Time is everywhere we are. Maybe that’s why we take a lot of things about it for granted: for example that the past is fixed and unchangeable, and that the future is open and changeable.

When is now? As crazy as the question seems at first – after all, now is, surely, right this moment in the present – we also realise that any instant of now will be over before the thought is completed. The present is an amorphous period with fuzzy edges within a continuum of past and future, so we don’t know where it begins or where it ends. All we can know is that our now instantly becomes the past. Although we seem to feel and know what the present moment means that doesn’t make it a temporal fact. Vienna Circle philosopher Rudolf Carnap recounted how Einstein told him that ‘the experience of the now means something special for man, something essentially different from the past and the future, but this important difference does not and cannot occur within physics.’