Original spin
Anil Ananthaswamy’s feature on the possibility of a spinning cosmos (15 October, p 44) had me reaching for a copy of Austrian logician Kurt Gödel’s paper on rotating universes, written to mark Albert Einstein’s 70th birthday in 1949.
Gödel shows the “absurdity” that results from a rotating universe, namely the ability to travel into any region of the past, present or future, including one’s own recent past. However, his proof is only for non-expanding universes. For expanding, rotating universes he merely comments that, in contrast with our universe (if it is non-rotating and expanding), “an absolute time might also fail to exist”.
Have Gödel’s ideas been extended to the expanding case, and with what result? If such paradoxes remain, then a rotating universe would be an even more radical idea than suggested.
From Colin Parrish
As well as explaining the existence of matter, perhaps a spinning universe might explain dark energy. Imagine a spinning disc: the perimeter is travelling faster than the centre. Ball-bearings placed near the edge would naturally be projected outwards at a greater velocity than those near the middle. Would galaxies near the extremity of a whirling universe similarly recede from us at greater speeds than those nearby?
Doncaster, South Yorkshire, UK
From Robin Stokes
Surely if the universe is spinning this has to be with respect to some defined co-ordinate system outside the spinning object? If so, is there somewhere outside the universe?
Armidale, New South Wales, Australia
The editor writes:
• There may be universes in which the question is settled over whether the abstract property called “spin” implies an external frame of reference: but we don’t appear to live in one.
Navigation nostrums
One reason for the slow uptake of electronic navigation on ships (22 October, p 26) is the lack of adoption of open standards by the major chart agencies around the world. For example, the UK Hydrographic Office (UKHO) offers chart services that will work in Electronic Chart Display and Information Systems (ECDISs); but in a proprietary encrypted format.
If the International Maritime Organization is to be serious about getting wider use of such tools, it needs to make access to chart data easier by compelling organisations such as UKHO to follow the lead of the American National Oceanic and Atmospheric Administration, which makes charts available in open, unencrypted standards.
From Lee Taylor
Wendy Zukerman faithfully reports the state of navigational equipment on-board ships and the official line on the use of ECDIS at sea: that of the International Maritime Organization and the big insurers. As a navigator, I can report that we do prefer to have such systems on the bridge. They are particularly useful when planning a passage. As an aid to navigation, however, they can be a liability.
It is all too tempting to navigate according to where the computer tells you you are relative to what the computer thinks is surrounding you, rather than keeping your eye on your surroundings, out of the window and on the radar, and navigating according to what is really there.
I am particularly concerned that some vessels may sail entirely without paper charts, when there are two separate electronic systems on board. I have never seen an ECDIS system that has convinced me that is it is a safe alternative to paper charts – the systems make the navigator’s job easier, not necessarily safer.
It remains safer to navigate by visual means and by radar in tandem with regularly updated paper charts.
Gillingham, Kent, UK
Information input
Max Tegmark has two suggestions for what will happen to the information in an expanding universe: either information is created, meaning we can no longer make predictions; or the quantum “grain size” of the universe – the effective “Planck length” – increases, leading to a breakdown of nuclear physics that Tegmark calls the “big snap” (24 September, p 8). Neither is acceptable.
There is, however, a third solution, which is that the universe is not a closed system, but rather is still connected to the multiverse from which new space/time is being introduced, thus allowing an increase in information without the problems Tegmark’s scenarios lead to. This would mean that the expansion of the universe would have to continue infinitely.
I suggest we all start looking for the inlet valve.
Facts on the ground
In your story on the lawsuit against TransCanada’s Keystone XL Pipeline in North America, the statement that our legal challenge is about “nothing more than mowing tall grass” is not accurate (15 October, p 4).
We believe it is a violation of law for TransCanada to begin any work on the proposed pipeline before being granted a permit and while there is an ongoing public process in which thousands of Americans have expressed opposition to the pipeline. This is no mere legal technicality, but rather ensures that TransCanada does not undermine the public process and create a presumption that the pipeline is a done deal.
Forest not so fine
Your article on the study of habitat fragmentation in Borneo carried out in co-operation with loggers states that 75,000 hectares of primary forest in Sabah is being cleared to develop oil-palm plantations (22 October, p 7). This is not the case.
The plantations are being developed on areas of highly degraded, effectively second-growth forests that have been logged repeatedly over more than 40 years; large parts burned during the major fires that swept Sabah in the early 1980s.
No primary forests will be affected by the Stability of Altered Forest Ecosystems project or by the development of the associated plantations. Also, I am not a member of the Round Table on Sustainable Palm Oil (RSPO) and nor is the Royal Society SEARRP. Our programme acts as an advisory body to the RSPO.
Consistent we are
Your story “I’m autistic, I don’t care what you think” was interesting (15 October, p 19). I have autism, and I think researcher Keise Izuma got it right. We are more likely than neurotypicals to be consistent in our behaviour, regardless of whether we are observed or not.
Incidentally, terminology has moved on. “Is autistic” is no longer an acceptable expression. The term “has autism” is technically accurate. Autism is what we have, it is not what we are.
Baby nose best
The importance of the smell of the nipple for breastfeeding (8 October, p 12) is beautifully illustrated by a tale told to us by a midwife friend. A mother had been feeding her baby for eight days when, one morning, the baby suddenly refused to feed. It turned out the mother had washed with her husband’s shower gel earlier. She showered again without the gel and the baby resumed feeding.
Sticks and pyramids
With reference to the controversy over Tutankhamun’s club foot (8 October, p 10), Zahi Hawass, while Egypt’s antiquities minister, gave an apparently convincing argument in support of the boy king having had such a condition. An extraordinary number of ceremonially anointed walking stick-shaped “batons” were found in the treasure chamber, annex and antechamber of his tomb. If King Tut had a club foot, perhaps he was given these to assist him in his journey to the afterworld.
Wise old bird
The speculation, in an article on the evolution of our brains, that a dinosaur or bird could have evolved considerable intelligence instead of us was engaging (24 September, p 40). I suggest another candidate: the dinosaurs’ other flying cousins, pterosaurs, which had a high brain-to-body-size ratio compared with dinosaurs.
Birds that colonise isolated islands sometimes become flightless. The same could have happened to pterosaurs. They had three functional digits on the front of each wing, which may not have been useless if they became flightless. Fossilised tracks show that pterosaurs walked on all fours.
In an alternate world, where the Cretaceous-Tertiary extinction event did not take place, we might expect their wings to have reverted to limbs that they could walk on and maybe grasp with.
Blade runner
You describe a wind turbine with extendable blades (22 October, p 26). Why would they be better than blades that vary their pitch – their angle to the breeze – which are a well-understood feature of most propeller-driven aircraft?
Copernican caveat
Further to your review of Dava Sobel’s book on the heliocentric theory of Copernicus (24 September, p 61), the Polish astronomer was not alone in overturning long-entrenched beliefs. In the same era, Christopher Columbus’s voyage to the New World eventually banished notions of the globe having a dark underside, academic and clerical opposition notwithstanding.
Copernicus later tried, unsuccessfully, to make his theory more acceptable by dedicating it to Pope Paul III, emphasising that its simplicity and order were in fact a tribute to the wisdom of God.
Ripe economics
Feedback is right to welcome the removal of the wasteful “sell-by” date from food packaging (15 October, p 64) but misses a more ironic effect. Many cheeses improve with age and are just approaching their prime at the “sell by” date, but supermarkets then reduce the price to clear their shelves. The result is that cheese is one of the few products that gets cheaper as it gets better.
For the record
• In the Spaceport America story (22 October, p 12) we mistakenly said that Richard Branson is Virgin Galactic’s CEO – he’s the founder.