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6 ASTRONOMY • JULY 2018

BY DAVID J. EICHER

FROM THE EDITOR

Editor David J. Eicher

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D

id you know that if

Earth were squeezed

down into the size

of a grape, it would

become a black hole?

It’s true. Once thought to be

merely hypothetical, or rare,

black holes are now believed

to exist in the universe in the

trillions. In fact, most every

normal galaxy — those more

massive than dwarfs — har-

bors a black hole in its cen-

ter, our Milky Way included.

One of the more

intriguing concepts

associated with black

holes is the so-called

information paradox.

When we combine

two tenets of physics

— quantum mechan-

ics and general rela-

tivity — a conundrum arises

regarding black holes.

Mathematics suggests that

physical information could

disappear permanently into

a black hole, and this would

mean that many physical

states in the universe could

evolve into one state. This,

however, would violate a

widely held principle of sci-

ence: that the value of the

quantum state of a system at

one point in time should

determine its quantum state

at another time.

It’s perplexing stuff,

and the kind of thing that

cosmologists and particle

physicists love to argue

about over a beer. On p. 20,

science journalist Jesse

Emspak eloquently lays out

how new research on black

holes could test the limits

of Einstein’s theories.

While you consider the

black hole information para-

dox, don’t forget some other

amazing facts about these

strange creatures. One of the

staples of science fiction is

the possibility of using black

holes as “wormholes,” travel-

ing to other parts of the cos-

mos and thereby unleashing

all the dreams of countless

sci-fi movies. But there’s a

problem with that idea in

reality. A stellar black hole

would have sufficient gravi-

tational force such that it

would pull you into a miles-

long string of particles before

you entered the “edge” —

the event horizon, the point

beyond which nothing can

escape. So who wants to

travel around the universe as

an ex-human, now a long

strand of spaghetti?

If you approached and fell

into a supermassive black

hole, the kind that inhabits

the centers of galaxies, you

could actually survive

entrance into the event hori-

zon. But the black hole’s

massive singularity at

its center would tear

you apart, and that

would be the story’s

end, regardless of your

stance on the infor-

mation paradox.

So be glad that we

know of lots of black

holes and can share their

amazing physics, and that

we’re beginning to under-

stand all of their cosmologi-

cal implications. But don’t go

traveling near a black hole.

Trust me. It would simply

ruin your whole week.

Yo u r s t r u l y,

David J. Eicher

Editor

Fun with

black holes

Follow the Dave’s Universe blog:

http://www.Astronomy.com/davesuniverse

Follow Dave Eicher on Twitter: @deicherstar

Did you know that if Earth

were squeezed down into

the size of a grape, it would

become a black hole?