So SSC reckons its upcoming 1,750bhp Tuatara could be the worlds first 480kph production car. Engineering a car to do that sort of speed is such a leap into the (very expensive) unknown that you might not bet your pension pot on SSC hitting 480kph, at least not imminently.But its seeming increasingly inevitable that, at some point in the foreseeable, well witness a production car crack the triple-tonne. If not SSC, then maybe Koenigsegg. Or Bugatti. Or Hennessey. Maybe Dacia will make a late dash for it.Point is, assuming youre not, say, a dentist to great white sharks, if youre reading this, theres a very good chance youll live to see a world containing a bona fide 480kph road car.All of which got Top Gear – never a publication to turn down the chance for a bit of idle speculation – thinking. Forget 480, when might we see the first 640kph car? So we did some back-of-barmat calculations, and it turns out the answer is…April 11, 2079.Yes, according to science, thats the date upon which a production car will break the 640kph barrier. Youre welcome, world.Theres some irrefutable maths at work here. Admittedly maths performed by an editorial team with an average D-minus maths grade, but hey, at least that was achieved back in the days when a D-minus really meant something.Take a look at the graph above and youll see weve plotted the history of production car speed records over the last century-and-a-bit, from the Benz Velos 19kph in 1894, to the 445kph hit by the Koenigsegg Agera RS last year.True, production car speed records are notoriously disputable (just ask Mr Hennessey), and true, our source data came from Wikipedia. But even if you want to quibble the veracity of a few of the records, the general trend is pretty clear. And surprisingly linear.Wed rather thought that the trend line might show some flattening off in the last couple of decades, the rate of progress slowing as cars pushed further at the outer reaches of physics. Not so, it would seem. In fact, the Koenigsegg Agera RSs 445kph run last year was actually slightly ahead of the curve. Or, rather, ahead the straight line.So, assuming cars keep accelerating at the same rate, April 11, 2079 is when the 640kph barrier shall be broken. Sixty years time. Should be a good day, assuming the human race is still in existence at that point.And if the notion of a 640kph road car – a car that could cover nearly 180 metres in a second, a car that could theoretically, at full chat, circle the equator in just two-and-a-half days – sounds absurd, remember that 60 years is a long time in the automotive world.Sixty years ago, after all, the Aston Martin DB4 GT was just edging past 240kph. Back then, would the thought of a road car nudging 480kph within six decades would not have sounded even more implausible than a 640kph, licence-plate-wearing car seems today?2079, mark our words. Its going to happen. Of course, therell be the small matter of finding a piece of road long enough to get to 640kph. But hey, Bugatti and Koenigsegg and the rest have got a bit of time to call around local tarmacking firms to find some competitive quotes. They could all pitch in together, keep costs down.And then therell also be the small matter of finding a driver daft enough to keep whatever-it-is pinned to 640.We suspect a proper statistician might tell us our sample size is too small, or weve forgotten to carry the one, or were fundamentally too stupid to attempt this sort of mathematical crystal-ball gazing. But if you think you can do so much better, Professor So-Called Brian Cox, hit us with your equations in the comments section below.As a bonus, our Nobel-worthy maths also allows us to calculate precisely the date the 480kph will be broken, too. November 12, 2029. A Monday, conveniently. Weve already booked the day off work.