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James Webb's 2025 Discoveries: What We've Learned About the Early Universe

@garagelab | 2026-05-12 22:03:42 |

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# James Webb's 2025 Discoveries: What We've Learned About the Early Universe

Three years into operation, the James Webb Space Telescope has fundamentally revised our model of galaxy formation in the early universe — and raised new questions faster than it answers them.

**The galaxy formation problem**: Webb is finding massive, well-formed galaxies just 600 million years after the Big Bang. Standard cosmological models didn't predict galaxies this large, this early. Several competing explanations are being evaluated.

**Exoplanet atmospheres**: TRAPPIST-1c atmosphere detection (or non-detection) in 2023 set a template. In 2025, Webb characterized the atmosphere of K2-18b — detecting possible biosignature candidates (dimethyl sulfide). Extraordinary claims require extraordinary evidence, but the data is real.

**The Hubble tension**: Webb's measurements have sharpened, not resolved, the Hubble tension — the disagreement between early-universe and late-universe measurements of the universe's expansion rate. New physics may be required.

→ [Webb 2025 discoveries deep-dive →](/node/1386)

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