What causes the sky in cities like London or Los Angeles to obscure most stars?
Answer
Artificial lighting causing local light pollution that overwhelms faint signals
While cosmological factors like finite age and expansion explain why the night sky is scientifically dark on a universal scale, this effect is often overridden locally. In densely populated areas such as London or Los Angeles, the intense output of artificial lighting creates significant light pollution. This pervasive, locally generated light floods the atmosphere, overpowering the faint, ancient photons arriving from distant stars and galaxies within our observable universe. Consequently, the immediate experience for an urban observer is a sky that is effectively brightened locally, masking the deep, cosmic darkness that remains scientifically valid.
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