Well the speculation of how the universe is around us from the aspects of quantum mechanics would suggest that there is possibilities for "alternatives", however those alternatives wouldn't be within our sensor range unless they were generated to be so.
I take this perception based upon the Schrodinger atom.
This link should give you a bit of understanding:
http://www.colorado.edu/physics/2000/quantumzone/schroedinger.html
None the less for you lazy people, The way Schrodinger defined how an atom works, looked at how the electron generates a field of probability around the Nucleus through it's movements. In fact it was this wave formation that Heisenberg pointed out the "Uncertainty principle" when trying to measure the location of an electron.
I think Observation theory suggests that an event that is unobserved will do what it would have done, however if observed it might be likely that an alteration could occur based upon either the interaction of the observer of their view point for what they observed.
I suppose your question could be reiterated as,
"A tree falls in the forest, does it make a sound?".
Another method of looking at it is with a light switch (Binary system), where you can have a '1' or a '0', 'ON' or 'OFF'. In Schrodingers theoretical experiment involving a Cat (Or the one Wigner attempted with a 'Friend') the theory suggested that there wasn't/isn't just a '0' or '1', but an "Uncertain in-between".
The nearest method of explaining the uncertainty in this instance, is with fractal algorythms that are reconstructions of chaotic events (Albeit as these fractals are chaotic reconstructions, they are now no longer chaotic since they are "Observed".)
If all the above was too much, here is an experiment you could try at home for you to understand your question fully:
Firstly get a Webcamera, or normal Videocamera and set it up to either connect to your computer or your VCR/TV.
Point your camera at the television or Monitor and allow what is seen by the camera to be seen on the screen. Move the viewpoint enough so they you just see the screen and a little border, so you see multiple screens within each other in a long tunnel.
Now Move your hand between the screen and the camera, you'll see your movement occur in a delay all the way down the tunnel of screens until it disappears from view.
If you could generate a "Paradox or Uncertainty event" you could move your hand in one frame somewhere down that corridor of screens without actually moving your hand on the top one. (If you can do this trick properly, you should record it since it's something that parapsychologists would love to study)
[Also while you mucking around with a camera (This isn't for experimenting but it looks cool) tilt the camera 45 to 90 degrees in a direction, and then move towards the screen to remove the screens board from view, if you get it right the screen will start "Evolving patterns" (Or Chaos) based upon it's feedback of output to input. ]
