Comments from physicsworld.com
Recently physicsworld.com has been abuzz with
debate on geoengineering, thanks to the cover
story “Engineering the climate” in the
September issue of Physics World and a series of
online articles on technology-inspired ways to
rejig the environment. The first article described
how tree-shaped sodium-hydroxide absorbers
could scrub carbon dioxide from the atmosphere
(“Engineers call for ‘artificial trees’ to reduce
CO2” 27 August).
Using sodium hydroxide to absorb CO2 is just
entropically stupid. Sodium hydroxide is a co-product in the energy-intensive electrolysis of salt.
What happened to “cradle to grave” economic
accounting? Algae scrubbers for coal-fired power
stations are a better idea as a short-term solution
while we wean ourselves off fossil-fuel energy.
hughlaue, South Africa
Sodium hydroxide is energetically costly, but
alkaline earth orthosilicates – like olivine (aka
peridot) and wollastonite – are not, and finding
cubic myriametres of them is easy. Pulverizing the
necessary smaller amounts is harder, but not as
hard as making and remaking NaOH, and when
pulverized Mg2SiO4 sucks down CO2, entropy
increases. Thus, mining operations have
demonstrated carbon capture and storage on a far
larger scale than artificial trees ever will, and have
done so at zero marginal cost and without any
forethought on the part of the miners.
GRLCowan, Canada
A British company, SolarBotanic, has developed
something similar, except they make natural-
cultural history. One obvious example (of
many) is the conception underpinning our
great cathedrals, which ought at least to be
considered a great humanist achievement.
The religious thought that supports these
concepts is clearly not empty.
I would further argue that it is
Christianity that taught us how to think
scientifically in the first place (although
later, brilliant contributions from Muslim
scholars also deserve acknowledgement).
Ancient Greek thought was mathematical,
not scientific. It is widely acknowledged
that while Aristotle was an outstanding
biologist, he was too deeply misguided as a
physicist to be considered as such. And
Ptolemy’s geocentric synthesis – the
crowning achievement of Greek
mathematics – was considered just that:
a mathematical fiction that saved the
phenomena but was not actually true. It
was the Christian Galileo who was bold
enough to say that it was true that the
Earth went round the Sun. Truth is what
we are after.
Chris Jeynes
Ion Beam Centre, University of Surrey, UK
c.jeynes@surrey.ac.uk
looking artificial trees that convert light, heat,
sound, rain and wind energy into electricity; in
addition, these trees can capture and store CO2
and other pollutants. And they look much nicer.
hankw
Wouldn’t it just be easier to plant trees?
opalescent, US
Planting trees instead of creating artificial ones
seems to be a good idea, but the question is, do we
have enough room for all these trees we’d need to
plant? And I’m afraid the answer is no. I’m also
afraid that these artificial trees will need some
energy to create, even more energy to run, and that
they will run on a type of energy that produces CO2
in some other place, probably defeating their
purpose. The same goes for algae. Let’s let algae
absorb CO2 for a while (check mark: absorbed CO2
quota), then let’s use them as biofuel (check mark:
used biofuels quota) and happily release all
captured CO2 back to the atmosphere.
kasuha, Czech Republic
Days later, physicsworld.com reported on a
study by the Royal Society that discussed the
costs and benefits of several methods
(“Geoengineering could be needed to halt
climate change” 1 September).
Geoengineering is a form of technology that could
be employed on a massive scale and cause
unknown cascading effects (both positive and
negative) to human existence. Scientists are too
quick in implementing technologies without
contemplating the consequences first – all for the
Astrophotography issue
Regarding David Pye and Ray Crundwell’s
picture of Sirius (July p21), I think it is
possible that the colours shown in the star
streak are artefacts of the Bayer pattern on
the front of the camera’s CCD, particularly
if the track is only a few pixels wide. The
Bayer pattern is a layer of dye filters coated
over the CCD glass in a red–green–blue
(RGB) dot pattern. Single CCD cameras
use software to synthesize the final colour
of a pixel from the relative response of a
group of CCD pixels depending on
whether each CCD pixel is behind an R,
G or B filter. So a point source like a star,
finely focused, may not cover enough CCD
pixels and their filters to give the correct
colour balance. Moving the camera to give
a streak just illuminates different groups of
pixels, resulting in a varying colour balance.
So, how wide (in pixels) is the star streak,
and does it cover an adequate number of
pixels to give the correct colour balance?
A related, but opposite, problem in
astrophotography is that a bright star (all
stars are coloured!) saturates all the pixels
sake of “progress”. The geoengineering argument is
fundamentally flawed because it doesn’t first
recognize that it is our technologies that created
this problem to begin with. Throwing another
technology at a problem is not the only solution,
but it is the only one that allows us to continue what
we are doing and maintain the status quo for
humans. We should think very carefully about how
to proceed and why we are proceeding in that
direction. We should consider our personal lifestyle
choices and the impacts they have on the ecology.
Instead of scientists pursuing activities to promote
their research agendas, it would be much better to
see us trying to clarify much of the obfuscation
surrounding the use of technology in everyday life.
Which is easier to change: the world or yourself?
heliostat, Germany
Unfortunately, within the current economic and
technological framework, it may just be easier to
change the world. Rather than causing discomfort
to the over-consumptive masses, we’d tinker with
redoubtable global systems we just don’t
understand. Look, I have a sense of curiosity as
much as the next scientist, but when most of our
scientific and technological advancements have
been made ultimately in the name of consumerism
or war, I am led to question the fundamental value
of progress.
Jarrod, South Africa
Read these comments in full and add your own at
physicsworld.com
in the local Bayer group, and the camera’s
software then interprets the star image as
white, rather than the correct colour.
Simon Fedida
London, UK
windjammer@pobox.com
David Pye and Ray Crundwell reply:
While we recognize that digital
photography can sometimes lead to
artefacts, we feel sure that Simon Fedida is
incorrect in the case of our Sirius streak
image. First, his theory would suggest that
each coloured component of the streak
would only be about as long as it is wide,
but the length actually depends entirely on
how fast the camera shakes (faster shaking
equals longer streaks). Secondly, we have
many out-of-focus images that show the
colour sequences just as clearly;
incidentally, measurements of the sharper,
published image show that the streak is
consistently 4–4. 5 pixels wide. Thirdly, the
phenomenon of coloured scintillation is
already well known; all we did was to
record the effect with a camera in order to
share its beauty. It can be seen easily with
binoculars and we would encourage
