What we see is that there are in fact two entangled traditions of “knocking on things for good luck”: touching iron, and touching wood. We also find that they are widely distributed, but also have a pretty clear cluster around the Mediterranean and Europe.
Roman numerals: glyph reuse by design
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While technical and regulatory challenges make producing electricity for Earth difficult, Alkalai, a fellow at the Caltech-managed Jet Propulsion Laboratory, was struck by the idea of using the design to power space-based processors. (Aetherflux, a space solar power startup, has had a similar realization.)
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