Sorry but you always forgot that when you sleep your consciousness disappeared. Please take account for this fact. When all sensory shut down, really you feel nothing and of cos think nothing.
When you actually pass out, there's a very real sense of discontinuity. You find yourself on the floor, unsure how long you've been there (even if it was just seconds), and how exactly you got to that position (the previous recorded memory being you standing there and feeling woozy).
It's very different from just sleeping, where you still retain a feeling of continuity with both place and time.
Consciousness can end temporarily, perhaps permanently. This in no way suggests that it’s an illusion.
The claim that consciousness is an illusion has always seemed like nonsense to me; for, if consciousness is an illusion, who experiences that illusion? Answer: the conscious mind.
Consciousness is a trick for human neural network to simplify some calculations about the world. It was developed as an evolutionary trait and proved useful to survive. That's my opinion. It's not an illusion, it definitely exists as an particular configuration of neurons.
My consciousness doesn't seem to disappear when I fall asleep, only my awareness of my bodies sensations. I often go to sleep reading, and the thoughts I'm having about the book I'm reading will continue for quite some time, even after my eyes close. I know this because I often startle myself awake by dropping my book. I also have similar experiences as I wake up, my consciousness slowly starts to incorporate my sensations of reality with the thought process that is continuously going in my head.
I think memory shuts down when you sleep. So that it still feels like something to be sleeping, only we cannot recall it when we awake, because it is not persisted in memory. This is the same reason we cannot remember what it is like to be a rock, even though it does feel like something to be a rock.
When I woke up after surgery I felt that 1.5 hours had passed. But in actuality it was something around 4 hours since I went under. It turned out that 1.5 hours before I woke up I had been brought out of anesthesia and after that I simply slept. I didn't have any dreams at all, but at least my internal clock had started working. A clock presumably doesn't need consciousness, but there's definitely a qualitative difference between anesthesia and sleep. And as I sometimes suddenly wake up with a solution to some problem, with no recallable dream preceding it, my personal subjective opinion is that there's some level of consciousness going on even in sleep. That anesthesia experience was so very different from anything I had experienced before, with no recall whatsoever of the time that had passed.
How do you estimate time elapsed without external inputs? Experiments where people cut themselves from external stimuli seem to show that on the contrary, we don’t good internal clocks on this regard.
I nearly always "know" how long I have been asleep, unless there's been excessive drinking involved (and that would be long ago). "Normal" drinking doesn't seem to affect this. And for shorter naps (less than two hours) it's pretty accurate.
People probably do this based on experience. You know from the wall clock time that you slept, say 7 hours. So on a daily basis, you know what 7 hours of sleep feels like and from that you can extrapolate: if you think you slept about half as much, maybe it was 3 hours. Kind of thing.
When you actually pass out, there's a very real sense of discontinuity. You find yourself on the floor, unsure how long you've been there (even if it was just seconds), and how exactly you got to that position (the previous recorded memory being you standing there and feeling woozy).
It's very different from just sleeping, where you still retain a feeling of continuity with both place and time.