7 WHY HAS NATURE TRIPLICATED ITS BASIC BUILDING BLOCKS?

Say Lego launched a version of its bricks in which each brick was hundreds of times bigger than a standard brick. And say it then launched another version in which the bricks were thousands of times bigger. You would be forgiven for thinking the company had gone bonkers. But this is exactly what nature has done with its fundamental building blocks – the quarks and leptons.

Normal matter is made of just two kinds of quark and two kinds of lepton. But there also exists a second ‘generation’ of quarks and leptons in which all the particles are identical to the first apart from being hundreds of times heavier, and a third generation in which they are identical but thousands of times heavier. The heavier generations take a lot of energy to create so are rarely seen today. However, it is likely they played some critical role in the Big Bang. But why the wildly different masses of the particles in each generation? Dr Steven Weinberg, an American physicist and Nobel laureate, has recently made an interesting speculation.

The basic building blocks of matter gain their masses by interacting with the Higgs field, an invisible fluid that fills all of space. You can think of them interacting with the Higgs particle, a localised hummock in this energy field. Weinberg points out that particles which interact most strongly with the Higgs field end up with masses close to that of the Higgs particle, and these are the particles of not of the first but the third generation. Maybe, speculates Weinberg, they are the only particles that interact directly with the Higgs. Maybe the second generation get their masses by interacting with an undiscovered particle that interacts directly with the Higgs. And maybe the first generation get theirs by interacting with a second undiscovered particle that interacts with the first.

It is like that playground game in which a message is passed down a line of children and what is relayed gets ever further removed from what was originally said. Perhaps with each lower generation, the particles become further removed from ‘feeling’ the Higgs field, so its massgenerating effect is ever diluted. Weinberg does not know how such a mechanism could work in detail. But other physicists feel he may have provided a hint of how to solve the puzzle of nature’s triplicated building blocks.