Fundamental physics

One of the most contested issues in astrophysics is our understanding of the Universe’s expansion. Adam Riess discusses why there is disagreement and what might resolve it.

Recent observations suggest that dark energy is changing over time. Theorists wonder if dark matter is, too.

By combining the language of groups with that of geometry and linear algebra, Marius Sophus Lie created one of math’s most powerful tools.

Every elementary particle falls into one of two categories. Collectivist bosons account for the forces that move us while individualist fermions keep our atoms from collapsing.

A new argument explores how the growth of disorder could cause massive objects to move toward one another. Physicists are both interested and skeptical.

Promise and controversy continues to surround string theory as a potential unified theory of everything. In the latest episode of The Joy of Why, Cumrun Vafa discusses his progress in trying to find good, testable models hidden among the ‘swampland’ of impossible universes.

Black hole and Big Bang singularities break our best theory of gravity. A trilogy of theorems hints that physicists must go to the ends of space and time to find a fix.

From living matter to molecules to elementary particles, the world is made of “chiral” objects that differ from their reflected forms.

Last year, an enormous map of the cosmos hinted that the engine driving cosmic expansion might be sputtering. Now physicists are back with an even bigger map, and a stronger conclusion.