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How does weak gravitational lensing help astronomers study dark energy?

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Weak gravitational lensing is a powerful tool for astronomers to study dark energy by measuring its influence on the growth of large-scale structures in the universe.1

While gravitational lensing involves the bending of light by massive objects, weak lensing specifically refers to the subtle distortions in the shapes of distant galaxies caused by the gravitational field of intervening matter. Because dark energy acts as a repulsive force that works against gravity, it retards the formation of large-scale structures like galaxy clusters.21

By observing these subtle shape distortions, astronomers can track how the formation of these structures has been suppressed over the last few billion years—the period during which dark energy became the dominant component of the universe. This data helps researchers understand the history of cosmic structure and provides insights into the properties of dark energy, such as its equation of state.1