&gt; The BICEP2 team thought they detected gravitational waves with their Cosmic Microwave Background (CMB ) measurements from their Antarctic observatory. By chance the ESA had the Planck observation satellite measuring a broader spectrum. Matching the two observations the BICEP2 measurements were capturing light interference from space dust in-between the observatory and the source.<p>This is a bit different, though. BICEP2 was claiming a detection of a polarization signal in the cosmic microwave background, which if present, would point to existence of primorial gravitational waves resulting from cosmic inflation. But, as you note, the multi-wavelength observations of Planck (not taken by chance, but part of a carefully planned all-sky survey with somewhat coarser resolution compared to BICEP2) showed that the polarization signal measured by BICEP2 was consistent with foreground dust, rather than primordial gravitational waves.<p>&gt; If gravitational waves are found, this will be the biggest thing since Smoot and COBE and confirmation of the Gurth Inflation theory.<p>It will be huge, but the gravitational waves LIGO would detect are not primordial or from inflation, but rather from supernovae and compact binary mergers (neutron star pairs, stellar-mass black hole pairs, etc.). So a LIGO gravitational wave detection would not provide any evidence for or against inflation. But it would tell us a lot about stellar explosions and the evolution of compact binaries.<p>EDIT: I should note that LIGO could detect or place constraints on some &quot;exotic&quot; gravitational wave sources – cosmic strings, for example.