In a comment to the Illusions post, Pascal gets Quantum on our asses:
“God does not play dice” - Einstein
To which Louis de Broglie replied: “And who are YOU to tell God what He can do?”
The quantum uncertainty principle is just as much a fundamental fact of Science as the light spectrum of atomic Elements.
Basically, it states that if God doesn't play dice, only He can ever know it.
Or, more matter-of-factly, that if you imagine quantum particles in the Universe as ants in a colony, there is nothing smaller than an ant that you can send in to gather information, but your added robot-ant will disturb the information by its presence. "Oi! Move on, buddy, I've got corn grains to carry here! Make yourself useful, go guard the Queen's Chamber with those big choppers of yours. And watch where you put your feet, will ya? Sheesh..."
Here's a simple example of the uncertainty principle:
A spectral line represents a given wavelength of light (or other energy emission). But a spectral line always has a certain width, amounting to a frequency range. Why is that? Because the laws of physics show this: if there was only one, mathematical photon wavelength, one exact frequency instead of a narrow range at best, its energy would be infinite. It would amount to dividing a given intensity by a width of zero. Even with one single photon, this still applies. There's no escaping it, just like death and taxes. ;-)
As soon as you get a little far above a beach, it appears as a continuous surface. But at a small scale it'll always be made of grains, and its physical properties will differ from those of a true fluid or a normal solid. Which will be noticeable even at a scale far bigger than grains.
Inversely, under a moderately powerful microscope, sand will appear as a heap of tiny rough rocks. It may appear in very different fashions, none of which is truly representative of what we can only understand with mathematical tools, namely "the big picture". Sand is a peculiar solid (a "grainy matter") that sometimes behaves like a liquid. When you stroll on a beach, you have the illusion that this can't happen... until a sandstorm rises, Allah forbid!
Mud is even more complicated in behaviour, because it's grains closely mixed with liquid, at a scale where tiny surface forces have a tremendous cumulated effect.
Did you know that tar is actually a liquid? Hit it with a hammer, and it shatters. Leave it in a pierced barrel, and it'll run. Veeeeerrrrry slooooowwwwwly. It is viscosity at a very unusual scale. Glass is similar, in reality. It is an incredibly viscous amorphous solid. A window could theoretically become a puddle on the floor at ordinary temperature. The thing is, it would take millions of years, provided erosion doesen't get it first! Its stability is purely an illusion created by our own time scale. Compared to minerals, we live very fast dog years...
Our senses are sophisticated measure instruments, which give us a reprepsentation of the world, in a certain fashion which is USUALLY the most efficient. For who and what we are. But they have their limits, all of them put together still have their limits. Only with our intelligence can we get past that illusion... one slow step at a time.
Given enough speed and kinetic energy, a water-filled balloon can go right through the armor of a battle tank like a red-hot knife through butter. Unless the air friction evaporates it first in a cloud of steam. A feather in the void of space could possibly kill an astronaut, because no air slows it down. We're just not used to such things happening. We live in the illusion of our habits.
An infant could move an aircraft carrier with one hand. In the wieghtlessness of space, or even in a very calm water harbour. All it takes is the patience to overcome the inertia of a great mass and wait till you see a visible result, so keep pushing!
The fragile silk sheet of a parachute can hold a man in the air. A spider's silk is way tronger than steel or Kevlar, and would make great (and lightweight) bullet-proof vests. It would seem that an unarmed frail cleric could halt the Scourge of God with mere words.
So, always beware of what you take for absolutely and universally certain. Keep an open mind. We only know as much as we have already learned or discovered, and yet not always.
"It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so." — Mark Twain