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Two ways of measuring the universe’s expansion rate yield two conflicting answers. Many point to the possibility of new physics at work, but a new analysis argues that unseen errors could be to blame.
New observations of extreme astrophysical systems have “brutally and pitilessly murdered” attempts to replace Einstein’s general theory of relativity.
In new computer experiments, artificial-intelligence algorithms can tell the future of chaotic systems.
Atomic clocks are letting physicists tighten the lasso around elusive phenomena such as dark matter.
A recent experiment shows how quantum mechanics can make heat flow from a cold body to a hot one, an apparent (though not real) violation of the second law of thermodynamics.
A surprise discovery announced a month ago suggested that the early universe looked very different than previously believed. Initial theories that the discrepancy was due to dark matter have come under fire.
Gravitational waves have opened up new ways to test the properties of black holes — and Einstein’s theory of gravity along with them.