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17
18
January/February 2018^ DISCOVER^27
TOP: WESLEY PEGDEN. BOTTOM: ZAKIR CHOWDHURY/BARCROFT MEDIA VIA GETTY IMAGES
Fighting Politics With Math
❯
EVEN SHORT-LIVED atmospheric greenhouse
gases, like methane, leave an imprint in the
oceans that can last centuries, according to a
paper published in the Proceedings of the National
Academy of Sciences in January.
A hotter atmosphere warms the oceans, which
expand, leading to sea level rise. This can be a slow
process. Gases can take anywhere from a decade
(methane) to 1,000 years (carbon dioxide) to transfer
their energy to the oceans. And once gases arrive
there, it’s hard to get them out. The takeaway is
that if humanity stopped cranking out greenhouse
gases immediately, sea levels would still rise for
centuries before the heat dissipates through Earth’s
atmosphere and into space, says study co-author
Susan Solomon, an atmospheric scientist at MIT.
The study brings grim news for low-lying islands
like Tuvalu in the South Pacific and coastal cities
worldwide. “It’s not a tsunami,” Solomon says of
the watermark rise. “It’s very, very slow. But it’s
inexorable.” ERIC BETZ
Sea Level Rise: Slow But Inexorable
❯
IN MARCH, PENNSYLVANIA
MATHEMATICIANS proved
a theorem that rigorously
demonstrates congressional
districts in their home state are
gerrymandered, drawn to give one
political party an unfair advantage.
Their work, which appeared in
The Proceedings of the National
Academy of Sciences, supports
an ongoing lawsuit demanding
better boundaries and joins
other mathematical efforts to
analyze districting fairness.
The method tests districts by
applying small, random changes to
their boundaries — say, including that
neighborhood instead of this one.
Such tweaks shouldn’t consistently
change election outcomes, assuming
the boundaries started out fair. But
if the changes lead to alternate
outcomes, the mathematicians proved
it meant the district was biased from
the beginning — in Pennsylvania’s
case, in favor of the Republican Party.
“It’s important to have
rigorous ways of demonstrating
[gerrymandering], so the decision
is not just another partisan
debate,” says Wesley Pegden, a
mathematician at Carnegie Mellon
University in Pittsburgh, who worked
on the theorem.
The new work may also be useful
in other scientific areas that involve
random sampling, like how proteins
fold and statistical physics.
STEPHEN ORNES
Sea levels could rise for centuries, in part due to greenhouse gases
transferring their energy to the oceans. This would contribute to
flooding in coastal cities like low-lying Chittagong, Bangladesh.
Slightly tweaking congressional districts can reveal whether
the state in question — Wisconsin here — is gerrymandered.