One thing that's fascinated me about quantum theory is the discovery of the observer effect, which has been demonstrated with the famous two-slit experiment.

Basically in this experiment, a single particle of matter, say an electron, is fired at a screen with an electron gun that can shoot single particles. Between the screen and the gun is a board with two tiny slits parallel to each other. The electron can go through either slit and strike the screen on the other side, leaving a tiny mark we can measure, or it will hit the board and stop. It could also miss the board and the screen, or never even make it out of the gun in the first place.

These many different paths each electron can take has a certain probability associated with it. The electron going through the left slit, for example, could be orders of magnitude more likely to occur than the electron missing the board and screen completely. You can change these probabilities by changing the arrangement of the gun, board and screen, or by defining a determined path for the electron in some manner, perhaps with an electric field.

Now, the experiment sounds pretty simple at this point. You can easily imagine the electron as a tiny ball flying through one of the slits in the board and leaving a mark on the screen. You can see how it might bounce off the board instead and never hit the screen. You can see, if not easily, that the electron could miss everything, or never leave the gun, however unlikely that is to occur.

So, what would you expect to find when you actually run this experiment? You'd be in fine company if you say the electron will leave a single mark on the screen where it hits, and that running this experiment many times will result in two solid lines on the screen where the balls went through the slits and hit the screen. Most people would assume this is what is most likely to happen, given the setup described. What really happens, however, is far stranger than anything you could imagine.

The electron does go through one slit, yes, but it also goes through the other, and bounces off the board, and misses the board, and never leaves the gun, all at the same time.

Instead of a two lines marking the screen, showing where the particles went through the slits, we get bands of interference when we carry this experiment out over and over. This can only mean that something is interfering with the electron as it travels through the experiment, and since we're only sending one electron through at a time, it must be the electron itself that's the source of this interference.

The electrons are interfering with themselves in some way to cause a wave pattern to occur, even when we fire only one electron through the experiment at a time. Instead of matter behaving like a solid ball, it's behaving like a wave. Light can do the same thing, but but light's just weird anyways. That this happens with solid matter is proving even weirder.

"Blasphemy!" you cry. How can a single particle do all that at the same time? The secret lies in the way the quantum world works. It all has to do with probability. Since each of these outcomes is likely to a certain degree, they're all present in the actual outcome to that degree. A particle can be described as a packet of probability, with all of it's various wave states present to some degree relative to it's current environment. By combining the possible wave states together in proportion with their probability, we get what we now recognize as a particle. A fuzzy little bundle of energy with a certain likelihood of being in many places or states at the same time.

But what's this have to do with observers? Ah, someone is paying attention. If you thought quantum theory was strange, you're about to meet the most bizarre discovery ever.

It has been observed (heh) that an observer can alter the probability of an outcome in such a way as to make it most likely. The act of observation changes reality at a fundamental level, so much so that a world with an observer is very different than one without. Let's introduce an observer into our experiment to see if we can find out exactly where these electrons go.

Ok, so let's put a little camera next to the board so we can see the slits. We'll run the experiment a bunch of times, and this time when it creates our interference patter on the screen, like it did last time, we can watch as all these electrons go by and find out what's really going on. Sounds logical enough, so let's do it.

Wait! There's a problem. There's no interference patter now! The electrons make two solid lines on the screen where they went through the slits, but that's it. What? That's exactly what we were expecting to happen the first time we ran this experiment, but we got an interference pattern instead. But when we look at the electrons the pattern doesn't appear, and we're left with two simple lines to represent the slits. How odd. Perhaps the camera is messing with the electrons somehow. Let's take it out and see.

Yep. The presence of the camera seems to cause the two lines to appear, while taking it away shows the interference pattern again. Let's try leaving the camera there, but turning it so it can't see the electrons, just to see if it's the physical presence of the camera's matter, or if it's the camera's observation that's affecting our experiment.

Well, what do you know. Leaving the camera in place, but observing something other than the experiment causes an interference pattern, but turning it to see the experiment causes the two simple lines to appear instead. It's finally clear, the act of observation is somehow affecting the electrons probability in some way.

What's the deal with observers and observation? What qualifies as observation, and is there a way to measure anything without direct observation? How can science remedy this unintuitive anomaly in objective reality? Is there even an objective reality, or could our entire understanding of matter and energy be seriously flawed?

I've wondered if somehow this ability of an observer to alter reality is showing us something about time, and free will. If Michio Kaku is correct in describing time like a flowing river that can fork or whirlpool, are these observer anomalies the mechanism for forking this river of time?

Is consciousness somehow part of this? What does it mean when we make a conscious decision to act? Have we chosen a new time stream apart from the one our spouse has chosen, so that the spouse in the days following after that choice is not really the same person we married? Where does this leave God?

I think I hear baby Jebus crying....