Editor's pick: The sweet side of a sugar tax
Tom Sanders expresses scepticism about the likely impact of a sugar tax on obesity and related health problems in the UK (16 January, p 26). It is true that in Mexico, the direct impact of the sugar tax on calorie intake appears to be small. But sugar has an impact on calorie intake beyond its own caloric value.
The increase in US obesity rates after the 1960s followed a 500 per cent increase in the consumption of sugary drinks and a 150 per cent increase in sugar added to processed foods.
A of minority US adolescents found that consumption of sugary drinks was associated with decreased satiety and depressed levels of the hunger-regulating hormone ghrelin.
Consistent with these results, a survey of 75 countries from 1997 to 2010 found that a 1 per cent rise in soft drink consumption was associated with an additional 2.3 obese individuals and 0.3 diabetic individuals per 100 adults.
So a soda tax seems certain not only to make a significant impact on obesity-related ill health but also to boost government revenue.
Wollongong, New South Wales, Australia
The editor writes:
• For more on how sugar affects satiety, read our “gut thinking” feature (21 November 2015, p 30).
The tale of the secret telescope
Nigel Henbest alludes to Chester Moor Hall's invention of a lens with little chromatic aberration (19/26 December 2015, p 73). There is more to it than he recounts.
As Henbest reports, around 1729 Hall worked out that he could make an achromatic lens by combining a strong positive lens of crown glass and a weak negative one of flint glass. Hall was paranoid that whoever he asked to make these lenses would steal his idea, so he commissioned each lens from a different optician.
Unfortunately, they both subcontracted the job to the same man: George Bass. Bass worked the principle out immediately but kept the secret. He duly made the lenses and built Hall a telescope around them in 1733. It still exists.
Bass and Hall made several more achromatic telescopes, which impressed astronomers of the day, but the technique remained secret for 20 years. Then Bass discovered that John Dollond was working along similar lines and revealed the formula. Dollond promptly patented it, which naturally led to a lawsuit.
The judge ruled that although Hall's priority was clear, he had had 20 years to do something about it, so Dollond deserved patent protection for bringing the idea to market. Dollond's achromatic telescopes were available from about 1758.
First class post
We prefer to go by a ‘non-empty subset’ of mathematicians, just to make things clear
to the search for collective nouns
Self-driving cars on the starting grid
You quote transport researcher Steven Shladover as saying that the limitation on an urban traffic grid is the time it takes vehicles to start moving when a traffic light changes to green (23 January, p 21). He thinks that this is something autonomous cars don't improve.
It is a familiar experience for drivers to be several cars back from the lights and, once they have changed, to have to wait seconds before being able to move, as other drivers must realise that the car in front has set off before moving themselves. I would have thought this is exactly where autonomous cars would help: they could all move off in unison, maintaining the much shorter stopping distance possible with vehicle-to-vehicle communication.
Self-driving cars on the starting grid
Self-driving cars will make gridlock worse because, as well as cars with people in them, there will be empty ones on the move whereas cars with drivers would have to be parked somewhere.
Winchester, Hampshire, UK
The editor writes:
• On one hand, yes, the empty cars will have to go somewhere. But on the other, driverless cars could mean that employees who drive to work – the main cause of gridlock – are dropped off by a car that then whizzes off to pick up other people.
Deeper reasons for keeping archives
Karin Ljubic Fister discusses storing data in plant DNA (16 January, p 27). Archiving addresses two different scenarios.
In the first, we want to preserve information for future humanity. A second deals with the case of “intelligent” humans being absent through bombing ourselves back to the Stone Age, or extinct due to climate change, for instance.
Assuming we do not sterilise our planet, encoding an enduring archive in the DNA of something with a long history of endurance, such as bacteria or cockroaches, would make our data available to our successors. Life will then take care of the need for regularly refreshed copies.
Perhaps our own “junk” DNA already carries the archived data of some ancient intelligent species, or evidence for how “we” blew it last time.
More solar system surprises in store
It seems to me that the solar system holds more great mysteries beyond the six you highlighted (23 January, p 28). There appears to be a diverse menagerie of objects, notably asteroids and comets, the true nature of which we have only just begun to explore.
Take, for example, one of the largest periodic comets known: . This strange body occupies a near-circular orbit beyond Jupiter. Since its discovery in photos from 1927, it has displayed energetic outbursts or eruptions between four and eight times a year, powered by some mysterious source yet to be identified.
After a quantum-indeterminate past
Joshua Sokol discusses how we define the future as the direction in which entropy increases, and says that we could rewind time to the big bang, when the universe had less entropy (16 January, p 8). But if the laws of physics are time-symmetrical, this must also apply to unpredictable quantum events. So if we were able to run time backwards, things would not have to be the same as they were. If the past is as indeterminate as the future, what right have we to say that a low-entropy big bang is the one correct version of our past?
Does 'fine tuning' have meaning?
Mary-Jane Rubenstein writes that modern physics considers it strange to find our universe so hospitable to life, when nearly any other values for the fundamental constants would not have allowed life to form (19/26 December 2015, p 64). A proposed solution to the problem is offered by a multiverse containing many different values of physical constants.
While this is a fair description of contemporary debates in physics, the fact is that we don't know whether there is any meaning to the notion of “fine-tuning” of physical constants. Indeed, if there is only one universe, in what sense can we give meaning to the notion of “fine-tuning of constants”?
An empirical approach fails, because there are no other universes to observe for comparison. A probabilistic approach fails because, at the level of the universe as a whole, probability is not well defined, nor can it be empirically verified.
Whatever we may mean by fine-tuning of constants, it must be rooted in mathematical, aesthetic, philosophical or theological assumptions.
For example, we may be assuming that the mathematical form of physical laws remain fixed when considering alternative values of physical constants. This gives a privileged status to the physical laws that they need not necessarily have.
There is a clear affinity here between modern physics and philosophical-theological inquiry, fertile ground for asking deep questions about chance, necessity, naturalness, meaning, causality, creation and existence.
Does 'fine tuning' have meaning?
Within any infinite multiverse there will be many very clever sentient species – biological, machine, and other types not yet conceived of. Some of these will have worked out exactly how the multiverse works and will thus be able to control it.
If just one species decides to destroy the whole thing – and this must happen, due to the infinite possibilities expressed in the multiverse – then our universe also cannot exist. There is, therefore, no multiverse.
Flood prevention scheme vindicated
I was pleased to see a photo of our church on your leader page, standing dry above floodwaters (9 January, p 5). It illustrates the success of our local flood alleviation scheme.
This was put in place in the mid-1980s on behalf of British Coal during the sinking of the coal mines in its Selby Complex. It has kept the majority of the village dry since then. Alternately higher and lower river banks mean that water flows over the lower banks into selected fields and the villages stay dry.
I have noticed, after many years living close to the river Ouse, that floods now tend to be associated with high rainfall: many years ago, they were mostly caused by a thaw of heavy snow in the hills.
The light fantastic? I did it back in 1968
Nicola Jones reports on attempts to communicate data with light (9 January, p 30). What took you so long? My thesis – submitted for a BSc in electrical engineering at the University of Nottingham, UK, in 1968 – was titled A line-of-sight communication channel based on a light-emitting gallium arsenide diode. The department had only three diodes with a capacity of 1 ampere. After burning out two I could foresee doom, so I tried pulse amplitude modulation. The transmitter worked a treat.
Incidentally, my thesis referenced a New 杏吧原创 article titled “Light from semiconductors” ().
For the record
• The Zika virus spread to between its arrival in Brazil last year and the time of writing of our report (30 January, p 9).