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BY STEVE NADIS
structure of the black holes thought to
litter the universe. Their conversation
led to questions asked all too often at
BHI: What would happen if you fell into
a black hole of this sort? Where would
you go and, more to the point, where
would you die?
What distinguished this discussion
from most at the BHI was that this time,
Narayan, Chesler and Curiel resolved
to actually find some answers to these
enduring questions.
BLACK HOLE BOUNTIES
They were by no means the first to delve
into this issue. In 1915, Albert Einstein
unveiled his general theory of relativity,
encapsulated within 10 exceptionally
complicated equations. They show how
the universe’s distribution of matter and
energy affects its geometry, or curvature,
and how that curvature, in turn, is mani-
fested as gravity.
Less than a year later, Karl
Schwarzschild published the first solu-
tion (one of many) to those equations.
It provided an explicit description of
the gravitational field of an ideal con-
figuration of matter: perfectly spherical,
electrically neutral and non-spinning.
If this mass were compact enough,
Schwarzschild found, the sphere’s cen-
ter would have a bizarre property: Its
curvature and density would be infinite,
resulting in what’s called a singularity,
a literal wrinkle in the fabric of the
cosmos.
Physicists consider such an object,
now called a Schwarzschild black hole,
to be an idealized concept. Actual stuff
in the universe, including black holes, is
always spinning, and has other imperfec-
tions, too.
It was not until 1963, nearly a half-
century later, that the mathematician
and physicist Roy Kerr came up with his
own solution to Einstein’s equations, one
that describes the space and gravitational
field surrounding a real-life, rotating
black hole — subsequently dubbed a
Kerr black hole. However, when other
physicists, building on Kerr’s result, tried
to explore the crazy physics within these
Ta k ing
the Plunge
What physicists found when they finally probed
the insides of realistic black holes.
The average person doesn’t spend a lot of time thinking
about black holes, which is why a place like the Black Hole
Initiative (BHI) exists. Founded in 2016 at Harvard University,
it is the world’s first academic center devoted solely to the study
of these fantastical, enigmatic objects.
After a BHI seminar last year, Harvard astrophysicist Ramesh
Narayan talked with some colleagues — physicist Paul Chesler
and philosopher and physicist Erik Curiel — about the inner
O
«
OUT THERE
What would
happen
if you fell
into a
black hole?
Where
would you
go and,
more to the
point, where
would you
die?