Yet the precise rate of this expansion, called the Hubble constant, remains a point of crisis in modern cosmology. 2: They use changes to the cosmic microwave background (CMB) – radiation leftover from the Big Bang event – to estimate the Hubble constant. Scientists are yet to find lensed gravitational waves but there’s good reason to believe that they will in the next two decades. The rationale is that while lensed gravitational waves are expected to occur around 0.1% of the time, a decade’s worth of observations should turn up thousands of them. Detectors ‘see’ lensed gravitational waves as multiple copies of the same wave with a time delay.

Source: The Hindu July 17, 2023 08:21 UTC