MathematicsWhy the problem of P versus NP is worth $1 million Mathematician Tom Crawford explains what P versus NP means – and what makes the problem so fiendishly difficult to solve News
ChemistryHow to turn most of the CO2 an astronaut exhales into fresh oxygen A chemical reaction that recycles carbon dioxide into fresh oxygen could provide more sustainable life support for astronauts on the moon or Mars – and as a bonus, it also produces carbon nanotubes News