21

Question of the Week / Re: QotW - 18.07.29 - What is the minimum area required to sustain one human being?

« on: 27/07/2018 08:26:58 »

The area of the UK is about one acre (0.4 hectare) per person. When fully cultivated, the country was just about sustainable at 20th century standards of living when we had a coal industry. For indefinite sustainability without fossil fuels we would need to reduce the population to not more than 20,000,000.

At a population of 5,000,000 (around 10 acres per person - roughly the population density of the USA) the quality of life in the UK would be better than any civilisation has ever experienced, and indefinitely sustainable. However the attractiveness of such a society would lead to threats of invasion followed by mass immigration and a diluition of that quality, so as we reduce the population (as we surely must) we need to deploy more personnel defending our very long coastline - we may need to settle at 10,000,000.

22

Physics, Astronomy & Cosmology / Re: How real is (my understanding of) the Copenhagen Interpretation?

« on: 27/07/2018 00:14:25 »

Another important point, that has been mentioned in this thread, but not explicitly focused on is this: Nothing can ever be known exactly--there is always some uncertainty.

It is absolutely crucial to distinguish between uncertainty - the confidence limits of a measurement - and indeterminacy - the fact that ΔpΔx ≥ h.

We can measure the density or x-ray diffraction pattern of solid hydrogen and thus deduce the effective diameter d_H of a hydrogen atom with an uncertainty of, perhaps, ± 0.1% But the fact that  d_H >> d_proton is due to the indeterminacy of the electron.

23

General Science / Re: Is zero an even number, odd number, or neither?

« on: 25/07/2018 22:25:56 »

An integer is a counting number. It is a response to "how many?" I have 0 friends. 0 is an integer.

24

General Science / Re: Is zero an even number, odd number, or neither?

« on: 20/07/2018 13:42:15 »

An even number is an integer which is "evenly divisible" by two. This means that if the integer is divided by 2, it yields no remainder. Zero is an even number because zero divided by two equals zero, which despite not being a natural number, is an integer.

25

Just Chat! / Re: Would it be illegal to ?

« on: 14/07/2018 16:07:42 »

So do as the man says. Buy one lottery ticket and win the £10k you need to start the next phase. When you have won £1,000,000 show me the evidence (a suitcase full of fifties will suffice) and I'll help you develop the project. The promise of certain world domination and my eternal friendship for £1 is surely attractive, and you can probably  find £1 between the sofa cushions..

26

Just Chat! / Re: Would it be illegal to ?

« on: 14/07/2018 12:24:42 »

Get  gorilla to pick the shares. In all laboratory trials, gorillas and octopi have outperformed human experts in predicting stuff like football results and share  prices.

The difference is that the outcome doesn't matter to a stockbroker. He gets commission on the value of the transaction, not whether it makes a profit. Same with casinos - in the long run you are beting against the other players, not the house.

27

Physiology & Medicine / Re: Why do men have breasts?

« on: 14/07/2018 12:17:15 »

Good question as it raises fundamental questions of sex, gender and a whole bunch of stuff that people find puzzling.

At the cellular level, your sex is determined at conception by whether the incoming sperm donates an X or a Y chromosome and is immutable thereafter (at least in the vast majority of cases) because all subsequent cells are either XX or XY.

Your gross anatomy (type and location of organs)  is determined by sex, but fine variants (relative sizes of organs and skeleton, distribution of hair) are determined by hormones and nutrition, both in utero and subsequently, and can vary with age - female facial hair and male breasts being fairly common in the elderly. Whilst breast development is certainly driven by hormones that may be present in a male, AFAIK male lactation requires so many more precursors as to be practically unknown.

Gender is much more subjective and nowadays is considered as much a matter of choice as of sex. AFAIK true hermaphrodism, carrying a fully functional set of both testes and ovaries, is unknown in mammals but normal in earthworms, but where the fine anatomy of an infant is equivocal, gender assignation is (or at least was) a clinical decision possibly supported by surgery.

Human life has become more complicated by the finding that organ transplants don't necessarily have to be sex matched. Perhaps Elizabeth I wasn't kidding when she claimed to have the heart of a man!

I guess the answer to the question is that, there being no evolutionary disadvantage to male nipples, it is fairly efficient for babies of both sexes to have them and allow their later size and function to be determined by hormones, but the difference between ovaries and testes and the necessary means for delivery and reception of sperm and the implantation of an embryo  is too great to allow for equivocation in utero.

28

General Science / Re: How do people allergic to H2O deal with their saliva as it is 99% water?

« on: 12/07/2018 20:46:26 »

What is the excipient in an epipen?

29

Physics, Astronomy & Cosmology / Re: How real is (my understanding of) the Copenhagen Interpretation?p

« on: 12/07/2018 18:04:12 »

Certainty is undefined. What we know (with absolute certainty!) is that either ΔpΔx ≥ h, or the universe would collapse to a singular point. It hasn't, and we have a pretty good idea of the value of h. 

Thinks for clarifying that.  All I have to do now is work out why the Universe would collapse. 

Easy. If ΔpΔx = 0, every electron will spiral in to the nucleus of its atom, emitting a continuous spectrum of electromagnetic radiation as it does so. That's just classical electrostatics and  electrodynamics, and is the Achilles heel of  the classical Bohr atom.

As h > 0, there are finite solutions to the Schrodinger equation and thus nonzero orbital dimensions and shapes, with quantised energy differences between them. Hence a noninfinitesimal universe, the hydrogen bond, stereochemistry, and us. Though the existence of politicians, philosophers and priests still baffles me. What are they for?

30

Physics, Astronomy & Cosmology / Re: How real is (my understanding of) the Copenhagen Interpretation?

« on: 06/07/2018 18:03:08 »

The Copenhagen Interpretation of quantum theory holds that there is no reality at a quantum level, without observation.

And there's the problem. You start with an undefined and probably undefinable concept "reality" then add an equally undefined "observation". That's OK if you want to build a mathematical model in which the undefined variables cancel each other and you end up with a testable prediction, but you can't take the axioms too seriously. It's a bit like "aether" and "conventional current" - helpful but ultimately meaningless!

It's generally preferable to begin with experimental observations, e.g. light is quantised, and work out how these relate to other experimental observations like atomic spectra.

Heisenberg's indeterminacy is mathematically obvious, and no more than a correct formulation of Zeno's paradox. Speed is Δx/Δt, position is x. The larger we make  Δx and Δt, the more precisely we can measure their ratio, but the less meaning we can assign to either x or t. The clever bit is mixing in mass, then guessing that ΔpΔx ≥ h, so whilst we might have a very good idea of the position of a cannonball at any given moment, it becomes very difficult to locate an atom or an electron as m decreases. Ultimately this explains why the hydrogen atom has a finite (but fuzzy) diameter instead of collapsing, and to everyone's surprise h turns out to be a universal constant.

The key to quantum physics is, I think, to accept and use it as a series of statements about what actually happens and not to attempt to derive or "interpret" it from common sense, philosophy, or classical physics.

31

Just Chat! / Re: How is company performance measured?

« on: 02/07/2018 23:00:59 »

It all depends on what you are looking for.

As a potential employee, you might consider that a company with a low profit/earnings ratio would be good to work for as they spend lots of their income on wages, but as an investor you would have to look carefully at the maturity of the enterprise: a startup may lose money for several years until the product hits the market and you make a fortune, but an established business with a low PER isn't going to repay your investment.

I started a niche company as a small cash cow, but investors saw it as a capital growth opportunity - and we still argue about it!

Share price history is often quoted as an indicator, but that is based largely on how prospective investors think the company is likely to perform rather than actual sales and costs.

It is logical to look at the actual product: is it unique, well protected, and secure against failure of suppliers? Even so, that doesn't guarantee that anyone will buy it! On the other hand, the US Academy of Sciences told the Wright Brothers "there is no conceivable military use for the airplane" and a UK government inquiry concluded in the 1950s that "about five computers will be sufficient for all the country's needs".

My grandmother used to say that "whatever happens, people need to eat and drink", but whilst her fish shop provided a comfortable living for the family, the pub next door went bust.

The answer to the fundamental question of capitalism is "nobody knows".

32

General Science / Re: What are the leading technological and social challenges that need addressing?

« on: 22/06/2018 13:26:19 »

The only variable over which we have complete control, and which will devastate everyone's life if not controlled, is human population.

The solution is simple, does not require anyone to actually do or make anything,  and in the long run saves money. However there is no possibility of any individual or corporation profiting from it in the short term, so it won't happen and we are doomed.

33

Just Chat! / Re: How about invisible ?

« on: 22/06/2018 08:55:38 »

Nice demo!

34

General Science / Re: What's the resolution of the human eye?

« on: 21/06/2018 16:23:48 »

Angular resolution: about 1 arcminute, approximately 0.02° or 0.0003 radians, which corresponds to 0.3 m at a 1 km distance.

So roughly 3300 linear pixels in the centre field, which is fairly unimpressive compared with most birds or even a cheap desktop scanner. The clever bit is the integrating and interpolating capability of the brain. I remember noting that I could clearly see the 0.5 cm diameter tow rope trailing from an aeroplane 300 m above me - well below the theoretical resolution of a human eye but clearly discernible by a combination of integration, interpolation and training. Much more difficult to see the rigging of a small boat or radio mast at the same distance because they aren't moving across the visual field.

35

Physics, Astronomy & Cosmology / Re: Is it possible for something to absorb light without reflecting it?

« on: 21/06/2018 12:12:46 »

A "black body" comes close to a perfect absorber. If you drill a small hole in a large hollow sphere, almost everything that enters the sphere stays inside it.

36

Physics, Astronomy & Cosmology / Re: Can we measure the one way speed of light?

« on: 20/06/2018 17:41:33 »

the fabric of space

Please set down the physical characteristics of this wondrous fabric. Density? Elastic modulus? Viscosity? ε_FS and μ_FS?

If I can move relative to it, what is it fixed to?

37

Physics, Astronomy & Cosmology / Re: Can we measure the one way speed of light?

« on: 20/06/2018 07:30:06 »

Wholly different experiment, wholly different result.

In my experiment the source does not move during the measurement.The only moving part is the locally oscillating part of the receiver, and the measurement is of the Doppler shift between the fixed and moving parts of the receiver when the direction of the incoming beam is fixed.

Your "ring experiments" are also irrelevant. c is the speed of light in vacuo, not in a medium. c_m is subject to all sorts of variations.

38

The Environment / Re: Is the greenhouse effect a stupid mistake?

« on: 13/06/2018 07:40:16 »

In summary, you seem to be saying that clouds dominate the radiative heat transfer to and from the surface of the earth. That is obvious to anyone who has ever stood underneath one, but it seems to have escaped the notice of so-called climate scientists who persist in counting fleas like CO2 and CH4 whilst studiously ignoring the H2O elephant they are riding on. Thus leading to statements like "global warming has altered the rainfall pattern" when it is obvious that the rainfall pattern is what determines global temperature.

39

Technology / Re: could this clockwork supply a city with renewable energy?

« on: 12/06/2018 23:49:26 »

This is a great invention ,  great as a dynamo or electrical motor, I wonder why da vinci didn't invent it?

Practically every clock built before 1400, and quite a few modern grandfather and cuckoo clocks, use a falling weight as the energy store. da Vinci didn't invent it because it was already old technology before he was born.

Short-term high power interventions like Dinorwig are used to bridge a few minutes' gap until conventional coal or gas powered stations can be brought on line in periods of sudden demand. They have no value in terms of stabilising the grid against the enormous and long-duration fluctuations caused by windmills, tidal mills or solar cells. Once the grid becomes more than 20% dependent on unreliables, each new generator needs to be backed by at least 5 days' storage capacity, just as with coal, gas or diesel stations, which is why "free" electricity is actually uneconomic - the energy density of non-chemical stores is pathetic..

40

Technology / Re: could this clockwork supply a city with renewable energy?

« on: 12/06/2018 10:13:39 »

22.5 million tonnes of rock is a plug 1 km high with a cross-sectional area of 1000 m², that is, about 7 times the mass of the Hoover Dam (I would use concrete rather than loose rocks, for obvious reasons).

You might be able to cast this mass at the bottom of a 2 km deep hole x 35 m diameter, then haul it up 1000m  on the ropes BC has designed. So you need a primary shaft that will span at least 35 m and two primary bearings capable of carrying a load 1000 times greater than any bearing yet produced. These will need foundations....it's beginning to look like an order of magnitude bigger project than anyone has ever attempted.


Why do I mention the Hoover Dam? Because it works, powers Las Vegas, and is by no means unique.