What is Quantum Physics?
Quantum physics is the study of how energy and matter behave at the smallest scales — atoms and particles. At this level, the normal rules of everyday life stop working properly.
Energy Comes in Chunks
In 1900, Max Planck discovered that energy is not smooth and continuous. It comes in small fixed packets called "quanta." This was the first clue that something strange was going on at tiny scales.
Light Acts Like a Particle Too
In 1905, Einstein showed that light is made of small energy packets called photons. This explained why shining light on metal knocks out electrons — a fact normal wave theory could not explain.
The Double-Slit Experiment
When particles like electrons are fired through two slits, they create a wave-like interference pattern, even when fired one at a time. But if you try to observe which slit they go through, the pattern disappears. Observing the particle changes its behavior.
Superposition
Before being measured, a quantum particle can exist in multiple states at once. It only "picks" one state the moment it is measured. This is called superposition.
Schrödinger's Cat
This is a famous thought experiment. A cat in a box is linked to a random quantum event. Until the box is opened, the cat is considered both alive and dead at once, according to strict quantum rules. It shows how strange superposition becomes at bigger scales.
Uncertainty Principle
Werner Heisenberg showed that you cannot know both a particle's exact position and exact speed at the same time. The more precisely you know one, the less precisely you know the other. This is not a tool problem — it is a real limit of nature.
Entanglement
Two particles can become linked so that measuring one instantly affects the other, even if they are far apart. Einstein called this "spooky action at a distance." Experiments have confirmed entanglement is real.
Why It Matters
Quantum physics is not just theory. It is the reason computer chips, lasers, and MRI machines work. It also powers new technology like quantum computers.