[EFFECTS ON SATELLITES] High-energy particles degrade solar panels.
They also penetrate circuitry and generate
Feeling the Full Brunt spurious signals that can corrupt
data or even cause a satellite to
The harshness of space takes a toll on satellites even spiral out of control.
Impact of a Coronal Mass Ejection The 1859 Superstorm at the best of times. A superstorm would cause years’
worth of damage within a few hours.
NORMAL CONDITIONS: Earth’s magnetic ﬁeld typically deﬂects the charged particles streaming The authors have reconstructed what happened in
out from the sun, carving out a teardrop-shaped volume known as the magnetosphere. On the sun- 1859, based in part on similar (though less intense) How to
facing side, the boundary, or magnetopause, is about 60,000 kilometers from our planet. The ﬁeld events seen by modern satellites. UTC is Coordinated
Universal Time — basically, Greenwich Mean Time.
also traps particles in a doughnut-shaped region known as the Van Allen belts. If a storm were on its way,
August 26 we could do the following:
Large sunspot group
appears near longitude Satellite operators put
Magnetic ﬁeld line 55 degrees west on the sun; off critical command
ﬁrst CME possibly launched. sequences. During the
storm itself, they
monitor their birds and
Sun Van Allen belts CME arrives at Earth with a
override any spurious
glancing blow because of
the solar longitude of its
source; its magnetic orien- SUNSPOTS
GPS users switch to
tation is northward.
Magnetosphere backup navigation
August 28 07:30 UTC systems.
Greenwich Magnetic Obser- Solar particles and radiation puff up the
vatory detects a distur- atmosphere, increasing the drag forces Astronauts avoid
bance, signaling compres- on low-orbiting satellites. space walks.
FIRST STAGES OF IMPACT: When the sun ﬁres off a coronal mass ejection (CME), this bubble of
Electrons can collect on
ionized gas greatly compresses the magnetosphere. In extreme cases such as superstorms, it can sion of the magnetosphere.
satellites and cause static
push the magnetopause into the Van Allen belts and wipe them out. electrical discharges that
August 28 22:55 UTC physically damage the
Main storm phase begins, circuitry ( ).
with large magnetic distur-
bances, telegraphic disrup- CORONAL MASS EJECTION
tions and auroral sightings
as far south as magnetic lat- w w w. S c i A m . c o m
itude 25 degrees north.
Sunspots Coronal mass ejection August 30
[EFFECTS ON POWER]
from ﬁrst CME end. Darkness Falls
September 1 11:15 UTC Electric currents in the ionosphere induce electric currents in the ground and in pipelines.
CME magnetic ﬁeld (S) Astronomer Richard C.
Earth’s magnetic ﬁeld (N)
Carrington, among others,
sights a white-light ﬂare on
the sun; the large sunspot Electric currents
MAGNETIC RECONNECTION: The solar gas has its own magnetic ﬁeld, and as it streams past our group has rotated to longi- in the ionosphere
planet, it stirs up turbulence in Earth’s magnetic ﬁeld. If this ﬁeld points in the opposite direction as tude 12 degrees west.
Earth’s, the two can link up, or reconnect—releasing magnetic energy that accelerates particles
September 2 05:00 UTC
and thereby creates bright auroras and powerful electric currents.
Greenwich and Kew magnet-
ic observatories detect dis-
Turbulent ﬁeld lines
turbances followed immedi-
CME plasma ately by geomagnetic chaos;
second CME arrives at Earth Transformer
within 17.5 hours, traveling Induced
at 2,380 kilometers per sec- current
Reconnected ond with southward mag-
Auroras region netic orientation; auroras
region Current appear down to magnetic
latitude 18 degrees north.
Main phase of geomagnetic
disturbances from second
CME ends; scattered auro-
ral sightings continue, but
with diminishing intensity. These currents surge The entire East Coast and much of the rest of the country would
into transformers and lose power. This map shows the blacked-out regions expected
AURORA SIGHTINGS Induced from a severe storm like that of 1921, which would induce ground
can fry them. It would
82 S C I E N T I F I C A M E R I C A N August 2008 take weeks or longer for current ﬁelds of about 20 volts per kilometer. Scientists have yet to model
workers to ﬁx them all. the effects of a full-blown 1859-like storm on the power grid.
rent (DC). The DC ﬂows up the transformer could bring down the entire grid. Other indus- that improves the accuracy of GPS position esti-
ground wires and can lead to temperature spikes trial countries are also vulnerable, but North mates. Commercial aircraft had to resort to in-
of 200 degrees Celsius or higher in the trans- America faces greater danger because of its prox- ﬂight backup systems.
former windings causing coolant to vaporize imity to the north magnetic pole Because of the High-energy particles will interfere with air-
How Time Is Not Like Space
Physicists, artists and graph makers of all kinds routinely depict time as another dimension of space, creating a unified spacetime — shown here as a three-
dimensional block in which a ball bounces off a wall. Relativity theory holds that spacetime can be sliced up in various ways. But not all are equally sensible.
The usual way takes slices of space at successive moments of time, creating a movie of the ball’s
motion. Each frame leads to the next, according to the familiar laws of physics.
An alternative considers slices not from past to future but from left to right. Each slice is part
space, part time. To the left of the wall, the ball appears in two positions; on the right, it does not
appear at all. If this slicing seems strange, it should: it makes the laws of physics very unwieldy.
2 34 ●
[A NEW VIEW OF TIME]
Who Needs Time, Anyway? 1 beat
Time is a way to describe the pace of
motion or change, such as the speed
of a light wave, how fast a heart beats,
or how frequently a planet spins ...
... but these processes could
LIGHT: be related directly to one
300,000 kilometers per second another without making
reference to time.
75 beats per minute
240,000 kilometers per beat
1 rotation per day
Thus, some physicists argue that time is a common currency, making the world easier to describe
1 cup of coffee
but having no independent existence. Measuring processes in terms of time could be like using
money ( ) rather than barter transactions ( ) to buy things.
50 cups of coffee
per pair of shoes
VS. 1,000 cups
per used car
$2 $100 $2,000
[see “A Quantum Threat to Special Relativity,” recently investigated timeless theories [see “A
by David Z. Albert and Rivka Galchen; S����- Simple Twist of Fate,” by George Musser, on
����� A�������, March 2009]. page 14]. But to convey the basic problem that
mundane activity. The great strength of multi-
touch is letting multiple people work together on
a complex activity. It is hard to remember how
LED liberating the mouse seemed when it freed peo-
ple from keyboard arrow keys some 25 years
[HOW IT WORKS]
ago. Soon the multi-touch interface could help
untether us from the ubiquitous mouse. “It’s
Tracking Fingers Pressure-sensitive
very rare that you come upon a really new user
The most advanced multi-touch interface,” Han says. “We’re just at the begin-
Light ning of this whole thing.”
screens respond to the motion and Reﬂection scattered
pressure of numerous ﬁngers. In the sensor toward
reﬂection [INSIDE LOOK]
Perceptive Pixel design ( ), sensor
projectors send images through an
acrylic screen onto the surface facing
the viewer. When ﬁngers or other
objects (such as a stylus) touch the A projector inside Microsoft’s
surface, infrared light shone inside the multi-touch table, called Infrared cameras
acrylic sheet by LEDs scatters off the projector Surface, sends imagery up
ﬁngers and back to sensors. Software through the acrylic top. An
interprets the data as ﬁnger move- LED shines near-infrared light
LED up as well, which reﬂects off
ments. Tapping the screen brings up To create a signal, LEDs bounce light through the acrylic
command menus when desired. objects or ﬁngers back to var-
sheet. No light escapes. But if a ﬁnger is placed against the ious infrared cameras; a com- Computer
face ( ), light will scatter off it toward the sensors. puter monitors the reﬂections
Also, a pressure-sensitive coating ﬂexes when pressed to track ﬁnger motions.
Computer ﬁrmly or lightly, making the scattered ﬁngertip signal
appear slightly brighter or dimmer, which the computer Projector
interprets as more or less pressure. LED light
prefrontal cortex Nucleus accumbens
Subthalamic nucleus Mediodorsal thalamus
ba- Globus pallidus
um- internal segment
rive cingulate cortex
iven Amygdala Anterior limb
es— of the internal
ion, Ventral tegmental area capsule
BRAIN AREAS that become
activated in response to Subgenual
reward or risk include those cingulate
shown above, among others.
pallidum hypothalamus Brain stem
WHAT Pedunculopontine nucleus
Periventricular gray/periaqueductal gray
Tuberculosis occurs in virtually every country in the world, although it is most wide-
spread in developing nations. The incidence of TB caused by strains of resistant to
two or more of the first-line drugs for the disease — so-called multidrug-resistant TB
(MDR-TB) — has been rising as a result of improper use of antibiotics. Worse still is exten-
sively drug-resistant TB (XDR-TB) — a largely untreatable form identified in 2006; as of
June 2008, 49 countries had confirmed cases. Sadly, that figure most likely underesti-
mates XDR-TB’s prevalence.
AN ILL WIND TB
Brain Tuberculosis, caused by the bacterium , occurs in both latent and active forms. People can become infected by breathing
in even just a few bacteria released into the air when those with active TB cough, spit or talk. causes coughing, the
most familiar symptom, because it accumulates abundantly in the lungs, but it can harm other organs as well ( ).
Reported cases of
Lung tends to concentrate in the air sacs, or alveoli, of the tuberculosis per
lungs because it prefers environments rich in oxygen. In 100,000 citizens
Macrophage most people, the immune system is able to keep bacterial
replication in check, dispatching defensive cells known
as macrophages to the site of infection, where they 0–24
form a shell around the bacteria. But in 10 percent of 2
Alveolus infected individuals, breaks down the shell,
after which it can begin to multiply. 50–99
300 or more
Kidney Multidrug-resistant TB
Scan highlights infection in lung.
Unfettered by the immune system, the bacteria destroy the tissue of
the lungs; some may also make their way into the bloodstream and infect Percent of MDR-TB
other parts of the body, including the brain, kidneys and bone. Eventually among new TB cases
affected organs may sustain so much damage they cease to function, and 1994-2007
the host dies. More than 6%
Less than 3%
the problem is that bacteria are autonomous some of those proteins might be worth consid-
life-forms, selected throughout evolution for ering as drug targets. Analysis of the TB genome
their ability to adapt and respond to external also hinted that, contrary to conventional wis-
threats. Like modern aircraft, they have all dom, the bacterium is perfectly capable of living Extensively drug-resistant TB
manner of redundancies, bypasses, fail-safes in the absence of air— a suggestion now verified.
and emergency backup systems. As Jeff Gold- Under such anaerobic conditions, Mtb’s metab-
blum’s character in Jurassic Park puts it, life olism slows down, making it intrinsically less
finds a way. Until we truly appreciate the com- sensitive to existing antibiotics. Targeting the
plexities of how TB interacts with humans, new metabolic elements that remain active under
drugs against it will remain elusive. The good these circumstances is one of the most promis-
i h ki h i i f h i i
[STAGES TO WATCH]
From Animal Microbe to Human Pathogen
The process by which a pathogen of animals evolves into one exclusive to humans occurs in five stages. Agents can become stuck in
any of these stages. Those in early stages may be very deadly (Ebola, for example), but they claim few lives overall because they cannot
spread freely among humans. The better able a virus is to propagate in humans, the more likely it is to become a pandemic. [PREVENTION PROPOSAL]
DISEASE EXAMPLES: Reichenowi malaria Rabies Ebola Dengue HIV
Building a Surveillance Network
By monitoring microorganisms in wild animals and the people who are frequently exposed
to them, scientists may be able spot an emerging infectious disease before it becomes
widespread. To that end, the author recently organized the Global Viral Forecasting Initia-
tive (GVFI), a network of 100 scientists and public health officials in six countries ( and
) who are working to track potentially dangerous agents as they move from
Stage 1: Pathogen is present in animals into human populations. The GVFI focuses on tropical regions ( ) in particu-
animals but has not been detected lar, because they are home to a wide variety of animal species and because humans there
in humans under natural conditions. commonly come into contact with them through hunting and other activities. Eventually
the GVFI hopes to expand the network to include more countries with high levels of biodi-
Stage 2: Animal pathogen has been trans- COUNTRY: Cameroon versity, some of which are shown here ( ).
VIRUSES PREVIOUSLY SPAWNED: HIV COUNTRY: China
mitted to humans but not between humans. SENTINEL POPULATION UNDER STUDY FOR NEW PATHOGENS: VIRUSES PREVIOUSLY SPAWNED: SARS, H5N1
People who hunt and butcher wild animals SENTINEL POPULATION : “Wet market” workers
Stage 3: Animal pathogen that can be trans-
mitted between humans causes an outbreak of
disease but only for a short period before dying out.
Stage 4: Pathogen exists in animals and undergoes a regular
cycle of animal-to-human transmission but also sustains long
outbreaks arising from human-to-human transmission.
Stage 5: Pathogen has become exclusive to humans. COUNTRY: Democratic Republic of the Congo
Nature, VIRUSES PREVIOUSLY SPAWNED: Primary study site (human and animal testing) Tentative site for future study
Marburg, monkeypox, Ebola Secondary study site (animal testing only) Tropical region COUNTRY: Malaysia
SENTINEL POPULATION : VIRUSES PREVIOUSLY SPAWNED: Nipah
People who hunt and butcher wild animals SENTINEL POPULATION : Wildlife hunters
[WHAT ASTRONOMERS LOOK FOR]
Glowing in the Dark
Infrared Light Reveals Disks and Thus Planets or Their Building Blocks
A stronomers generally detect planets indirectly, by virtue
of their effects on the velocity, position or brightness
of their host stars. For most of the cases discussed in the
A circumstellar disk of dust and gas, like the one that gave rise to the planets of our solar system, absorbs
starlight and emits infrared radiation. We observe a composite of direct starlight and disk emission.
article, astronomers focus on one type of indirect sign:
the presence of a disk of dust orbiting the star. A so-called
protoplanetary disk occurs around newly born stars and is
thought to be the site of planet formation. A so-called debris Starlight
disk occurs around mature stars and is thought to arise from
collisions or evaporation of comets and asteroids, thus
signaling the likely presence of planets now or in the past.
Observers identify both types of disk from how they
absorb starlight and reradiate the absorbed energy at infra- Light from disk
red wavelengths ( ). NASA’s Spitzer Space Telescope,
launched in 2003, has proved to be a veritable disk discovery
machine. Its large field-of-view infrared cameras can cap-
ture hundreds of stars in a single image and pinpoint those
with evidence of disks for further study.
Spitzer builds on the successes of past infrared telescopes,
such as the Infrared Astronomical Satellite (IRAS) mission in
the 1980s and the European Space Agency’s Infrared Space Brown dwarf plus disk
Observatory (ISO) in the mid-1990s. Unlike IRAS, which was Disk
an all-sky survey, Spitzer points at specific celestial bodies for
intensive study, and the five-year-plus lifetime of its liquid- An example is the brown dwarf OTS 44,
Brightness (arbitrary units)
helium coolant far exceeds that of any previous mission. The whose spectrum ( ) initially
telescope has studied everything from extrasolar planets to falls off at infrared wavelengths but
then flattens — indicating that the dwarf,
galaxies in the early universe. whose spectrum would be expected to peak at
The coolant is now running out, and the telescope will short wavelengths ( ), is surrounded by
soon start to warm from nearly absolute zero to 30 kelvins. cooler material whose spectrum peaks
Even so, it will be able to operate at the short-wavelength at longer wavelengths ( ).
end of the infrared band through at least the middle of 2011. Even when the system is
Taking up the slack will be the newly launched Herschel too far away for telescopes
Space Observatory and the James Webb Space Telescope to resolve spatially, the spectrum 1 3 10 30
(JWST), planned for launch in 2013. — reveals the blending of light. Wavelength (microns)
Vaccines Mimic Infection to Avert It IMMUNE MEMORY
Some of the B and T cells become long-lived memory
Vaccines deliver a killed or weakened pathogen, or pieces of it, to trigger an immune response that generates “memory” cells primed to
cells, standing guard against a future infection.
recognize the same microorganism quickly in the future. These cells can later block true infections or at least minimize illness.
Killer T cells
Attempted infection Memory T cells and B cells
COMMON ling f
V VACCINE TYPES ropha
■ ATTENUATED: Live des
Injection but weakened whole c
virus or bacterium.
T cell precursors Infected cell Minimal reproduc-
Virus in Helper T cells
exposure to antigen t
Maturation without causing disease. can
Infected cells to lymph nodes pe
Cytokines Whole but “killed”
Antibodies and unable to
B cell remain in the body as “memory” cells — some- reproduce or to
Lymph node times for decades — ready to squelch any at- cause disease.
Macrophage Antigen tempted reinfection by the same organism. Vac- ad
cines replicate this process by introducing a ■ SUBUNIT: Fragments the
whole pathogen or fragments of it that will be of the pathogen, such k
VACCINE ADMINISTRATION DENDRITIC CELL MIGRATION AND INTERACTIONS as genetic material
A small dose of live but weakened virus is one common form of Loaded with foreign material (antigen), dendritic cells mature and migrate recognized as a foreign invader. Not all vaccines
or external pro-
vaccine. Injected into the skin, the virus will infect some cells to lymph nodes to interact with T cells and B cells, components of the succeed in generating a full immune response,
and reproduce slowly. “Innate” immune system cells, such as “adaptive” immune system. Displaying antigen and emitting cytokines, teins, provide
macrophages and dendritic cells, engulf and digest foreign the dendritic cells induce T cells to mature into helper and killer types; the but some pathogens can be stopped by antibod- antigen for immune
material and infected body cells. Dendritic cells also emit helper T cells also signal to incite the killer T cells to attack infected cells ies alone, so killer T cells are not needed for cells to recognize. l
signaling chemicals called cytokines to sound an alarm. and induce B cells to produce antibodies tailored to the pathogen. protection.
The nature of the pathogen and how it causes
ill i d i ’ id
Adjuvants PATHOGEN RECOGNITION TLR NATURAL TRIGGER
Dendritic cells contain Toll-like receptors (TLR) that each recognize ●● ●
1 2 6 Bacterial lipoproteins
molecules typical of many pathogens, such as bacterial proteins or ●
3 Double-stranded RNA
distinctive viral gene motifs ( ). Adjuvants that trigger Lipopolysaccharide (LPS),
one or a combination of TLRs can simulate different natural threats.
Adjuvants enhance immune responses to vaccine heat-shock proteins,
antigens by several mechanisms, but their most Killer T cells respiratory syncytial virus
●5 Bacterial flagellin protein
potent effects are likely to be through activation
7 8 Single-stranded RNA
of microbe-recognition receptors on dendritic Bacterial CpG DNA
cells. Depending on the type of threat they sense, ●
dendritic cells will direct other immune cells to ●
11 Bacterial profilin protein
respond in different ways. Vaccine designers Helper T cells
can use this knowledge to choose adjuvants that
will not only boost immune response but also IL-12 DENDRITIC CELL DIRECTIONS
Dendritic cells’ signaling determines
emphasize the desired responses.
how T and B cells will mature and
proliferate. For example, the cytokine
Antibody-inducing helper T cells interleukin-12 favors development of
killer T cells and a helper T subtype
lar keys, a group known as the Toll-like recep- needed to defend against intracellular
tors (TLRs) seemed most important for driving pathogens, whereas IL-6 favors a
the dendritic cells’ behavior [see “Immunity’s helper T type that induces B cells to
produce antibodies. IL-6, together
Early-Warning System,” by Luke A. J. O’Neill; Inflammation-inducing helper T cells with IL-23, induces still another helper
S��������� A�������, January 2005]. T subtype that promotes inflamma-
tion. Interleukins themselves are also
To date, 10 functional Toll-like receptors under study as adjuvants.
have been identified, and each recognizes a dif- IL-23
ferent basic motif of viruses or bacteria. TLR-4
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