Apple TV’s Emmy-winning spy thriller “Slow Horses” is gathering its reins for a sixth season, and it’s further ahead than most people think. In fact, “Slow Horses” Season 6 has already been filmed.

The velocity of light in vacuum, c, is approximately 3 × 10 8 m s −1, fast enough to make 7.5 round-the-world trips in a single second, and to move a distance of 300 mm in 1 ns. This ultrahigh speed ...