the universe with the ingredients needed to make planets we see around the universe today, and of course the chemicals needed to make living things.

Jupiter and Saturn rise before midnight. Jupiter is the bright one. Mercury lies low in the dawn glow.

The moon will be new on the 10th.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.