6000 Angstroms.
(Assuming you meant “EEG” here) … There’s still one difference that I consider important.
Just as we can detect certain types of brain activity when people say, “I’m experiencing God,” we can also detect certain types of brain activity when people say “I’m seeing the color yellow.” However, in the case of seeing yellow, we can go further than that. We can use frequency-sensitive photodetectors to show that, almost every time a person sees yellow, there are photons with a wavelength of approximately 5500 Angstroms impinging upon that person’s eyes. (I say “almost always” because people also experience hallucinations, negative afterimages, etc…)
However, there’s no external stimulus we’ve (yet) figured out a way to detect that coincides with the sensation of “I’m experiencing God.” It is as though all of the experiences of God are the equivalent of hallucinations or negative afterimages.
Now, of course, it may be that there is some external stimulus that has a high positive correlation with both the subjective experience of God and the EEG measurements that correspond to “spiritual” brain activity, but we simply haven’t found out what it is yet. It may be ultraviolet light or gamma rays. It may be vibrations in the Earth. It may be certain chemicals in the air. Or it may be a disembodied sky god throwing His righteous thunderbolts (which we also have not yet found a way to detect) into the brains of the faithful.
Or it may be that the human brain isn’t a perfect instrument of detection, and tends to give “false positives” as a kind of survival mechanism. For example, if there is no predator lurking in the bushes but you think there is, so you run away, this doesn’t have much of a negative impact on your chances of survival (other than that you’ll waste energy running needlessly). If, however, there is a predator lurking in the bushes but you think there isn’t, so you just stand there and allow the predator to pounce on you, this has a severe negative impact on your chances of survival. Therefore, our ancestors would have had a lot of selection pressure against failing to detect things that are there, but very little selection pressure against detecting things that aren’t there.
Perhaps the detection of a spiritual presence is one of these false positives.