This week–
saswato das
SOME cosmologists think that our
universe has been cycling through
an endless series of big bangs and
big crunches. If so, it implies the
universe is doomed to repeat the
same thing over and over. A new
study, however, suggests that with
each big bang, the universe mostly
forgets its past and starts anew.
The accepted wisdom in
modern cosmology is that it is
meaningless to ask what came
before the big bang. That’s because
the big bang is what physicists
call a “singularity” – a moment
at which the equations of physics
break down. “No one is happy
with the big bang singularity,”
“Most, but not all, of the
information about what
came before the big bang
gets irretrievably lost”
says Martin Bojowald, a theorist
at the Pennsylvania State
University, University Park.
Bojowald works on loop
quantum gravity (LQG) – a theory
that seeks to unify the otherwise
incompatible theories of
general relativity and quantum
mechanics. In LQG, space-time
is made of tiny interconnected
loops, each only 10-35 metres
across, that form a smooth fabric
16 | NewScientist | 7 July 2007
much like a shirt’s fabric is
smooth even though it is woven
from separate threads.
Bojowald and his colleagues
have run the equations of LQG
backwards and shown that they
can avoid the singularity. They
showed that as the universe
collapses, it reaches a point at
which it bounces back in a big
bang, and the process repeats
(New Scientist, 24 April 2006, p 15).
Does that mean that one day
we can, either mathematically or
via observations, know about the
pre-big bang universe? To answer
this question, Bojowald developed
a simple LQG model to determine
the limits of what we can know. In
his model, he assumed that the
physical properties of the universe
were the same everywhere
and that the kind of matter it
contained did not interact with
itself. The model included gravity
but not radiation.
The model showed that most,
but not all, of the information
about what came before the big
bang gets irretrievably lost
through the big bang transition.
And in a perpetual cycle of big
bangs and crunches, this
information loss means no two
universes are ever the same.
Bojowald calls this “cosmic
forgetfulness” (Nature Physics,
DOI: 10.1038/nphys654).
Cosmologist Paul Steinhardt
of Princeton University says
that Bojowald’s model is right
in principle. “It’s important to
lose some information, but not
everything,” he says.
Thomas Thiemann of the Max
Planck Institute for Gravitational
Physics in Golm, Germany, says
that although some of Bojowald’s
assumptions may turn out to be
too simple, the model is “the
cleanest derivation of a pre-big
bang scenario that any physical
theory has delivered so far”. l
Clive Champion/Foodpix/Jupiter
Before the big bang
there was amnesia
–Better starve ’em?–
Organic tomatoes
win on level
farming field
IS ORGANIC food healthier for you,
after all? A 10-year study comparing
organic tomatoes with those grown
conventionally suggests that it may
be. It’s the kind of evidence that proorganic groups have been desperate
to dig up, as most studies have
suggested otherwise.
According to the new findings,
levels of the flavonoids quercetin
and kaempferol were found to be on
average 79 and 97 per cent higher,
respectively, in organic tomatoes.
Flavonoids such as these are known
antioxidants and have been linked
to reduced rates of cardiovascular
disease, some forms of cancer and
dementia, says Alyson Mitchell, a
food chemist who led the research at
the University of California, Davis.
Differences in soil quality,
irrigation practices and the handling
of harvested produce have made
direct comparisons difficult in the
past, says Mitchell. So in this study,
due to be published in the Journal of
Agricultural and Food Chemistry, the
researchers used data from a longterm project in which standardised
farming techniques are used to
reveal trends in crop productivity.
Mitchell’s team say the finding
can be explained by the availability
of nitrogen. Flavonoids are produced
as a defence mechanism that can be
triggered by nutrient deficiency. The
inorganic nitrogen in conventional
fertiliser is easily available to plants
and so, the team suggests, the lower
levels of flavonoids are probably
caused by overfertilisation.
Previous research has found no
differences between organic and
conventional crops such as wheat
or carrots. Meanwhile a study
proclaiming that organic milk had
higher levels of omega-3 fatty acids
failed to convince the UK’s Food
Standards Agency (FSA), which
pointed out that these short-chained
fatty acids do not have the healthpromoting benefits offered by longchained omega-3 oils.
This latest study does not prove
that a healthy diet must be organic.
The evidence of health benefits for
flavonoids is conflicting, says Peter
Bramley at Royal Holloway, University
of London. And even if such benefits
exist, higher flavonoid levels do
not necessarily make organic food
healthier, says John Krebs, former
chair of the FSA and now at the
University of Oxford. “This depends
on the relevance of the differences to
the human body,” he says. “Tomato
ketchup has higher levels of lycopene
than either organic or conventional
tomatoes. So if you wanted lots of
lycopene you should eat ketchup.”
Duncan Graham-Rowe l
www.newscientist.com