A Black Hole Mystery Wrapped in a Firewall Paradox

by Dennis Overbye

The New York Times, August 12, 2013

http://www.nytimes.com/2013/08/13/science/space/a-black-hole-mystery-wrapped-in-a-firewall-paradox.html?hpwhttp://&_r=0&pagewanted=all

This time, they say, Einstein might really be wrong.

A high-octane debate has broken out 

among the world’s physicists 

about what would happen 

if you jumped into a black hole, 

a fearsome gravitational monster 

that can swallow matter, energy and even light. 

You would die, of course, but how? 

Crushed smaller than a dust mote 

by monstrous gravity, 

as astronomers and science fiction writers 

have been telling us for decades? 

Or flash-fried by a firewall of energy, 

as an alarming new calculation seems to indicate?

This dire-sounding debate 

has spawned a profusion of papers, 

blog posts and workshops over the last year. 

At stake is not Einstein’s reputation, 

which is after all secure, 

or even the efficacy of our iPhones, 

but perhaps the basis 

of his general theory of relativity, 

the theory of gravity, 

on which our understanding 

of the universe is based. 

Or some other fundamental 

long-established principle of nature 

might have to be abandoned, 

but physicists don’t agree on which one, 

and they have been flip-flopping 

and changing positions almost weekly, 

with no resolution in sight.

“I was a yo-yo on this,” 

said one of the more prolific authors in the field, 

Leonard Susskind of Stanford. 

He paused and added, 

“I haven’t changed my mind 

in a few months now.”

Raphael Bousso, 

a theorist at the University of California, Berkeley,

said, “I’ve never been so surprised. 

I don’t know what to expect.”

You might wonder who cares, 

especially if encountering 

a black hole is not on your calendar. 

But some of the basic tenets 

of modern science 

and of Einstein’s theory 

are at stake in the “firewall paradox,” 

as it is known.

“It points to something missing 

in our understanding of gravity,” 

said Joseph Polchinski, 

of the Kavli Institute 

for Theoretical Physics 

in Santa Barbara, California, 

one of the theorists 

who set off this confusion. 

Down this rabbit hole are many 

of the jazzy magical mysteries 

of modern physics: Black holes. 

The shortcuts through space and time called wormholes. 

Quantum entanglement, 

also known as spooky action at a distance, 

in which particles separated by light-years 

can still instantaneously appear to remain connected. 

The reward for going down this hole 

could be a new understanding 

of why we think we live in a universe 

with space and time at all, 

with suitably unpredictable consequences. 

After all, if Einstein hadn’t been troubled 

a century ago by logical inconsistencies 

in the Newtonian universe, 

we might not have GPS systems, 

which rely on his theory of general relativity 

to keep time, in our pockets today.

Falling Bodies

Black holes are the most 

extreme predictions of Einstein’s theory, 

which describes how matter and energy 

warp the geometry of space and time 

the way a heavy sleeper causes a mattress to sag. 

Too much matter and energy in one place 

could cause space to sag so far 

that the matter inside it would disappear 

as if behind a magician’s cloak, 

collapsing endlessly to a point 

of infinite density known as a singularity. 

Einstein thought that idea was ridiculous 

when it was pointed out to him at the time, 

in 1916, but today astronomers agree 

that the universe is speckled 

with such dark monsters, 

including beasts lurking 

in the hearts of most galaxies 

that are millions and billions of time 

more massive than the Sun. 

Many of them resulted 

from the collapse of dead stars.

General relativity is based 

on what Einstein later called 

his “happiest thought,” 

that a freely falling person 

would not feel his weight. 

It is known simply 

as the equivalence principle; 

it says that empty space 

looks the same everywhere 

and to everyone.