  A plane lights on monochromatically and immediately after lights off, while
an observer starts moving out from the plane, perpendicularly to it, with
constant proper acceleration. Special relativity predicts that the observer
will see a light circle always in the direction opposite to the plane, without
Doppler effect, and that the circle will seem to progressively shrink to a
point.
  -----
  Ebeno eklumi^gas unukolore kaj tuj poste mallumi^gas, dum observanto
ekmovi^gas orte el ebeno kun konstanta propra akcelo. Special-relativeco
anta^udiras, ke observanto vidos luman cirklon ^ciam en direkto mala al la
ebeno, sen Dopplera efiko, kaj ke tiu cirklo ^sajnos progrese eti^gi ^gis
punkto.
