1

Physics, Astronomy & Cosmology / Re: Can you measure the one way speed of light without synchronised clocks?

« on: 18/04/2021 22:54:54 »

Generate a radio signal at a convenient frequency and measure the wavelength at any point, by any means you wish (diffraction, quarter-wave dipole, whatever) . v = fλ by definition.

2

Chemistry / Re: How do I calculate radioactive dose rate at a distance?

« on: 14/04/2021 23:11:46 »

That's correct for a point source.

If the source is distributed over a significant area of radius r (such as contamination of a working surface or distribution in a human body) the dose rate at distance d  is independent of d at close range (d<r) , decreasing as roughly 1/d if d < 5r and tending to 1/d² if d > 10r.

But you didn't come here for the obvious answer, did you? 

3

COVID-19 / Re: Side effect of COVID vaccines

« on: 14/04/2021 00:24:48 »

Yep, I had my second Pfizer vaccination 3 days ago. First one produced no symptoms, but yesterday was quite miserable and I decided I wasn't fit to fly. Shows that the system is working, but I think it would be worth warning folk that it can impair your performance a bit.

4

Just Chat! / Re: Is there a universal moral standard?

« on: 13/04/2021 00:12:25 »

That's why we like having wars and battles.

You are obviously a politician. When you say "we" you mean "you". And probably a Tory politician, since you clearly have no idea what you are talking about.  I haven't met anyone who was involved in a war and liked it. The only people who look forward to war are those who stand to profit by it, not those who have to fight it.

You would do well to stand at a border and address the approaching refugees. Tell them that they should go home because they are missing all the fun.

5

Technology / Re: Why do wind turbines shut down?

« on: 12/04/2021 11:42:56 »

So existing generation types are still a necessity.

And always will be until someone devises the means to store 5 days' worth of electricity at winter consumption levels, because 5 days with no wind is pretty common. And of course you need to install four times the anticipated peak load capacity so that you can recharge the store at the same time as supplying actual demand, during the next 5 days.

Why four times? Because wind generators rarely deliver more than 50% of rated output. There's a very narrow band of windspeeds between rated output and shutdown to prevent blade damage.

If we replace oil-burning transport and gas heating, we will need to increase wind energy production  by a factor of about 1200%, and vastly overhaul the distribution grid.

In the interim, the electricity supply cannot be considered secure if more than 20% comes from wind and solar.

It's all very sad, but inevitable. If you want to run the country entirely on renewable electricity, you need to install an awful lot of hardware,  some of which will hardly ever be used. Coal, gas and liquid fuels are very easy to store with negligible hardware cost. It is a serious question whether the UK, one of the windiest populated areas of the planet, could be powered by renewables at an economic cost.

6

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 08/04/2021 12:14:20 »

Plutonium is a real bugger because it is chemically active, forms compounds with pretty much anything, so can accumulate in bones instead of being excreted, and emits α particles that do massive damage in a short distance, at least 20 and possibly 200 times more biologically damaging than the same dose of γ radiation.   

The practical problem with α and low-energy β radiation isn't shielding from them (a sheet of paper will stop almost all α's) but detecting them in order to prevent or locate ingestion. Never mind needles, you can have a haystack of Pu or Th and not know about it unless you have reason to suspect its presence and something a bit smarter than your average geiger counter to detect it.

7

General Science / Re: Does ginger help with travel sickness?

« on: 08/04/2021 11:30:55 »

The problem seems to be associated with a disconnect between visual information and the orientation data coming from your  semicircular canals, which respond much more slowly and can even get "stuck" in a high-g manouver so you think you are still turning/climbing or whatever when the car/plane recovers to straight and level.

Acute poisoning can produce the same effect, apparently interfering with either or both perceptual systems, so the stomach reacts autonomically to void its contents - hence the vomiting drunk.

Taking control certainly helps as the conscious brain anticipates the next acceleration or, on a boat, tries to offset it, and overrides the autonomic response.

Ancient Chinese sailors discovered the value of ginger and whilst I'm quite happy throwing a car or plane around the place, I never go sailing without ginger biscuits - even though I don't understand the biochemistry.

On a long sea passage the brain seems to learn the fundamental roll frequency of the boat, so you gradually get better at standing on the deck, but the rolling sensation can persist for a day or so on land - very odd!

8

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 06/04/2021 10:09:27 »

The design life of a nuclear power station is rarely more than 20 years. Most seem to last longer, but subject to major upgrade if not dismantling and demolition.

Given that the halflife of some fission products exceeds 250,000 years, and the fact that no manmade structure has survived half as long, your preferred timescale is unrealistic.   

9

Just Chat! / Re: Do most men believe their penis is most important?

« on: 04/04/2021 18:43:56 »

The sensory homunculus is actually a serious construction showing the male body mapped with "equal concentration of nerve endings" instead of "equal areas". Oddly, there is also a motor neuron homunculus but no female version of either.

10

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 03/04/2021 11:11:54 »

The 737MAX has a failsafe which has so far killed 346 people who would have completed their journeys safely without it.

The shutdown sequence for the RBMK reactor has worked every time. Problem with Chernobyl is that the operators were experimenting with a "home-made" emergency procedure (using the residual momentum of the generators and pumps to close down the system without using the backups) that was strictly forbidden in the manual.     

Fukushima was correctly designed to withstand the "100 year" tsunami but not the 1000 year beast that killed it. To do so would have made the design uneconomic. Part of the problem is one of public perception: "reactors are dangerous so must be sited on the coast" or "humans cannot be trusted to fly airplanes".

The Chernobyl TV series was superb, and can be summed up in a single phrase: Kruger and Dunning meet Stanley Milgram.

11

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 02/04/2021 15:19:19 »

I disagree. They had all read the book which clearly set out the correct procedure for shutting down with part-spent fuel, and the reasons for not doing what they did. This was not sloppy execution of a routine shut-down but a planned and deliberate exploration of a forbidden part of the operating envelope. The point was to see if time could be saved by cutting a corner that had been thoroughly researched by the designers.

"Safe as a samovar" has some resonance. Way back in the 1950s  my father attended a course on nuclear reactors for the Central Electricity Generating Board. His summary was "a very complicated way to boil water."

12

The Environment / Re: 7.7 billion people and counting: what can we do about human over-population?

« on: 02/04/2021 15:12:15 »

In some cases that will include sex education, but in many places it is limited by religion.

The world's greatest problems would be quickly solved if we could ban religion. 

13

Physics, Astronomy & Cosmology / Re: What causes nuclear power plant meltdowns?

« on: 02/04/2021 12:22:07 »

Chernobyl was caused by the design of the  reactor being a positive coefficient design.

That in itself is not a problem. RBMK reactors are relatively simple and generally problem-free as long as you read the handbook. Trouble with Chernobyl 4 was that the operators decided to ignore the BIG RED WARNING in the book, and drove it into a known unstable condition. The exercise was executed as planned, so this was not a matter of "pilot error" but must be seen as deliberate sabotage. That's the problem with the laws of physics - they always win. 

14

Just Chat! / Re: Is there a universal moral standard?

« on: 01/04/2021 17:26:27 »

1. It is morally good to do stuff that you would like others to do to you or that you would do to your nearest and dearest. You can be prosecuted for failing to render obvious assistance to someone in immediate danger.  Problem with human rights legislation is that everyone's right is someone else's duty, which is why the EU is a Bad Thing. But whilst helping the obvious acute case is morally good, not intentionally seeking out people in distress is not morally bad because we quickly run into questions of judgement: what do we mean by "better off"? I have two televisions and a crippling mortgage, you have no TV but own your house: who pays whom? 

2. No question. Criminal activity is wrong by definition and failing to report a crime is a crime. Everyone is somebody's "brother", so there's no excuse!

3. Not seen

4. 10:1 may well apply in wartime, but the question is vague. How much harm? How much good?  If I can save a life by taking 1% of 100 people's income, that's very different from killing one to amuse another. It's a serious current question because we can expect a few fatalities from mass vaccination, so we look at the ethics from an individual "acceptable risk" perspective. If we take no precautions, there is a 4% probability that you will eventually die from COVID. That is not considered an acceptable risk by sane people, because there is no concomitant benefit. If you receive a vaccine there is a 1 in 10,000,000 chance that it will kill you. Most people consider that an acceptable risk because it reduces the risk of COVID death from 4% to "negligble" even if we ignore the societal benefit.

Nice guy, but the problems aren't particularly difficult.

 

15

Physics, Astronomy & Cosmology / Re: Is it possible to weaponize the wind?

« on: 01/04/2021 13:20:31 »

I doubt that anyone brought up on a diet of goat curry, and living in a cave for a year with a dozen unwashed disciples of the Almighty, would be much worried by  a dainty Western fart filtered through a beard. Whatever happened to the hand grenade?

16

Just Chat! / Re: Useless factoid of the day

« on: 29/03/2021 11:34:13 »

A 3-dimensional pie is called a pudding.

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The Environment / Re: 7.7 billion people and counting: what can we do about human over-population?

« on: 29/03/2021 11:25:45 »

1.  Reduce childbirth by contraceptive pills and educating young girls to feel free, safe and secure if un-married.

Marriage is irrelevant, and most abuse occurs within marriage, but free contraception is a good idea.

2. Reduce elderly population by encouraging euthanasia for those who cannot look after themselves at home

Allow, don't encourage.

3. Allow God to choose who lives or dies when He sends a pandemic to protect us from overpopulation.

Is that the god that created cholera and blessed both the Spanish Inquisition and ISIS. Or were you thinking about the benign and omnipotent being that allowed the Romans to crucify his son? Anyway, the past pandemic killed those of working age and the present one preferentially kills those too old to reproduce, so unless you want a biblical plague that kills the firstborn, it won't have the desired effect.

4.  Have a world war noting that Chris sees this as negative as it causes a baby boom due to insecurity.

and doesn't kill many people. COVID has now killed more Americans in one year than died in WWII. The Russians lost at least 20,000,000 people over 6 years in that conflict but again mostly people of working age.

If we do nothing, people will eventually starve or kill each other anyway.

18

Physics, Astronomy & Cosmology / Re: Do Certain Astronomical Phenomenons Affect US?

« on: 28/03/2021 10:02:29 »

To answer the question directly, yes. Capricornians are physically, intellectually and morally superior to all other beings. And, given the extent of that superiority, remarkably modest about it.

19

Physiology & Medicine / Re: Is it desirable for Mankind to be smaller in stature?

« on: 25/03/2021 11:57:38 »

No reason why we should lose the technology and knowledge, but our descendants would all have a better quality of life if they were fewer than present population.

At 10% of present levels, the UK, for instance, would be wholly self-sufficient in food and energy for as long as the sun shines. The population density would be similar to that of Sweden, which is by no means a sociologically or technologically backward nation. No traffic congestion, no air pollution (we have wind where the Swedes have wood) and 10 acres of land  for everyone (you can live off 1 acre of fertile temperate land). Not a bad prospect for your great grandchildren, and achievable by everybody doing nothing.   

20

Just Chat! / Re: What are you doing in quarantine?

« on: 24/03/2021 10:23:35 »

shaving

Or not. It's a great time to cultivate that academic beard and idiotic ponytail.