Look Back

Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe.

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Hubble's 33rd Anniversary: A look back at some of the telescope's most impressive images

SETI's new machine learning algorithm works like Google's "reverse image search" on a galactic scale, and has already uncovered eight currently unexplained signals. Researchers train the algorithm on simulated alien signals, then look back through old data to see if we missed anything in the noise.

A look back at Lyndon B. Johnson's space legacy, 50 years after his death

A Look Back at Science’s 2022 Breakthroughs

2021 Natural Disasters: A Look Back

Webb – The Most Powerful Space Telescope Ever Built – Will Look Back in Time to the Dark Ages of the Universe