There's another thread more appropriate for that discussion, minime, Questioning Consciousness, running 66 pages, now
But really without qualifiers or quantifiers like limiting magnitudes and intensities it's an undefinable question you're asking without the possibility of any answer being the correct answer or with the possibility all would be correct. It's all relative. If I asked my LL what big thing happened this spring, he'd tell me the biggest thing for him this spring was his doctor telling him his prostate cancer had metastasized into his spine and will soon affect his brain; that he had not five years, but two, to live. The terrible Schoharie County limo accident that killed 20 would be the biggest thing to happen to some. For me, listening to my LL to me his sentence had been shortened. The world stage is too vast, with far too many big things happening all the time, relative to one's scope of perspective.
Besides, it's a trick question. Fractals are infinitely small as well as infinitely large. Doesn't that correlate to having the same effect upon everything else, for everything big to someone somewhere at any given time could be utterly insignificant to another, whether or not they witnessed the other's big thing.