[quote=So Boerd]
Of course. Let me make up some possible evidence... In this hypothetical, suppose there was a hand which materialized out of air and wrote "I am God" on the nearest available surface to them at the same time all over the world. Some instances were videotaped, however they can't make the hand appear again. Is this sufficient?
[/quote]

Nope. It's not repeatable. Ergo, not scientific.

Plus, the source isn't necessarily a god. To quote one of Clarke's three laws: [url=http://en.wikipedia.org/wiki/Clarke%27s_three_laws]Any sufficiently advanced technology is indistinguishable from magic[/url]. I'm sure if you brought me back in time with a laptop to the medieval age, I could amaze them with my ability to instantly resolve any kind of mathematical equation with the calculator application in Windows.