Alien Dawn: A Classic Investigation into the Contact Experience (48 page)

That still left many problems.
When Newton had explained the solar system in his
Principia,
his mathematics described exactly why the planets moved as they did.
But Bohr’s mathematics failed to explain with the same exactitude what the electrons were doing inside the atom.
Even when the German physicist Arnold Sommerfeld pointed out that the atom would work better if the orbits were elliptical, this still failed to solve the problem.
For the next twelve years, quantum theory was in a state of confusion, taking one step forward and two steps backward, or, if it was lucky, just marking time.
In 1922, Bohr met a brilliant young student named Werner Heisenberg, and admitted that he had reached an impasse.
Atoms, he told Heisenberg, were not ‘things’.

Then what could they be?
In 1923, a student at the Sorbonne named Louis de Broglie had an apparently absurd idea.
If light waves behave like particles, why should particles not behave like waves?
The idea of ‘matter waves’ admittedly seemed a contradiction in terms.
But, if the atom was not a ‘thing’, it followed that electrons were not things either.
If an electron was not a little hard ball, perhaps it was a wave inside the atom, rather like a spring bent round into a circle, or a snake with its tail in its mouth.
This would explain why electrons had orbits, since only certain wavelengths could fit into an exact circle.
Or perhaps, de Broglie added as an afterthought, electrons consisted of a particle
associated
with a wave—an idea that was greeted with even less enthusiasm.

In spite of which, de Broglie’s matter-waves were confirmed when beams of electrons were fired at a crystal.
The crystal lattice is, in effect, a series of slits, and slits cause light rays to bend (diffract).
The electron beam diffracted just as if it was a light beam.
And so, in an experiment performed later, did a beam of neutrons.
Particles
did
behave like waves.

By 1927, no fewer than three complete ‘quantum theories’ had solved Bohr’s impasse.
They were proposed by Werner Heisenberg, Paul Dirac and Erwin Schrodinger

In 1925, on a holiday in Heligoland, Heisenberg decided to forget Bohr’s ‘solar system’ atom, and concentrate on the mathematics.
He pictured atoms as oscillators, or vibrators—rather like those mattresses that are supposed to induce relaxation.
What he wanted to find was some connection between vibrations and the lines in light spectra.
He finally succeeded in finding a mathematical formula that would describe all the states inside the atom.
Heisenberg had broken the code of the spectrum.
He was so excited that he left the house at 3:00 in the morning and spent the rest of the night sitting on top of a tall rock.

There was one point that troubled Heisenberg.
In his quantum mathematics,
p
times
q
did not equal
q
times
p
, thereby apparently violating the laws of arithmetic (
p
and
q
stood for the position and momentum of a particle).
This problem was solved when news of Heisenberg’s breakthrough reached a Cambridge graduate student named Paul Dirac, a brilliant mathematician, who saw immediately that the paradox could be explained in terms of the work of a Dublin mathematician of the nineteenth century, William Rowan Hamilton.
Hamilton had been working on this problem of whether light is made of waves or particles, and had produced a set of equations that would describe the motion of a wave or a particle, and in which A times B did
not
equal B times A.

Erwin Schrödinger, a physicist of the old school, was unhappy with this new tendency to turn quantum physics into complicated algebra; he continued to believe firmly that it ought to be possible to visualise an atom.
During the Christmas of 1925, on holiday in the Tyrol with his latest mistress (he was a famous womaniser), Schrödinger had a sudden inspiration.
Brooding on de Broglie’s ‘matter-wave’, he produced a wave formula, which he called by the Greek letter psi (
), and which allowed him to think of an electron wave in the same terms as a wave on a pond.
Or, rather, imagine a ball of dough which begins to dance to syncopated music, and shoots out waves as it does so; this is a crude approximation to Schrödinger’s atom.
Schrödinger’s wave function was regarded as the greatest advance so far in quantum physics.

At first sight, these three great breakthroughs sounded contradictory; in fact, Schrödinger himself recognised that they were three statements of the same basic ideas.

It was Dirac whose ‘quantum algebra’ produced the next major breakthrough.
One of his equations, dealing with an electron moving at almost the speed of light, had a plus as well as a minus in it, and seemed to predict the existence of a positive particle similar to the electron (which has a negative charge.) In due course, the positron was discovered in the laboratory, earning Dirac the Nobel Prize.

But by then another vital principle of quantum physics had been discovered by Heisenberg—the famous ‘uncertainty principle’.
Superficially, this sounds unremarkable.
What Heisenberg stated—in 1927—was simply that it is impossible to measure both the position and the speed (momentum) of a particle.
It sounds unremarkable because it seems to be a merely practical limitation.
To measure the speed and position of a billiard ball requires simply that you shine a light on it (otherwise you cannot see it), and then measure how long it takes to get from A to B.
You cannot shine a light on an electron because it is too small; all you could do would be to make a single photon bounce off it, which would be like hitting the billiard ball with a golf club, and would obviously affect your measurement.

An analogy from everyday life might help.
Imagine a behavioural psychologist writing a book about human behaviour (classical physics
is
a kind of behavioural science), and beginning a chapter on sex by explaining that it is an appetite exactly like eating and drinking.
But, having embarked on this analogy, he realises that sex is in some respects quite different from the appetite for food.
A starving man may die; no sex-starved man ever died from lack of sex.
Starting from this recognition, he may end by grasping that sex, unlike food, is 90 percent ‘in the mind’, and cannot be understood as a purely physical need.
His position could then be compared to Bohr’s recognition that an atom is not a ‘thing’.

And in that same year, 1927, Niels Bohr dotted the i’s and crossed the t’s of Heisenberg’s uncertainty principle.
In discussions with Heisenberg, he produced what is known as the Copenhagen Interpretation, or the Principle of Complementarity.
He said, in effect: forget whether an electron is a wave or a particle.
If we ask an electron about its position (which is a particle property) we get an answer that suits a particle.
If we ask it about its momentum (which is also a wave property) we get an answer that suits a wave.
Stop asking which is correct, and recognise that the two answers complement each other.

In other words, not being able to measure both the speed and position of a particle is not just a practical limitation: it is inherent in the nature of reality itself.

Another quantum physicist, Max Born, had interpreted Schrödinger’s wave function psi as a measure of the
probability
that the electron would be in one place or another.
Schrödinger had protested, and made his point with his famous illustration of a cat locked in a box with a cyanide capsule.
A quantum process—like radioactive decay—can trigger a hammer which may or may not smash the capsule and kill the cat.
According to Born, said Schrödinger, the cat exists in a state that cannot be described as either alive or dead—until someone opens the box.
And that, he said, is plainly absurd.

And yet that, in a sense, was exactly what the Copenhagen Interpretation was saying.
Observing a subatomic process causes a collapse of the wave function, and makes it turn into a particle.
But, before the wave function collapses, the electron is in a state of probability, which
cannot
be pinned down more accurately.

Einstein objected bitterly.
He agreed with Schrödinger.
Something is really happening inside the atom, even if experimental limitations prevent us from discovering what it is.
‘God does not play dice’, he said indignantly.

He devised a ‘thought experiment’ to disprove Bohr—it is known as the Einstein–Podolsky–Rosen paradox, or EPR.
Suppose, he said, two electrons collide at the speed of light, and bounce off in opposite directions.
It
would
be possible to measure the speed of one and the position of the other; and since they are virtually identical—except for flying in opposite directions—this would amount to disproving the uncertainty principle.

Not so, said Bohr.
The two electrons are part of the same system, so, if you cause one wave function to collapse, you cause both to collapse at the same time.

No, said Einstein, for since they are travelling at the speed of light, and it is impossible to exceed the speed of light, one particle cannot possibly know what is happening to the other.

But this argument was won by Bohr.
In 1982, a group in Paris, led by Alain Aspect, carried out the two-particle experiment, and discovered that Bohr was correct.
If you cause one photon to swerve upward at an angle of 45 degrees, the other will swerve downward by 45 degrees.
So it would seem that, like identical twins, the photons somehow feel connected, even when flying apart at the speed of light.
This also confirmed the work of the Belfast scientist John S.
Bell, who had arrived at the same conclusion mathematically.
(It is popularly known as ‘Bell’s Inequality Theorem’.)

There is one more step in this argument—a step that to the ordinary reader may seem to throw the whole question into hopeless confusion, yet brings us back, once more, to the problem of the nature of UFOs.

There is one particularly baffling experiment that underlines the Alice in Wonderland paradoxes of quantum physics.
In its simplest form, it is known as the double-slit experiment.
If I shine a beam of light through a narrow slit, with a screen on the other side, it will form a slit of light on the screen.
If I now open up another slit at the side of the first, two overlapping slits of light will form on the screen.
But there will be certain dark lines in the overlap portion, due to interference—the crest of one wave cancelling out the trough of another.

Now suppose that the beam is dimmed so that only one photon at a time can pass through either of the slits, and suppose that, instead of a screen, you have a photographic plate.
Over a long period, you would expect two slits of light to appear on the plate—but no interference lines, since one photon cannot interfere with itself.
Yet, when this experiment is performed, the result is still two slits of light with interference lines.

There is something stranger still.
If a photon counter is placed over the two holes, to find which is used by each photon, the interference effect immediately vanishes, as if being watched made the photon behave itself.

How can this be?
Does the photon split into two?
Or does the wave somehow divide, and pass through both holes?
If so, why does it hit the screen in a precise spot?
And why does it behave like a wave when unobserved, and a particle when observed?