OPINION

NATURE|Vol 459|25 June 2009

“Science journalists don’t get to witness earlier
drafts of history-making because these are partof the peer-review process.” Toby Murcott, page 1054
However, the concept of free
will may become confused if
it is linked with an absence ofdeterminism.
As an example, let us consider
three schoolgirls, X, Y and Z,
confronted with the proof of
Pythagoras’s theorem: X has atalent for mathematics and enjoys
working out proofs; Y is weak inthis domain and is unquestioning;
Z has average ability but herdecisions are capricious. The
teacher instructs them to believe
the theorem because it is correct.
Y accepts it immediately, X first
confirms for herself that the proof
is valid, but Z (possibly influenced
by a ‘quantum event’ in herbrain) refuses to agree. Although
the behaviour of X and Y is
predictable and determined, given
their personalities and abilities,
Z’s is not.
Heisenberg’s suggestion would
support the conclusion that only
Z’s decision was ‘free’. But X could
be judged as the one who madethe really free (autonomous)decision. Y’s decision is formally
free, having been determinedby her accepting nature, but it
is undermined because it stems
from the teacher’s authority. Z’s
reaction is not free at all, because
it was not determined by Z herself
but by a random event in one ormore of her brain cells.
In short, deciding freely does
not imply a lack of determinism— rather, it is determined bycentral aspects of our personality:
our long-term needs, theemotions accompanying their
non-fulfilment, and our rational
thinking about the means tosatisfy those needs. Our decisions
may therefore not be completelyfree, because they are not always
exclusively determined by thesecentral (core) factors. A person
who stops smoking on rational
grounds is freer than another who
makes a decision to stop but fails
to do so.
Quantum events have no
relevance here: the question iswhether we are influenced moreby our core factors than by drives
that are not rationally founded,such as habit, addiction or

external pressure. Consciousness
and the experience of positiveor negative emotions could
well play a part in our decisions:in my opinion, these are notepiphenomena — mere parallel
events — but essential forbringing about determining
factors that underlie our free will.
This would not exclude a purely
naturalistic explanation of theprocesses that we experience as
consciousness.
Etienne Vermeersch University ofGhent, Blandijnberg 2, 9000 Ghent,Belgium
e-mail: etienne.vermeersch@ugent.beReaders are welcome to comment
at http://tinyurl.com/m2ybmo

How air capture could
help to promote a
Copenhagen solution
SIR — Your News Feature ‘Sucking
it up’ (Nature 458, 1094–1097;
2009) reports on the issue of thecapture of carbon dioxide fromair. This is timely, as in February
this year, President Obama andthe Canadian Prime Minister,
Stephen Harper, agreed to work
together on carbon captureand sequestration as part of aneffort to build a North American
environmental and energy accord.
US and Canadian government
funding for ‘carbon capture andstorage’ (CCS) projects hasballooned during the past six
months, and in May the US energy
secretary, Steven Chu, announced
CCS funding of $2.4 billion, which
specified for the first time “CO2capture from the atmosphere”.
Conventional CCS has beenused successfully since 1996,
but it has many critics. It has
been blocked in global climate
negotiations and is likely to be acontentious issue at meetingsof COP15 — the conference of
the United Nations Framework
Convention on Climate Change,
to be held in Copenhagen in
December this year — which will
decide on the future of the Kyoto
Protocol after 2012.

Opposition to CCS, andsupport for the attendant ‘cleaner
coal’ approach, is motivated byincentives to continue using fossil
fuels, rather than making thetransition to renewable sources ofenergy, and by the effort needed
to retrofit and clean up existingfossil-fuel plants, which areresponsible for more than 40%
of global emissions. In new power
plants, conventional CCS can atbest neutralize carbon emissions.
Air capture could satisfy these
critics, as well as potentiallystrengthening the president’sproposal. The technology is underevaluation by the American
Physical Society and is rapidly
gaining support in the business
community. It will encouragenations to cooperate at global
negotiations, including China anddeveloping countries, because
the ubiquity of air means that
this technology can be used byeveryone; small emitters such
as Latin America and Africa
will be able to decrease theiratmospheric carbon beyond
what they actually emit. Whendriven by renewable energy, aircapture will help the transition torenewable energy. Incorporating
air capture into the Clean
Development Mechanism of
the Kyoto Protocol would bea big step forwards.
Two footnotes to your News
Feature are in order. First, G.C.
is co-inventor and co-owner of
the air-capture company Global
Thermostat’s technology. Second,P.E.’s mention of how much it
might cost on a global scale toreduce CO2 is only an estimate —specific costs for the company’s
technology are awaiting data fromthe commercial demonstration
plant that is to be built in thenear future.
Graciela Chichilnisky Departmentsof Economics and Statistics, andColumbia Consortium for Risk
Management, Columbia University,New York, New York 10027, USAe-mail: chichilnisky1@gmail.com
Peter Eisenberger Department ofEarth and Environmental Sciences,
Columbia University, New York,New York 10027, USA)''0DXZd`ccXeGlYc`j_\ijC`d`k\[%8cci`^_kji\j\im\[!"#$%!"#&'()**+,-)./+.0+12.//'''!"#&

Planck’s power lies in
its unique instrument
combination
SIR — Your News Feature ‘The
test of inflation’ (Nature 458,820–824; 2009) highlights someof the exciting scientific data to becollected by the European Space
Agency’s Planck spacecraft, andthe theoretical issues underlying
its objectives to study themoments after the Big Bang.
You discuss the new highfrequency 52-bolometer
detector, but do not mention the22-radiometer low-frequency
instrument (LFI). However, it is
this unique combination of Planck
radiometers and bolometers in
an integrated focal assemblythat is key to achieving the broad
spectral coverage needed toseparate foreground emission ofgalactic and extragalactic origin
from the cosmological signal.
This feature is essential in
searching for subtle signaturesin the cosmic microwave
background, including possible
clues from an inflationary era of
the Universe (such as polarization
B-modes and non-Gaussianity).
Planck’s 70-gigahertz radiometers
will observe the sky in thefrequency band that is least
contaminated by foregrounds,
and with a sensitivity and angularresolution surpassing that of all
previous experiments.
Following the 1989 Cosmic
Background Explorer differential
microwave radiometer and the2001 Wilkinson microwave
anisotropy probe, the Planck
radiometric instrument will
use polarization-sensitive
detectors based on indium
phosphide HEMT (highelectron-mobility transistor)
cryogenic amplifiers cooled to20 K. It is the data from thesedetectors, combined with thebolometer data, that will give
Planck its superiority over its
predecessors.
Nazzareno Mandolesi and Planck LFI
co-investigators IASFBO – INAF,
Via Gobetti 101, 40126 Bologna, Italye-mail: mandolesi@iasfbo.inaf.it

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