Griffon

The question posed in the OP is quite intesting. As are some of the responses. The 'fact' that electricity is the result of electron flow is one of those things that many people 'know' because that is what they've been taught. There are many similar things that many people believe they 'know'. Our understanding that electricity is the flow of electrons is the result of a whole body of theory supported by observation and experiment. There isn't as far as I know a simple 'clincher' of a fact or observation that could prove to the sceptic that that is how it is. But I might be wrong. I hope someone might suggest one.

Interesting how such a simple observation is telling us something fundamental about the universe.

I'm an agnostic too, but I'm quite content being so. Being agnostic doesn't mean sitting on the fence. The word agnostic, which was coined by the 19th century scientist Thomas Huxley, means to be without spiritual knowledge. Agnosticism is more an intellectual view on what is knowable. If someone is dithering between belief and disbelief in a deity then they are, to put it simply, just a ditherer - not an agnostic. As Dawkins' book, I found it very interesting and agreed with much of what he had to say .... although I found the way he expresses his views somewhat strident at times. Nevertheless I think he makes a very good case for disbelief in a deity. It somewhat surprised me that Dawkins doesn't seem to understand what agnosticism is either. He too seems to be under the mistaken impression that to be agnostic is to be undecided about the issue. Ironically of course, Dawkins is in some ways the modern equivalent of Huxley who in his day was a great proponent of Darwin's theory of evolution. Dawkins should at least have given his predecessor the courtesy of reading and understanding what he thought on the topic of spiritual matters.

I must say I prefer to think of these two operations in terms of two functions f and g. I could try and explain it, but frankly wiki do a better job with animated graphs etc. http://en.wikipedia.org/wiki/Convolution

They're growing wood for burning in power stations because it is renewable. Willow I seem to recall is grown for this purpose. Wood has only half to two thirds the energy density of coal though.

Particle physicists have found the Higgs boson though. As for space .... I agree it's difficult to imagine a limit to space without wondering what's beyond it. But is that because our minds are trapped in only being able to visualise up to three dimensional space? I can visualise a two dimensional space which is limited in extent - the surface of a sphere for example. Space could be infinite of course, which might get around your problem?

Steam engines are external combustion engines and they're quite a good way to turn a dirty fuel (coal) into useful kinetic energy. A good way that is until clean fuels like diesel came along for use in internal combustion engines. Steam engines were less efficient and highly labour intensive. I read somewhere that a steam engine took several hours from cold to get to running condition. You just climb into a Diesel engine and start it, I think. There may be some advantage in using renewable fuels like wood to power steam engines. Although it might be more efficient to burn wood in power stations and use electric trains - I haven't done the efficiency calculations though. Arguably the best use of steam engines is in the heritage tourist industry. Britain has quite a few heritage railway lines running steam engines that are still very popular for tourists.

Yes. The interesting thing too is that we can define mass and say quite a lot about what it does, how it behaves etc., but not really what it actually is. In fact maybe the concept of what something actually is is meaningless. Maybe this is an apocryphal story but I seem to recall reading that Newton was asked what is gravity to which he replied he had no idea.

I think it's all been said in this thread so far. But something which never ceases to amaze me is that scientists like Newton, Gallileo etc came up with some of these concepts like mass, force and so on from first principles. They must have had extraordinary insight, especially for the time, which is of course a mark of their genius.

"No body can explain the famous Two slit experiment that quantum physics is based on." I don't agree. What happens in a two slit experiment is well described by quantum physics. I don't see your explanation provides any additional or indeed necessary insight.

There is an argument that our reality is more likely to be a simulation than the real thing. It goes something like this. All intelligent and technological species will eventually reach the stage at which they can create simulated worlds. In fact very many simulated worlds of all sorts of variations. Some of the worlds will themselves contain technological species which will in turn create virtual realities and so on. So, the argument goes, there is s high probability that we unknowlingly exist in a simulated rather than real universe. I'm not saying I necessarily believe any of this. I'm just relaying the idea.

I don't understand what you mean except in the sense it's always good to observe the behaviour of any physical system in different ways, novel ways in particular.

Constructive interference in a thin film of thickness d and refractive index n for a particular wavelength λ is given by d = Nλ / 2n for N = 1, 2, 3 .... So with increasing thickness the colours progress through blue, green, yellow, red. Repeating with each order of N = 1, 2, 3 .... The equation above applies for light reflected perpendicularly from the surface. At a reflecting angle θ the equation for constructive interference is d = Nλ / 2ncos(θ)

Are the several versions of this thread starter visible evidence of quantum superposition?

I recommend Richard Feynman's very readable book QED The Strange Theory of Light and Matter in which he explains how quantum electrodynamics accounts for all optical phenomena including diffraction, without resorting to a wave explanation.

Why should our minds that evolved to meet the challenges we faced on the African savannah be up to the task of truly understanding the universe, which is essentially what science sets out to do? We have no idea whether we understand 0.001% or 99% of what there is to understand. We might unlock the bottleneck in progress if we found a way to somehow enhance the human mind by directly interfacing with computers - possibly quantum computers.

Yes, the unreasonable effectiveness of mathematics in the natural sciences as Eugene WIgner described it. But I was really thinking of the ineffectiveness of the fairy stories we construct to visualise physical systems we can't in fact see. Electrons in orbit of nuclei, that sort of thing. These constructs are ultimately unhelpful I think. We cannot really know what such inaccessible systems are like apart from how they behave in certain situations - the results of experiments or observations in other words.

Do you mean the wave-particle duality of matter? I've long thought that duality a problem of human invention rather than being real. The behaviour of entities like electrons or photons is described by the equations of quantum mechanics. The outcome of particular experiments is provided by those equations. That's all we can know about them.

Perhaps all students of computer science should read this classic paper by Alan Turing in which he explores whether machines can think. http://www.turingarchive.org/viewer/?id=463&title=1

Why is it described as a theorem, which is a mathematical term, rather than a theory?

Yes. Not "equivalent to zero" though. Isn't there an infinitessimally small probability of pulling a green ball out of a bag containing an infinite number of red balls? But you still might get lucky!

Might this imply that the star is not old at all? It just formed in an environment that had a low metalicity? [Response to Arch2008's post]

I'm sort of thinking out loud here, without knowing anything about the debate to which you refer ... What does "infinitely rare" mean? Crudely put I would have thought that the chance of finding an infinitely rare particle amongst the infinite set of all particles is one over infinity - so damn near zero it might as well be. On the other hand, you just might get lucky!

Those distant galaxies are old now, assuming they still exist. Presumably they now consist of many younger stars and perhaps a few older objects that date from the earliest times - much like our galaxy. There's no way of knowing of course.

Reply to Michel12345 Yeah, I'm saying the same thing in a different way. Distant galaxies are older, sure, because the light has taken longer to get here. So we inevitably see them as they were millions or even billions of years ago. But there's no reason why nearer things should not be older too. That's a nice wy to put it I think. I suppose th e amazing thing is that stars have such a wide range of life durations. A few million for stars that burn bright and short. 8 billion or so years for sun-like stars, and at least as old as the universe for stars like HD140283.