How will we recognize extra-terrestrial life if we have never seen it? The answer lies in reducing the search to its barest essentials as measured by physics and chemistry, with help from statistics and data mining.
Only one of the planetary systems discovered around Sun-like stars reminds us of our Solar System. What fraction of stars have planets, how many of these are similar to the Solar System, and how many types of planetary systems are there?
Phytoplankton play a significant role in the Earth's climate system. Could ocean fertilization be used to stimulate the growth of these microscopic plants and reduce global warming? Or would this lead to unintended and undesirable consequences?
How much matter is in the Universe, and does it contain unseen dark energy that opposes matter's gravitational pull? Once we have the answers to these questions, we will understand the fate of the Universe.
Hydrothermal systems on the ocean floor support luxuriantly diverse life. Some metabolic types extend back to antiquity, while others celebrate Nature's infinite adaptability to extreme environments. This newly discovered realm has redefined the limits of life on this planet and others.
In this century, neuroscientists hope to learn the biological basis of perception, memory, and other activities of mental life. Recent experiments have shown how signals are processed in the brain, and how they enable an organism to make sense of its visual world.
Disagreements about difficult political decisions, not scientific uncertainties, cause global warming to be controversial. The geological record indicates that Earth's climate is very sensitive to perturbations, that the rise in the atmospheric concentration of greenhouse gases will cause calamities.
