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[MUSIC PLAYING]
Many scientists at the start of the story of quantum
mechanics were very resistant to these new ideas.
And they have very good reasons for resisting them.
These ideas seemed to offer an explanation for observable
phenomena, and there were no other good explanations.
But they disagreed with the core ways we
thought about the world.
And as I said, it's important to understand that even many
of the scientists involved really did not want the world
to have to be described this way.
Including, for example Max Planck.
And Max Planck was initially very resistant to the ideas of
quantum mechanics, even though he was the
person who started it.
Now, as the theory developed, as a good scientist he
eventually did come to accept it, but with great reluctance.
And I expect we all know of many people who only believe
what they want to believe.
And there's possibly a moral lesson here.
But the reluctance in the case of quantum mechanics to
believing it is extremely understandable.
The problem was not only that it struck at our whole way of
thinking about the world.
If this quantum theory was correct, it would mean we
would have to completely rewrite physics.
And any new scientific theory has got a very
high hill to climb.
It has to give exactly the same answers as the old
theories everywhere those old theories or
previous models worked.
And yet, it also has to successfully describe the
phenomena that we couldn't understand before.
Now, the prior theories of mechanics, like Newton's laws,
work very well in a broad range of situations.
Our models for light similarly were quite deep.
And it achieved a remarkable unification of
electricity and magnetism.
Maxwell's equations from the 19th century are one of the
major triumphs of 19th century physics.
So how could we, in some sense, possibly throw away all
these models, which also do work very well in certain
domains and scales?
How could we possibly come up with a new basis for all of
these that was fundamentally different, but nonetheless
gave the same answers everywhere they did.
That requirement that any new quantum mechanical theory
should also give results that correspond in these
appropriate domains with the classical results is called a
correspondence principle, by the way.
Of course, it was also true as we looked more deeply at these
various phenomena, and light, and atoms, that there simply
was no way we could explain them with our classical view.
And those classical models would themselves lead to
contradictions with observed reality.
For example, as we discussed, when we would try to make a
model of the atom, with the electrons circling around some
charged nucleus--
like a satellite in orbit round the earth--
we meet major inconsistencies.
Existing mechanics and electromagnetic theories, I
said, would predict that any such orbiting electron would
constantly be emitting light.
But atoms, for example, in their ground states simply do
not do that.
The challenge for quantum mechanics was not an easy one.
To resolve these problems of light and the structure of
matter, we actually had to tear down much of our view of
the way the world works to a degree never seen since the
introduction of natural philosophy and the modern
scientific method in the Renaissance.
Scientists were simply forced to construct a completely new
set of principles for the physical world.
These were and still are in many cases completely bizarre.
And they are certainly very different from what our
intuition, or what we might call our common sense, says
that they should be.
And many of these principles simply have no analogs in our
normal view of reality.
But we're forced to do this.
If we do not do this, we actually cannot
understand our world.
And we will prevent the development of large areas of
engineering that can create very powerful and useful
technologies.