Africans make their mark in science

AHIGH-POWERED physics conference has just taken place at the Skukuza conference centre in the Kruger National Park. I was invited to open the proceedings. There were 100 delegates from all over the world. They ranged from the UK to Poland, from Denmark to the US, from Australia to Japan, from Spain to Namibia, from Zimbabwe to Rwanda, and I could go on.

The conference was MECA SENS 2017 and it has never been held in Africa before. That strange looking name derives from Mechanical Stress Evaluation by Neutron and Synchrotron Radiation. What this mouthful means is that these fellows use beams, like a beam of neutrons out of a nuclear reactor and a high-powered X-ray beam from a very fancy nuclear accelerator called a synchrotron.

They use these beams to penetrate deep into materials such as stainless steel and fancy aluminium alloys to find out what happens to their atoms when you pull, twist or squeeze the metal.

That type of knowledge is really important for the building of nuclear reactors and other hi-tech devices such as an Airbus or Boeing. If a piece of stainless steel is used in nuclear reactor construction and by bad luck that piece had not been cooled correctly when it was made in the first place then it can happen that some of the alloy atoms have “frozen” into the wrong positions in the iron matrix.

What that could mean is that the stainless steel is maybe 20 percent less strong than it was supposed to be. That is serious when the nuclear engineers build a reactor to very precise tolerances and find that what they thought was like a very strong face brick is actually only a weak low-grade common stock brick.

You would not want to discover something like that five years after the house was built and the engineer signed off on the integrity of the structure.

What the scientists who gathered at the Kruger Park do is very much like brick laying with atoms. They look at things like: if the “bricklaying” did go wrong during the making of the metal or maybe as a result of incorrect welding, what will happen if you twist the metal. Will it break and where.

Momentous discoveries With these beams these fellows can “see” rows of atoms and take pictures of them. When I was at school my teachers told me that atoms were too small for humans to ever actually see them. That has turned out to not be true.

Round about the time when Einstein was making momentous discoveries and predictions, about a century ago, another physics development was unfolding in parallel. That was called; Quantum Mechanics.

The “mechanics” part is a bit silly, because there is nothing “mechanical” about it, but the fellows at the time had no clue what they were finding, because it was all so odd. With quantum mechanics and Einstein’s seemingly crazy ideas all at the same time the scientists of the day were scientifically shell-shocked.

One of the strange things that came out of the quantum mechanics part was that a beam of particles also exhibits a wave-like nature. Science called this the wave-particle duality.

So, to cut a long complex story short, a beam of electrons or neutrons also acts like light, with a wave character. So it is possible to send a beam of neutrons through a solid hunk of steel and then their wave nature will cause them to project a picture of the atoms inside.

If you want to witness real excitement, just watch some of those scientists in the Kruger Park looking at a picture of rows of atoms in aluminium where they can clearly see where a crack is beginning.

The sort of crack that makes an Airbus suddenly fall out of the sky when an engine breaks apart or the tail snaps off. Or that splits a nuclear reactor pressure vessel open at midnight on a Sunday and gives the chief engineer a bad start to his week.

The folks gathered in the Kruger Park included some very smart senior people with world-wide reputations built up over decades. But they also included very smart post-graduate students from South Africa, Botswana, Algeria, Italy, China and elsewhere. The students are doing great work and are following in the footsteps of the seniors.