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Astronomy

How the Integrated Sachs–Wolfe Effect Reveals Dark Energy

Quick fact

The integrated Sachs–Wolfe effect is so subtle that it was only confirmed in the early 2000s by cross-correlating CMB temperature maps with galaxy surveys, providing independent evidence for dark energy.

Why this is interesting

Photons from the early universe carry a hidden message about dark energy—one that only appears when they travel through gravitational wells that are changing. Why would the expansion of the universe alter the energy of light that passed by billions of years ago?

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How the Integrated Sachs–Wolfe Effect Reveals Dark Energy

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