This is the second part of three posts in which I wanted to lay out the various possible causes of concern regarding the BICEP2 result, and provide my own opinion on how seriously we should take these worries. I arranged these reasons to be sceptical into three categories, based on the questions
- how certain can we be that BICEP2 observed a real B-mode signal?
- how certain can we be that this B-mode signal is cosmological in origin, i.e. that it is due to gravitational waves rather than something less exciting?
- how certain can we be that these gravitational waves were caused by inflation?