Atom 2. The Key to the Cosmos (1 of 26)

Atom

In this three-part documentary series, Professor Jim Al-Khalili tells the story of one of the greatest scientific discoveries ever: that the material world is made up of atoms. The book that accompanies the Atom series is published by Icon Books.
First Aired: BBC Four Thu 26 Jul, 2007 21:00-22:00

As we gazed up at the heavens, we asked where we had come from, how all the stars were created, how all the elements were made, even how the universe itself had begun.

One of mankind's greatest achievements is that we've answered these questions.
What is truly remarkable is that this understanding has come through the study of the smallest building blocks of matter - atoms.
As we peered inwards, we realised we could explain what we saw when we peered outwards.
The atom has helped us solve the greatest mysteries of existence.
Everything in the world we see is made out of tiny objects called atoms and yet we only proved their existence at the beginning of the 20th century.
The first shock was to discover how small they were, less than a millionth of a millimetre across, there are trillions in a single grain of sand.
Amazingly, we now have a pretty good idea of the number of atoms in the known universe.
Now, given the vastness of the universe and the minuteness of the atom, it's not surprising that this is a mind-numbingly huge number, it's one followed by over 70 zeros, that's a trillion, trillion, trillion, trillion, trillion, trillion atoms.
We don't only know the raw number of atoms in the cosmos we also know that they come in 92 different flavours.
These are called the elements and you'll recognise many of them as familiar parts of the world around us.
Oxygen, iron, carbon, tin, gold and so on.