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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 contained 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.
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 contained 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.
