No terminator on the full moon!

No, this is not about another sequel of the science fiction movie or whether Arnold Schwarzengger is planning a trip to the moon … It is more about an astronomical term, where »terminator« describes the day-night border of a celestial body. This is the visible border between the illuminated side and the dark side of the object, being the border between day and night on the celestial body. The word »terminator« derives from Latin »terminare« = conclude, restrict.

The best way for us people to observe this is on the moon. For example at half moon, the terminator runs through the centre of the moon and therefore creates the visible semicircle. This means that the terminator can be seen during each phase of the moon cycle, with two exceptions: new moon and full moon. As there is either no illuminated side (new moon) or no shadow side (full moon) visible, hence no light-shadow border.

But even when there is no terminator during full moon, it immediately emerges afterwards. »I’ll be back« … doesn’t this sound familiar?