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Astronomers thought that all Type Ia supernovas shine with the same brightness, making them incredibly useful cosmic yardsticks. But uncertainty over what causes these explosions has led researchers to reconsider their assumptions.
The newly developed theory of emergent gravity, proposed as an alternative to dark matter, struggles in one of its first trials.
Does the force of gravity change at large scales? Perhaps not, but a new theory of dark matter shows why that could appear to be the case.