If the Earth’s poles are switching, then rather than rare bursts of chaos, disrupting events will become commonplace and persistent. Electrical and electronic technologies will become less reliable, more vulnerable to long-term crashes and damage. Unless we devise ways to protect our systems, signs are that we will no longer be able to count on these cornerstones of modern civilization: the electrical infrastructure; the satellites society depends on more and more in ways people barely recognize; our means of communication; how we get around. It’s like an intricate structure of dominoes set to fall in unexpected patterns, each failure reinforcing the next.
CHAPTER 29
trout noses and pigeon beaks
Only about a dozen scientists around the world are doing experiments to solve the curious riddle of precisely how living creatures use the Earth’s magnetic field to navigate. Michael Winklhofer is one of them. The day I met him, I had taken a flight to Düsseldorf in northern Germany, and then a long cab ride to his office at the University of Duisburg-Essen. He was standing outside the campus’s cafeteria building waiting for me when I arrived, hands in his pockets and narrow shoulders hunched against the cold.
This rarefied area of study, known as magnetoreception, was considered crank science in the 1960s. But by the 1980s, a series of careful studies had shown just how common the magnetic sense is among the planet’s species, and how crucial to the acts of feeding and reproduction. The discipline took off in prestige. As a student, Winklhofer attended a lecture on magnetotactic bacteria—the ones that respond to the Earth’s magnetic field—and was hooked.
Once we were in his office, and my luggage was stowed in a corner, he showed me a short video on his computer of one of the classic experiments. On the screen were bacteria in pond sediments. They need to know up from down because they continually travel between the water and the mud, pivoting between an oxygenated environment and one that doesn’t have oxygen. The experiment involves putting a small magnet near the bacteria and then moving it around. The bacteria rotate in perfect harmony with the magnet’s movement, acting like the needle on a compass. The bacteria’s magnetic sensibility is critical to their survival. Other studies have shown that in parts of the Earth where the magnetic field is parallel to where the mud and water meet—at the magnetic equator, for example—the density of magnetotactic bacteria drops dramatically. Winklhofer played the video several times, immersed in it, still fascinated with what those bacteria were doing. He and others are looking at fossils of magnetotactic bacteria to try to read in them the field’s movements over time.
From single-celled bacteria, this magnetic sixth sense spreads upward through the Linnaean taxonomic chart to more complex creatures. It is present in butterflies, honeybees and fruit flies, fish, lobsters, newts and sea turtles, migrating songbirds, whales and wolves, deer, rats, and many other animals. They are born with it, Winklhofer said. Bees make new hives pointing in the same magnetic direction as the hives of their parents. Termite mounds are always aligned north to south. Worms are oriented to the hemisphere they were born in; Australian worms used in lab experiments always point up in test tubes in the northern hemisphere, while North American ones point down. Chinook salmon inherit a magnetic map along with the ability to taste and smell the differences among rivers. Marine turtles can spend decades at sea before returning to the very beach where they were born in order to lay eggs in their turn. Magnetoreception is as intrinsic as the sense of touch. A superb navigational tool, it is unaltered by time of day, season, or weather, present no matter where you are on the planet.
But how do species convert an intangible magnetic field into flesh and blood? There are two leading theories, each of which relies on the presence of unpaired spinning electrons. Both may be in play at the same time, but they’re proving hard to pin down, Winklhofer said. Most magnetic species have cells that contain tiny amounts of magnetite, or lodestone, or a related ferrimagnetic substance, whose unpaired spinning electrons can line up to amplify a magnetic force. Deposits of magnetite and other ferrimagnetic molecules have been discovered in living tissue across the web of life. Magnetotactic bacteria, for example, have as much as 2 percent magnetite or a similar substance in their bodies by weight. Mollusks make toothed tongues out of magnetite, and snails that live near hot deep-sea vents make scales like roof tiles out of another ferrimagnetic molecule. Humans have lodestone molecules in our brains, heart, spleen, and liver, although the question of whether we perceive the magnetic force is hotly controversial. One researcher suggested we have consigned it to our subconscious. Perhaps we draw on it now under the cover of magical flashes of insight. The theory is that the magnetite acts as a tiny compass, patching magnetic information into the nervous system, allowing a creature to read the field. It’s like having a built-in GPS. Homing pigeons, for example, have six nerve cells containing magnetite at six different spots on the skin of their upper beaks. Rainbow trout have magnetite cells in their noses.
The second idea is that certain molecules containing an unpaired spinning electron each can pair up to become a chemical compass within the body that tracks the field’s inclination. The molecules are thought to be contained within a protein and fixed in a cell, perhaps in the retina, so they don’t float around. These electrons line up according to the Earth’s magnetic field. In birds, they seem to be triggered by the quality of light available. Birds may even be able to process images of the magnetic field in the part of the brain responsible for vision, meaning they can see field lines, or perhaps their absence.
Researchers in magnetoreception grasped early that a pole switch might affect the creatures they studied, both because there could be more than one pair of poles during a reversal and because the field itself would be so weak. Kenneth Lohmann, a biologist at the University of North Carolina and a pioneer in magnetoreception, wrote in a 2008 paper that rapid field changes during a reversal could disrupt on a massive scale animals’ ability to return home to nest, leading animals to establish new birthing areas when they can’t find their old ones. That’s important because it could potentially change survival rates of the young in the short term.
In turn, that’s important because some of the species that rely on the magnetic field to orient themselves are endangered today for other reasons than a potential switch in the direction of the Earth’s field. Mainly, that means humans have destroyed their habitat or hunted or fished them to the brink. All seven species of migratory sea turtle, for example, are at risk of extinction in the wild. Kemp’s ridley sea turtles are in the most danger, according to the World Conservation Union’s red list, with a global population of fewer than ten thousand. Many species of whale, which migrate for food and birthing spots, are endangered. One in eight birds is at risk of extinction, and recently the migrating swooping insectivores, such as swallows, have seen sharp declines in numbers across Europe and North America. Bees are in trouble all over the world. Could this be the straw that breaks the camel’s back for some species?
Winklhofer said that biologists and geophysicists have been investigating this question for several years and have come to the conclusion that as long as a reversal isn’t instantaneous and as long as the species’ populations are robust enough to begin with, most will eventually adjust. Researchers working with robins, for example, which are sensitive to inclination, or dip, rather than the north-south direction, have found that they can adjust to a field that has a dramatically lower intensity than they are used to. They can also adjust to poles in radically different places. They just need time. He pointed out that species that navigate using the field are used to recalibrating frequently because the field changes slightly all the time. Songbirds, for example, calibrate their magnetic sensibility at twilight every day, finely attuned to any secular variations.
He pulled up another file on his computer. This one showed a re-creation of the magnetic field at the height of the most recent reversal. Several poles showed up at mid-latitudes. The magnetic e
quator ran north-south. It looks impossible to navigate, but his analysis is that species may be able to adjust to it, especially those that rely on inclination rather than the north-south direction of the poles. “Biology,” he said, “is flexible.”
There are two wild cards for the Earth’s life forms during a reversal. The first is the depth of the extinction risk already present for species that migrate and navigate using the poles. It’s unclear how much the extra stress of a reversal will affect them, just as it’s unclear how more routine geomagnetic disturbances do. NASA recently teamed up with two other organizations to investigate whether solar storms, with the accompanying disruption of the Earth’s magnetic field, are linked to whale strandings that are common in New Zealand; Australia; and Cape Cod, Massachusetts. The second uncertainty is how much solar and cosmic radiation will strike the Earth’s surface during a reversal. Even an extra 5 to 10 percent more radiation will have injurious effects, but scientists have not been able to calculate exactly what it would mean, Winklhofer said: “Without data, this is where science ends.”
CHAPTER 30
a suit of stiff black crayon
The sun was quiet during all six Apollo missions that landed humans on the moon. Neither astronauts nor vessels were exposed to violent storms that throw off damaging solar energetic particles. It was an extraordinary piece of luck. But in August 1972, midway between the date the astronauts of Apollo 16 had returned home and when those of Apollo 17 took off on the final voyage, the sun spewed out the biggest storm it had produced in a century.
Earlier in his career, as Daniel Baker became more involved in NASA and in space weather, he began to wonder what would have happened if a solar storm had struck while astronauts were walking on the moon during that fabled Apollo era. The moon no longer has an internally generated magnetic field or an atmosphere to protect against radiation, leaving astronauts exposed apart from their space suits. He asked what the emergency plan had been. The answer? The astronauts were instructed to dig a hole, and then the more senior would lie down in the hole and the junior would lie on top of him, shielding his superior’s body with his own. The hope was that at least one astronaut would be undamaged enough to make it back to Earth. The August 1972 storm was so strong that any humans exposed to it would have suffered acute radiation sickness and would likely have died, Baker said. “It points out that without the protection of a magnetic field, we are very susceptible.”
Space, rather than being the calm, empty, and benign place our forebears envisioned, is full of lethal ionizing radiation. When the poles reverse and the Earth’s shield is weakened, some of that solar and galactic radiation will reach into the lower atmosphere and even parts of the surface, Baker said. If people and other species cannot escape to safer parts of the planet, they will suffer the effects of radiation, both debilitating and fatal, some of it akin to what the astronauts would have experienced had they been on the moon in August 1972. During a reversal, Baker expects to see more cancer affecting the eyes, mucous membranes, and stomach lining. He expects to see widespread, acute radiation poisoning of the type seen in the wake of radiation accidents and nuclear warfare. That means both immediate and chronic effects on human health. And while some geophysicists said it’s hard to tell how much increased radiation will accompany a reversal and that the fallout may not be as severe as Baker predicted, many said that a common estimate is for cancer rates to increase by 20 percent across the board. That “war on cancer” is looking a lot more challenging.
Scientists and physicians have studied the effects of radiation on living tissue since the short electromagnetic waves, dubbed X-rays—after the scientific unknown x—were discovered in 1895 by Wilhelm Röntgen, the Dutch/German physicist. He famously took an X-ray of the left hand of his wife, Anna, showing the startling, ghostly images of the bones within her hand, plus the outline of the wedding ring on her finger. He won the Nobel Prize in physics for the discovery in 1901. Reports of damage from exposure to the mysterious rays began almost immediately, including burns, hair loss, and death. One of the first deaths from cancer caused by X-ray exposure was Clarence Dally, a glassblower who worked with the American electricity magnate Thomas Edison in his efforts to make an X-ray focus tube. Being right-handed, Dally repeatedly tested the X-ray on his left hand. When it became too injured, he switched to his right. He died in 1904 at age thirty-nine, but not before his left arm had been amputated at the shoulder, and the right above the elbow in a failed bid to stop the galloping damage. Edison abandoned X-rays in horror.
A year after Röntgen discovered X-rays, the French physicist Henri Becquerel found evidence that uranium spontaneously ejects particles—this is the weak nuclear force at work—making what was soon called a “radioactive” substance. Radioactive materials are also ionizing. They are uncommon in nature. Immediately after Becquerel discovered uranium’s odd characteristics, Marie and Pierre Curie experimented with it and discovered the radioactive substances radium and polonium. Together, the three received the Nobel Prize in physics in 1903. As with X-rays, the injuries and deaths from working with spontaneously radioactive material began to mount quickly, although the dangers were not fully recognized for decades. At one time, radium cures were on offer to freshen one’s complexion or clear one’s bowels. Marie Curie, who carried tubes of radioactive material around in her lab-coat pockets, died in 1936 at age sixty-six from aplastic anemia, or damage to her bone marrow, likely from exposure to radiation. Her notes in the National Library of France in Paris are still encased in lead-lined boxes, a radioactive shield.
Today, most of the work estimating the risks of illness and death from radiation of any sort, whether from radioactive substances or ionizing electromagnetic radiation, comes from research on the survivors of the Hiroshima and Nagasaki atomic bombs dropped in 1945. There is also information about people who were exposed to radiation during nuclear accidents or whose nuclear medicine treatments went awry. When it comes to data on space travelers, the twenty-four Apollo astronauts are the only humans to have left lower-Earth orbit. In addition, there are records from astronauts who have orbited Earth on shuttles or resided on the International Space Station, all of which activity has taken place within the protection of the Van Allen belts. Any other information on damage from solar and galactic particles is experimental or theoretical.
At the most basic level, radioactive substances and radiation from electromagnetic waves and solar and cosmic energetic particles damage living beings in similar ways. Differences among them have to do with how much energy the particles or waves have, how big the particles are, and how close you are to them. Spontaneous radioactive decay, like the uranium, radium, and polonium the Curies worked with, involves a large, unwieldy atom with too many neutrons that is trying to become stable. A common way for an atom to do that is to throw off subatomic particles, tiny bits of itself. Sometimes a radioactive atom throws off a neutron or two in what’s called neutron release. Sometimes it’s two neutrons and two protons joined together, making a new helium nucleus with a positive charge. That’s called alpha decay. Sometimes it throws off an electron. That’s beta decay. Sometimes the protons and neutrons rearrange themselves, like people taking their seats for a concert after a cocktail party, and the atom emits electromagnetic energy in the form of gamma rays. The point for us is that charged particles or energetic neutrons or nuclei or tiny fast electromagnetic waves are being emitted that can cut through cells and damage them.
Take uranium as an example. It exists naturally on Earth in three isotopes. It always has 92 protons in the nucleus—because when the number of protons changes, so does the name of the element—but different numbers of neutrons, either 146, 143, or 142. You add the neutrons to the protons to name the isotope. The most common on Earth is uranium-238, which has 146 neutrons. It stabilizes itself by alpha decay, transforming into thorium-234, with 90 protons and 144 neutrons, shedding a helium nucleus (two protons, two neutrons) in the process. The is
otopes created during radioactive decay are called daughters. Eventually, after many alchemical transformations, uranium-238 becomes lead-206—boring and stable.
Some radioactive isotopes lend themselves to fission, meaning you can bombard them with neutrons to prompt them to split into lighter isotopes that then spontaneously keep splitting and releasing energy in a chain reaction. Uranium-235, with 143 neutrons, is prone to chain reactions. Uranium-238 can be converted into plutonium-239, which chain reacts. The bomb that struck Hiroshima contained uranium-235; the one dropped on Nagasaki, plutonium-239. Scientists have also learned how to harness the power of these types of radioactive chain reactions in nuclear power reactors to produce electricity, often using uranium-235.
Here’s how it connects to a reversal. All living things are made from atoms bonded into molecules through their electrons. Ionizing radiation and radioactive emissions break the bonds, either damaging the cell directly or creating knock-on chemical changes in a cell that can lead to its damage or death. As they break the bonds, they free up electrons, setting them in motion and endowing them with enough energy to ionize and excite other molecules in the tissue along a track of damage known as a linear energy transfer, or LET. The strength of the energy transferred is measured in megaelectron volts, or MeVs, named after Alessandro Volta, who invented the voltaic pile. X-rays are low LET. Galactic cosmic rays are very high. The energy transfer can create highly unstable ions within a tissue. The ions want to gain stability, so they scavenge bits from other molecules, damaging tissue in the process. A prime spot for an unstable ion to grab something is from a strand of DNA. Medical articles on the damage from ionizing radiation often feature microscope photographs of DNA. The tracks left by the radiation resemble rips left by a jagged knife dragged through a ribbon.
The Spinning Magnet Page 24
