Matter that moves forever — but isn't perpetual motion
In 2012, a Nobel laureate proposed matter that oscillates forever in its ground state — like a pendulum that never stops. This sounds like perpetual motion, which is impossible. Yet time crystals were experimentally created in 2017. How can something move eternally without violating physics?
Since the 19th century, physicists have known that perpetual motion machines are impossible. The laws of thermodynamics demand that any moving system will eventually stop — friction, radiation, and entropy always win.
Then in 2012, Frank Wilczek — who won the Nobel Prize for explaining the strong nuclear force — proposed something that sounded impossible: a time crystal.
A regular crystal (like diamond or salt) has atoms arranged in a repeating pattern in space. A time crystal has particles that repeat in time — they oscillate forever, returning to the same configuration periodically, even in their lowest energy state.
Here's why time crystals aren't perpetual motion machines:
Does useful work forever without energy input. Would create energy from nothing. Impossible — violates thermodynamics.
Oscillates forever but cannot be harnessed. Already in ground state — no energy can be extracted. Motion exists but does no work.
If you try to extract energy from a time crystal, it "melts" — the periodic motion stops. The crystal dances forever, but only when nobody's watching (trying to use it).
Normally, the laws of physics don't care when you start your clock. This is "time-translation symmetry" — the universe behaves the same yesterday, today, and tomorrow.
Time crystals spontaneously break this symmetry. Their behavior depends on when you look at them. They're not the same at all times — they oscillate between distinct states. This is analogous to how regular crystals break space-translation symmetry (atoms aren't everywhere, they're at specific places).
"It's a new phase of matter. We've added an entry to the catalog of possible phases of matter." — Norman Yao, Berkeley physicist
Two teams created real time crystals in 2017:
Harvard (Mikhail Lukin): Used diamond crystals with nitrogen vacancies — defects where carbon atoms are missing. Applied microwave pulses to flip the spins periodically. The spins oscillated at twice the driving period — the defining signature of discrete time crystalline order.
Maryland (Christopher Monroe): Trapped 10 ytterbium ions in a line using electromagnetic fields. Zapped them with lasers. The ions developed a stable oscillation at a different frequency than the laser pulses.
In 2021, Google's quantum computer created a time crystal using 20 superconducting qubits, maintaining stable oscillations for hundreds of cycles.
Wilczek's original idea — spontaneous oscillation without any external input — was proven impossible in 2014. But "discrete time crystals" survive: they need periodic driving (like laser pulses), but respond at a different frequency.
This frequency mismatch is key. The crystal isn't just passively following the drive — it has its own rhythm that resists perturbation. Even if you change the driving slightly, the crystal maintains its stable period.
Time crystals may revolutionize:
Quantum Computing: Their stable oscillations could serve as error-resistant quantum memory, maintaining coherence where other systems decohere.
Ultra-Precise Timekeeping: Clocks based on time crystals might achieve unprecedented accuracy.
Fundamental Physics: They offer a new window into non-equilibrium physics — systems that never reach thermal equilibrium.