At the smallest scales, particles don't have definite positions or velocities. They exist as clouds of probability. The universe doesn't run on certainty—it runs on chance.
A particle doesn't have to be "here" or "there." Until measured, it exists in all possible states simultaneously.
Schrödinger's cat isn't just a thought experiment. At the quantum level, particles really are in multiple states at once. Not "we don't know which"—both, actually.
Click the box to "observe" the particle and collapse its superposition.
Is light a wave or a particle? Both. Neither. It depends on how you look.
In the double-slit experiment, single particles create interference patterns—as if each particle goes through both slits at once and interferes with itself.
But if you try to watch which slit it goes through, the interference disappears. The act of observation changes the result.
A particle hits a barrier it doesn't have enough energy to cross. Classically, it should bounce back. But quantum mechanics says: sometimes it just... appears on the other side.
The particle doesn't go over or around. It "tunnels" through—because its probability wave extends beyond the barrier.
This isn't rare. Tunneling powers the Sun (enabling fusion) and makes your flash drives work (quantum tunneling in transistors).
Two particles become "entangled"—their quantum states linked. Measure one, and you instantly know the other's state, no matter how far apart they are.
Einstein called it "spooky action at a distance" and thought it proved quantum mechanics was incomplete. But experiments confirm: entanglement is real.
The correlation isn't sending information faster than light. The particles were never really separate—they're one quantum system, regardless of distance.
The act of measurement changes what's being measured. Not because your instruments are clumsy—because observation and reality are entangled at the quantum level.
Before measurement: probability cloud. After measurement: definite state. What collapses the wave function? We still don't fully know.
Some interpretations say consciousness plays a role. Others say decoherence happens automatically. The debate continues.
Zoom in far enough, and spacetime itself becomes uncertain. At the Planck scale (10⁻³⁵ m), space and time foam and bubble with quantum fluctuations.
Virtual particles pop in and out of existence constantly. "Empty" space is never truly empty—it's a seething quantum soup.
This isn't theoretical. The Casimir effect proves vacuum fluctuations exert real, measurable force.
At the deepest level we can probe, reality is not deterministic. It's probabilistic. Particles exist in superposition. Observation changes outcomes. Space itself fluctuates.
This doesn't mean "anything goes." Quantum mechanics is incredibly precise—we can predict probabilities to 12 decimal places. But certainty? That's the illusion. The universe plays dice.
Understanding uncertainty means accepting that some questions don't have definite answers—and that's not a bug, it's how reality works.