## The Bistromathic Drive – a HHGG geek out flashback

The Bistromathic Drive is a starship propulsion system introduced in the The Hitchhiker’s Guide to the Galaxy novel Life, the Universe and Everything, the third book of the series.

The Bistromathic Drive is used in Slartibartfast’s craft Bistromath and works by exploiting the irrational mathematics that apply to numbers on a waiter’s bill pad and groups of people in restaurants.

The novel Life, the Universe and Everything describes bistromathics as follows:

“ Bistromathics itself is simply a revolutionary new way of understanding the behaviour of numbers. Just as Albert Einstein’s general relativity theory observed that space was not an absolute but depended on the observer’s movement in time, and that time was not an absolute, but depended on the observer’s movement in space, so it is now realized that numbers are not absolute, but depend on the observer’s movement in restaurants. ”

Further explanation of the theory behind bistromathics:

“ The first nonabsolute number is the number of people for whom the table is reserved. This will vary during the course of the first three telephone calls to the restaurant, and then bear no apparent relation to the number of people who actually turn up, or the number of people who subsequently join them after the show/match/party/gig, or to the number of people who leave when they see who else has shown up.

The second nonabsolute number is the given time of arrival, which is now known to be one of those most bizarre mathematical concepts, a recipriversexcluson, a number whose existence can only be defined as being anything other than itself. In other words, the given time of arrival is the one moment of time at which it is impossible that any member of the party will arrive. Recipriversexclusons now play a vital part in many branches of mathematics, including statistics and accountancy, and also form the basic equations used to engineer the Somebody Else’s Problem field.

The third and most mysterious piece of nonabsoluteness of all lies in the relationship between the number of items on the bill, the cost of each item, the number of people at the table and what they are each prepared to pay for. (The number of people who have actually brought any money is only a sub-phenomenon in this field.)

”

The bridge instruments of the Starship Bistromath are ensconced in fake wine bottles.

The central computational area is a fake Italian restaurant table with seating for twelve encased in a glass cage. The table is decked with a faded red and white check tablecloth with mathematically positioned cigarette burns. A group of robot customers sit round the table, attended by robot waiters.

The mathematics play themselves out in the complex interplay between continuously circulating keys, menus, watches, cheque books, credit cards, bill pads and scribblings on paper napkins.

Slartibartfast explains that “On a waiter’s bill pad, numbers dance. Reality and unreality collide on such a fundamental level that each becomes the other and anything is possible.”

Should the ship’s captain sit at the table, the mathematical functions speed up; the customers become more vociferous and wave at each other. Eventually, the equation balances, and the customers become polite and civil once more. The more heated the argument, the more complex the equation, and the farther the ship may travel.

Effectively, the ship takes advantage of the strange rules that only restaurants operate under by turning itself into a controlled, artificial restaurant. This allows a ship equipped with a bistromathic drive to accomplish feats quite outside the normal capabilities of spacecraft, such as travelling two thirds across the galactic disk in a matter of seconds. The drive is notably more controllable than the Infinite Improbability Drive. It is also said to “make the Heart of Gold seem like an electric pram.”