Antti_U

Massless things move through Higgs field without resistance I.e. at speed of light and they by definition do not experience time or distance. You ask whether an observer needs to have mass. An observation means a mechanism for recording a delta in an event. If you don’t experience time then by definition you cannot be an apparatus capable of observing a delta. Sorry I’m not a scientists, just common sense application answer and happy to be challenged:)