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Posted by on Oct 31, 2009 in Early blogs | 0 comments

What I like about quantum mechanics.

What I like about Quantum Mechanics.

Please note that the text follows the video.

My name is Bryan Sanctuary and I am a theoretical and physical chemist and I would like to tell you what I like about quantum mechanics (QUANTUM MECHANICS) in this my first submission to this blog.

Purpose of this blog

The purpose of the is blog is to stimulate discussion into the interpretation of quantum mechanics.  I am sure that you have ideas, questions, comments about quantum mechanics and reactions to what I say.  I invite you to submit those in my blog and perhaps we can stimulate a lively discussion and even get to some answers as to what quantum mechanics really means.

Insight into the microscopic world

But what do I like best about quantum mechanics?  That’s easy.  It is the insight, the deep insight quantum mechanics give us into the microscopic world.

Now we live in a macroscopic world which is governed by classical or Newtonian mechanics.  If someone tosses you a ball you intuitively put up your hand and catch that ball.  You do not have to understand classical mechanics.  You don’t have to calculate a trajectory.  You don’t need to know anything about forces or gravity.  You simply instinctively put up your hand and catch the ball.

Now in the microscopic world, things are quite different.  The microscopic world is governed by a different mechanics, and that is quantum mechanics.  And the only way we can get insight into the microscopic world is through the mathematical equations.  I think Heisenberg said it first.  He was one of the founders of quantum mechanics and said that our ability to visualize in the microscopic world; to gain in intuition; to understand microscopic processes, comes only from understanding the mathematical equations that govern quantum mechanics.

Now I am not suggesting that you become a mathematician.  Far from it.  There are many people who understand quantum mechanics.  They work with it daily and they develop an intuition of how the microscopic world works.   So they don’t have to do long complicated calculations.  They know what happens at the microscopic level, so if someone tosses then an electron, they know how to catch it.

The Chemical Bond

The chemical bond can only be described by quantum mechanics.  It is a100% quantum entity.  Think of all the chemical bonds that are being made and broken everyday, throughout the world, throughout the universe.  They are all governed by the laws of quantum mechanics.

HCl chemical bond


Another thing I like about quantum mechanics is that it can predict properties that do not exist in the macroscopic world, such as spin.  An electron is a particle with a certain mass, a certain charge and a spin of ½ magnitude.  This spin is 100% quantum with no analogue in the macroscopic world.

Electron spin

The hydrogen atom also has spin of ½ which resonates.  This spin is smaller that that of an electron but it is still the same sort of angular momentum.  Other particles have spin.  Carbon-13 has a spin ½ too.  A chlorine atom has a spin of three halves.  Photons have a spin of 1.  Many particles have spin. Today sophisticated instruments have been developed to look at the resonances of many particles and this is called Nuclear Magnetic Resonance (NMR).  These instruments give us spectra and these spectra can all be understood by applying the laws of quantum mechanics.  That is the position and intensities of all these lines are completely determined by quantum mechanics. And this is a particularly simple molecule but by understanding such spectra we can obtain important properties of molecules, such as structure, function and reactivity.

Now NMR started way back in the 1940’s when scientist were simply interested to see if they could make the spin of a proton resonate.  This was fundamental research. This was good science, and the two people credited with the discovery of NMR, Felix Bloch and Purcell Pound, had no idea of the tremendous consequences of their experiments.  They did not then know about chemical shifts and that NMR would develop into one of the most useful tools to many areas of scientific research.  And today Magnetic Resonance Imaging (MRI) allows us to non-invasively look inside a body, with great benefit to human-kind and of course medical research too.

NMR: Nuclear Magnetic Resonance

The basis of understanding the microscopic world.

QUANTUM MECHANICS, therefore, is the basis for our understanding and control of the microscopic world.  Think of microelectronics.  We have microprocessors all around us, based primarily on solid state physics.

New materials.  Just think of new fabrics, new plastics, new polymers all developed in laboratories by scientists doing chemistry or engineering who understand how the quantum world works and are able to create these new materials.

Nanotechnology is a relatively new field of research with tremendous potential.  A nanometer is ten to the minus 9 meters that is 0.000000001 meters.  We know that particles and molecules can self assemble into larger structures.   But scientists can intervene in these processes to assemble the sorts of structures that can do different things.  Here we see a nano tube, but there are many more that can perform different tasks, like nano-size machines.

Today with the use of powerful computers, it is possible to solve the Schrödinger equations to obtain the structures of complicated molecules.  Here we see hemoglobin.  Such structures allow scientists to understand how such complicated molecules function.   There a many beautiful structures of proteins.  In biochemistry and pharmacology for example, scientists can study various biochemical pathways and can intervene in these to control them, and even stop them, when something goes wrong, like cancer.

So quantum mechanics gives us deep and useful insight into how the microscopic world works.  I have talked about chemistry, physics, biochemistry, pharmacology and many other fields of science.  And the ideas that come from this fundamental research, like the example of the resonating hydrogen atom, can be taken over by engineering and companies that do research and development.  These lead to new processes and new products which benefit human kind.

What does quantum mechanics mean?

But what does quantum mechanics mean?  What is the real meaning of the wave function?  What are the real consequences of quantum mechanics?  How can non-locality happen?  Is Nature really entangled?  Is Nature fundamentally statistical?

These questions have been debated since quantum mechanics was first formulated in the 1920’s with no real resolution.  Today however many of the gedanken (or thought) experiments of those days can be performed in the laboratory which give us new insight.  However quantum mechanics is so successful that I believe the vast majority of people don’t care about the real meaning of quantum mechanics.  It has been debated so long that that they have given up.  It has been debated since the beginning of quantum time with no real clear resolution, so they continue to use quantum mechanics in their research and are happy to leave it at that.

Richard Feynman

I think the famous Nobel Prize winner Richard Feynman summed it up best.  He obtained his Nobel Prize for formulating quantum mechanics using what are now called Feynman Path approach.  And about the foundations of quantum mechanics, Richard Feynman is purported to have said, perhaps with his tongue in his cheek, “Shut up and calculate!”

Richard Feynman

However I believe, and I am sure that Professor Feynman believed it too, that these questions are fundamental to our understanding of the microscopic world.  We should not give up trying to find the answers.

Coming soon

Well that is all for this first submission.  Next time I want to talk a bit about how scientists approach problems and some of the philosophical consequences of quantum mechanics.  After that I will tell you what I do not like about quantum mechanics.

See you then.

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