More on this book
Community
Kindle Notes & Highlights
Read between
January 7 - January 20, 2019
By energy conservation, this heat energy is just equal to the energy lost by the glass of water in falling from the table. Thus that little bit of heat energy would be just enough to raise the glass back again to the table!
However, we do need to replace the energy that we continually lose in the form of heat. Indeed, the more ‘energetic’ that we are, the more energy we actually lose in this form. All this energy must be replaced. Heat is the most disordered form of energy that there is, i.e. it is the highest-entropy form of energy.
We take in energy in a low-entropy form (food and oxygen) and we discard it in a high-entropy form (heat, carbon dioxide, excreta). We do not need to gain energy from our environment, since energy is conserved. But we are continually fighting against the second law of thermodynamics.
Entropy is not conserved; it is increasing all the time. To keep ourselves alive, we need to keep lowering the entropy that is within ourselves. We do this by feeding on the low-entropy combination of food and atmospheric oxygen, combining them within our bodies, and discardin...
This highlight has been truncated due to consecutive passage length restrictions.
In this way, we can keep the entropy in our bodies from rising, and we can maintain (and even increase) our internal org...
This highlight has been truncated due to consecutive passage length restrictions.
Where does this supply of low entropy come from? If the food that we are eating happens to be meat (or mushrooms!), then it, like us, would have relied on a further external low-entropy source to provide and maintain its low-entropy structure. That merely pushes th...
This highlight has been truncated due to consecutive passage length restrictions.
This procedure, photosynthesis, effects a large reduction in the entropy. We ourselves make use of this low-entropy separation by, in effect, simply recombining the oxygen and carbon within our own bodies.
How is it that the green plants are able to achieve this entropy-reducing magic? They do it by making use of sunlight. The light from the sun brings energy to the earth in a comparatively low-entropy form, namely in the photons of visible light.
The earth, including its inhabitants, does not retain this energy, but (after some while) re-radiates it all back into space. However, the re-radiated energy is in a high-entropy form, namely what is ...
This highlight has been truncated due to consecutive passage length restrictions.
Contrary to a common impression, the earth (together with inhabitants) does not gain energy from the sun! What the earth does is to take energy in a low-entropy form, and then spew it all back again into space, but in a high-entropy form (Fig. 7.7). What the sun has done for us is to supply us with a huge source of low entropy. We (via the plants’ cleverness) make use of this, ultimately extracting some tiny part of t...
This highlight has been truncated due to consecutive passage length restrictions.
All this is made possible by the fact that the sun is a hot-spot in the sky! The sky is in a state of temperature imbalance: one small region of it, namely that occupied by the sun, is at a very much higher temperature than the rest. This fact provides us with the required powerful low-entropy source.
Why is the sun such a hot-spot? How has it been able to achieve such a temperature imbalance, and thereby provide a state of low entropy? The answer is that it has formed by gravitational contraction from a previously uniform distribution of gas (mainly hydrogen). As it contracted, in the early stages of its formation, the sun heated up. It would have continued to contract and to heat up even further except that, when its temperature and pressure reached a certain point, it found another source of energy, besides that of gravitational contraction,
What about the low-entropy nuclear energy in the uranium-235 isotope that is used in nuclear power stations? This did not come originally from the sun (though it may well have passed through the sun at some stage) but from some other star, which exploded many thousands of millions of years ago in a supernova explosion!
Let us return to our quest for the origin of the second law of thermodynamics. We had tracked this down to the presence of diffuse gas from which the stars have condensed.
DOES THE BIG BANG EXPLAIN THE SECOND LAW?
Has our search come to its end? Is the puzzling fact that the entropy in our universe started out so low – the fact which has given us the second law of thermodynamics – to be ‘explained’ just by the circumstance that the universe started with a big bang?
Recall that the primordial fireball was a thermal state – a hot gas in expanding thermal equilibrium. Recall, also, that the term ‘thermal equilibrium’ refers to a state of maximum entropy. (This was how we referred to the maximum entropy state of a gas in a box.) However, the second law demands that in its initial state, the entropy of our universe was at some sort of minimum, not a maximum!
As the universe expanded, the permitted maximum entropy increased with the universe’s size, but the actual entropy in the universe lagged well behind this permitted maximum. The second law arises because the actual entropy is always striving to catch up with this permitted maximum.
Let us first consider what theory tells us will be the ultimate fate of our sun. The sun has been in existence for some five thousand million years. In another 5-6 thousand million years it will begin to expand in size, swelling inexorably outwards until its surface reaches to about the orbit of the earth. It will then have become a type of star known as a red giant.
What is a black hole? It is a region of space – or of space-time-within which the gravitational field has become so strong that even light cannot escape from it. Recall that it is an implication of the principles of relativity that the velocity of light is the limiting velocity: no material object or signal can exceed the local light speed (pp. 252, 272). Hence, if light cannot escape from a black hole, nothing can escape.
We can imagine that for a sufficiently massive and concentrated body, the escape velocity could exceed even the velocity of light! When this happens, we have a black hole.
HOW SPECIAL WAS THE BIG BANG?
What have we learnt from all this? We have learnt that our theories are not yet adequate to provide answers, but what good does this do us in our attempts to understand the mind?
In my opinion, when we come ultimately to comprehend the laws, or principles, that actually govern the behaviour of our universe – rather than the marvellous approximations that we have come to understand, and which constitute our SUPERB theories to date – we shall find that this distinction between dynamical equations and boundary conditions will dissolve away.
Another argument which is sometimes invoked in this context is the so-called anthropic principle (cf. Barrow and Tipler 1986). According to this argument, the particular universe that we actually observe ourselves to inhabit is selected from among all the possible universes by the fact that we (or, at least some kind of sentient creatures) need to be present actually to observe it!
It is an amazing fact that this simple procedure can be applied in the future direction without any other knowledge of a system needing to be invoked. Indeed, it is part of the theory that one cannot influence these probabilities: quantum-theoretical probabilities are entirely stochastic!.
What are we to do with our expensively constructed box and its totally uninteresting contents? The experiment is to be the most boring imaginable. We are to leave it untouched – forever!
How does all this relate to the physics which governs the actions of our brains? What could it have to do with our thoughts and with our feelings? To attempt some kind of answer, it will be necessary first to examine something of how our brains are actually constructed.
what kind of new physical action is likely to be involved when we consciously think or perceive?
WHAT ARE BRAINS ACTUALLY LIKE?
INSIDE OUR HEADS is a magnificent structure that controls our actions and somehow evokes an awareness of the world around. Yet, as Alan Turing once put it,1 it resembles nothing so much as a bowl of cold porridge! It is hard to see how an object of such unpromising appearance can achieve the miracles that we know it to be capable of.
The picture of a superb computing device seems to be presented to us. The supporters of strong AI (cf. Chapter 1, etc.) would hold that here we have a supreme example of an algorithmic computer – a Turing machine in effect – where there is an input (like the Turing machine’s input tape on the left) and an output (like the machine’s output tape on the right), and all sorts of complicated computations being carried out in between.
To strong AI supporters, these activities of the brain would simply be further algorithmic activity, and they might propose that the phenomenon of ‘awareness’ arises whenever such internal activity reaches a sufficient level of sophistication.
I hope that this brief sketch, though in numerous ways inadequate, will give the reader some idea of what a human brain is like and what it does in a general way. So far, I have barely touched upon the central issue of consciousness.
WHERE IS THE SEAT OF CONSCIOUSNESS?
If all that one needs to be conscious is an active reticular formation, then frogs, lizards, and even codfish are conscious!
What evidence do we have that lizards and codfish do not possess some low-level form of consciousness? What right do we have to claim, as some might, that human beings are the only inhabitants of our planet blessed with an actual ability to be ‘aware’?
Although frogs and lizards, and especially codfish, do not inspire me with a great deal of conviction that there is necessarily ‘someone there’ peering back at me when I look at them, the impression of a ‘conscious presence’ is indeed very strong with me when I look at a dog or a cat or, especially, when an ape or monkey in the zoo looks at me. I do not demand that they feel as 1 do, nor even that there is much sophistication about what they feel.
If ‘awareness’ is merely a feature of the complexity of an algorithm – or perhaps of its ‘depth’ or some ‘level of subtlety’ – then, according to the strong-AI view, the complicated algorithms being carried out by the cerebral cortex would give that region the strongest claim to be that capable of manifesting consciousness.
There are some other points of difference between brain action and computer action that seem to me to be of much greater importance than the ones so far mentioned, having to do with a phenomenon known as brain plasticity. It is actually not legitimate to regard the brain as simply a fixed collection of wired-up neurons.
The interconnections between neurons are not in fact fixed, as they would be in the above computer model, but are changing all the time. I do not mean that the locations of the axons or dendrites will change.
Many people appear to be of the opinion that the development of parallel computers holds the key to building a machine with the capabilities of a human brain.
IS THERE A ROLE FOR QUANTUM MECHANICS IN BRAIN ACTIVITY?
According to Deutsch’s analysis, quantum computers cannot be used to perform non-algorithmic operations (i.e. things beyond the power of a Turing machine), but can, in certain very contrived situations, achieve a greater speed, in the sense of complexity theory (see p. 181), than a standard Turing machine.
How might this relate to the action of a brain containing a significant number of single-quantum-sensitive neurons? The main problem with the analogy would be that the quantum effects would very quickly get lost in the ‘noise’ – the brain is too ‘hot’ an object to preserve quantum coherence (i.e. behaviour usefully described by the continued action of U) for any significant length of time.
Is the brain to be regarded as ‘observing itself’ whenever a thought or perception emerges into conscious awareness?
A plausible case can be made that there is an essential non-algorithmic ingredient to (conscious) thought processes.
IN DISCUSSIONS OF the mind–body problem, there are two separate issues on which attention is commonly focused: ‘How is it that a material object (a brain) can actually evoke consciousness?’; and, conversely; ‘How is it that a consciousness, by the action of its will, can actually influence the (apparently physically determined) motion of material objects?’ These are the passive and active aspects of the mind–body problem. It appears that we have, in ‘mind’ (or, rather, in ‘consciousness’), a non-material ‘thing’ that is, on the one hand, evoked by the material world and, on the other, can
...more
On the other hand, one might believe that consciousness is merely a passive concomitant of the possession of a sufficiently elaborate control system and does not, in itself, actually ‘do’ anything. (This last would presumably be the view of the strong-AI supporters, for example.)
Somewhat preferable, to my way of thinking, would be a rather more scientific version of this sort of argument, namely the anthropic principle, which asserts that the nature of the universe that we find ourselves in is strongly constrained by the requirement that sentient beings like ourselves must actually be present to observe it. (This principle was briefly alluded to in Chapter 8, p. 458, and I shall be returning to it later.)
