Page 66 - Electrical Properties of Materials

Philosophical implications 49

Had philosophers been content asking this and similar questions, the history
of philosophy would be an easier subject to study. Unfortunately, driven by
usual human passions (curiosity, vivid imagination, vanity, ambition, the desire
to be cleverer than the next man, craving for fame, etc.), philosophers did try
to answer the questions. To the modern scientist, most of their answers and
debates don’t seem to be terribly edifying. I just want to mention Berkeley who
maintained that matter would cease to exist if unobserved, but luckily there is
God who perceives everything, so matter may exist after all. This view was
attacked by Ronald Knox in the following limerick:
There was a young man who said, ‘God
Must think it exceedingly odd
If he finds that this tree
Continues to be
When there’s no one about in the Quad.’
Berkeley replied in kind:

Dear Sir:
Your astonishment’s odd:
I am always about in the Quad.
And that’s why the tree
Will continue to be,
Since observed by
Yours faithfully,
God.
You do, I hope, realize that only a minority of philosophical arguments
were ever conducted in the form of limericks, and the above examples are not
typical. I mention them partly for entertainment and partly to emphasize the
problem of the tree in the quad a little more.
In the light of quantum mechanics we should look at the problem from a
slightly different angle. The question is not so much what happens while the
tree is unobserved, but rather what happens while the tree is unobservable. The
tree can leave the quad because for a brief enough time it can have a high
enough energy at its disposal, and no experimenter has any means of knowing
~
about it. We are prevented by the uncertainty relationship ( E t = h)from
ever learning whether the tree did leave the quad or not.
You may say that this is against common sense. It is, but the essential point
is whether or not it violates the Laws of Nature, as we know them today.
Apparently it does not. You may maintain that for that critical t interval
the tree stays where it always has stood. Yes, it is a possible view. You may
also maintain that the tree went over for a friendly visit to the quad of another
college and came back. Yes, that’s another possible view.
Is there any advantage in imagining that the tree did make that brief
excursion? I cannot see any, so I would opt for regarding the tree as being
in the quad at all times.
But the problem remains, and becomes of more practical interest when
considering particles of small size. A free electron travelling with a velocity
6
10 ms –1 has an energy of 2.84 eV. Assume that it wants to ‘borrow’ the
same amount of energy again. It may borrow that much energy for an interval