You are not in the present. This sounds like the admonition of a cranky guru, but it is – literally – true. The present always escapes us because we aren’t quick enough to grasp it. It’s like a tiny ball of mercury always rolling away from us just out of our reach. That is because our senses aren’t designed to apprehend reality at the precise instant that reality (however defined) actually happens. For instance, when you look at an object or someone’s face you are seeing that object or that face in the past. Admittedly, it’s not very far back in the past – a fraction of a second, but all the same what you are registering in your brain is not what is happening exactly now. (The light transmitting the image has to travel a distance to reach your retinas, after all, and then the brain has to process the information – and that takes time.) So what is now exactly? And how can it be measured? Or can it be? Well, it turns out, that there is another, more obscure measurement of time called the attosecond. One hundred attoseconds is to one second as a second is to 300 million years, which should give you some idea about just how thinly sliced you can carve up a second. While light can zoom around the world seven and a half times in a single second, light can barely make it from one end of a molecule to another in a single attosecond. Scientists can’t even measure a single attosecond; the shortest interval of time that it is possible to measure is12 attoseconds. But if you were capable of perceiving life in attoseconds you wouldn’t be able to watch a movie or a TV show because it would appear to you as a series of still frames. It would be like watching a lugubriously slow slide show – not very entertaining. But we would be able to see a flash of light exactly when it occurred; we would be able, finally, to be here in the now – exactly now – but think of how bored and impatient we would be waiting for everyone – and everything – else to catch up.