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- Sep 14, 2004
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2005 represents the 125th anniversary of the journal Science. To commemorate the event, Science published a list of 125 important scientific questions. Here are the 125 questions, followed by elaborations of the top two. By the way, if you are good at mathematics, answer questions 120-125 and receive $1 million for each verifiably correct answer.
http://www.sciencemag.org/sciext/125th/
1. What is the Universe made of?
2. What is the biological basis of consciousness?
3. Why do humans have so few genes?
4. To what extent are genetic variation and personal health linked?
5. Can the laws of Physics be unified?
6. How much can human life span be extended?
7. What controls organ regeneration?
8. How can a skin cell become a nerve cell?
9. How does a single somatic cell become a whole plant?
10. How does Earths interior work?
11. Are we alone in the Universe?
12. How and where did life on Earth arise?
13. What determines species diversity?
14. What genetic changes made us uniquely human?
15. How are memories stored and retrieved?
16. How did cooperative behavior evolve?
17. How will big pictures emerge from a sea of biological data?
18. How far can we push chemical self-assembly?
19. What are the limits of conventional computing?
20. Can we selectively shut off immune responses?
21. Do deeper principles underlie quantum uncertainty and nonlocality?
22. Is an effective HIV vaccine feasible?
23. How hot will the greenhouse world be?
24. What can replace cheap oil and when?
25. Will Malthus continue to be wrong?
26. Is ours the only Universe?
27. What drove cosmic inflation?
28. When and how did the first stars and galaxies form?
29. Where do ultrahigh-energy cosmic rays come from?
30. What powers quasars?
31. What is the nature of black holes?
32. Why is there more matter than antimatter?
33. Does the proton decay?
34. What is the nature of gravity?
35. Why is time different from other dimensions?
36. Are there smaller building blocks than quarks?
37. Are neutrinos their own antiparticles?
38. Is there a unified theory explaining all correlated electron systems?
39. What is the most powerful laser researchers can build?
40. Can researchers make a perfect optical lens?
41. Is it possible to create magnetic semiconductors that work at room temperature?
42. What is the pairing mechanism behind high-temperature superconductivity?
43. Can we develop a general theory of the dynamics of turbulent flows and the motion of granular materials?
44. Are there stable high-atomic-number elements?
45. Is superfluidity possible in a solid? If so, how?
46. What is the structure of water?
47. What is the nature of the glassy state?
48. Are there limits to rational chemical synthesis?
49. What is the ultimate efficiency of photovoltaic cells?
50. Will fusion always be the energy source of the future?
51. What drives the solar magnetic cycle?
52. How do planets form?
53. What causes ice ages?
54. What causes reversals in Earth's magnetic field?
55. Are there earthquake precursors that can lead to useful predictions?
56. Is there--or was there--life elsewhere in the solar system?
57. What is the origin of homochirality in nature? Why are amino acids are always left-handed, and sugars are always right-handed?
58. Can we predict how proteins will fold?
59. How many proteins are there in humans?
60. How do proteins find their partners?
61. How many forms of cell death are there?
62. What keeps intracellular traffic running smoothly?
63. What enables cellular components to copy themselves independent of DNA?
64. What roles do different forms of RNA play in genome function?
65. What role do telomeres and centromeres play in genome function?
66. Why are some genomes really big and others quite compact?
67. What is all that "junk" doing in our genomes?
68. How much will new technologies lower the cost of DNA sequencing?
69. How do organs and whole organisms know when to stop growing?
70. How can genome changes other than mutations be inherited?
71. How is asymmetry determined in the embryo?
72. How do limbs, fins, and faces develop and evolve?
73. What triggers puberty?
74. Are stem cells at the heart of all cancers?
75. Is cancer susceptible to immune control?
76. Can cancers be controlled rather than cured?
77. Is inflammation a major factor in all chronic diseases?
78. How do prion diseases work? Prions are misfolded proteins.
79. How much do vertebrates depend on the innate immune system to fight infection?
80. Does immunologic memory require chronic exposure to antigens?
81. Why doesn't a pregnant womans immune response reject her fetus?
82. What synchronizes an organism's circadian clocks?
83. How do migrating organisms find their way?
84. Why do we sleep?
85. Why do we dream?
86. Why are there critical periods for language learning?
87. Do pheromones influence human behavior?
88. How do general anesthetics work?
89. What causes schizophrenia?
90. What causes autism?
91. To what extent can we stave off Alzheimer's?
92. What is the biological basis of addiction?
93. Is morality hardwired into the brain?
94. What are the limits of learning by machines?
95. How much of personality is genetic?
96. What is the biological root of sexual orientation?
97. Will there ever be a tree of life that systematists can agree on?
98. How many species are there on Earth?
99. What is a species?
100. Why does lateral transfer occur in so many species and how?
101. Who was LUCA (the last universal common ancestor)?
102. How did flowers evolve?
103. How do plants make cell walls?
104. How is plant growth controlled?
105. Why aren't all plants immune to all diseases?
106. What is the basis of variation in stress tolerance in plants?
107. What caused mass extinctions?
108. Can we prevent extinction?
109. Why were some dinosaurs so large?
110. How will ecosystems respond to global warming?
111. How many kinds of humans coexisted in the recent past, and how did they relate?
112. What gave rise to modern human behavior?
113. What are the roots of human culture?
114. What are the evolutionary roots of language and music?
115. What are human races, and how did they develop?
116. Why do some countries grow and others stagnate?
117. What impact do large government deficits have on a country's interest rates and economic growth rate?
118. Are political and economic freedom closely tied?
119. Why has poverty increased and life expectancy declined in sub-Saharan Africa?
List of outstanding mathematics problems: http://www.claymath.org/millennium/. Receive $1 million for each problem you solve.
120. Is there a simple test for determining whether an elliptic curve has an infinite number of rational solutions?
121. Can a Hodge cycle be written as a sum of algebraic cycles?
122. Will mathematicians unleash the power of the Navier-Stokes equations?
123. Does Poincaré's test identify spheres in four-dimensional space?
124. Do mathematically interesting zero-value solutions of the Riemann zeta function all have the form a bi?
125. Does the Standard Model of particle physics rest on solid mathematical foundations?
1. What Is the Universe Made Of?
Charles Seife
http://www.sciencemag.org/cgi/content/full/309/5731/78a
Every once in a while, cosmologists are dragged, kicking and screaming, into a universe much more unsettling than they had any reason to expect. In the 1500s and 1600s, Copernicus, Kepler, and Newton showed that Earth is just one of many planets orbiting one of many stars, destroying the comfortable Medieval notion of a closed and tiny cosmos. In the 1920s, Edwin Hubble showed that our universe is constantly expanding and evolving, a finding that eventually shattered the idea that the universe is unchanging and eternal. And in the past few decades, cosmologists have discovered that the ordinary matter that makes up stars and galaxies and people is less than 5% of everything there is. Grappling with this new understanding of the cosmos, scientists face one overriding question: What is the universe made of?
This question arises from years of progressively stranger observations. In the 1960s, astronomers discovered that galaxies spun around too fast for the collective pull of the stars' gravity to keep them from flying apart. Something unseen appears to be keeping the stars from flinging themselves away from the center: unilluminated matter that exerts extra gravitational force. This is dark matter.
Over the years, scientists have spotted some of this dark matter in space; they have seen ghostly clouds of gas with x-ray telescopes, watched the twinkle of distant stars as invisible clumps of matter pass in front of them, and measured the distortion of space and time caused by invisible mass in galaxies. And thanks to observations of the abundances of elements in primordial gas clouds, physicists have concluded that only 10% of ordinary matter is visible to telescopes.
But even multiplying all the visible "ordinary" matter by 10 doesn't come close to accounting for how the universe is structured. When astronomers look up in the heavens with powerful telescopes, they see a lumpy cosmos. Galaxies don't dot the skies uniformly; they cluster together in thin tendrils and filaments that twine among vast voids. Just as there isn't enough visible matter to keep galaxies spinning at the right speed, there isn't enough ordinary matter to account for this lumpiness. Cosmologists now conclude that the gravitational forces exerted by another form of dark matter, made of an as-yet-undiscovered type of particle, must be sculpting these vast cosmic structures. They estimate that this exotic dark matter makes up about 25% of the stuff in the universe--five times as much as ordinary matter.
But even this mysterious entity pales by comparison to another mystery: dark energy. In the late 1990s, scientists examining distant supernovae discovered that the universe is expanding faster and faster, instead of slowing down as the laws of physics would imply. Is there some sort of antigravity force blowing the universe up?
All signs point to yes. Independent measurements of a variety of phenomena--cosmic background radiation, element abundances, galaxy clustering, gravitational lensing, gas cloud properties--all converge on a consistent, but bizarre, picture of the cosmos. Ordinary matter and exotic, unknown particles together make up only about 30% of the stuff in the universe; the rest is this mysterious anti-gravity force known as dark energy.
This means that figuring out what the universe is made of will require answers to three increasingly difficult sets of questions. What is ordinary dark matter made of, and where does it reside? Astrophysical observations, such as those that measure the bending of light by massive objects in space, are already yielding the answer. What is exotic dark matter? Scientists have some ideas, and with luck, a dark-matter trap buried deep underground or a high-energy atom smasher will discover a new type of particle within the next decade.
And finally, what is dark energy? This question, which wouldn't even have been asked a decade ago, seems to transcend known physics more than any other phenomenon yet observed. Ever-better measurements of supernovae and cosmic background radiation as well as planned observations of gravitational lensing will yield information about dark energy's "equation of state"--essentially a measure of how squishy the substance is. But at the moment, the nature of dark energy is arguably the murkiest question in physics--and the one that, when answered, may shed the most light.
2. What Is the Biological Basis of Consciousness?
Greg Miller
http://www.sciencemag.org/cgi/content/full/309/5731/79
For centuries, debating the nature of consciousness was the exclusive purview of philosophers. But if the recent torrent of books on the topic is any indication, a shift has taken place: Scientists are getting into the game.
Has the nature of consciousness finally shifted from a philosophical question to a scientific one that can be solved by doing experiments? The answer, as with any related to this topic, depends on whom you ask. But scientific interest in this slippery, age-old question seems to be gathering momentum. So far, however, although theories abound, hard data are sparse.
The discourse on consciousness has been hugely influenced by René Descartes, the French philosopher who in the mid-17th century declared that body and mind are made of different stuff entirely. It must be so, Descartes concluded, because the body exists in both time and space, whereas the mind has no spatial dimension.
Recent scientifically oriented accounts of consciousness generally reject Descartes's solution; most prefer to treat body and mind as different aspects of the same thing. In this view, consciousness emerges from the properties and organization of neurons in the brain. But how? And how can scientists, with their devotion to objective observation and measurement, gain access to the inherently private and subjective realm of consciousness?
Some insights have come from examining neurological patients whose injuries have altered their consciousness. Damage to certain evolutionarily ancient structures in the brainstem robs people of consciousness entirely, leaving them in a coma or a persistent vegetative state. Although these regions may be a master switch for consciousness, they are unlikely to be its sole source. Different aspects of consciousness are probably generated in different brain regions. Damage to visual areas of the cerebral cortex, for example, can produce strange deficits limited to visual awareness. One extensively studied patient, known as D.F., is unable to identify shapes or determine the orientation of a thin slot in a vertical disk. Yet when asked to pick up a card and slide it through the slot, she does so easily. At some level, D.F. must know the orientation of the slot to be able to do this, but she seems not to know she knows.
Cleverly designed experiments can produce similar dissociations of unconscious and conscious knowledge in people without neurological damage. And researchers hope that scanning the brains of subjects engaged in such tasks will reveal clues about the neural activity required for conscious awareness. Work with monkeys also may elucidate some aspects of consciousness, particularly visual awareness. One experimental approach is to present a monkey with an optical illusion that creates a "bistable percept," looking like one thing one moment and another the next. (The orientation-flipping Necker cube is a well-known example.) Monkeys can be trained to indicate which version they perceive. At the same time, researchers hunt for neurons that track the monkey's perception, in hopes that these neurons will lead them to the neural systems involved in conscious visual awareness and ultimately to an explanation of how a particular pattern of photons hitting the retina produces the experience of seeing, say, a rose.
Experiments under way at present generally address only pieces of the consciousness puzzle, and very few directly address the most enigmatic aspect of the conscious human mind: the sense of self. Yet the experimental work has begun, and if the results don't provide a blinding insight into how consciousness arises from tangles of neurons, they should at least refine the next round of questions.
Ultimately, scientists would like to understand not just the biological basis of consciousness but also why it exists. What selection pressure led to its development, and how many of our fellow creatures share it? Some researchers suspect that consciousness is not unique to humans, but of course much depends on how the term is defined. Biological markers for consciousness might help settle the matter and shed light on how consciousness develops early in life. Such markers could also inform medical decisions about loved ones who are in an unresponsive state.
Until fairly recently, tackling the subject of consciousness was a dubious career move for any scientist without tenure (and perhaps a Nobel Prize already in the bag). Fortunately, more young researchers are now joining the fray. The unanswered questions should keep them--and the printing presses--busy for many years to come.
