AST-023intermediate

Lookback Time & Cosmic Perspective: Physical Mechanisms

Because light travels at a finite speed, every astronomical observation shows an object as it was when the detected light left it. Lookback time explains why astronomers cannot obtain a real-time image of a distant galaxy and why observing extremely distant systems gives direct access to earlier epochs of star and galaxy formation.

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intermediate45 minFact checked

Lookback Time & Cosmic Perspective: Physical Mechanisms

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AST-022Lookback Time & Cosmic Perspective: Structures & Vocabulary→

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AST-024Lookback Time & Cosmic Perspective: Observation, Measurement & Evidence→

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Because light travels at a finite speed, every astronomical observation shows an object as it was when the detected light left it.

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Electromagnetic radiation propagates through space at the speed of light in vacuum.

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