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Plant Sciences, Zoology & Evolution / Why is compost black?

« on: 04/01/2021 00:01:51 »

I spent a happy couple of hours today spreading some good home-made organic muck  on the vegetable beds.

Said compost began its career as grass clippings, sawdust, vegetable peelings, paper, fruit skins, fallen leaves, dead flowers, chicken poo, and weeds. None of which was black. But after a couple of years it was uniformly black. Why?   

2

COVID-19 / The first sign of common sense?

« on: 15/12/2020 10:54:13 »

The Independent

Netherlands imposes strict five-week lockdown lasting through Christmas.

The Netherlands will go into a tough five-week Covid-19 lockdown following a spike in infections, with the closure of schools, non-essential shops, and museums and gyms, Dutch prime minister Mark Rutte announced on Monday.

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COVID-19 / What happened here?

« on: 01/12/2020 12:09:43 »

Is this evidence of resurrection, or tampering with UK death statistics?

4

COVID-19 / Is the R value a useful parameter?

« on: 03/08/2020 15:46:07 »

Apologies for a long post, but it's something I've had in mind for some years and seems very appropriate right now.

It is doubly unfortunate that epidemiologists have chosen the symbol R to denote the “effective reproduction number” of an infective agent, and politicians have seized upon R as an indication of viral virulence, or their “success” in controlling a pandemic.

For anyone unacquainted with the terminology, R is the average number of persons infected by a single carrier of a disease. That sentence will have triggered a “caution” response in numerate readers, and a howl of derision from anyone who has travelled in a crowded train. If the specific infectivity of a virus is constant, R is obviously dependent on the behavior of the carriers, not the virus: R_COVID = 0 for a hermit in a desert, maybe 20 for someone who sneezes his way around the London Circle Line at 8 am. 

As shown by experiment, there is no scientific justification for relaxing social distancing or quarantine rules when R decreases: doing so merely allows it to increase again.  And R is an average of the entire population exposed by all recent behaviors including total isolation: it does not indicate the likelihood of any individual becoming infected at a particular time and place.  R is an effect, not a cause or a decision parameter.

Why doubly unfortunate? Because some years ago I proposed a risk index R as a means of communicating risk to the public, and the present COVID pandemic demands a simple, efficient parameter that can be used for public information and emergency planning. So in deference to the World Health Organisation, I’d like to relaunch the risk index with the Cyrillic symbol Я (pronounced Ya).

Define Я = 10 + log₁₀ P where P is the probability of an event.

If the event is inevitable, P = 1 and Я = 10

If the event is so unlikely that no living human will see it,  Я < 0.1

The logarithmic scale is actually familiar to the public and consistent with our intuitive appreciation of risk. Winds of Beaufort force below 4 are of no consequence. Force 5 is inconvenient, 6 is mildly hazardous and 10 is “seldom experienced inland” with trees uprooted and major structural damage. Likewise the Richter earthquake scale: up to 4 is of scientific interest, 5 – 6 causes recoverable damage and anything above 8 is a disaster.

In everyday life we consider Я ≤ 5 “worth it” for the fun or benefit. The UK annual risk index for death in a road accident is about 5, but deep sea fishing with an annual Я_DEATH approaching 7 is a dangerous profession in northern waters.

My original interest was in efficiently communicating the risk of diagnostic x-rays. The natural incidence of cancer gives Я_{<DEATH|CANCER>}  ≈ 9.4 (no apologies to this audience for Dirac notation, and I’m sure Joe Public will get the idea pretty quickly).  Against this, we have Я ≤ 4 for a dental x-ray (negligible – could save you pain and infection, and safer than driving to the clinic) and 7 for a repeated abdominal CT (worth the risk to avert a greater one).

In a pandemic, I think honest public information demands activity-specific values of Я_<Y|X> , the risk index of an individual contracting Y whilst doing X. Early in the UK outbreak I cancelled a biannual jazz concert on the estimated Я_<COVID|GIG> of 8.4 (unacceptable, however good the band) given the likely size and packing density of the audience and the probable local incidence of infection.  I take no pleasure in being right in this instance – by the original date, two members of the prospective audience of 100 were indeed infectious, one becoming very seriously ill a few days later.

It should be possible to estimate and publish general Я values for, say, working in an office, a ventilated factory, or an outdoor team, and travelling to work by bus or train.  You can subtract an appropriate value for each type of face mask. Those of a social science bent might study crowd behavior in theatres, pubs etc and on beaches, and estimate appropriate Я values that would be far more meaningful and specific than the current global R that allegedly “informs” political decisions. Individuals can then make properly informed choices about their work and leisure. 

5

New Theories / Can heat affect Earth's rotation?

« on: 01/08/2020 11:28:25 »

[Mod edit: Topic split from "Can windmills affect Earth's rotation?"]
https://www.thenakedscientists.com/forum/index.php?topic=80136.0


Any windmill extracts kinetic energy which we eventually turn into heat.

Ignoring second-order effects such as thermal winds, the source of kinetic energy is the rotational energy of the planet, so it must eventually stop spinning.

Now that really will induce some climate change!   

6

COVID-19 / Can we organise an effective national quarantine?

« on: 05/07/2020 23:55:16 »

Assuming that COVID remains a significant disruptor of daily life for the next 6 months, would this suggestion find any favour?

Starting now, government prepares for a full national quarantine period beginning on Christmas Eve. Don't call it "lockdown" because that sounds like a punishment: it's a cure.

Starting today, we build national stocks of basic food and hygiene supplies. No different from provisioning a ship for a month at sea, except we have enough to deliver 4 x 1 week packages to everyone. Actually it's easier than provisioning a ship as we can assume that everyone has access to clean water, so no limit on dehydrated foodstuffs.

On 18 December we begin distributing the first week's packages with a "do not open before 24 December" label. Remote locations will get a whole month's supply but most of the mainland will get 4 deliveries on the same day each week. Not a big deal as the Post Office and courier services will be shifting a lot of packages anyway.

From midnight on 24 Dec there is a compulsory prohibition on all but essential travel for 2 weeks. Essential means only those services and personnel previously identified as such, patients needing urgent treatment, and corpses. All retail and high street trading is closed. Included in essential services is a door-to-door COVID testing program for everyone. No need for tracing as nobody is going anywhere. There being nobody in the streets apart from emergency services, we should have enough police manpower to help with testing. On 7 January those households with a clean bill of health are released and all others remain under curfew until 28 January. 

Given 6 months notice and the experience of the current shambles, people should be able to cope with staying at home during what is mostly a holiday period anyway, and everyone gets the "clarity" that seems to be the current watchword. There being negligible business or holiday travel, hotels can accommodate the homeless and anyone arriving from overseas, and gear up for providing compulsory 2 week quarantine for all arriving passengers until further notice. 

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Just Chat! / Wold anyone like to try a fun new game?

« on: 10/05/2020 12:41:10 »

"Grandpa's Workshop" is a collaborative strategy game for two or more players. Anywhere, anytime.

Player 1 writes down six problems

Player 2 writes down six solutions

Roll the dice and start the discussion!

Example: "world peace" ↔ "watering can with a bit missing"

Fun for all, and everyday experience for grandfathers.

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Plant Sciences, Zoology & Evolution / Did COVID's cousin kill the dinosaurs?

« on: 02/04/2020 17:11:04 »

I've never accepted the idea that the dinosaurs were wiped out by climate change. A sudden shift of temperature, sunshine, or whatever, might eliminate several land-based species, but unless all the oceans froze (for which we have no evidence) the seagoing dinos (of which there were plenty) would simply have migrated to somewhere warmer or colder that suited them.

However the rapid spread of this year's killer virus does provide a plausible model for the sudden disappearance of a whole raft of related species.

Any thoughts (or better still, actual knowledge)?     

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The Environment / Time for a new economics?

« on: 18/03/2020 10:24:39 »

However you measure it, the world is in a global economic recession, with everybody doing less of everything for the next few months. The environmental effect will be like 9/11 but on a far bigger scale. So here's an opportunity to explore the overall impact of decreasing economic activity on the entire ecosystem including human happiness, and possibly to radically review the underlying expansionist assumptions of politics and economics.

One immediate realisation has been that children are an economic burden, not an asset.

It was noticeable that cloud cover altered dramatically over the USA in the aftermath of 9/11 - the grounding of almost all flights worldwide will surely have an effect on weather, and if it is beneficial, perhaps could lead to a change in behaviour: if we can survive with less frequent travel, why not  spend longer at your destination (longer holidays, relaxed business ….) and halve the number of flights required?

Any predictions? 

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The Environment / What is the carbon footprint of a new railway?

« on: 24/01/2020 19:09:27 »

I'm wondering whether new railways really make ecological sense. To make and lay four rails (one track in each direction) on ballast, without taking into account any landscaping or trackside equipment, my estimate is about 1000 tonnes of CO2 emitted per mile of new track.

I'd be grateful for any refinement of the figures. My estimate is based on 300 kg concrete sleepers laid at 0.8 m separation and 60 kg/meter of steel rail, plus an allowance for bringing the materials to site by road.

Assuming you already have the vehicles to hand, how many train journeys must be made before the total CO2 emission is less than making the same journey by plane?

And the CO2 footprint of the vehicles themselves?   

11

Just Chat! / Is high speed rail a Good Thing? It's even quicker and cheaper by bus!

« on: 21/01/2020 15:04:09 »

Current thinking is that the HS2 rail line from London to Birmingham will cost over £100,000,000,000 - 5 times the original estimate and rising.

It will save 15 minutes compared with the fastest trains running today.

There are about 20,000,000 taxpayers in the UK, so HS2 will cost you £5,000 even if you don't use it.

It now takes 3 hours to travel from Cambridge to Birmingham via London, or 2 hr 45 minutes (at half the price) by direct crosscountry train*. So I will get nothing for my £5000, despite being a frequent rail user.

What benefit will you get?

*Footnote: it's even quicker and cheaper by bus!


 

12

Technology / Is renewable energy good for the environment?

« on: 06/07/2019 14:25:05 »

Wind turbines convert at best about 70% of incident wind power to mechanical power, though this is only over a narrow range of wind speeds. 50% over all conditoins is a sensible figure. About 90%  of this is converted to electrical energy, with 5 - 10% further losses in distribution transmission and maintenance ( not just ohmic and transformer losses, but including routine helicopter inspection of power lines and the replacement of pylons, switchgear etc.) to the consumer. 0.5 x 0.9 x 0.95 =  42.75% overall efficiency. Where does the rest go? As heat.

Solar panels probably convert 20% of incident radiation to electricity. In doing so they occupy land that would otherwise be used for crops (which absorb carbon dioxide) and distort drainage by forming an impermeable sheet over the soil. About half of the remaining 80% is reflected as longwave infrared, contrtibuting to atmospheric warming by radiation, and the remainder is removed by convection, heating the lower atmosphere (I regularly fly over a solar farm on the approach to my local airfield - what a ride!). Allowing 5% transmission losses once again, we have a system that generates four times as much heat as electricity!

Now put that electricity into an electric car. You can recover about 90% of the input energy from a new battery,  and maybe transfer 90% of that to the wheels, but by the time the battery needs replacement (and never mind the energy cost of making a new battery) it is down to 50% recoverable capacity. Say over the life of the car, a total of 60% of input energy is useful, 40% wasted as....heat!

Whatever the merits of renewable energy, it adds a heck of a lot to global warming!

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That CAN'T be true! / Healthy Eating or Dodgy Science?

« on: 10/02/2019 17:27:47 »

Just copied this from an apparently authoritative on-line source

Gouda cheese has 819 mg of sodium per gram, and American cheese has 1,671 mg of sodium per gram. That’s a lot! Next time, make sure to cut down on the amount. It’s not bad if you cut it out completely, but this would be a sad day indeed.

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General Science / Why is the atmosphere transparent to CO2 lasers?

« on: 30/09/2018 16:22:11 »

The object of laser weapons is to deliver a huge amount of energy in a short pulse, to cause failure by adiabatic heating of the target. Most work has been done with carbon dioxide lasers because they are easy to make up to very large sizes, and considerably more efficient than most other solid or gas lasers. Nobody seems to have told the military that atmospheric carbon dioxide has a strong enough infrared absorption to destroy the earth's climate, and they just go on merrily shooting down drone targets, oblivious to the facts of global warming enthusiasts, which clearly prove that they can't work.

15

That CAN'T be true! / Do 40% of driving accidents really happen at night?

« on: 01/03/2018 11:12:16 »

An advert for yellow spectacles just appeared amongst the good stuff on this forum, with the shock horror headline "40% of driving accidents happen at night!" So obviously I won't buy the specs or drive during daytime.

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Plant Sciences, Zoology & Evolution / Do dogs think like us?

« on: 24/11/2017 23:49:23 »

Dogs come in a huge range of sizes, shapes and colours, but we assign them all to one species. Selective breeding has produced breeds that hardly resemble wild dogs or wolves - indeed  many that would probably not survive without human assistance.

Cats, foxes, badgers, and many other medium-sized quadrupeds, are based on the same general form as dogs.

If you take your young mutt to a dog park where he can run free with others, it's pretty clear that he recognises everything from a chihuahua to great dane, whippet to St Bernard, as a dog, and at such long range that it can only be by sight. But unless he has read the Kennel Club breed standards book, he won't have seen many quadrupeds apart from his parents and siblings, and there's not a lot of morphological difference between, say, a miniature pomeranian and a fluffy cat. But somehow Rover classifies them all as canis familiaris, just as we do.

How? Why?

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Physiology & Medicine / How to survive in the desert?

« on: 24/08/2017 18:02:43 »

Due to a minor navigational error, ace pilot Alan has run out of fuel in the Sahara instead of landing in Dublin (180°, 280° - anyone can make a mistake). Fortunately he has some water and has finally worked out how to locate himself with the GPS.

What is his best strategy for survival if he is (a) 20 (b) 100 (c) 300 miles from the nearest town and has (i) 5 liters (ii) 20 liters or (iii) 100 liters of water?

You may assume that he is, of course, athletically fit and has a reasonable number of Mars bars or non-melting equivalent, or that he is prepared to eat his dead passenger. 

18

The Environment / Is global warming essential for the continuation of terrestrial life?

« on: 08/06/2017 13:05:01 »

We have great ice core records of global temperature and CO2 concentration, going back over a million years. Lots of peole argue over their interpretation, but what about their existence?

The fact that we have a sample of snow that fell a million years ago means that it didn't evaporate. And the fact that it is umpteen meters below the surface means that neither did the subsequent snowfalls.  In other words, Antarctica is - or at least has been for the last million years -  an unlimited sink for water. For as long as the ice caps have been accruing, there has been a net transfer to the polar regions: some layers are thinner than others but AFAIK there are no actual gaps - accretion is continuous and inexorable. So eventually, all the water in the atmosphere will be frozen at the poles, gradually replaced by evaporation from the oceans and then frozen, until the planet consists of two ice caps with no water liquid or gas anywhere else - a bit like Mars?

Fortunately the planet seems to go through occasional warming cycles, and since life depends on the availability of water, global warming appears to be essential to the maintenance of life.

19

Technology / All-electric transport for the UK?

« on: 08/06/2017 00:25:09 »

Attracted by the latest Tesla X in a showroom, I wondered what would happen if the idea caught on and everyone  used electric transport? So I did some calculations...

There are about 30,000,000 cars in the UK. Average use is say 2 hours per day, so divide by 12 and multiply by, say, 20 kilowatts per car, and we are using about 50 GW  of power for personal transport.

There are about 5,000,000 trucks, vans and buses. Average use say 10 hours per day at 50 kW means we are using a bit over 100 GW  for shifting goods and passengers.

So in order to keep moving, we need to supply 150 GW of electricity (assuming 100% battery efficiency).

The present generating capacity available to the national grid is 55 GW, of which 70% is already committed in winter.

"Who Killed the Electric Car"  is an excellent DVD which points the finger of conspiracy at the oil industry,  General Motors, and the vehicle component manufacturers and service organisations for suppressing the very successful GM "EV", but I think there may be an even bigger elephant in the room - the sheer impossibility of generating enough electricity (from what?)  and distributing it, if the idea of electric road transport really catches on..

20

Technology / Can you email me a sandwich?

« on: 12/05/2017 21:55:15 »

Cool, please email me a sandwich.

Happy to help. Since I gave up pointless commuting and started working from home, I've occasionally ordered lunch by email from a local sandwich van, pizza shop or curry kitchen. Vastly more efficient for all concerned (especially if I'm holding a 3-way Skype conference with a manufacturer in Germany and a technician in Scotland) and far less polluting.