Superconductivity

Heike Kamerlingh Onnes cooled mercury to 4.2 Kelvin in 1911, expecting its resistance to gradually decrease—instead, it vanished completely, plummeting to zero. His lab notebooks show his disbelief: he tested his equipment three times, convinced something was broken. This wasn't a subtle effect but a dramatic cliff-edge where electricity suddenly flowed forever without losing energy, a phenomenon that had no place in existing physics.

Superconductivity works because electrons, normally repelling each other like antisocial commuters, actually pair up and move in lockstep through the material. These "Cooper pairs" form when electrons create tiny vibrations in the atomic lattice that attract other electrons—imagine one person's footsteps on a trampoline creating a dip that pulls another person toward them. Below the critical temperature, billions of these pairs move as one coherent quantum wave, making it impossible for individual electrons to scatter and lose energy as heat.

Superconductors expel magnetic fields completely (the Meissner effect), which means a magnet will float above them as if held by an invisible hand. Japan's maglev trains use superconducting magnets to achieve 375 mph by eliminating friction entirely. In a famous 1997 experiment, physicist Andre Geim levitated a live frog using powerful superconducting magnets—the frog was fine, and Geim later won the Nobel Prize (for graphene, but still). This magnetic repulsion is so stable that toy versions let you balance magnets in mid-air indefinitely.

For over a century, superconductivity required temperatures colder than outer space, making it wildly impractical—liquid helium cooling costs thousands per liter. In 2020, scientists achieved superconductivity at 59°F, but only under pressures 2.6 million times atmospheric pressure, essentially requiring a diamond vice. If we crack room-temperature superconductivity at normal pressure, we'd revolutionize power grids (zero transmission loss), electronics (superfast computers), and transportation overnight. It's the $1 trillion problem that keeps materials scientists awake at night.

Every MRI machine contains miles of superconducting wire wrapped into coils, producing magnetic fields 60,000 times stronger than Earth's. These fields must stay perfectly stable for hours while you're scanned, which would be impossible with normal electromagnets—they'd overheat in seconds and consume a power plant's worth of electricity. The superconducting magnets are always on, perpetually cooled by liquid helium, which is why MRI machines make that distinctive humming sound and why metal objects become dangerous projectiles near them.

Despite discovering superconductivity in 1911, physicists couldn't explain it until 1957 when Bardeen, Cooper, and Schrieffer published their BCS theory—winning them the Nobel Prize. Even today, "high-temperature" superconductors (discovered in 1986) still lack a complete theoretical explanation, making them a maddening black box. We can use them and predict some behaviors, but we can't fully explain why they work, which is like having a car you can drive but whose engine operates on mysterious principles you can only partially describe.