【 以下文字转载自 LifeScience 讨论区 】
发信人: McKinsey (雪山环抱的小镇·科罗拉多), 信区: LifeScience
标  题: another100
发信站: 水木社区 (Sat Jul  2 07:00:33 2005), 站内

So Much More to Know …
From the nature of the cosmos to the nature of societies, the following 100
questions span the sciences. Some are pieces of questions discussed above;
others are big questions in their own right. Some will drive scientific
inquiry for the next century; others may soon be answered. Many will
undoubtedly spawn new questions.

Is ours the only universe?
A number of quantum theorists and cosmologists are trying to figure out
whether our universe is part of a bigger "multiverse." But others suspect
that this hard-to-test idea may be a question for philosophers.

What drove cosmic inflation?
In the first moments after the big bang, the universe blew up at an
incredible rate. But what did the blowing? Measurements of the cosmic
microwave background and other astrophysical observations are narrowing the
possibilities.

When and how did the first stars and galaxies form?
The broad brush strokes are visible, but the fine details aren't. Data from
satellites and ground-based telescopes may soon help pinpoint, among other
particulars, when the first generation of stars burned off the hydrogen "fog"
that filled the universe.

Where do ultrahigh-energy cosmic rays come from?
Above a certain energy, cosmic rays don't travel very far before being
destroyed. So why are cosmic-ray hunters spotting such rays with no obvious
source within our galaxy?

What powers quasars?
The mightiest energy fountains in the universe probably get their power from
matter plunging into whirling supermassive black holes. But the details of
what drives their jets remain anybody's guess.

What is the nature of black holes?
Relativistic mass crammed into a quantum-sized object? It's a recipe for
disaster--and scientists are still trying to figure out the ingredients.

Why is there more matter than antimatter?
To a particle physicist, matter and antimatter are almost the same. Some
subtle difference must explain why matter is common and antimatter rare.

Does the proton decay?
In a theory of everything, quarks (which make up protons) should somehow be
convertible to leptons (such as electrons)--so catching a proton decaying
into something else might reveal new laws of particle physics.

What is the nature of gravity?
It clashes with quantum theory. It doesn't fit in the Standard Model. Nobody
has spotted the particle that is responsible for it. Newton's apple contain
ned a whole can of worms.

Why is time different from other dimensions?
It took millennia for scientists to realize that time is a dimension, like
the three spatial dimensions, and that time and space are inextricably
linked. The equations make sense, but they don't satisfy those who ask why we
perceive a "now" or why time seems to flow the way it does.

Are there smaller building blocks than quarks?
Atoms were "uncuttable." Then scientists discovered protons, neutrons, and
other subatomic particles--which were, in turn, shown to be made up of quarks
and gluons. Is there something more fundamental still?

Are neutrinos their own antiparticles?
Nobody knows this basic fact about neutrinos, although a number of
underground experiments are under way. Answering this question may be a
crucial step to understanding the origin of matter in the universe.

Is there a unified theory explaining all correlated electron systems?
High-temperature superconductors and materials with giant and colossal
magnetoresistance are all governed by the collective rather than individual
behavior of electrons. There is currently no common framework for
understanding them.

What is the most powerful laser researchers can build?
Theorists say an intense enough laser field would rip photons into
electron-positron pairs, dousing the beam. But no one knows whether it's
possible to reach that point.

Can researchers make a perfect optical lens?
They've done it with microwaves but never with visible light.

Is it possible to create magnetic semiconductors that work at room
temperature?
Such devices have been demonstrated at low temperatures but not yet in a
range warm enough for spintronics applications.

What is the pairing mechanism behind high-temperature superconductivity?
Electrons in superconductors surf together in pairs. After 2 decades of
intense study, no one knows what holds them together in the complex,
high-temperature materials.

Can we develop a general theory of the dynamics of turbulent flows and the
motion of granular materials?
So far, such "nonequilibrium systems" defy the tool kit of statistical
mechanics, and the failure leaves a gaping hole in physics.

Are there stable high-atomic-number elements?
A superheavy element with 184 neutrons and 114 protons should be relatively
stable, if physicists can create it.

Is superfluidity possible in a solid? If so, how?
Despite hints in solid helium, nobody is sure whether a crystalline material
can flow without resistance. If new types of experiments show that such
outlandish behavior is possible, theorists would have to explain how.

What is the structure of water?
Researchers continue to tussle over how many bonds each H2O molecule makes
with its nearest neighbors.

What is the nature of the glassy state?
Molecules in a glass are arranged much like those in liquids but are more
tightly packed. Where and why does liquid end and glass begin?

Are there limits to rational chemical synthesis?
The larger synthetic molecules get, the harder it is to control their shapes
and make enough copies of them to be useful. Chemists will need new tools to
keep their creations growing.

What is the ultimate efficiency of photovoltaic cells?
Conventional solar cells top out at converting 32% of the energy in sunlight
to electricity. Can researchers break through the barrier?

Will fusion always be the energy source of the future?
It's been 35 years away for about 50 years, and unless the international
community gets its act together, it'll be 35 years away for many decades to
come.

What drives the solar magnetic cycle?
Scientists believe differing rates of rotation from place to place on the sun
underlie its 22-year sunspot cycle. They just can't make it work in their
simulations. Either a detail is askew, or it's back to the drawing board.

How do planets form?
How bits of dust and ice and gobs of gas came together to form the planets
without the sun devouring them all is still unclear. Planetary systems around
other stars should provide clues.

What causes ice ages?
Something about the way the planet tilts, wobbles, and careens around the sun
presumably brings on ice ages every 100,000 years or so, but reams of climate
records haven't explained exactly how.

What causes reversals in Earth's magnetic field?
Computer models and laboratory experiments are generating new data on how
Earth's magnetic poles might flip-flop. The trick will be matching
simulations to enough aspects of the magnetic field beyond the inaccessible
core to build a convincing case.

Are there earthquake precursors that can lead to useful predictions?
Prospects for finding signs of an imminent quake have been waning since the
1970s. Understanding faults will progress, but routine prediction would
require an as-yet-unimagined breakthrough.

Is there--or was there--life elsewhere in the solar system?
The search for life--past or present--on other planetary bodies now drives
NASA's planetary exploration program, which focuses on Mars, where water
abounded when life might have first arisen.

What is the origin of homochirality in nature?
Most biomolecules can be synthesized in mirror-image shapes. Yet in
organisms, amino acids are always left-handed, and sugars are always
right-handed. The origins of this preference remain a mystery.

Can we predict how proteins will fold?
Out of a near infinitude of possible ways to fold, a protein picks one in
just tens of microseconds. The same task takes 30 years of computer time.

How many proteins are there in humans?
It has been hard enough counting genes. Proteins can be spliced in different
ways and decorated with numerous functional groups, all of which makes
counting their numbers impossible for now.

How do proteins find their partners?
Protein-protein interactions are at the heart of life. To understand how
partners come together in precise orientations in seconds, researchers need
to know more about the cell's biochemistry and structural organization.

How many forms of cell death are there?
In the 1970s, apoptosis was finally recognized as distinct from necrosis.
Some biologists now argue that the cell death story is even more complicated.
Identifying new ways cells die could lead to better treatments for cancer and
degenerative diseases.

What keeps intracellular traffic running smoothly?
Membranes inside cells transport key nutrients around, and through, various
cell compartments without sticking to each other or losing their way.
Insights into how membranes stay on track could help conquer diseases, such
as cystic fibrosis.

What enables cellular components to copy themselves independent of DNA?
Centrosomes, which help pull apart paired chromosomes, and other organelles
replicate on their own time, without DNA's guidance. This independence still
defies explanation.

What roles do different forms of RNA play in genome function?
RNA is turning out to play a dizzying assortment of roles, from potentially
passing genetic information to offspring to muting gene expression.
Scientists are scrambling to decipher this versatile molecule.

What role do telomeres and centromeres play in genome function?
These chromosome features will remain mysteries until new technologies can
sequence them.

Why are some genomes really big and others quite compact?
The puffer fish genome is 400 million bases; one lungfish's is 133 billion
bases long. Repetitive and duplicated DNA don't explain why this and other
size differences exist.

What is all that "junk" doing in our genomes?
DNA between genes is proving important for genome function and the evolution
of new species. Comparative sequencing, microarray studies, and lab work are
helping genomicists find a multitude of genetic gems amid the junk.

How much will new technologies lower the cost of sequencing?
New tools and conceptual breakthroughs are driving the cost of DNA sequencing
down by orders of magnitude. The reductions are enabling research from
personalized medicine to evolutionary biology to thrive.

How do organs and whole organisms know when to stop growing?
A person's right and left legs almost always end up the same length, and the
hearts of mice and elephants each fit the proper rib cage. How genes set
limits on cell size and number continues to mystify.

How can genome changes other than mutations be inherited?
Researchers are finding ever more examples of this process, called
epigenetics, but they can't explain what causes and preserves the changes.

How is asymmetry determined in the embryo?
Whirling cilia help an embryo tell its left from its right, but scientists
are still looking for the first factors that give a relatively uniform ball
of cells a head, tail, front, and back.

How do limbs, fins, and faces develop and evolve?
The genes that determine the length of a nose or the breadth of a wing are
subject to natural and sexual selection. Understanding how selection works
could lead to new ideas about the mechanics of evolution with respect to
development.

What triggers puberty?
Nutrition--including that received in utero--seems to help set this
mysterious biological clock, but no one knows exactly what forces childhood
to end.

Are stem cells at the heart of all cancers?
The most aggressive cancer cells look a lot like stem cells. If cancers are
caused by stem cells gone awry, studies of a cell's "stemness" may lead to
tools that could catch tumors sooner and destroy them more effectively.

Is cancer susceptible to immune control?
Although our immune responses can suppress tumor growth, tumor cells can
combat those responses with counter-measures. This defense can stymie
researchers hoping to develop immune therapies against cancer.

Can cancers be controlled rather than cured?
Drugs that cut off a tumor's fuel supplies--say, by stopping blood-vessel
growth--can safely check or even reverse tumor growth. But how long the drugs
remain effective is still unknown.

Is inflammation a major factor in all chronic diseases?
It's a driver of arthritis, but cancer and heart disease? More and more, the
answer seems to be yes, and the question remains why and how.

How do prion diseases work?
Even if one accepts that prions are just misfolded proteins, many mysteries
remain. How can they go from the gut to the brain, and how do they kill cells
once there, for example.

How much do vertebrates depend on the innate immune system to fight
infection?
This system predates the vertebrate adaptive immune response. Its relative
importance is unclear, but immunologists are working to find out.

Does immunologic memory require chronic exposure to antigens?
Yes, say a few prominent thinkers, but experiments with mice now challenge
the theory. Putting the debate to rest would require proving that something
is not there, so the question likely will not go away.

Why doesn't a pregnant woman reject her fetus?
Recent evidence suggests that the mother's immune system doesn't "realize"
that the fetus is foreign even though it gets half its genes from the father.
Yet just as Nobelist Peter Medawar said when he first raised this question in
1952, "the verdict has yet to be returned."

What synchronizes an organism's circadian clocks?
Circadian clock genes have popped up in all types of creatures and in many
parts of the body. Now the challenge is figuring out how all the gears fit
together and what keeps the clocks set to the same time.

How do migrating organisms find their way?
Birds, butterflies, and whales make annual journeys of thousands of
kilometers. They rely on cues such as stars and magnetic fields, but the
details remain unclear.

Why do we sleep?
A sound slumber may refresh muscles and organs or keep animals safe from
dangers lurking in the dark. But the real secret of sleep probably resides in
the brain, which is anything but still while we're snoring away.

Why do we dream?
Freud thought dreaming provides an outlet for our unconscious desires. Now,
neuroscientists suspect that brain activity during REM sleep--when dreams
occur--is crucial for learning. Is the experience of dreaming just a side
effect?

Why are there critical periods for language learning?
Monitoring brain activity in young children--including infants--may shed
light on why children pick up languages with ease while adults often struggle
to learn train station basics in a foreign tongue.

Do pheromones influence human behavior?
Many animals use airborne chemicals to communicate, particularly when mating.
Controversial studies have hinted that humans too use pheromones. Identifying
them will be key to assessing their sway on our social lives.

How do general anesthetics work?
Scientists are chipping away at the drugs' effects on individual neurons, but
understanding how they render us unconscious will be a tougher nut to crack.

What causes schizophrenia?
Researchers are trying to track down genes involved in this disorder. Clues
may also come from research on traits schizophrenics share with normal people.

What causes autism?
Many genes probably contribute to this baffling disorder, as well as unknown
environmental factors. A biomarker for early diagnosis would help improve
existing therapy, but a cure is a distant hope.

To what extent can we stave off Alzheimer's?
A 5- to 10-year delay in this late-onset disease would improve old age for
millions. Researchers are determining whether treatments with hormones or
antioxidants, or mental and physical exercise, will help.

What is the biological basis of addiction?
Addiction involves the disruption of the brain's reward circuitry. But
personality traits such as impulsivity and sensation-seeking also play a part
in this complex behavior.

Is morality hardwired into the brain?
That question has long puzzled philosophers; now some neuroscientists think
brain imaging will reveal circuits involved in reasoning.

What are the limits of learning by machines?
Computers can already beat the world's best chess players, and they have a
wealth of information on the Web to draw on. But abstract reasoning is still
beyond any machine.

How much of personality is genetic?
Aspects of personality are influenced by genes; environment modifies the
genetic effects. The relative contributions remain under debate.

What is the biological root of sexual orientation?
Much of the "environmental" contribution to homosexuality may occur before
birth in the form of prenatal hormones, so answering this question will
require more than just the hunt for "gay genes."

Will there ever be a tree of life that systematists can agree on?
Despite better morphological, molecular, and statistical methods,
researchers' trees don't agree. Expect greater, but not complete, consensus.

How many species are there on Earth?
Count all the stars in the sky? Impossible. Count all the species on Earth?
Ditto. But the biodiversity crisis demands that we try.

What is a species?
A "simple" concept that's been muddied by evolutionary data; a clear
definition may be a long time in coming.

Why does lateral transfer occur in so many species and how?
Once considered rare, gene swapping, particularly among microbes, is proving
quite common. But why and how genes are so mobile--and the effect on
fitness--remains to be determined.

Who was LUCA (the last universal common ancestor)?
Ideas about the origin of the 1.5-billion-year-old "mother" of all complex
organisms abound. The continued discovery of primitive microbes, along with
comparative genomics, should help resolve life's deep past.

How did flowers evolve?
Darwin called this question an "abominable mystery." Flowers arose in the
cycads and conifers, but the details of their evolution remain obscure.

How do plants make cell walls?
Cellulose and pectin walls surround cells, keeping water in and supporting
tall trees. The biochemistry holds the secrets to turning its biomass into
fuel.

How is plant growth controlled?
Redwoods grow to be hundreds of meters tall, Arctic willows barely 10
centimeters. Understanding the difference could lead to higher-yielding crops.

Why aren't all plants immune to all diseases?
Plants can mount a general immune response, but they also maintain molecular
snipers that take out specific pathogens. Plant pathologists are asking why
different species, even closely related ones, have different sets of
defenders. The answer could result in hardier crops.

What is the basis of variation in stress tolerance in plants?
We need crops that better withstand drought, cold, and other stresses. But
there are so many genes involved, in complex interactions, that no one has
yet figured out which ones work how.

What caused mass extinctions?
A huge impact did in the dinosaurs, but the search for other catastrophic
triggers of extinction has had no luck so far. If more subtle or stealthy
culprits are to blame, they will take considerably longer to find.

Can we prevent extinction?
Finding cost-effective and politically feasible ways to save many endangered
species requires creative thinking.

Why were some dinosaurs so large?
Dinosaurs reached almost unimaginable sizes, some in less than 20 years. But
how did the long-necked sauropods, for instance, eat enough to pack on up to
100 tons without denuding their world?

How will ecosystems respond to global warming?
To anticipate the effects of the intensifying greenhouse, climate modelers
will have to focus on regional changes and ecologists on the right
combination of environmental changes.

How many kinds of humans coexisted in the recent past, and how did they
relate?
The new dwarf human species fossil from Indonesia suggests that at least four
kinds of humans thrived in the past 100,000 years. Better dates and
additional material will help confirm or revise this picture.

What gave rise to modern human behavior?
Did Homo sapiens acquire abstract thought, language, and art gradually or in
a cultural "big bang," which in Europe occurred about 40,000 years ago? Data
from Africa, where our species arose, may hold the key to the answer.

What are the roots of human culture?
No animal comes close to having humans' ability to build on previous
discoveries and pass the improvements on. What determines those differences
could help us understand how human culture evolved.

What are the evolutionary roots of language and music?
Neuroscientists exploring how we speak and make music are just beginning to
find clues as to how these prized abilities arose.

What are human races, and how did they develop?
Anthropologists have long argued that race lacks biological reality. But our
genetic makeup does vary with geographic origin and as such raises political
and ethical as well as scientific questions.

Why do some countries grow and others stagnate?
From Norway to Nigeria, living standards across countries vary enormously,
and they're not becoming more equal.

What impact do large government deficits have on a country's interest rates
and economic growth rate?
The United States could provide a test case.

Are political and economic freedom closely tied?
China may provide one answer.

Why has poverty increased and life expectancy declined in sub-Saharan Africa?
Almost all efforts to reduce poverty in sub-Saharan Africa have failed.
Figuring out what will work is crucial to alleviating massive human suffering.



The following six mathematics questions are drawn from a list of seven
outstanding problems selected by the Clay Mathematics Institute. (The seventh
problem is discussed on p. 96.) For more details, go to www.claymath.org/mille
nnium.

Is there a simple test for determining whether an elliptic curve has an
infinite number of rational solutions?
Equations of the form y2 = x3  ax  b are powerful mathematical tools. The
Birch and Swinnerton-Dyer conjecture tells how to determine how many
solutions they have in the realm of rational numbers--information that could
solve a host of problems, if the conjecture is true.

Can a Hodge cycle be written as a sum of algebraic cycles?
Two useful mathematical structures arose independently in geometry and in
abstract algebra. The Hodge conjecture posits a surprising link between them,
but the bridge remains to be built.

Will mathematicians unleash the power of the Navier-Stokes equations?
First written down in the 1840s, the equations hold the keys to understanding
both smooth and turbulent flow. To harness them, though, theorists must find
out exactly when they work and under what conditions they break down.

Does Poincaré's test identify spheres in four-dimensional space?
You can tie a string around a doughnut, but it will slide right off a sphere.
The mathematical principle behind that observation can reliably spot every
spherelike object in 3D space. Henri Poincaré conjectured that it should
also work in the next dimension up, but no one has proved it yet.

Do mathematically interesting zero-value solutions of the Riemann zeta
function all have the form a  bi?
Don't sweat the details. Since the mid-19th century, the "Riemann hypothesis"
has been the monster catfish in mathematicians' pond. If true, it will give
them a wealth of information about the distribution of prime numbers and
other long-standing mysteries.

Does the Standard Model of particle physics rest on solid mathematical
foundations?
For almost 50 years, the model has rested on "quantum Yang-Mills theory,"
which links the behavior of particles to structures found in geometry. The
theory is breathtakingly elegant and useful--but no one has proved that it's
sound.
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