13 Things That Don't Make Sense (7 page)

After three decades of trying to find an answer, the researchers investigating the Pioneer anomaly have nothing. If it’s frustrating,
it’s also intriguing—so intriguing, in fact, that even NASA’s head honcho, Michael Griffin, has become interested. Turyshev
has had a number of conversations with Griffin about Pioneer. Maybe that’s why, after years of studying Pioneer in their spare
time, NASA researchers now have money for the project.

And rightly so. From the start, the Pioneer investigators have been almost exemplary when dealing with things that don’t make
sense. They won’t embrace the extraordinary until they rule out the ordinary. Turyshev is almost pathologically opposed to
talking about the exotic physics ideas, even the tamer ones, like a modified version of Newton’s law. Nieto is the same. He
is proud of all the Pioneer investigators have achieved so far, all the possible explanations they have ruled out. And his
gut feeling is that the explanation for the Pioneer anomaly will turn out to be something like forgetting to turn off the
lights. Or whatever is the NASA equivalent.

EVERY
month, one or two new papers appear that espouse some exotic explanation for the Pioneer anomaly. The arguments often appear
slightly unhinged; perhaps, for instance, the expansion of the universe caused the clocks involved in the measurements of
the Pioneer probes’ position to accelerate relative to each other? If that were true, Einstein’s special relativity would
require the analysis to be redone. The trouble is, this kind of outlandish phenomenon (and more than one has been offered)
would also affect the motions of the outer planets, and these planets are not doing anything odd.

Or maybe the signal photons, the particles of radiation that carried information from the craft, had their wavelengths altered
by the expansion of the universe? The researchers offering this suggestion admit that it fails a crucial test: it would push
the apparent position of the Pioneer probes the wrong way. Perhaps the anomaly has to do with the signal photons having their
quantum states shifted, or their being accelerated according to the laws of
nonlinear electrodynamics
, a theory developed in 2001 by a pair of Brazilian physicists? Or maybe the answer lies with John Moffat’s extra universal
force, the force that would also explain dark matter? The proponents of MOND think their theory also explains the Pioneer
anomaly. Or, depending on which way you want to see things, is backed up by it.

Nieto disagrees. The MOND hypothesis doesn’t tie in with the Pioneer data, he says; it doesn’t produce the right kind of drift.
He is OK—more OK than Turyshev, at least—with all the speculation. He wants to push the boundaries; he wants to know more
than we know at present. But not at any cost; he understands the dangers of scientists wanting something extraordinary to
be true. “If you go into it believing you’re going to find something—oh God, you are in for trouble,” he says.

In the end, Nieto believes they will find a straightforward explanation for the Pioneer anomaly. He is not deflated by this
prospect, he says—not at all. We will have gained innumerable analysis techniques, and experience of handling data with exquisite
precision, he points out. We will know the anatomy of a spacecraft—and of the space and time it travels in—with an intimacy
that we never would have gained without Pioneer.

And if he’s wrong—if all that effort reveals a force that is new to physics—so much the better. “For science it’s a win-win,”
Nieto says. Anderson also thinks the Pioneer anomaly is most likely a false alarm. But he is leaving a door open for something
revolutionary because he can’t help but notice the parallels with another anomaly, one that Einstein inadvertently solved
when he came up with general relativity.

IN
1845 Urbain Jean Joseph Leverrier, the French astronomer best known for the discovery of Neptune, calculated that Mercury’s
elliptical orbit around the Sun would experience a shift in its
perihelion
, the point of closest approach to the Sun, with each revolution.

This shift, or
precession
, is due to the gravitational pull of the other planets in the solar system. It is not unique to Mercury; the perihelion of
every planet’s orbit exhibits a similar precession. Mercury’s, however, was not what it should have been. When Leverrier worked
out, using Newton’s laws, how big the shift should be, it didn’t match the value astronomers had worked out from their observations.
The discrepancy was forty-three seconds of an arc—just a little more than one hundredth of a degree—per century.

Noticing such a tiny anomaly was a hugely impressive feat for the time, equivalent to measuring the diameter of a penny from
thirty miles away. But no one was patting themselves on the back; faced with the discrepancy, the scientists had no choice
but to find an explanation. Astronomers tried various ad hoc fixes. Leverrier, perhaps inspired by the way he had been able
to predict Neptune’s existence by reference to other planetary orbits, thought the Mercurial discrepancy must be a sign that
there was another planet waiting to be discovered. Others suggested the Sun had some kind of uneven weight distribution, or
that dust clouds in between the Sun and Mercury were affecting the orbit. Nothing worked. It was only in 1915, when Einstein
pointed out that a massive object like the Sun would warp the space around it, that an explanation for the anomaly was found.

Using his equations for general relativity, Einstein worked out that the warp in space, added to the tug of the other planets,
would give a value for Mercury’s perihelion precession of 42.9 arc seconds per century. It was a weighty validation for Einstein’s
newly minted theory and led to its immediate acceptance. And, according to John Anderson, it’s a lesson for those who would
discount the potential impact of the Pioneer anomaly.

If the explanation for the Pioneer anomaly is mundane, Turyshev’s careful approach will almost certainly find it. If the explanation
is something extraordinary, however, even the most meticulous sifting through the landscape of dull possibilities won’t help.
Mercury has taught us that ruling out the ordinary is not always going to lead to the answer.

Perhaps Pioneer doesn’t offer enough data to build a picture of another force in the universe, Anderson says. But even if
no one uses the errant flight path to create a breakthrough in physics, Pioneer could at least provide the validation for
a theory developed by other means. Einstein didn’t create general relativity because of the problem with Mercury’s orbit,
but the problem was hugely significant in proving Einstein’s radical ideas were right. If the orbit of Mercury provided the
perfect validation for one of the most important breakthroughs in science, perhaps the Pioneer spacecraft will one day do
the same.

IS
some unforeseen breakthrough coming? So far we have gathered evidence that the constituent parts of the universe are largely
unknown, that the four-hundred-year-old law of gravitation could be in need of a rewrite, and that an unknown force might
be responsible for pushing two of our spacecraft—craft that were predicted to offer a test for Newton’s law of gravitation—off
course. Kuhn might call this a sign of impending crisis. It certainly seems, as the foundations creak a little, that our current
picture of the cosmos might have to change in the near future.

It’s an exciting thought, but it doesn’t allow us to say anything concrete about the future of science. All we can do is press
on and add a new finding to the pile of evidence.

3

VARYING CONSTANTS

Destabilizing our view of the universe

F
lap your arms and see if you fly. Chances are, you won’t. The downward pressure of your arms on the air, and the equal and
opposite reaction upward, are not enough to lift your body weight against gravity. The exact figures involved come from Newton’s
universal law of gravitation. (Whatever its accuracy over cosmological distances, it works just fine here.) The lift you would
need to generate for takeoff involves the mass of the Earth, your mass, your distance from the center of the Earth, and a
number known as
Big G.

Newton’s equation arose from the simple observation that two masses pull on each other, and Big G is a measure of how strong
that pull is. The interesting thing is, there is no rationale for that number, no explanation for why Big G has the value
it does. Scientists have worked out its value from experiments that balance the gravitational pull against another known force,
such as the centrifugal force that wants to throw Earth out of its orbit, but just as scientists don’t know where gravity
comes from, they also don’t know why it should have the strength that it does.

Big G has another, more scientific name:
the gravitational constant.
It is probably the most familiar of the fundamental constants of physics, the collection of numbers that describe just how
strong the forces of nature are. Though every one of their values is derived from experiments, not from some fundamental understanding,
they are integral to what we call the laws of physics: the constants make the laws work when we use them to describe the processes
of nature. And because we assume that flying by flapping our arms will be as difficult tomorrow as it is today—that is, we
assume that the laws of physics are immutable, eternal—we have to assume the constants don’t change either. Which is why John
Webb has got himself into such trouble.

The laws and constants have helped us define and tame the natural world. But what if there are no immutable laws? What if
the constants aren’t constant? Or, as Webb puts it, a wry smile playing across his lips, “Who decided they were constant,
anyway?”

WEBB
is a professor of physics at the University of New South Wales in Sydney, Australia, but his first encounter with this question
came while he was a graduate student in England. One of his professors, the cosmologist and mathematician John Barrow, suggested
they resurrect a question first raised in the 1930s by the British physicist Paul Dirac: Have the laws of physics remained
the same for all time?

What is known as the
standard model
of physics inserts something like twenty-six numbers in its equations in order to accurately describe the strengths of the
various forces in nature. The values we have for those numbers come from experiments done on Earth, and mostly in the twentieth
century. Who’s to say whether the same experiments done on Alpha Centauri, or 10 billion years ago, would give the same result?

If you want to check whether something has been the same for a long time, you need a sample that’s as old as possible. Webb
and Barrow quickly realized they had access to a perfect sample: the light emitted, 12 billion years ago, by quasars, the
hearts of young galaxies. The emission of light from a star involves a constant that is officially known as the
fine structure constant
, but is more often referred to as
alpha
. The quasar light would depend on alpha as it was 12 billion years ago, so analyzing that light would provide the best possible
chance of answering Paul Dirac’s question. By 1999 John Webb had what looked like an answer.

The photons of light that carried his answer had traveled 12 billion light-years across the cosmos and landed on Earth in
Hawaii, at the Keck Observatory that sits on the summit of Mauna Kea. But what was most interesting about the light arriving
at the Keck telescope was the light that
didn’t
arrive. Just as Vesto Slipher had done at the Lowell Observatory eight decades earlier, Webb and his team spread the light
out into a spectrum. There were gaps in Webb’s spectrum: his rainbow had missing colors. That wasn’t interesting in itself;
on a 12-billion-year journey through space, you’d expect the light to encounter some matter—clouds of gas are the usual culprits—that
absorbs light of particular wavelengths. This leaves breaks in certain parts of the spectrum, as if a decorator has left a
few vertical white stripes in the middle of your orange bedroom wall.

The interesting part of Webb’s discovery was that the breaks were in the wrong place. Every atom, whether it is in an interstellar
gas cloud or on the sole of your foot, will only absorb photons of particular energies. The energies in question differ for
each atom; it is something like the atomic version of a fingerprint. As a result, by looking at the spectrum of light—and
what is missing from it—you can fairly easily work out what atoms the light encountered.

The fingerprints in Webb’s spectrum corresponded to two atomic encounters. One involved absorption by magnesium atoms; the
other, by iron. It was clear from Webb’s spectrum that the quasar’s light had passed through clouds of magnesium and iron
on its trip to Earth. But there was a problem. Although it was unmistakable which of the well-known absorptions the gaps in
the spectrum were meant to correspond to, they were slightly out of place, as if someone had nudged the spectrum. For some,
the absorption lines were nudged slightly to the left. For others, they were shifted a little to the right.

Webb sat down and redid the calculation. All the shifted lines made sense if he made one little adjustment. All he had to
do was allow that when the light was racing through the interstellar dust clouds, the fine-structure constant was very slightly
different from what it is today.

It sounds like a straightforward conclusion, but it took some guts to go public with the suggestion. Webb has been attacked
for this; people, as he politely puts it, have “questioned his sanity” in remarking that a constant of nature might change
over time. Especially one as central to physics as alpha.

ALPHA
determines what happens every time a photon hits some piece of matter. Look at the wall opposite you; whatever color you see,
you see because of alpha. A photon of light hits an atom in the paint. The atom absorbs the photon’s energy and uses that
energy to send out a photon that hits your eye. The energy of that photon determines the wavelength of the light it produces—in
essence, what color you see. If the wall is orange, the photon has one energy; if it is violet, the energy is very slightly
higher (it is still only equivalent to the energy in a billionth of a billionth of a raisin). To work out what color you’ll
see from a particular paint, you need to do a calculation that invokes alpha and the quantum structure of the atoms and molecules
in the paint.

On the face of it, alpha is just a number. It is, roughly, 0.0072974, or 1/137 if you prefer fractions. The recipe for this
number is fairly straightforward (though it depends on what units you’re working in). First, multiply the charge on an electron
by itself. Then divide that by a number called
Planck’s constant.
This is a staple of quantum physics; physicists refer to it simply as
h
, and it describes the relationship between a photon’s energy and the wavelength—the color—of its light. Next, divide what
you’ve got by the speed of light. Now multiply the whole thing by 2π. Now you have alpha.

The thing is, alpha is not just about interior decoration choices; it is a pillar of physics and central to our entire description
of the universe, beginning to end. Alpha determines how much energy there is in “empty” space, dictating how the newborn universe
would expand. Once the first three minutes were over, alpha came into play in the electromagnetic interactions between the
newly formed protons: it determined what kinds of photons filled the void.

When the first stars formed, as hydrogen atoms collapsed together and their nuclei fused under the intense gravity, alpha
determined how much light and heat they gave out. And since radiation of all kinds give us our only view of the early universe,
alpha tells us almost everything we know about the story of the cosmos. It might be made of nothing more than the speed of
light, a rather boring number from quantum theory, pi, and the charge on an electron, but it is tied in to almost every process
in the universe. Which makes it all the more unsettling that it might once have had a value that’s different from the one
we currently assign it.

Alpha’s significance is due to the fact that it is the most important constant in one of our most important theories of physics:
quantum electrodynamics
, or
QED.
This governs any and every interaction between the charged subatomic particles: the protons and electrons. QED brings together
quantum theory, relativity, electricity, and magnetism to describe the origins of electromagnetism. Alpha is also linked,
via the “electroweak theory” that gained Steven Weinberg, Abdus Salam, and Sheldon Glashow the 1979 Nobel Prize in Physics,
to the “weak force” that gives rise to phenomena such as radioactive decay in atomic nuclei. Since electromagnetism and the
weak force are two of the four fundamental forces of nature, it is fair to say that alpha plays a pivotal role in the universe.

Not that the theory provides a value for alpha; scientists have had to do intricate experiments with electrons to work out
what number they should plug into the QED formulas. Just as experiments gave us the gravitational constant that tells us how
much the Earth and the Sun pull on each other in Newton’s theory, the experimentally sourced alpha tells us how strongly charged
particles affect each other. And it is not allowed to change by much.

Tweak alpha too far, and small atomic nuclei—those of helium, for example—would blow apart as the protons repelled each other.
Stars wouldn’t shine. Grow alpha by 4 percent, and the stars wouldn’t have ever produced carbon—and thus we wouldn’t exist.

Not that John Webb wants to change alpha by quite that much. Webb’s absorption lines all makes sense if you allow it to have
been smaller by just a millionth of its present value 12 billion years ago.

It seems, on the face of it, an almost inconsequential correction. A constant of physics, one that hardly anyone outside the
subject has heard of, may have had a slightly different value in the past. It’s put on a little weight, got one-millionth
bigger in 12 billion years. Big deal. But it is a big deal. If it is true—and ten years later Webb still prefaces all his
statements with this cautionary clause—if it is true, it opens a door to all kinds of unsettling ideas. We have built our
story of the universe, and our explanations of how everything behaves within it, on the premise that the constants are, and
always have been, constant. And, as we have seen, if the constants change, so do the laws. John Webb’s observations are threatening
to unleash a lawless universe.

Webb knows this; he is not rushing in to make any claims. He is an astonishingly careful man. He has already spent nigh on
a decade trying to find the fault with his own results. His research team have dissected every result, carried out ruthless
and rigorous statistical analyses, checked everything for some casual error. They have found nothing wrong. In fact, their
analyses have taken them to the point where the varying alpha result has much more credibility than is generally required
in any other area of physics. You don’t even need Webb’s level of certainty to claim a Nobel Prize for the discovery of an
entirely new particle.

Nonetheless, most of the discussion about Webb’s results tends to be about how they must be wrong—how there must be some error
in the analyses. So, can we check? The obvious thing to do is to look at Webb’s claim about alpha using something other than
starlight and telescopes. The trouble is, you can’t redo Webb’s work in a simple laboratory experiment because it has to do
with alpha’s variation over a cosmological timescale. You can’t measure how light interacts with matter in June, July, and
August, find a consistent result every time, and claim Webb is wrong. He isn’t claiming alpha is varying now; all he’s saying
is that it was very slightly different 12 billion years ago. If you want to do an experiment to test Webb’s suggestion that
alpha was different in the past, you need some evidence from the distant past. Fortunately, though, there is a way to get
some: take off your lab coat, put on a pith helmet, and head into colonial Africa.

GO
to eBay’s French site, and type in the word
Brazza
. Chances are, the word means very little to you, but you’ll bring up a range of collector’s items for auction: matchboxes,
pens, portraits, and cigars, to name but a few. In 1880s Paris, Brazza merchandise was all the rage. Pierre Savorgnan de Brazza,
the French explorer (he was Italian by birth, but the Italian navy couldn’t satisfy his thirst for adventure), put the West
African territory of Gabon into French hands. And that made him a French national treasure.

Although the French named the Congo’s capital city after him, Brazza’s status as a treasure didn’t last his whole life. He
had established the Gabon colony with extraordinary integrity—there was fair trade, no slavery, and no subjugation by force
under Brazza’s governorship. With Gabon’s rich resources, it was a strategy that was bound to win him enemies, and he spent
the latter years of his life trying to beat down the flames of corruption and slavery that had begun to spread through the
colony. For his trouble, Brazza was smeared, vilified, and, according to his wife, eventually poisoned.

One of Brazza’s last acts was to establish the city of Franceville in the far east of Gabon as a place to resettle former
slaves. And it was near here, at Oklo, that French nuclear scientists made the extraordinary discovery that has had enormous
repercussions for John Webb’s work.