I have been studying Hulse Taylor PSR 1913+16 calculation of period shift which is regarded as indirect proof for gravitational waves, but I dont understand one thing. If you look on the graph of Cumulative period shift, around every 10 years the shift doubles. https://en.wikipedia.org/wiki/File:PSR_B1913+16_period_shift_graph.svg It is in seconds, so it seems no big deal, but the final inspiral is calculated to happen in 300 millions years, which a lot of time. But when the cumulative period continues to double like every 10 years, the final inspiral would happen much sooner, estimating it certainly at less than 100 000 years. So what is wrong with my understanding of it? Is the period shift something which has some periodic nature, so the period shift is not always decreasing, but also increasing? I couldnt find any published detailed description of the calculation and how this would fit both geometrically increasing period shift and 300 millions year to inspiral. It would be helpful, if somebody could link detailed and complete calculation.