I've always been inclined to think of dreams by trying to relate them to the time I spent asleep. Especially when I wake up remembering several dreams and they all seem quite "long" I start thinking about how long I might have been dreaming out of the whole time I was asleep. (Is it me or does sleep when dreaming seem like "you get more out of it"? :D )

Of course, dreaming doesn't happen the whole time being asleep, only in certain periods (that's all I know about it), so you will never have a night's sleep where you dream from beginning to end.

But that got me thinking. Why do we assume that the "speed" of dreams is the same as the speed of consciousness? What we do in our conscious state is a constant sort of data processing function, we perceive things and respond to them. But while asleep there is no perception happening. And so there is no need to respond to anything either. Which means.. there is no reason to assume that dreams "happen" at the same speed, is there?

In fact, dreams are supposed to be spawned by the brain as a way to keep you asleep while detecting that you are about to wakeup. But it stands to reason that this reaction must be rather quick, it doesn't seem likely that you start waking up and then the dream kicks in and you sort of teeter on the brink of waking up but still sleep another two hours. What seems more likely to me is that this is a quick response, so you start waking up, you start dreaming, but that only keeps you asleep for a short period of time.

How short? Well, since there is no perception involved, you're not actually responding to sensory perception at all, it's just a (pre-calculated?) simulation. So dreams could actually be extremely short, and you wouldn't know it, because it's just a representation of things in the brain.

So when people say things like "my life flashed before my eyes", we think that is silly, because how could you relive so much "real time" of life in such a short period of time? But if you think about it in the terms stated so far, it makes perfect sense. It doesn't take much time to experience fragments from your whole life, because you aren't responding to perception, you are just replaying it in your head. And you don't need any time to think about it either, you aren't thinking about it, just feeling it.

So how fast? Well, considering how fast you brain can respond to sensory perception that you aren't thinking about consciously, like recognize faces, voices, associate images with each other, recognize patterns and so on, this could actually be pretty damn fast.