Scientific.American.Reports.Special.Edition.on.Astrophysics.June.12,2007




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Scientific.American.Reports.Special.Edition.on.Astrophysics.June.12,2007
Published by
Scientifi c American, Inc., 415 Madison Avenue, New York, NY 10017-1111.
(ISSN 1048-0943)
Volume 17
Number 1
2007
92 pages {pdf}
Copyright
© 2007 by Scientific American, Inc.


1 Letter from the Editor
THE FORCES WITHIN

4 The Reluctant Father of Black Holes
by Jeremy Bernstein
Albert Einstein’s equations of gravity are the foundation of the modern view of black holes;
ironically, he used the equations in trying to prove that these objects cannot exist.

12 An Echo of Black Holes
by Theodore A. Jacobson and Renaud Parentani
Sound waves in a fluid behave uncannily like light waves in space.
Black holes even have acoustic counterparts.
Could spacetime literally be a kind of fluid, like the ether of pre-Einsteinian physics?

20 Quantum Black Holes
by Bernard J. Carr and Steven B. Giddings
Physicists could soon be creating black holes in the laboratory.

28 How to Build a Time Machine
by Paul Davies
It wouldn’t be easy, but it might be possible.

VIOLENT BIRTHS

34 The Brightest Explosions in the Universe
by Neil Gehrels, Luigi Piro and Peter J. T. Leonard
Every time a gamma-ray burst goes off, a black hole is born.

42 The Galactic Odd Couple
by Kimberly Weaver
Why do giant black holes and stellar baby booms, two phenomena with little in common,
so often go together?

50 Colossal Galactic Explosions
by Sylvain Veilleux, Gerald Cecil and Joss Bland-Hawthorn
Enormous outpourings of gas from the centers of nearby galaxies may ultimately help explain both
star formation and the intergalactic medium.

58 The Midlife Crisis of the Cosmos
by Amy J. Barger
Although it is not as active as it used to be, the universe is still forming stars and building
black holes at an impressive pace.

BENDING PHYSICS

66 Information in the Holographic Universe
by Jacob D. Bekenstein
Theoretical results about black holes suggest that the universe could be like a gigantic hologram.

74 The Illusion of Gravity
by Juan Maldacena
The force of gravity and one of the dimensions of space might be generated out of the peculiar
interactions of particles and fields existing in
a lower-dimensional realm.

82 Black Hole Computers
by Seth Lloyd and Y. Jack Ng
In keeping with the spirit of the age, researchers can think of the laws of physics as computer programs
and the universe as a computer.