  The polarization of the Cosmic Microwave Background (CMB) provides a plethora
of information about the early universe. Most notably, gravitational waves from
the Inflationary epoch (the leading explanation of the origin of the universe)
create a unique CMB polarization $B$-mode signal. An unambiguous detection of
the inflationary $B$-mode signal would be a window into the physics of the
universe as it was $10^{-36}$ seconds after the Big Bang, at energy scales many
orders of magnitude larger than what the LHC can produce. However, there are
several instrumental and astrophysical sources that can obfuscate the
inflationary $B$-mode signal. One of the most difficult parameters to calibrate
for CMB telescopes is the absolute orientation of the antenna's polarization
sensitive axis. A miscalibration of the polarization orientation rotates the
much brighter $E$-mode signal, producing a false $B$-mode signal. The current
best uncertainty on polarization orientation in the CMB community is
$0.5^\circ$, set from extrapolating IRAM measurements of the Crab Nebula
supernova remnant at 90 GHz to 150 GHz, where the CMB signals peak. This
accuracy is not sufficient to convincingly detect $B$-modes predicted by
currently allowable models of Inflation. We suggest to precisely measure the
Crab Nebula's polarization, which can be calibrated absolutely to $0.1^\circ$
from measurements of the polarized emission of Mars, and use these data to
calibrate current and upcoming CMB experiments. In addition to inflationary
$B$-modes, more precise calibration will allow us to better constrain the sum
of the neutrino masses and set limits on exotic physics such as parity
violation through cosmic polarization rotation.
