Quantum electrodynamic threshold

In a 2003 cover story of Scientific American, there's an article about magnetars, pulsars with extremely strong magnetic fields.
What makes the theory about magnetars so tricky is that the fields are stronger than the quantum electrodynamic threshold of 4 × 10 gauss (4 × 10 teslas or 4 gigateslas). In such strong fields, bizarre things happen:
* X-ray photons readily split in two or merge together.
* The vacuum itself is polarized, becoming strongly birefringent, like a calcite crystal.
* Polarized light waves change speed and hence wavelength when they enter a very strong magnetic field.
* A light wave can glide past an electron with little hindrance if the field prevents the electron from vibrating with the wave.
* Atoms are deformed into long cylinders thinner than the quantum-relativistic wavelength of an electron. Fields about 10 gauss (10 teslas) squeeze electron orbitals into cigar shapes. In a field of 10 gauss (10 teslas), a hydrogen atom becomes 200 times narrower.

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