Collisions

The polished cue slides back and forth under the pool player's chin; he holds his breath as he pushes it forward decisively.   The cushioned 'thunk' of the cue hitting a ball rings out, followed shortly afterwards by the 'clack' of two or more balls colliding. 

It's a familiar sight and sound to anyone who has ever played pool except - here's the thing - those items never actually touch.  


'Touch' is simply an illusion.  True enough, the cue and the balls get very (very) close together - an angstrom or two apart perhaps, but they never actually truly 'touch'. In the same way, the player's hand never touches the pool table, or indeed his feet never truly touch the ground. 

Welcome to the strange world of the quantum;  a world where some of the rules in the world of the 'large' (like us, buildings, planets) don't always apply. In fact, the rules are so markedly different that scientists are still working on theories which combine both Einstein's theory of general relativity together with quantum theory into one, unified theory.


This is the world of the very, very small.  To try and give you an idea of the scale of these things, grab a ruler and look at a single millimetre.   Now take that millimetre and divide it into 10 parts.  Now divide one of those parts into (literally) a million pieces.  That's roughly the same size as a single atom.

So, these things are tiny - the smallest things known to man, right?

Wrong.   You've probably heard the phrase splitting the atom (it's this procedure used to such terrible effect in nuclear bombs) and science has done just that, revealing a jumble of bits floating around inside, namely a nucleus surrounded by a cloud of negatively charged electrons.

Objects like pool balls don't touch each other because of one of the four fundamental forces of nature - the electromagnetic force.   This means that the 'cloud' of electrons within the atoms of the cue repel the cloud of electrons in the ball.  Think of them as billions and billions of tiny opposing magnets if you like.

While "the electromagnetic repulsion of a lovers hand" doesn't have quite the same ring to it, this is what 'touch' actually is. A kiss, a clap, a crash - almost any sort of collision really - they're all just illusions that true contact is being made.

So apart from these electrons repelling any others it comes into contact with, what else is in an atom?  

The nucleus is made up protons (positively charged) and neutrons (neutrally charged) particles and gives the atom its 'mass' but not its size.  To paraphrase Bill Bryson, if you imagine that the nucleus of an atom is the size of a pea then the entire atom in which it resides would be somewhere around the size of a cathedral (and the pea would be many thousands of times heavier than it).

On the subject of protons, do you remember the periodic table of elements when you were at school?  Hydrogen in the top left corner and then the rest in a strange looking table; things like iron, gold, lead, uranium and the like?   Well, that was arranged by a Russian scientist named Mendeleev who even predicted where there were gaps in the table at the time.   One of the reasons he was able to do that was that he realised that the atomic weight of elements was sequential:   Hydrogen had 1 proton, Helium has 2, and so on.  He was able to spot the gaps and correctly predict that the new elements, once discovered, would slot neatly in.  

I digress; back to the atom.  We know that a single atom is tiny (1mm divided in 10 and then divided again by 1 million).  Scale that single atom up to the size of a cathedral and the nucleus is about the size of a pea.  Making up the nucleus are protons and neutrons - these must be the smallest things in the known universe, right?

Not quite.   A relatively recent world of sub-atomic particles is being researched at the moment:  namely quarks, leptons and bosons.   These fundamental particles are the smallest things currently known to man and some of them are not even really known. 

The most famous of these is probably the Higgs boson and it is this theoretical particle which scientists believe - hope - gives everything their mass. It's been called the God particle but more and more scientists seem to be distancing themselves from this nomenclature, perhaps due to the uneasy cross-over into religious territory.


The desire to improve our knowledge in particle physics - including but certainly not limited to this Higgs boson - has led to experiments taking place all over the world.  Principally these have including the (soon to be retired) Tevatron particle collider in the US and more famously, the Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (initialised using its French translation as CERN).

This collider is a multi-national research effort costing billions of pounds, employing tens of thousands of scientists and researchers and hopes to answer some fundamental questions behind the laws of nature:  things like is the Higgs theory of correct? Are there other dimensions?  What is dark matter?

The idea is that two streams of protons are pushed round and round the 27km ring some 600 feet underground getting faster and faster until they're travelling at around 11,000 circuits per second  (about 3 metres per second slower than the speed of light).   Then they smash them together and see what happens in the tiny fractions of a second after a collision (hence the name).

....and I think I'll call a halt to it there as there are a thousand directions this could go and I have to go and make tomorrow's lunch for the other half.


Finally, my caveat:   I should say, this really is layman's science - I got a D in science GCSE and it's nothing to do with my job.  So (for any actual scientists reading this) there may well be minor inaccuracies and exceptions to the above but I hope I've got things pretty much correct.