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Jun 17, 2019

Cosmologists have a standard set of puzzles they think about: the nature of dark matter and dark energy, whether there was a period of inflation, the evolution of structure, and so on. But there are also even deeper questions, having to do with why there is a universe at all, and why the early universe had low...


May 6, 2019

For decades now physicists have been struggling to reconcile two great ideas from a century ago: general relativity and quantum mechanics. We don’t yet know the final answer, but the journey has taken us to some amazing places. A leader in this quest has been Leonard Susskind, who has helped illuminate some of the...


Mar 4, 2019

Quantum mechanics is our best theory of how reality works at a fundamental level, yet physicists still can’t agree on what the theory actually says. At the heart of the puzzle is the “measurement problem”: what actually happens when we observe a quantum system, and why do we apparently need separate rules when it...


Jan 28, 2019

String theory was originally proposed as a relatively modest attempt to explain some features of strongly-interacting particles, but before too long developed into an ambitious attempt to unite all the forces of nature into a single theory. The great thing about physics is that your theories don’t always go where you...


Jan 7, 2019

Sir Roger Penrose has had a remarkable life. He has contributed an enormous amount to our understanding of general relativity, perhaps more than anyone since Einstein himself -- Penrose diagrams, singularity theorems, the Penrose process, cosmic censorship, and the list goes on. He has made important contributions to...