Waste not鈥�
I enjoyed Chelsea Wald’s look at uses for waste heat (13 April, p 30). Heat networks that use such resources, once known as district heating, haven’t been fashionable in the UK, but they are an interesting option for mitigating carbon dioxide emissions.
Scaling up electricity networks to meet climate change targets would require a lot more generation and transmission capacity. Tapping into waste heat to warm buildings or generate electricity for vehicles offers a much better option for the UK.
Light energy: think solar panels. Gravitational potential: hydroelectric power. Nuclear energy: fission (and fusion?). Kinetic energy: wind. Heat energy: geothermal. Sound energy: er, nothing springs to mind. Isn’t this one of the very few forms of energy we have yet to attempt to harness? How about using speakers, in reverse, to recapture some of that waste sound energy in factories.
From Paul Younger, Rankine Chair of Engineering, University of Glasgow
When it comes to capturing waste heat, it’s worth noting that ground source heat pumps tend only to deliver heat effectively to systems operating at temperatures below 55 掳C. This makes them suitable for new-build properties with, for example, underfloor heating, but not really viable for the vast existing building stock with traditional radiators designed to operate at about 70 掳C.
Also, Londoners need not wait for the completion of Crossrail to experience ground-sourced cooling of an underground station: head to , where cool air is already making deep platforms really comfortable, using groundwater pumped from a borehole.
Intelligent aliens
Although I hate to pour cold water on those looking for signs of large-scale alien technology (6 April, p 42), I have a more optimistic view of extraterrestrial intelligence.
If an advanced civilisation is intelligent and wise, they will have looked out to the heavens and accepted that the planet most beautiful and suitable for them is the one they evolved on. Their wisest course is to nourish it, reducing population and promoting biodiversity, living small and revelling in its beauty.
Such a culture wouldn’t need to create devices to capture the total output of their sun. They might live in nice little wooden houses and write poetry.
Measles questions
The UK measles outbreak in south Wales reminds us how easily near-extinct infections can take hold in pockets of susceptibility (20 April, p 4). In this case, the susceptible are a cohort of teenagers who missed having the MMR vaccine in earlier childhood, probably because of the false report that it caused autism, and the associated negative publicity.
It is good to see the opening of special clinics offering vaccination 鈥� an excellent response to increased, awareness-driven demand. The outbreak does raise questions, though.
Why are we only seeing large outbreaks now, given that the non-vaccinated group has been susceptible for a decade? Is it just that sufficiently large pockets of susceptibility have formed after years of under-vaccination? Or is the risk associated with these children entering high school?
Perhaps more important is the need to understand why we haven’t already seen large outbreaks in UK regions with lower vaccine coverage, such as London and the West Midlands. A better understanding of the social phenomena behind both vaccine avoidance and the mechanisms driving the outbreaks will help the prediction and mitigation of future epidemics.
Dark gravity?
Last year, you reported that dark matter might consist of both dark hydrogen and dark photons, rather than being a single thing (7 January 2012, p 30). Recent articles suggest that it may be far more complex (13 April, p 8 and 20 April, p 10).
Surely then, assuming dark energy to be a single phenomenon is flawed. If electromagnetism, the strong and weak forces and gravity make up only 15 per cent of the energy that current theories insist should exist, what is the logic in thinking the rest is a single force?
I like the idea of dark photons, but if it turns out that their paths are affected by dark gravity perhaps the 20th-century thinker who understood the universe best wasn’t Wolfgang Pauli, Enrico Fermi or Einstein, but that master of things both dark and cosmic 鈥� sci-fi author H. P. Lovecraft.
Marital confusion
You explained why the answer to the Jack-Anne-George marriage conundrum in your look at stupidity (30 March, p 30) is “yes” (13 April, p 28). I hope I am not alone in thinking that “cannot be determined” is a more useful, and arguably more accurate, answer.
Why? You asked: “Is a married person looking at an unmarried person?” but failed to define your terms. On a standard English reading of the problem, Anne could be widowed and not fit neatly into the married or unmarried categories, leaving the question unanswerable.
Downside of up
Rory Feeny wonders why we’re not seriously considering setting up an international body to fire nuclear waste into the sun (20 April, p 33).
Here’s one reason: the idea involves taking large gobbets of a substance that is dangerous to keep on Earth, even at depths of several miles, and strapping them on top of thousands of tonnes of high explosive. All in all, up seems far more risky than down.
Has Feeny considered the following: if you want to gum something up, you form an international agency. Also, rockets have a considerable rate of launch or stage failures and, if carrying nuclear waste, any such failure would most likely contaminate a very large area.
Westleigh, New South Wales, Australia
Bang on target
Your look at the search for the next breakthrough in physics was outstanding (2 March, p 37). I had just read Lawrence Krauss’s book on cosmic origins, A Universe From Nothing, and your special issue was a great wrap-up. The diagram of the standard models of particle physics and cosmology on a timescale was the icing on the cake; I’d hang a big copy on my wall.
No time, no space
Regarding whether the interior of a black hole exists or not (6 April, p 38), if the inside is a singularity with an infinite gravitational field, then time dilation, as predicted by relativity, will presumably mean time stops altogether as viewed from outside the event horizon.
If the interior doesn’t exist in time, could it be said to exist in the other three dimensions?
Animal transplant
Your editorial asks whether patients or society would accept “humanised” animal organs for transplant (20 April, p 3). For my part, if extensive anti-rejection treatment was needed and the transplant was likely to give only a little extra quality of life, I might opt for a shorter life with a dignified death. If the technical issues could be resolved, then I would consider hosting a humanised heart, kidney or whatever.
Physical benefits
Letters from Max Lang and Roy Knowles question the value of particle physics and cosmology. Knowles wonders if they are “just hobbies” (20 April, p 32).
It is very often the case that any practical advantages of research are not immediately obvious. That does not mean to say they won’t be later. As physicist Michael Faraday is reputed to have said to the then British Chancellor of the Exchequer William Gladstone, when questioned about the usefulness of electricity: “Why, sir, there is every probability that you will soon be able to tax it.”
Why study cosmology and particle physics? The global positioning system (GPS) depends on general relativity, because the atomic clocks it relies on drift if they are not calibrated for reduced gravity in orbit. Those clocks 鈥� not to mention all of nuclear medicine 鈥� are the fruit of particle physics. The history of science suggests that we dare not stop experimenting now.
Sydney, New South Wales, Australia
Real time
Thankfully, physicist Lee Smolin has concluded that time is not an illusion (20 April, p 30). Having read in previous issues of 快猫短视频 that reality could be an illusion (29 September 2012, p 45), and that some cosmologists think we are simply holographic projections (23 July 2011, p 31) on a two-dimensional brane dominated by unseen dark energy and matter within an infinite multiverse 鈥� which itself is just part of a computer simulation by a massively advanced civilisation (29 September 2012, p 41), I 鈥� if indeed I exist 鈥� was a bit worried for a moment.
Mind the puddles
Feedback’s jocular mention of a 10,000-millimetre waterproof rating for hiking gaiters (13 April) is actually a hydrostatic head rating. This means that if you were to have a column of water 10 metres tall pressed down on the fabric, the water could not force its way through.
So there’s no need for you to hike through a lake to check they work!
For the record
鈥� In our look at the use of robotics in building construction (20 April, p 22), we should have called engineering firm Laing O’Rourke’s venture Project Freefab, not Freeform.