Nicholas Strettell, of Ilam School, asks :-

Has anybody seen an atom?

Andrew Edgar, a physicist at the Victoria University of Wellington, responded.

No, atoms are too small to see with our eyes or with ordinary microscopes (which use light).

But we can in a sense "see" atoms with a new instrument called a Scanning Tunneling Microscope, invented in 1986 by two scientists called Rohrer and Binnig, working for IBM in Zurich, Switzerland. It was such a marvellous dicovery, and the pictures of atoms it produced were so dramatic, that they were awarded the Nobel prize for their work. This new "microscope" does not use light at all, but works by dragging a very fine needle across the surface of a material. When the needle comes to an atom sitting on the surface it has to go up and over the atom to get past. The instrument measures the movement of the needle, and we know that every time it goes up a bit it must have been climbing over an atom. By dragging the needle across the surface in a regular pattern, like a farmer ploughing a field, we can build up a contour map of the surface where the atoms stand out as bumps, just like the hills on an ordinary map. So we can see the bumps on the map, and we know the bumps are atoms, even though we can't see the atoms directly!

The people at IBM are very clever and have had some fun with their discovery - they found that by electrifying the needle they could drag loose atoms around and drop them off where they wanted to. So they spelt out the letters of their company name, IBM, in the form of atomic dots, where each dot was an atom, and this is the smallest writing ever in the history of the world!