english: If I point a beam through this notch at a mirror, five miles away, that beam is bouncing off the mirror and coming back to me through this notch.
non_english: Če posvetimo  s takim žarkom v ogledalo oddaljeno 8 km stran,  se žarek odbija od ogledala in vrača skozi zarezo. Ko pa je kolesce zavrtel hitreje,  se je zgodilo nekaj zanimivega.