  Current theories of the origin of the Universe, including string theory,
predict the existence of a multiverse containing many bubble universes. These
bubble universes will generically collide, and collisions with ours produce
cosmic wakes that enter our Hubble volume, appear as unusually symmetric disks
in the cosmic microwave background (CMB) and disturb large scale structure
(LSS). There is preliminary observational evidence consistent with one or more
of these disturbances on our sky. However, other sources can produce similar
features in the CMB temperature map and so additional signals are needed to
verify their extra-universal origin. Here we find, for the first time, the
detailed three-dimensional shape and CMB temperature and polarization signals
of the cosmic wake of a bubble collision in the early universe consistent with
current observations. The predicted polarization pattern has distinctive
features that when correlated with the corresponding temperature pattern are a
unique and striking signal of a bubble collision. These features represent the
first verifiable prediction of the multiverse paradigm and might be detected by
current experiments such as Planck and future CMB polarization missions. A
detection of a bubble collision would confirm the existence of the Multiverse,
provide compelling evidence for the string theory landscape, and sharpen our
picture of the Universe and its origins.
