What is Quantum Physics all about?

Notice that the electrons are moving in a kind of  smear and not in a path that is perfect and predictable

Light from the earth to the moon takes 1.3 seconds

13/01/2009 04:25 PM

The Large Hadron Collider at CERN on the Swiss-French border is making the news in good publications like the Globe and Mail.  People can understand that it is the world's largest machine and scientists are searching for the secrets of the atomic and sub-atomic world, but that's about all we can garner from the reports.

We thought we could put in a few key ideas that might allow the discerning reader to look for more information.  There is a ton of it and the CERN  and Perimeter Institute websites are good places to start.

Historical Background.

Classical Physics began with the Greeks and matured over time with the great Issac Newton defining the basic laws of classical mechanics.  Today most of our engineers use these same laws that have been refined over years of effort.  Our bridges and 'friges' all use them

Over time some disturbing things began to emerge.  Things were not just right with Newton's laws.  In 1905 with a series of 5 papers, Einstein altered the known scientific world with a few key ideas.

One of them he thought was very revolutionary.  We think that the others were too, but he said they were simply built upon old ideas and he refined them to meet what was then known.  Special Relativity was one such concept that built upon Newton's laws and refined them to account for the bending of light, time warp at high speed and the absolute constant of the speed of light.  Later he integrated these ideas in General Relativity.

The key revolutionary idea that Einstein had was about the nature of light.  He used a strange constant developed by Max Planck to show that light was just not a wave, but also exhibited particle properties.  He solved a puzzling problem that had been lurking for years on the edges of physics called the Black Body problem.

This was the beginning of the Quantum revolution, which he came to abhor.  It dealt with the atomic and subatomic world.  The mantle was passed to a group of scientists who had an intellectual hub in Copenhagen Denmark.  There a friend of Einstein's named Niels Bohr gathered about him a number of young scientists who developed the Quantum Theory.

Einstein spent the rest of his life resisting the full flower of the Quantum revolution that he in large part began.  Even Planck had a hard time dealing with what his famous Planck's Constant had fostered.

The Strange New World

Classical Physics deals with sizes and speeds that are human scale.  Quantum Physics deals with the very, very small while Cosmology deals with the size of and origins of the known universe, that is, the very large.

It so happens that when you get very small, very large or very fast, the whole world changes.  It's as if the Wizard of Oz and Alice in Wonderland got together to produce a magical world that is not like the one we see or live in, but guess what?  We do in fact live in such a world.  In fact the act of measuring these things in some strange way changes reality or better yet clouds what is loosely termed reality.

So what is so strange?  Repeated experiments in the 'small world' of Quantum Physics show that the very act of measuring something alters what is to be measured.  For instance, you may know a sub-atomic particles position, but not its velocity or visa versa. 

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It appears that every particle exists in a 'cloud of probabilities'  That is, something can be here, there or anywhere and the mere act of looking at it alters what is observed.   That is completely out of sync with the human way of looking at the known and everyday world.

There is nothing close to the Quantum world in our day to day lives.  Science tries to grab on to a few key ideas and call them laws.  Here are two:

  1. The speed of light is a constant
  2. Entropy is a fact of the universe.  That is, things go from an ordered state to disorder.  (there are many ways to state this law making it fascinating)

Law number 1 is accepted as a fact by scientists when measured in a vacuum, but not in other media such as water vapor.   Law number 2 is understandable to us.  For example a room does not go from messy to neat without intervention.  A cold soup does not get hot by itself, but a hot soup does get cold, if the ambient temperature is a constant in the room.


Einstein thought that nature was not perverse and hence his famous statement "God does not play dice with the universe".  He never could accept what Bohr wanted him to acknowledge.   He could not believe that beyond a certain point, observation fails and probability takes hold.

The philosophical argument is that of reality vs. probability and direct observation must give way to surrogate knowledge gained by seeing effects rather than classical causal laws.  The world is made up of `stuff` we cannot observe directly

So the LHC is designed to tell us more about that world, but it is not doing so with tiny nano instruments.  It is attempting to see experimental effects of the theory that started officially in the first 5 years of the 20th century.

The Word Quantum

The word Quantum is used in the physics jargon to distinguish it from the continuous world of Newton.  It appears that the Quantum world is discrete and does not obey the rules that we have gleaned from the larger space that we live in from day to day.  Quanta are discrete like particles and not like our traditional feeling about ourselves in time and space.

Remember the old Greek paradox wherein a person has to move from A to B, but to get there they have to go halfway and to go halfway, they have to go one quarter of the way.  So you get the infinite series of steps one half, one quarter, one eighth, etc.  Since this is an infinite series of steps, it should take an infinite amount of time.  That is the world of Newton, which was thought to be continuous and not the discrete world of Quanta

So the ultimate question that CERN is trying to answer is:  What is the universe made up. What are its origins and laws.

The search for these answers has begun in a 27 km tunnel in the bedrock of Europe