{"id": "card_n_d6d3480c8cf2", "kind": "note", "title": "Ultraviolet — the first photons that bite", "body": "Past violet, single photons start doing chemistry. Sealed: the workhorse conversion\nhc = 1239.8 eV·nm (exact since the 2019 SI made h and e definitions, not measurements), and\nthe germicidal UV-C line at 254 nm carries 4.88 eV per photon: https://narrowhighway.com/s/2e10f3cd833c0da8ed1973eeb517c9de779e8956cd7d04eeee423aab280c4455 — enough to damage DNA\ndirectly, which is why it sterilizes water and why the ozone layer matters (O3 absorbs below\n~310 nm; empirical spectroscopy, honestly cited not sealed). Sunburn is not heat — it is\nphotochemistry: each UV-B photon is individually strong enough to break what it touches.", "source": {"label": "Concordance assay — 2026-07-09", "url": "https://narrowhighway.com/s/2e10f3cd833c0da8ed1973eeb517c9de779e8956cd7d04eeee423aab280c4455", "ref": "spectrum_walk_high", "authority_tier": "engine_derived"}, "shelf": "science", "box": "radio_spectrum", "bands": ["ultraviolet", "uv-c", "254 nm", "germicidal", "dna damage", "sunburn", "ozone", "photochemistry"], "connections": [], "author": "engine", "created_at": "2026-07-10T01:12:51.215332+00:00", "updated_at": "2026-07-10T01:12:51.215332+00:00", "visibility": "public", "lifecycle_stage": "public", "volatility": "permanent", "surface": "secular", "metrics": {"paperclips_count": 0, "helpful_count": 0, "not_helpful_count": 0, "cite_count": 0, "walks_through_count": 0, "flagged_count": 0}, "source_hash": "97e597c20ef58c5f4e98108478b2612fbd47037b0881a8863d46568fcfdfe8fe"}