What's The Difference Between Lucid Dreaming and Day Dreaming?

What's the difference between lucid dreaming and day dreaming? After all, a lucid dreamer knows what they are dreaming and that they are dreaming, so wouldn't that mean they are awake, just day dreaming?

Rebecca says: When a person lucid dreams, his body is asleep. When a person day dreams, his body is awake. That's the main physiological difference - which we know for a fact because we can scientifically measure things like:

• Rapid Eye Movement (REM) - Lucid dreams occur during REM sleep, when your eyeballs flick about, often in the direction you are looking in your dreams. Day dreams occur during wakefulness, when there is no REM. Your eyes can be open, closed, moving or still, but none of these are consistent with the Rapid Eye Movements of sleep.
• Brainwave Measurements - Lucid dreaming creates brainwave frequencies in the Theta, Alpha, Beta and Gamma ranges while you're physiologically asleep. Day dreaming is typically limited to a relaxed Alpha state while physiologically awake. The fact that lucid dreaming exists tells us that consciousness is not a clear-cut indication of wakefulness... so knowing that you're experiencing a false reality doesn't mean you must be awake and merely day dreaming.
• Muscle Tone Measurements - When lucid dreaming, you typically have no awareness of your body in bed (except for a few transition moments when you wake up). Your body lies in a state of REM atonia (sleep paralysis) to prevent you from acting out your dreams. When day dreaming, you maintain partial or full awareness of the waking world, even though you may be imagining a second world in your mind. Your brain makes no attempt to control the imaginary body with motor neuron signals; the two are not hooked up when wakefulness prevails.

There are other marked differences between the sleeping body and the waking body, explained in the article Why Do We Sleep? These will help you differentiate between the bodily states during lucidity and day dreaming.

But what about the mental experience? Again, lucid dreams and day dreams are very different, although these differences are harder to measure. Because they are both internally generated, reporting of these states is a subjective task. I'll give you my personal view of the differences, which I think most lucid dreamers would roughly agree with:

While day dreams are fun (research shows we day dream for 70-120 minutes every day) they are really just waking thoughts. We slip in and out of day dreams, visualizing our hopes and fears, reflecting on the past, future and fantasy. We maintain awareness of the outside world, to some degree, and can stop and re-start the fantasy if our attention is directed back to reality. Day dreams are fairly intangible, so when you day dream of running across the sand, the sensation is not really there; it's only imagined.

In lucid dreams, the fact that you are asleep and switched off from the real world means you are fully immersed in the dream world - literally seeing, hearing and touching your surroundings in a way that can vividly mimic reality. Your brain perceives the lucid dream world as vividly as if it were waking reality and you are fully tuned in to the experience. The dreamscape is largely self-generating (even when you consciously manipulate parts of it) and allows for illogical and unexpected creations to appear from the unconscious mind...