21

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

« on: 06/03/2022 14:43:00 »

Choosing whom to kill would raise some moral dilemmas. Merely ridding the world of priests, politicians and philosophers would make life more peaceful but wouldn't have much impact on sustainability. You might then start on pensioners, but we have a limited life span anyway, and have contributed to the public good through our taxes and investments, so we should be allowed to enjoy our pensions. Companies that rashly introduced early retirement to save money on the short term often found that, within a year or two, everyone who knew anything useful or had acquired a significant skill, had disappeared. 

But every baby is a net consumer for about the next 20 years, without having contributed anything. So a baby not born is a significant exchequer saving and improvement in the future quality of life for those already here.

Killing people takes effort and organisation, and doing it on a big scale can pose problems disposing of the bodies. Not making babies is the perfect "do nothing" option, with no waste product.

22

Just Chat! / Re: Is there a maximum frequency for a gamma ray?

« on: 24/02/2022 17:32:42 »

If you (alancalverd) get a moment, is there a useful link to some information about how the latest high energy gamma rays are actually generated?   X-rays are easy enough... just accelerate some electrons into a tungsten target inside an x-ray tube - but can you really push those frequencies up higher to the gamma range just by increasing the velocity of those electrons?  Are your machines producing medical gamma rays directly from nuclear decay these days?   Even if they are produced directly from nuclear decay, where are you (we) going to get even higher frequency gamma rays from after that?

Sorry I missed the question earlier!
Nuclear decay isn't terribly useful for tele-radiotherapy applications. By the time you have enough  gamma flux to be useful, you have a very large radionuclide source that you can't switch off, can't modify the spectrum, and its output is continually decreasing and probably being contaminated with decay product gammas and betas. AFAIK all existing 1.3 MeV cobalt teletherapy units (apart from a few exotic "gamma knife" systems) are being phased out.

Linear accelerators are very useful up to about 15 MeV, producing a large controllable flux of electrons which we do indeed bash into a target to make x-rays (same as gammas, but man-made rather than of nuclear origin).

Betatrons can produce small fluxes of 300 MeV electrons and x-rays which are useful for industrial radiography, and synchrotrons currently go up to 15 TeV (CERN LHC source) but I'm unaware of any routine medical use of  photons above 15 MeV.

23

Just Chat! / Re: Is there a maximum frequency for a gamma ray?

« on: 21/02/2022 22:33:59 »

At the lower end, there is a limit to the energy of a photon we can observe at Earth's surface,

True-ish of cosmic radiation, but we've been generating bucketloads of 15 MeV photons for radiotherapy for as long as I have been in the business, and AFAIK work is proceeding on a high-brightness 6 GeV source in China.

24

Just Chat! / Re: Is there a maximum frequency for a gamma ray?

« on: 21/02/2022 11:05:41 »

The Planck length has no physical significance apart from being, theoretically,  the shortest length of an object that can be measured with a photon. That doesn't imply the converse that you can't have a photon with a shorter wavelength.

25

The Environment / Re: Is hydrogen a better fuel source for the environment?

« on: 15/02/2022 23:20:24 »

That is 3 times the drag for the same distance at 3 times the speed, that is very convenient.

No, it is 9 times the drag force, over the same distance. Energy = force x distance.

26

Plant Sciences, Zoology & Evolution / Re: Why does an earthworm look the same on both ends?

« on: 27/01/2022 22:22:21 »

Relax, chaps! The story was amusing but sadly has fallen among pedants.

It's easy to criticise Cronin for being unobservant, but at the same time she should be applauded for entertaining at least one real kid and exercising the minds of three boys who never grew up (every scientist is a Peter Pan at heart) in this forum.

And full marks to said real kid for asking a penetrating question, plus a star for Dad's effort: the bilateral near-symmetry  of animals gave Alan Turing much food for thought.

IIRC earthworms always tunnel forwards but make a vertical U-turn to bring their heads to the surface to eat.

Meanwhile I heard a great line from a woman interviewed in a serious (Radio 4, anyway) program about twins. She said "When I get dressed  to go out I think "I could be really beautiful", then I look at my sister and realise I couldn't.

27

Physics, Astronomy & Cosmology / Re: Homework help. Statistics for Physics.

« on: 20/01/2022 21:02:45 »

 Hence, the question is already "out there" and the marking scheme (almost a model answer) has already been circulated by the University to this year's students who were using the past paper purely for revision or practice.

As it's in the public domain I don't see a problem in principle - you aren't intending to profit from reproducing the contentious part, and there's a public interest case for discussing it openly.

28

Plant Sciences, Zoology & Evolution / Re: Can we teach chimpanzees to become cavemen?

« on: 14/01/2022 17:39:39 »

Chimpanzees are too strong, dexterous and intelligent to behave like humans.

29

Physics, Astronomy & Cosmology / Re: Whats a branch of physics with high potential that has unjustified disinterest

« on: 11/01/2022 05:24:13 »

Atmospheric physics. That is, real physics, not modelling and curve fitting.

School textbooks and teaching. Lots of people do it, very few do it well. Massive potential to alter the perceptions and behavior of everyone.

30

General Science / Re: Is this a feasible system for recycling CO2?

« on: 08/01/2022 12:19:01 »

Cranks may care to read the small print in my contract. There is a very substantial consultancy fee for examining the prototype.

31

General Science / Re: Is this a feasible system for recycling CO2?

« on: 07/01/2022 16:55:47 »

Alan, don't you work with MRIs? I assume you know what happens when a magnet quenches...

Indeed. But suffocation incidents are usually associated with the loading and cooling process, not a subsequent quench. We have exhaust stacks to vent quench gas safely once the magnet is assembled.
My own MRI units  used room-temperature resistive magnets or high-temperature supercons cooled with gaseous helium, but now I'm working with other people's kit, fraught with the dangers of liquid refrigerants.
Fortunately modern MRIs don't use nitrogen - one less problem - and capture helium boiloff, saving a lot of money. Time was that liquid helium was cheaper than beer when vast quantities were used for North Sea divers maintaining oil and gas rigs, but so much was exhausted to the cosmos that it is now more expensive than champagne.

32

Cells, Microbes & Viruses / Re: How can we test new vaccines quickly?

« on: 24/12/2021 22:32:59 »

I saw a brief TV interview with a spokesman for a European country - was it Austria? - who said that their national health service would charge the full cost of treatment to anyone presenting with COVID who was eligible for free vaccination but had not accepted it. SImple, brilliant response to antivaxers.

33

That CAN'T be true! / Re: Why can't water vapour be the driver of today's climate change?

« on: 28/11/2021 18:59:01 »

The concern I see is that trusting on CO2 mitigation alone is likely to not have the compensating correction in the window of time that models predict critical events approaching 2050.  The proposed solutions being implemented currently CANNOT ever support the current energy demands let alone future demands.  Clean, sustainable combustion with adequate on-demand power is attainable including carbon, heat and water vapor mitigation, to a net neutral emissions model which is still being grossly overlooked. 

I'm delighted to welcome thoughtful comment!

34

Physiology & Medicine / Re: blood glucose levels

« on: 26/11/2021 14:04:35 »

So the science agrees with me. Reduce starch and sugar intake ->  reduce adipose tissue -> reduce insulin resistance -> reduce blood glucose! Just as well I read the book,then.

35

Chemistry / Re: Why does HNO3 exist but HPO3 does not?

« on: 26/11/2021 11:12:03 »

https://pubchem.ncbi.nlm.nih.gov/compound/Metaphosphoric-acid

tells you how to make it and what it is used for. Interestingly it causes skin burns and eye damage, and its principal use is in cosmetics!

36

Physiology & Medicine / Re: blood glucose levels

« on: 26/11/2021 10:29:49 »

T'other way around. Reducing starch and sugar intake results in weight loss because the body has to burn fat instead.

Glucose In, Glucose Out, to paraphrase a saying from the early days of computing (nowadays it's Policy In, Garbage Out).  So less glucose in, less ends up in the bloodstream.

37

The Environment / Re: Is Rising CO2 level a Problem?

« on: 25/11/2021 09:08:20 »

Vostok data I think is related to the procession of the earth. Of course this is based on time scales of centuries.

The temperature rises occurred steeply, over a period of  2 - 10,000 years, and the falls were asymptotic over 100,000 years. Precession is sinusoidal, not sawtooth. The current rise began about 15 - 20,000 years ago and is actually less steep than some of the previous ones.

One of the things I find interesting is that the range of both temperature and CO2 has been pretty constant over 500,000 years, and the cycle seems to be slowing - though that's based on a rather small sample of 4 previous peaks.

But it's good to meet someone more interested in the data than the models!

38

Question of the Week / Re: QotW - 21.11.28 - Why do ant bites hurt so much?

« on: 24/11/2021 15:18:41 »

Latin name for an ant is formica - from which we get formic acid HCOOH. Different species inject various amounts when attacked or to kill their prey. Some people are allergic but even if you have no secondary reaction, it's a powerful acid and causes tissue damage.

39

The Environment / Re: Is Rising CO2 level a Problem?

« on: 24/11/2021 15:06:17 »

Beware, ST, other moderators do not tolerate rational dissent on this subject.

I've always looked at Mars for a comparator - more earthlike with more CO2 but much cooler than you would find if CO2 were as significant a greenhouse gas as some would like you to believe.

Not sure you can ascribe Vostok data to the sun. Does it really undergo sudden huge increases in output followed by slow decreases over 100,000 years? It looks vaguely plausible but surely someone would have noticed the continuing and steepening change over the last 100 years. The evidence seems to be that it hasn't changed much since 1970.

40

Just Chat! / Re: Why do we have world problems?

« on: 17/11/2021 15:33:54 »

I think that true sociopaths, who have the ability to lie with a straight face, are mostly born rather than made, but it is possible that childhood experience may contribute to this trait. Surviving a boarding school education almost demands it if you have no other talent, and those politicians educated in the state system were probably called Billy-no-mates. A degree in Philosophy, Politics and Economics will introduce you to the works of the world's most notorious parasites, and defiling a pig will pretty much guarantee a safe Tory seat.

My mother said that most Labour politicians were caught with a hand in the till, and most Tories, with a hand up a skirt, but times have changed and whilst a sly wink is now cause for dismissal (though blatant adultery is not), corruption has become as acceptable as incompetence.