Panning for Gold.

FEATURES It's been more than a century since Albert Einstein predicted the existence of gravitational waves, half a century since Joseph Weber first attempted to detect them, and just seven years since they were finally spied by Italian postdoc Marco Drago in data from the Laser Interferometer Gravitational-Wave Observatory (LIGO). But perhaps the most pernicious signal frustrating primordial B-mode prospectors is a type of fool's gold from the CMB itself: primordial E-modes masquerading as B-modes. This weak lensing effect can also change the light's polarization pattern, flipping photons from E-modes to B-modes. Former E-modes that have been twisted into lensed B-modes are a nuisance for primordial B-mode prospectors, and neither BICEP Array nor Simons Observatory can remove them with just their small telescopes. [Extracted from the article]