Chemistry – Mark Lorch
News about carbon dioxide generally focuses on how we are producing way too much of it, resulting in the twin environmental evils of climate change and ocean acidification. So it is somewhat surprising to hear that, this summer, the UK and much of Europe has been suffering from a CO2 shortage. Booker, a wholesaler to bars and restaurants, is rationing sales. And soft drinks giant Coca-Cola says its UK bottling plant was interrupted by the shortage.
Despite what we hear about the environmental impact of carbon dioxide, the chemical actually has a multitude of uses, particularly in the food industry. Most obviously, it provides the bubbles in your beer and fizzy drinks. But it also has a host of other uses. It is used to stun chickens before they are slaughtered; foods are packaged in the gas to keep them fresh; and frozen carbon dioxide (dry ice), at -80C, is used to keep food cold during shipping.
Given the masses of CO2 we produce from burning fossil fuels, why the shortage? The thing is that extracting CO2 from the air is actually quite difficult, as it only makes up 0.04 per cent of the atmosphere. Instead, the primary source of CO2 for use in food and drinks is as a by-product of the fertiliser industry.
The key part of fertiliser production is the Haber-Bosch process, which reacts hydrogen gas with nitrogen to produce ammonia. The source of nitrogen is simple: there’s plenty of it in the air. The hydrogen gas is more difficult to get hold of, but the most common way is through steam-reforming, which involves mixing natural gas and steam at very high temperatures. As well as hydrogen gas, this process creates carbon dioxide, which is captured and bottled for the various industries that need it.
Over the summer there isn’t a huge demand for fertiliser, which mainly gets used in the autumn and spring. Since there isn’t a huge amount of call for their main output, CO2 production plants schedule their maintenance to take place during the summer. And this year they’ve all done it at once. That’s why, although there may have been plenty of heat this summer, the fizz has been rationed.
Mark Lorch lectures in chemistry at Hull University
Biology – Lydia Leon
The first appearance of zero as a symbol representing numerical “nothing” has been traced back to fourth-century India. This critical development underpins mathematics, physics and the computational advancements upon which the modern world rests. An understanding of this most abstract of numbers generally appears in children at around four years old.
Other cognitively advanced animals such as chimps, rhesus monkeys and African grey parrots can also conceptualise the absolute and relative meaning of zero. A recent study published in Science demonstrated this capacity in the honey bee. Bees have previously been shown to use tools, learn from each other, possess elaborate short-term memory and count up to four. But this is the first evidence of them dealing with abstract concepts.
In the experiments, the bees were shown white cards with between two and five dark shapes on them. One group was rewarded with sugary water when they flew to cards with higher numbers and others were rewarded when they went to lower numbers. Once the scientists were convinced they understood the concepts of “less” and “more” they introduced new cards with either one or no (zero) shapes on them to test whether they would rank the blank display at the bottom of the sequence. The bees consistently identified the card with no shapes on it as that of the lowest value when tested over subsequent experiments. The accuracy of their discrimination between zero and bigger numbers was higher when the difference in magnitude the blank and the contrasting cards was greater. This shows, critically, that the empty card had numerical meaning.
The Australian team now have plans to research how the brains of these bees work to process and understand zero. The research will have implications beyond a greater understanding of these fascinating creatures. Working out how an organism with fewer than one million neurons (humans have over 86 million) can efficiently perceive something so abstract also has exciting implications for artificial intelligence research.
Lydia Leon has a PhD in women’s health from University College London
Physics – Ceri Brenner
Dark matter: it’s a cosmology puzzle. This hypothetical form of matter has never been observed directly. Scientists argue it exists on the basis that the universe is expanding and that the expansion rate now is faster than it was. How is it that, with all the gravitational force from matter that we see, the universe is still expanding? This is where the theories of dark energy and dark matter come in. Theoretical models that describe an ever increasing rate of expansion predict that the universe is 68 per cent dark energy, 27 per cent dark matter and only five per cent observed matter.
So, what is dark matter? We don’t have an answer, just a few ideas. That, in essence, is what physics is all about – someone has an idea, someone thinks about how to test it, someone analyses whether the observation agrees or disagrees with the idea. The peer review process assesses whether the idea, the data, and the discussion are suitable to be published.
With dark matter being, well, dark, then how do we observe and test these ideas? We instead need to make indirect observations by looking at the observable parts of the universe to see if dark matter is impacting them in any way that might indicate its properties. The EDGES collaboration has managed an extraordinary feat by observing electromagnetic signals emitted from just 180 million years after the Big Bang. Their paper, published recently in Nature, describes how observations of the very early Universe when the first stars were forming – the beautifully named Cosmic Dawn – show that the temperature of the gas that made up the Universe back then was half that of the expected value. This lower-than-expected temperature is thought to be an effect of interactions between visible and dark matter. Follow-on papers in Nature and Physical Review Letters theorise that this temperature drop can be explained if one per cent of dark matter particles have a tiny weak charge – a million times smaller than that of the electron – but a mass 100 times that of the electron. Looking into the Cosmic Dawn is revealing the dark side.
Ceri Brenner is a physicist who works for the Science and Technology Facilities Council
