You may have noticed that our language (English) has difficulty dealing with the nature of Spacetime. In everyday usage, our concepts of space and time are treated as separate entities. As if space is the eternal background against which events in time occur.

Einstein coined the word Spacetime in an effort to reconcile this difference. In his view, what is eternal is spacetime, space and time considered together. The implications of this new view actually apply to daily life. But not in ways we can easily observe. Unfortunately, even professional scientists often find it easier to ignore them. Which can lead to mistaken ideas if we're not careful.

This can be especially troublesome when dealing with the quantum realm. For example, here's a quote from a recent online article: "Quantum computers are highly sensitive to any unintentional interactions with their environments. This leads to the phenomenon of decoherence." An apparently innocuous statement. What does it have to do with spacetime? Spacetime is all about cosmology, right? The realm where the speed of light might be a factor.

Consider this: the quantum realm is assumed to be the realm of the very small, where it would seem that the speed of light is even less a factor than it normally is for us. But what exactly is the quantum realm all about? It's about what hasn't happened yet. It's about the future. Once something happens, it's history. Its occurrence is frozen in time. It's no longer in the either/or state that puzzled so many of the early observers of quantum behaviors.

Like, for example, the famously puzzling double slit experiment, where photons (or electrons, or anything else that can go through either slit) are observed to, unexpectedly, act more like waves than particles, and make wavy spread-out patterns on a detector screen.

Unless the experimenter inserts a detector in front of the double slit, and duly detects the particle nature of the photons, just as Einstein had predicted. Then, perversely enough, if the photons are allowed to pass on through the double slit, they dutifully pile up behind either one slit or the other. See? No waves going on here!

The issue turns out to be that, whichever way the experiment is run, once a wave/particle hits the screen that event is history. And the history will forever say that what arrived was either a wave or a particle. Not both. End of story. Start of history.

Where does this confusion come from?

Spacetime
We can draw a "map" of spacetime. You may have seen examples of this. Looking at such a map (shown flat, as if drawn on paper) it may not be obvious that it shows only one dimension of space. The other dimension available on a flat map is used to display time. Einstein called points on this sort of map "events". Every such event is a unique point in spacetime. The map is intended to illustrate the way the finite speed of light limits access between different points in spacetime.

Let's suppose there's a line at the bottom marked off in units of distance, and a line up the side marked off in units of time. Pick a point on the bottom line, right in the middle say. Then as long as that point doesn't change its position in space, its journey through time will be a line straight up the map. But if the point's position in space does change over time, it will trace a line that veers off from the vertical to either the right or the left. It's allowed to do that. But there's a limit. That limit is called the speed of light.

Einstein showed that even light can't move instantly. On the diagram, the light speed limits of motion are shown by left and right diagonals drawn from the starting point. No diagonal of motion can go outside the light speed V, because to do so it would have to exceed the speed limit. Can't get there from here. (There's a reason for that limit, which has to do with the laws of mass and inertia, but that's discussed elsewhere. If you've read this far in this series of essays, you probably already know that.) 

Now for convenience we've talked about straight lines, lines that represent constant speeds. But you know from your own experience that, except maybe for light (and gravity waves, as it turns out) there's really no such thing as constant speed. Not forever anyway, there's always some pushing needed to get started, and more pushing or pulling to go faster or slower or change directions. So lots of curvy motions are possible. But on our relative time and distance map, there's always that light speed limit. 

Okay, now I have to caution you about what "lots of curvy motions" might mean. We can't get carried away and draw loops and squiggles inside the V. The light speed limit always applies, so when a point we've selected moves up the map, it carries its light V with it. 

(Note: The "V" is for one distance dimension, strictly right or left on our map. You'll hear talk of a light "cone" but that's not a huge improvement because it only covers two of our three distance dimensions. In reality we have three spatial dimensions. You could try to picture a three-dimensional sphere, but then where would you put your time line? Better just stick with our 1-D map.) 

So the thing to notice here is that our V is actually made up of a stack of horizontal distance lines, representing the sequence of moments in time. Our event point can only move to the next line up and only to positions between the arms of the V for that unique event. Once it moves, it has a new V. Points aren't allowed to move faster than light, or backward in time.

The Quantum realm: entanglement and decoherence 
Entanglement is the condition in which particles have interacted in a way that constrains their mutual quantum properties. After an entanglement event occurs, all future events affecting either particle will affect both, regardless of any subsequent separation. This appears to violate the light speed limit. But more truly the effect is created in the realm of the future, where probabilities prevail. Quantum probabilities are not constrained by spacetime physics. They already occupy positions on the Spacetime map that the time line hasn't reached.

Decoherence is the result of observation, and is a measure of the state of an object at the moment when a possible future becomes an event on a timeline, with a fixed history. It is the memory of a Now.

The Sea of Dreams 
This is another name for the quantum realm, the realm of possible futures. It is within this realm that a Now at the forefront of a timeline connects to its next spacetime event.

Is the sea of dreams part of our reality? Not exactly. Dreams are expectations. Expectations become realities when they link to a Now. They become dream histories, leaving the endless sea of dreams open to future links. When we say, "I have a dream," we may be anticipating a possible future. When we say, "I had a dream," we are recalling a past dream event, a dream history. But every Now offers new possibilities, and if a Now recalls a past event that can be linked to a future event, the possibility can become a probability and then a Now, forever to be linked to that past event in your mind that helped you find it.

Perhaps referring to our possible futures as a sea of dreams is misleading. Dreams can imply sleep, and some of us don't remember much of our sleep experience. But all of us remember our awake awareness. And internally they are much the same. 

Awake dream awareness differs from sleep dream awareness only in the level of our awareness of others. They differ in the intensity of this awareness. When awake, our perceptions of reality tend to overwhelm us, shunting aside our dreams in the endless now, now, now pressures of available otherness. 

Some of us, maybe all of us, can shut down the intensity of our awareness of otherness, can focus our attention narrowly, into a state that is nearly dreamlike. I, your writer here, can speak only for myself in this regard. Awareness is a very personal thing. But the evidence of my own awareness experience (whether reading, writing, watching a show, even cooking eggs, anything calling for focused attention) is that this is likely true for all of us.

Perhaps I should designate the state of mind that allows us to contemplate the nature of awareness as a kind of meta-awareness. It is in a sense other than, higher than, our usual awareness that focuses mainly on otherness, taking self-awareness for granted.

Some of us (I'm looking at you here Ray) may be naturally in a permanent state of meta-awareness, natively as confounded by our own existence as we are by that of others. Most of us, I suspect, give up on meta-awareness early, taking the entire world of our experience for granted as simply what is, just the way things are. "Ours is not to reason why, ours is but to do and die," as Tennyson put it.

Our whole experience of physical reality is an observation of otherness. But whenever we attempt to understand our place in this otherness, the otherness becomes an aspect of self, and physical reality dissolves into the sea of dreams.

It may well be that "sea of dreams" is just another way of saying "quantum spacetime". That when we dream, we are in a possible future, linking to points in spacetime which we are not physically visiting. And possibly never will. To that degree the sea of dreams might be called the sea of imagination.

Happy sailing.