Supernovas And The Meaning Of “Now”

Many people talk about a star going supernova “now” but not visible to us for a thousand years. It is true that if we see a supernova today, and we if know that it is a thousand light years away, then we can truly say that the light has been a thousand years en route to us. Well and good, but that is not the same thing as saying that the supernova exploded “in the year 1009”. With reservations for hypothetical communication by tachyon or quantum entanglement, the only possible linkage between the explosion of the supernova and the Gregorian calendar is the speed of light, or the speed of information if you will. To put it another way: prior to 2009, there was no possible connection between the event and ourselves. The earliest moment in which a connection can be established, permitting information to arrive, is what we generally call “now”.

Consider how we speak in ordinary life. If you are spotting for me with line-of-sight, and you say, “The general is getting out of the car… NOW”, you don’t explain that he did so a millisecond ago but that the light is only now reaching your eyes. The reason is not only because the time interval concerned is so small as to be hardly measurable and certainly of no practical importance, it is also because in ordinary language, that is what “now” means – the time at which we perceive stuff happening around us.

The times when stuff is not happening around us, we call “past” and “future”. In the case of the supernova, in the only sense of its “happening” that has any meaning for us, it is happening to us “now”, and not in the year 1009. Someone who didn”t know how slow light really is on the galactic scale would look up and say, “Hey, that star is exploding now”, and in fact he would be right to do so; for there can be no access to anything behind the advancing wave-front of information. What hasn’t yet arrived at light-speed hasn’t happened; we can’t say anything about it and can’t do anything with it, we just have to sit and wait for it like Beckett’s two tramps, so we might as well call it the future and be done with it.

Posted on July 13, 2009 at 09:06 by Hugo Grinebiter · Permalink
In: CULTURAL ODDS AND ENDS, Reflections On SF

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  1. Written by Ghost in the Machine
    on July 26, 2009 at 12:54
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    Which is why, I suppose, one has a ten-second delay on many radio and TV shows. And of course a significantly longer delay on news reporting in societies with drastic censorship.

    Hence the size of the anti-government demonstration or its very occurrence may be filtered. So if need be, the supernova doesn’t happen at all!

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