Sometime back, Hinnerk Schulz‑Hildebrandt, a biomedical optics engineer at Harvard Medical School, stumbled on something odd while checking a flight map on his phone. As his eye followed the flight ...

Last August Hinnerk Schulz-Hildebrandt noticed something strange while he was looking at a flight map on his phone. As his eye traced the plane’s flight path, he noticed that the line looked purple, ...