Biology
Can the human eye see a single photon?
The human eye can register a single photon. In a 2016 experiment, people detected single photons slightly better than chance.
Source: Tinsley et al. (2016), Nature Communications.
Context
Just about. In 2016 Tinsley and colleagues sent single photons to dark-adapted volunteers and asked whether they had seen anything. The answers were right slightly more often than chance.
Nobody experiences a single photon as a flash; it registers as a faint sense of something. But the rod cells in the retina are sensitive enough that one photon can tip the balance.
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