Some Science

The best of science, the worst of creationism

In 2000, a popular school textbook called Biology reluctantly dropped it’s prime example of evolution in action – industrial melanism in the peppered moth. Nothing in evolutionary biology had forced the change. The decision was entirely political,made in response to creationist attacks.

The loss of the peppered moth was a blow to science education in the US, as it is one of the easiest to understand examples of evolution by natural selection. So it is heartening to hear that biologists are fighting back. Thanks to their efforts, evidence that the moth is an example of evolution in action is more robust than ever.

This tawdry tale reveals much of what is good about science – and rotten about creationism. Creationists went gunning for the moth after a scientific disagreement over the fine detail of a seminal experiment done in the 1950s. They used the debate to portray the science behind industrial melanism as hopelessly flawed, if not fraudulent.

In response, one scientist patiently redid the experiment – it took him seven years. It is hard to think of another system of thought that is so stringently self-critical and self-correcting.

In science, everything is provisional . There are no preordained answers and fresh ideas are always welcome, so long as their proponents are happy for them to be tested.

That is not how creationists work. They already know the answer. They seek only evidence that confirms their conclusion, and distort or ignore the rest. Such an unreasoned approach is worthless. Creationists will keep trying to undermine the theory of evolution.

All science can do is continue, with dignity, to stick to it’s guns. As with the peppered moth, the best testable explanation will win out.

Conspiracy? Not in China

There’s no stopping a good conspiracy theory. For over 30 years, NASA has faced allegations that it faked the moon landings, and now it is the turn of the Chinese.

In October, the Chinese spacecraft Chang’e 1 entered lunar orbit, and last week the country released its first image of the lunar surface. Within hours of the picture’s release the internet rumour mill leapt into action on various Chinese blogs and forums, casting doubt on it’s validity and saying it bore an uncanny resemblance to a picture released by NASA in 2005.

The Chinese space agency replied that the pictures are similar because they are of the same part of the moon. NASA’s experience with conspiracy theories suggests that denying the rumour will only serve to keep it running. Ouying Ziyuan, chief scientist for the lunar probe, more or less guaranteed this by adding: “There is absolutely no forgery.”


Our solar future

In theory, solving the world’s energy problems should be pretty straightforward. Locate a piece of sun-drenched land about half the size of Texas, find a way to capture just 20 per cent of the solar energy that falls there and bingo – problem solved. You have enough power to replace the world’s entire energy needs using the cleanest, most renewable resource there is.

Can it really be that easy? For years, supporters of solar power have heralded every new technological breakthrough as a revolution in the making. Yet time and again it has failed to materialise, largely because the technology was too expensive and inefficient and, unlike alternatives such as nuclear and wind power, no substantial subsidies were available to kick-start a mass transition to solar energy. This time things are different. Aconfluence of political will, economic pressure and technological advances suggests that we are on the brink of an era of solar power.

The prospect of relying on the sun for all our power demands – conservatively estimated at 15 terawatts in 2005 – is finally becoming realistic thanks to the rising price of fossil fuels, an almost universal acceptance of the damage they cause, plus mushrooming investment in the development of solar cells and steady advances in their efficiency. The tried-and-tested method of using the heat of the sun to generate electricity is already hitting the big time but the really big breakthroughs are happening to photovoltaic (PV) cells.

Ever since the first PV cell was created by Bell Labs in 1954, the efficiency with which a cell can convert light into electricity has been the technology’s Achilles’ heel. The problem is rooted in the way PV cells work. At the heart of every PV cell is a semiconducting material, which when struck by a photon liberates an electron. This can be guided by a conductor into a circuit, leaving behind a “hole” which is filled by another electron from the other end of the circuit, creating an electric current.

Photons from the sun arrive at the semiconductor sporting many different energies, not all of which will liberate an electron. Each semiconducting material material has a characteristic “band gap” – an energy value which photons must exceed if they are to dislodge the semiconductor’s electrons. If the photons are too weak they pass through the material, and if they are too energetic then only part of their energy is converted to electricity, the rest into heat. Some are just right, and the closer the photons are to matching the band gap, the greater the efficiency of the PV cell.

Bell Labs discovered that silicon, which is cheap and easy to produce, has one of the best band gaps for the spectrum of photon energies in sunlight. Even so, their first cell had an efficiency of only 6 per cent. For a long time improvements were piecemeal, inching up to the mid-teens at best, and at a cost only military and space exploration programmes could afford. The past decade has seen a sea change as inexpensive cells with an efficiency of 20 per cent have become a commercial reality, while in the lab efficiencies are leaping forward still further.

Last year, Allen Barnett and colleagues at the university of Delaware, Newark, set a new record with a design that achieved 42.8 per cent energy conversion efficiency. Barnett says 50 per cent efficiency on a commercial scale is now within reach. Such designs, married to modern manufacturing techniques, mean costs are falling fast too.

As a result, in parts of Japan, California and Italy, where the retail price of electricity is among the world’s highest, the cost of solar-generated electricity is now close to, and in some cases matches, that of electricity generated from natural gas and nuclear power, says Michael Rogol, a solar industry analyst with Photon Consulting, based in Aachen, Germany. For example, in the US the average price of conventionally generated electricity is around 10 cents per kilowatt-hour. The cost of solar-generated electricity has fallen to roughly double that. This has created a booming market for PV cells – now growing by around 35 per cent annually – and private investors are starting to take a serious interest. The value of stocks in companies whose business focuses primarily on solar power has grown from $40 billion in January 2006 to more than $140 billion today, making solar power the fastest-growing sector in the global marketplace.

George W. Bush has acknowledged this new dawn, setting aside $168 million of federal funds for the Solar America Initiative, a research programme that aims to make the cost of PV technology competitive with other energy technologies in the US by 2015. Rogol thinks Bush’s target is achievable. He says the cost of manufacturing PV equipment has fallen to the point where, in some places, PV-generated electricity could already be produced for less than conventional electricity. Manufacturing PV cells at $1 per watt of generating capacity and the cost should be competitive everywhere.

Perhaps surprisingly, given its less than cloudless skies, one of the countries leading the solar revolution is Germany. In November 2003, amid rising oil and gas prices and growing concern over global warming, its parliament agreed a “feed-in-tariff” programme, which guarantees a market for solar power. Anyone who produces electricity from solar power can sell it to the national grid for between €0.45 and €0.57 per kilowatt-hour, which is almost three times what consumers pay for their electricity, roughly €0.19 per kilowatt-hour. Germany’s power-generating companies are required by law to pay this premium which is guaranteed until 2024. This guarantee has spurred enterprising individuals to invest in solar panels, confident of earning back the cost of their systems.

Source:  New Scientist


One Response to Some Science

  1. Calliope says:

    Not the moth 😮 I loved that over drawn and mostly singular example 😦 Granted it was a bit of a relief when the book finally moved onto embryology…you can only hear about a moth for so long before it gets a bit tediuous… The swallows were a good break though. They fly and sit on trees but they didn’t evolve solely in colour like the moths. Yay Swallows!

    Yeah…if it wasn’t obvious that’s the book I used >.>

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