Brief History of Time - III
Chapter 4: The Uncertainty Principle
This chapter introduces us to quantum mechanics. The famous Heisenberg’s uncertainty principle states that it is impossible to accurately determine the position and velocity of an object at a particular instant of time. It is a fundamental law applicable to all and sundry from honeybees to comets.
French scientist Marquise de Laplace had earlier suggested that there should be a set of fundamental laws that should allow us to predict everything that would happen in the universe, if we only knew the complete state of the universe at any particular time. Heisenberg sounded a death-knell to Laplace’s thoughts.
Since the uncertainty lay in determining position and velocity separately and simultaneously, a new branch of science called ‘Quantum Mechanics’ was developed by Heisenberg, Erwin Schroedinger and Paul Dirac in the 1920’s. In quantum mechanics, particles had a quantum state which was a combination of position and velocity; hence circumventing the uncertainty issue. A concrete tenet of quantum mechanics is the duality of matter. For some purposes it is helpful to think of particles as waves and for some purposes it is useful to think of waves as particles. Since quantum mechanics was based on the uncertainty principle, it introduced an element of unpredictability or randomness in science and naturally met with strong resistance. Today, QM is the foundation of modern science, the only areas where it has not yet been fully incorporated is gravity and the large scale structure of the universe.
Einstein’s general theory of relativity explains the large scale structure of the universe. It is what is called the classical theory, i.e. it does not take into account the uncertainty principle of quantum mechanics. The reason that this does not lead to any discrepancy with observations is because the gravitational fields we experience are very weak. In the case of black holes and the big bang, where gravitational fields would be immensely strong, quantum mechanics becomes important.
This chapter introduces us to quantum mechanics. The famous Heisenberg’s uncertainty principle states that it is impossible to accurately determine the position and velocity of an object at a particular instant of time. It is a fundamental law applicable to all and sundry from honeybees to comets.
French scientist Marquise de Laplace had earlier suggested that there should be a set of fundamental laws that should allow us to predict everything that would happen in the universe, if we only knew the complete state of the universe at any particular time. Heisenberg sounded a death-knell to Laplace’s thoughts.
Since the uncertainty lay in determining position and velocity separately and simultaneously, a new branch of science called ‘Quantum Mechanics’ was developed by Heisenberg, Erwin Schroedinger and Paul Dirac in the 1920’s. In quantum mechanics, particles had a quantum state which was a combination of position and velocity; hence circumventing the uncertainty issue. A concrete tenet of quantum mechanics is the duality of matter. For some purposes it is helpful to think of particles as waves and for some purposes it is useful to think of waves as particles. Since quantum mechanics was based on the uncertainty principle, it introduced an element of unpredictability or randomness in science and naturally met with strong resistance. Today, QM is the foundation of modern science, the only areas where it has not yet been fully incorporated is gravity and the large scale structure of the universe.
Einstein’s general theory of relativity explains the large scale structure of the universe. It is what is called the classical theory, i.e. it does not take into account the uncertainty principle of quantum mechanics. The reason that this does not lead to any discrepancy with observations is because the gravitational fields we experience are very weak. In the case of black holes and the big bang, where gravitational fields would be immensely strong, quantum mechanics becomes important.
6 comments
A few days break in the series because of insanities associated with work.
A truly amazing treatment of an amazingly difficult task! I'm sure the uninitiated would certainly like to take a lok at the book once they read this! Great work!
FYI, I'm a regular with your blog... Have visited this 'dark sanctotum' several times.. With your due permission, I'll add your space to my personal "Blogs of Note" :)
You rock!
p.s. hope u've been doing great :)
And heyyyyyyyyyyyyyy .. I think I worked out ur little enig"maniche"... Is soccer some connection ??!!!
hi 666,
There is also a Time /Energy complementarity angle to the uncertainty principle...
I don't remember if BHOT dwells on it , but the funda is you can either compute the energy associated with an event or its duration...this has some philosophical implications on life, this universe , and everything...for instance this feature of reality allows pairs of antiparticles to pop into existence out of pure void for a very short duration of time...similarly, as long as we are unable to compute the exact energy of our universe , i guess we're allowed to exist ( but of course this comment is too simplistic, nevertheless!!)
@Rudi: Thanks.. its an amazing experience reading the book slowly and carefully.
@J@$m!ne: You are blogrolled :-) My pen name in college mags does not have soccer leanings. Keep searching :-)
@Arkus: There is a mention of the antimatter, but I didnt understand much :-(( But the concept is truly fascinating
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