Interactive physics simulations that follow real laws. Every animation is mathematically accurate.
This website lets you play with the laws of physics. You'll see quantum particles exist in multiple places at once, watch electrons interfere with themselves, and discover why time slows down when you move fast. Each section includes the actual equations physicists use — but explained in plain English.
Before you look at a quantum particle, it doesn't have a definite location. Instead, it exists as a probability wave — spread out across space like a cloud. The denser the cloud, the more likely you'll find the particle there. This isn't "we don't know where it is" — it's "it literally is in many places at once." Only when you measure it does the wave "collapse" to one specific point.
● Click anywhere to collapse the wavefunction
Schrödinger Equation: iℏ(∂ψ/∂t) = Ĥψ
This is the master equation of quantum mechanics. It tells us how the wavefunction ψ evolves over time. The symbol ℏ (h-bar) is Planck's constant divided by 2π — it's tiny (10^-34 J⋅s), which is why we don't see quantum effects in everyday life.
This is the experiment that broke physics. Fire electrons one at a time through two slits, and they create an interference pattern — like waves overlapping. But each electron is a single particle! Somehow it goes through BOTH slits and interferes with ITSELF. Even weirder: if you try to detect which slit it took, the interference disappears. The electron "knows" you're watching.
The Uncertainty Principle: To detect which slit the electron took, you must interact with it — bounce a photon off it, for example. This interaction disturbs the electron's phase, destroying the delicate interference pattern. It's not that the electron "knows" you're watching; it's that measurement requires physical interaction, and that interaction changes the system.
Yes! Every object has a wavelength given by λ = h/mv. For electrons moving fast, this wavelength is comparable to atomic spacing — so they diffract like waves. For a baseball, the wavelength is 10⁻³⁴ meters — trillions of times smaller than an atom. That's why you don't diffract through doorways. The heavier you are, the more "particle-like" you behave.
● Adjust sliders to see when objects behave as waves vs particles
The Sun's core is 15 million degrees — not hot enough for hydrogen nuclei to overcome their electric repulsion and fuse. Classically, fusion shouldn't happen. But quantum mechanically, nuclei tunnel through the repulsive barrier. The wavefunction extends into the "forbidden" region, giving a tiny probability of appearing on the other side. This is also how scanning tunneling microscopes work, and how some radioactive atoms decay.
The Second Law of Thermodynamics says entropy (disorder) always increases. Not because of any fundamental law, but because there are vastly more disordered states than ordered ones. If you randomly rearrange particles, you're almost certain to create disorder. The arrow of time — why we remember the past but not the future — comes from this statistical fact. The universe is constantly shuffling toward its most probable state: uniform chaos.
GPS satellites orbit at 20,000 km/h. At that speed, their clocks run slower due to relativity — about 7 microseconds per day. But they're also in weaker gravity, which makes clocks run FASTER by 45 microseconds per day. The net effect: satellite clocks gain 38 microseconds per day. If we didn't correct for this, GPS would accumulate 10 km of error per day. Relativity isn't theoretical — it's essential technology.
We've covered quantum superposition, wave-particle duality, tunneling, entropy, and relativity. Each simulation followed real physics equations. The universe is under no obligation to make sense to us — but with mathematics, we can understand it anyway.