The Cosmic Landscape (62 page)

²
Physicists and chemists refer to ice, liquid water, and steam as three different phases of water: the solid, liquid, and gaseous phases.

³
In Linde’s original work he used the term
Self-Reproducing Universe.
I have used
Eternal Inflation
because it seems to be more common in the current literature on the subject.

⁴
An interesting and important question is whether there is any upward mobility on the Landscape. In other words can one of our fictitious organisms climb up to a higher altitude? The answer implied by the standard rules of quantum mechanics is yes—anything that can happen can also happen in the reverse direction.

⁵
I don’t mean to imply that there is universal agreement. At least one very experienced, highly regarded string theorist, Tom Banks, has argued that the reasoning concerning the Landscape is suspect.

⁶
A googol is defined as 10
¹⁰⁰
, i.e., one with one hundred zeros after it. A googolplex is ten to the googol power.

¹
General relativist:
an expert in Einstein’s General Theory of Relativity.

²
A
bit
is a technical term for an indivisible unit of information—a yes-no answer to a question.

³
The word
see
is being used in a physicist’s sense. It means reconstructing events from the output—in this case, the Hawking radiation. Such reconstruction would be incredibly complex, but in principle, it is just as possible as seeing the ordinary world through the light emitted and reflected from objects.

¹
See, for example, Paul Davies’s 1983 book,
God and the New Physics
(New York: Simon and Schuster).

²
Long after I had written this chapter, while
The Cosmic Landscape
was in the final stages of editing, I happened to read an essay by Richard Dawkins titled “Darwin Triumphant” (reprinted in
A Devil’s Chaplain: Reflections on Hope, Lies, Science, and Love
[New York: Houghton Mifflin, 2003]) in which Dawkins uses the term
Landscape
in exactly the way I am using it here. Some of the concepts are so similar to the ones in this book that at first I thought Dawkins must have access to my computer files. But if he did plagiarize my work, he must have solved the problem of time travel. “Darwin Triumphant” was written in 1991 and published that year in
Man and Beasts Revisited,
ed. M. H. Robinson and L. Tiger (Washington, D.C.: Smithsonian Institution Press).

³
Today, Bousso is professor of physics at the University of California at Berkeley.

⁴
Bulletin: Just as I was about to finish writing this book, Guth wrote a paper (Alan Guth and David I. Kaiser, “Inflationary Cosmology: Exploring the Universe from the Smallest to the Largest Scales,”
Science
307 [2005]: 884-90) in which he said, “This idea—that the laws of physics that we observe are determined not by fundamental laws, but instead by the requirement that intelligent life can exist to observe them—is often called the anthropic principle. Although in some contexts this principle might sound patently religious, the combination of inflationary cosmology and the landscape of string theory gives the anthropic principle a viable framework.” Has Alan just opened the closet door?

⁵
I am delighted to report that as I am writing this book, it has been announced that Gross and two others were awarded the Nobel Prize for their work on QCD.

⁶
Robert Laughlin,
A Different Universe: Reinventing Physics from the Bottom Down
(New York: Basic Books, 2005).

⁷
Of course too large a change in the microscopic starting point could lead to an entirely different macroscopic result—for example, a crystal instead of superfluid.

⁸
See Lee Smolin,
The Life of the Cosmos
(Oxford: Oxford University Press, 1997).

⁹
One might also think that planets shaped in the form of elongated ellipsoids, cubes, or even sea urchins would be solutions of the equations of physics. But this is not so. If the planet were big enough to hold an atmosphere, gravity would quickly pull the material together into the form of a ball. Not everything is possible.

¹⁰
The core of the earth is composed mostly of iron.

¹¹
Not all infinites are the same, according to Cantor. The integers—the even integers and the odd integers—are what mathematicians call a countably infinite set. The number of real numbers, all possible decimals, are a much bigger set that cannot be put into one-to-one correspondence with the integers, but all countable sets are the same size! Pocket universes are like the integers; they are things you can count.