When New York Mayor Michael Bloomberg imposed odd-even gas rationing in the city, he announced that people
with license plates "ending in an
even number or the number zero will be able to buy gas or diesel only on even
numbered days.”

So does that mean zero is an even number?

A New York Times story by Vivian Yee addresses this issue. Yee
quotes Walter
Neumann, chair of Barnard
College mathematics department, who says there’s no question. He explained that even integers, or
whole numbers, are numbers that can be divided by two without producing a
non-whole number. Four divided by
two equals two, five divided by two produces 2.5. Zero divided by two equals
zero, with no fraction or decimal left. So that should settle it, right?

Professor Hossein Arsham of the University of Baltimore
who has written about the concept of zero, told the Times that when an odd-even license plate driving system was
imposed in Paris in 1977 to reduce traffic during a smog alert, people whose
plate numbers ended in zero drove around whenever they wanted because police
weren’t sure how to categorize zero.

Roots of the concept of zero are shrouded in the deep past. The Babylonians used a symbol
considered to be an ancestor of zero as a place holder—a mark used to
distinguish—in our numbers—the difference between 1, 10 and 100. The ancient Greeks contemplated the
philosophical question of how nothing could be something, and wondered about
the existence of zero and the concept of the vacuum.

A Scientific American article by John Matson says the
number zero as we know it today was brought to the West about 1200 by the
Italian mathematician Leonardo of Pisa, also known as Fibonacci, who learned about Hindu-Arabic numerals when he
traveled in North Africa.
Fibonacci, considered the most talented Western mathematician of the
Middle Ages, realized the Arabic system made math more efficient than using
Roman numerals, and published a book that popularized the system in
Europe. Matson quotes Charles
Seife, the author of Zero: The Biography of a Dangerous Idea, as explaining that the idea originated in
the Fertile Crescent around 350 BCE, developed in India and moved through North
Africa before Fibonacci found it.
He explains that a "full throated zero” isn’t just a place holder, it’s
the average of minus one and plus one.

Matson also quotes Robert Kaplan, the author of
The Nothing That Is: A Natural History of Zero, as explaining that zero as a number in its own right began to take shape in
India, in the fifth century AD. But he says it was slow to spread because in
some cultures, the notion of zero had dark and magical connotations. Interestingly,
he adds, the idea of zero appeared in Mayan culture in the New World,
apparently from scratch, independent of discoveries elsewhere.

In New York, motorists with plates ending in an odd number
or a letter could fill up on odd numbered days. When Gov. Chris Christie
announced odd-even gas rationing in New Jersey—which
was in effect from Nov. 3 to Nov. 12—the
philosophical and mathematical nature of zero was left officially unaddressed,
as was the positioning of letters on the plate. Some drivers whose license
plates ended with letters rather than numbers thought they might get away with
exemption from the rule, but that didn’t fly with police, gas station
attendants, or motorists waiting in lines.