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Canberra Times 07/09/2009
Page: 6 Times Region: Canberra Circulation: 34354 Type: Australian Capital City Daily Size: 348.32 sq.cms MTWTFS-

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Does the universe contain an infinite

number of Kevin Rudds?

The year 2009 is the interTo mark the occasion, the Astronomical Society of
Australia recruited a small group of media-friendly astronomers to

national year of astronomy.

distance between the light and its point of origin. When this is done, our observable universe (the volume of the universe that we can
see) has a radius of about 47 billion light years. If the entire universe is spatially infinite, there are an infinite number of such volumes.

give lectures around Australia to spread the wonders of astronomy to the average punter, tall poppies and tax-paying beer drinkers. For this demographic, I chose to lecture on the controversial question,
"Is there more than one universe?"
yes.

mic microwave background
suggest that the geometry of the
universe is not spherical and finite,

Recent observations of the cos-

Recent observations of the cosmic microwave background suggest

that the geometry of
the universe is not spherical and finite,

The answer, I think, is probably
universe is everything there is, what possible sense does it make
to

but rather flat and infinite. An
ocean. You have a very long and
straight ruler. You hold it up to the

"That can't be

analogy might help to explain how this works. Suppose you are

right! If the

stranded in a boat on the open

but rather flat and
infinite.

talk about other universes?

Where would they be? How could they exist outside everything? The whole idea seems crazy and

horizon and see that the horizon has a small curvature to it. From
this curvature you can deduce the
finite size of the Earth. When we do an analogous geometry-testing

unscientific. And besides, how could you possibly test such an idea?" Despite these objections,
the idea of a multiverse. in some form or other, is being taken
seriously by an increasing number of scientists, led by a vanguard of theoretical cosmologists (e.g. Stephen Weinberg, Alex Vilenkin). The least controversial version of the multiverse idea is based on the

experiment in the universe, we
find the equivalent of a perfectly
flat horizon;

spatially infinite universe. There

consistent with a

are always uncertainties in our

observations so we cannot say for

sure that the entire universe is
spatially infinite. For example, if, in

idea that our finite observable

universe is embedded in a (possibly) infinite universe. Because of

the boat you measure a flat horizon, maybe you are on a planet that is so big that the curvature of the horizon is too small to
measure. With this caveat in mind,

the finite speed of light and the 13.7 billion-year age of the universe, light can only travel a certain distance during the 13.7 billion

the more precise our
measurements have become over

the past decade, the flatter our
entire universe is spatially infinite.

years since the Big Bang. The educated but nave reader will
estimate this distance to be

observable universe seems to be -

consistent with the idea that the

be true if the universe were not expanding. In an expanding uni-

13.7 billion light years. This would

verse we have to include a correction factor for the expansion of the

This has some important implications. One is that there are an infinite number of independent observable universes. That is. we

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Canberra Times 07/09/2009
Page: 6 Times Region: Canberra Circulation: 34354 Type: Australian Capital City Daily Size: 348.32 sq.cms MTWTFS-

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reader of this newspaper would
can divide the entire infinite universe into an infinite number of finite volumes whose centres are
more than 2 x 47 billion light years

estimate the probability of a Kevin Rudd evolving on a terrestrial planet as very, very small. Call this

their probability of happening is zero. If their probability is zero,
then they would not evolve again, even in an infinite universe.

probability "e". Maybe "e" is as
small as one part in a googol (i.e. 10 to the power of -100) or maybe it is

away from each other. We place
each volume that far apart because

The wonderful dilemma these considerations lead us to is that
either there are an infinite number of Kevin Rudds in the universe or that the probability of Kevin Rudd evolving is zero. Either way, this is just one of the lip-biting perplexities that the International Year of Astronomy invites us to ponder.
Dr Charles H. Lineweaver is from the Planetary Science Institute, Research School of Astronomy and Astrophysics and Research School of

one part in a googolplex (i.e. 10 to

that makes them independent of
each other. No event that has ever

the power of -googol). It doesn't
matter how small "e" is, as long as it is not zero. If "e" is not zero then there will be an infinite number of Kevin Rudds in the universe, since "e" times infinity equals infinity:
"e" x 8 = 8 . However, it is not easy

happened in one ball has ever affected anything in the neighbouring balls. In a very real sense, these independent observable universes are other universes, beyond our observable universe. If there are an infinite number of independent universes, then anything that can happen, will happen

to guesstimate the probability for

an independent volume of the

in one of them. Any objective

universe to produce a particular human being. I suspect that
individuals may be so quirky, that

Earth Sciences, at the Australian
National University.

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