1933

Meissner effect

• Meissner and Ochsenfeld discovered
• that superconducting materials
• present the illusion
• of perfect diamagnetism.
• When they cooled their samples
• below their transition temperatures
• the samples perfectly repelled an external
• magnetic field so none of the
• magnetic flux was lost, which is called
• conservation of the flux.
• If the same effect were true
• for visible light and you cooled
• a superconductor below its transition
• temperature, it would disappear.

Surface effects

• A superconductor
• responds to
• a magnetic field
• by generating persistent
• electric currents
• near its surface.
• *
• Lightwaves don’t
• actually bounce
• from mirrors
• but cause small
• secondary lightwaves
• that interfere
• and add up
• to the angle
• of reflection.
• *
• Molecules
• of a liquid
• pull together
• so they are
• under tension
• at their surfaces.
• *
• A superfluid is inviscid.
• Is magnetic flux
• a superfluid?

Ways to tell

• If you pinch yourself and don’t wake up
• you can tell you’re not dreaming.
• *
• If you pinch me and I say “ouch,”
• you can tell I’m not Italian.
• *
• If you throw a stone into a pit
• and you don’t hear it hit bottom,
• you can tell it’s bottomless
• or you’ve lost your hearing.
• *
• If your material levitates,
• you can tell you have found
• a room-temperature superconductor
• or an anti-gravitational principle.
• *
• If it walks like a duck,
• and it quacks like a duck,
• you can tell it’s at least
• a good imitation of a duck.
• *
• If you don’t see your reflection in a mirror,
• you can tell you have no soul.
• *
• If you can’t see through me,
• you can tell I might be teasing you.