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Between the past and the future of an event (for example, between the past and the future for you, where you are, and in the precise moment in which you are reading), there exists an “intermediate zone,” an “extended present”; a zone that is neither past nor future. This is the discovery made with special relativity. The duration of this “intermediate zone,”* which is neither in your past nor in your future, is very small and depends on where an event takes place relative to you, as illustrated in figure 3.2: the greater the distance of the event from you, the longer the duration of the extended present. At a distance of a few meters from your nose, the duration of what for you is the “intermediate zone,” neither past nor future, is no more than a few nanoseconds: next to nothing (the number of nanoseconds in a second is the same as the number of seconds in thirty years). This is much less than we could possibly notice. On the other side of the ocean, the duration of this “intermediate zone” is a thousandth of a second, still well below the threshold of our perception of time, the minimum amount of time we perceive with our senses, which is somewhere on the order of a tenth of a second. But on the moon, the duration of the “extended present” is a few seconds, and on Mars it is a quarter of an hour. This means we can say that on Mars there are events that in this precise moment have already happened, events that are yet to happen, but also a quarter-of-an-hour of events during which things occur that are neither in our past nor in our future. They are elsewhere. We had never before been aware of this “elsewhere” because next to us this “elsewhere” is too brief; we are not quick enough to notice it. But it exists, and is real. This is why it is impossible to hold a smooth conversation between here and Mars. Say I am on Mars and you are here; I ask you a question and you reply as soon as you’ve heard what I said; your reply reaches me a quarter of an hour after I had posed the question. This quarter of an hour is time that is neither past nor future to the moment you’ve replied to me. The key fact that Einstein understood is that this quarter of an hour is inevitable: there is no way of reducing it. It is woven into the texture of the events of space and of time: we cannot abbreviate it, any more than we can send a letter to the past. It’s strange, but this is how the world happens to be.
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