Incredible Journeys:
Exploring the Wonders of
Animal Navigation
David Barrie, Hachette
Australia, $32.99 (paperback)
Interweaving
interviews with
leading animal
behaviour experts
and groundbreaking
discoveries of Nobel
Prize-winning
neuroscientists,
author David Barrie
takes us on a tour of animal
navigation science. A stunning
diversity of animal navigators use
senses and skills we don’t have.
This book reveals these wonders.WikiCamps
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S
INCE THE APOLLO lunar landings
of the 1960s and ’70s, we have
understood that the Moon was
formed early in the Solar System’s
history as a result of something
colliding with the Earth.
An earlier hypothesis that the Moon
was an asteroid captured by our planet’s
gravity was discarded following the
discovery that the lunar rock and soil
samples returned by the Apollo
astronauts have identical chemistry to
those on Earth. The idea then became
accepted that early Earth suffered an
impact by an object about the size of
Mars that ejected a massive plume of
debris, which subsequently coalesced to
form the Moon. So confident were
planetary scientists of this scenario that
they even gave the impacting object a
name: Theia, after the mother of Selene
(the Moon) in Greek mythology.
But there was a problem. In any
random set of circumstances, the debris
lifted by the collision would be
composed mostly of material from
Theia. And planetary scientists esti-
mated that the chance of Theia having
the same composition as the Earth wasless than 1 per cent. More unlikely
scenarios were then explored, includ-
ing collisions at steep angles and very
low velocities.
Now, a new theory seems set to
solve the problem. Proposed by scien-
tists in the USA and Japan, it postulates
the collision occurred within the first
50 million years of the Earth’s existence
when its surface was an ocean of
molten magma. Theia, being smaller,
would have had a cooler, solid surface,
and the theory suggests much less of
its material would have gone into
the Moon.
This idea neatly solves the problem
of the Moon’s Earth-like composition
and also gives us new insight into
conditions in the early Solar System.Q:Are there any
‘lone stars’ between
the galaxies, and, if so,
how common are they?
Why are they not part of
a galaxy themselves,
if this is the case?
Would there be exoplanets
orbiting those lone stars?
Tim Burn, Adelaide, SAA: Yes, such stars do
exist. They’re known
as intergalactic stars,
and the first ones were
discovered back in 1997
using the Hubble Space
Telescope. They are
thought to be relatively
numerous, perhaps
accounting for half thestars in the Universe.
They have probably been
ejected from their parent
star systems by galaxy
collisions, or by encounters
with the supermassive
black holes at their
centres. And they could,
indeed, have their own
orbiting planets.Read
Analysis of lunar rocks from the Apollo
era suggest the Moon–Earth shared history
may have been more violent than we thought.ILLUSTRATION BY DANA BERRY/SWRI
buzz
FRED WATSON
is Australia’s
Astronomer-at-Large.July. August 23FRED ANSWERS YOUR QUESTIONS
Making our Moon
SPACE
One Strange Rock
Directed by American filmmaker
Darren Aronofsky and narrated
by actor Will Smith, this cinematic
series brings Hollywood to the
realm of natural history. In 10
hour-long episodes it explores
the fragility and wonders of life
on Earth as seen through the
eyes of the only people to have
left it behind – astronauts.
It combines science with the
perspectives of those who have
observed our planet from both
near and far.Watch