Kathryn Staite, of Kirkwood Intermediate School, asks :-

Is it possible to have a world in which everything is opposite that on Earth?

Murray Bartle, a physicist with the Institute of Geological and Nuclear Sciences, responded.

There are interesting opposites in physical matter which seem possible in other earth-like planets in unexplored space. These planets could be made of 'anti-matter', whereas our earth is made of 'matter'. Matter and anti-matter have opposite electrical and magnetic properties and destroy one another if they come together.

We describe atoms in molecules on earth as being composed of the 'matter' particles: protons, neutrons and electrons. The existence of anti-matter can be demonstrated in our laboratories by creating the building blocks for the anti-matter atom: anti-protons, anti-neutrons and anti-electrons which in an anti-matter world could form stable atoms, molecules, and the physical structure of living things.

On earth, anti-matter is not important in our daily lives because matter rapidly absorbs it (in a fraction of a second) and it vanishes with the production of light or heat. On the anti-matter earth, likewise, matter would not be important in the daily life of the people there because it would be absorbed. Matter and anti-matter earths cannot therefore exist together and must be separated at great distances in space. At present we know of no anti-matter planets or stars in the universe, or of course of other inhabitants.

I hope you continue to seek answers to interesting questions in science and maybe one day you will help answer such questions. If you or your class are ever visiting Wellington please contact me for a tour of our laboratory, where we apply geological and nuclear science to the benefit of New Zealand.