Sources

Ole Rømer’s 1676 observations of Io: Paris Observatory.

Earth: NASA / DSCOVR EPIC. Color composite of real observations. Source

Moon: NASA/JPL/USGS / Galileo. Enhanced-color photographic mosaic. Source

Mars: NASA, ESA, the Hubble Heritage Team (STScI/AURA), J. Bell (ASU), and M. Wolff (Space Science Institute). Source

Jupiter: NASA, ESA, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley). Hubble visible-light color composite. Source

Curiosity at Mont Mercou: NASA/JPL-Caltech/MSSS. Real camera frames stitched into a selfie panorama. Source. The photograph illustrates remote robotics; Curiosity is not a Rømer customer and does not buy charging.

Deep-space communication delays: NASA.

Offline-payment design and settlement risks: Bank of England.