  Magnetic reconnection is best known from observations of the Sun where it
causes solar flares. Observations estimate the reconnection rate a small, but
non-negligible fraction of the Alfv\'en speed, so-called fast reconnection.
Until recently, the prevailing pictures of reconnection were referring to
either resistivity or plasma microscopic effects, which was contradictory to
the observed rates. The alternative picture was either reconnection due to the
stochasticity of magnetic field lines in turbulence or the tearing instability
of the thin current sheet. In this paper I simulated long-term
three-dimensional nonlinear evolution of a thin, planar current sheet subject
to fast oblique tearing instability using direct numerical simulations of
resistive-viscous MHD. The late-time evolution resembles generic turbulence
with -5/3 power spectrum and scale-dependent anisotropy, so I conclude that the
tearing-driven reconnection becomes turbulent reconnection. The turbulence is
local in scale, so microscopic diffusivity should not affect large-scale
quantities. This is confirmed by convergence of the reconnection rate towards
$\sim 0.015 v_A$ with increasing Lundquist number. In this spontaneous
reconnection with mean field and without driving the dissipation rate per unit
area also converge to $\sim 0.006 \rho v_A^3$, the dimensionless constants
$0.015$ and $0.006$ are governed only by self-driven nonlinear dynamics of the
sheared magnetic field. Remarkably, this also means that thin current sheet has
a universal fluid resistance depending only on its length to width ratio and to
$v_A/c$.
