Science, the nature of theory, and global warming.

My summery slumbers have passed, but while having them, I had web discussions, including one on the nature of time. (More on that in a later post.) I also got entangled in a discussion on global warming, and got one comment that really annoyed me: I was accused of being logical. It was suggested that how you feel is more important. Well, how you feel cannot influence nature. Unfortunately, it seems to influence politicians, who end up deciding. So what I thought I would do is post on the nature of theory. I have written an ebook on what theory is and how to form theories, and while the name I gave it was not one that would attract a lot of readers (Aristotelian methodology in the physical sciences) it was no worse than “How to form a theory”. Before some readers turn off, I started that ebook with this thought: everyone has theories. For most, they are not that important, e.g. a theory on who trashed the letterbox. Nevertheless, the principles of how to go about it should be the same.

In the above ebook, I gave global warming as an example of where science has failed, not because we do not understand it, but rather the public has not really been presented with the issue properly. One comment about global warming is that scientists have not resolved the issue. That depends on what you mean by “resolved”. Thus one person said scientists are still working on relativity. Yes, they are, but that does not mean that what we have is wrong. The scientific process is to continually check with nature. So, what I want to do in some of my posts this year is try to give an impression of what science is.

The first thing it is not is mathematics. Mathematics are required, and part of the problem is that only too often scientists do not state clearly what they are saying, preferring to leave a raft of maths for the few who are closely in the field. This is definitely not helpful. Nor are TV shows that imply that theories are only made by stunning mathematics. That is simply not true.

The essence of science is a sequence of simple statements, which are the premises. For me, the correct methodology was invented by Aristotle, and the tragedy is, Aristotle made some howling mistakes by overlooking his own methodology. Aristotle’s methodology is to examine nature and from it, draw the premises, then apply logic to the statements to draw some conclusions, check with observation, and if the hypothesis still stands up, try to determine whether there are any other hypotheses that could have given equivalent predictions. Proof of a concept is only possible if one can say, “if and only if X, then Y”, in which case observing Y is the proof. Part of the problem lies in the “only”; part lies in seeing the wood for the trees. One of the first steps in analyzing a problem is to try to reduce it to its essentials by avoiding complicating features. This does not mean that complicating features should be ignored; rather it means we try to find a means of avoiding them until we can sort out the basics. If we do not get the basics right, there is no point in worrying about complicating factors.

To consider global warming, the first thing to do is put aside the kilotonnes of published data. Instead, in order to focus on the critical points, try modeling something simpler. Consider a room in your house in winter, and consider you have an electric bar heater. Suppose you set it to 1 Kw and turn it on. That will deliver 1 kilojoule of heat per second. Now, suppose doors are open or not open. Obviously, if they are open, the heat can move elsewhere through the house, so the temperature will be slower to rise. Nevertheless you know it will, because you know there is 1 kilojoule per second of heat being liberated.

The condition for long term constant temperature (equilibrium) is
(P in) – (P o) = 0
where (P in) is the power in and (P o) is the power out, both at equilibrium. This works for a room, or a planet. Why power? Because we are looking to see whether the temperature will remain constant or change, and to do that we need to see whether the system is changing, i.e. gaining or losing heat. To detect change, we usually consider differentials, and power is the differential of energy with respect to time. Because we are looking at differentials, we can say, if and only if the power flow into a system equals the power flow out is it at an energy equilibrium. We can use this to prove equilibrium, or otherwise, but we may have to be careful because certain other energy flows, such as radioactive decay, may be generated internally. So, what can we say about Earth? What Lyman et al. found was there is a net power input of 0.64 watts per square meter of ocean surface. That means the system cannot be at equilibrium.

We now need a statement that could account for this. Because the net warming effect is recent, the cause must be recent. The “greenhouse” hypothesis is that humanity has put additional infrared absorbers into the air, and these absorb a small fraction of the infrared radiation that would otherwise go to space, then re-emit the radiation in random directions. Accordingly, a certain fraction is returned to earth. The physics are very clear that this happens; the question is, is it sufficient to account for the 0.64 W? If so, power into the ground increases by (P b) and the power out decreases by (P b). This has the effect of adding 2 (P b) to the left hand side of our previous equation, so we must add the same to the right hand side, and the equation is now
(P in + P b) – (P o – P b) = 2 (P b)
The system is now not in equilibrium, and there is a net power input.
The next question is, is there any other cause possible for (P b)? One obvious one is that the sun could have changed output. It has done this before, for example, the “Little Ice Age” was caused by the sun’s output dropping with a huge decrease in sunspot activity. However, NASA has also been monitoring stellar output, and this cannot account for (P b). There are few other changes possible other than atmospheric composition for radiation over the ocean, so the answer is reasonably clear: the planet is warming and these gases are the only plausible cause. Note what we have done. We are concerned about a change, so we have selected a variable that measures change. We want to keep the possible “red herrings” to a minimum, so the measurements have been carried out over the ocean, where buildings, land development, deforestation, etc are irrelevant. By isolating the key variable and minimizing possible confusing data, we have a clear answer.

So, what do we do about it? Well, that requires a further set of theories, each one giving an effect to a proposed cause, and we have to choose. And that is why I believe we need the general population to have some idea as to how to evaluate theories, because soon we will have no choice. Do nothing, and we lose our coastal cities, coastal roads and coastal agricultural land up to maybe forty meters, and face a totally different climate. Putting your head in the sand and feeling differently will not cool the planet.

* Lyman, J. M. and 7 others, 2010. Nature 465:334-337.

Radiation: a space travel hazard?

Space travel is, not unnaturally a key part of much science fiction, but a recent article in the journal Science raised an important issue: radiation. Based on data from Curiosity, travelling to and from Mars employing the same type of trajectory as Curiosity (a standard orbital transfer trajectory) a person going there and back would receive approximately 660 millisieverts of radiation. For comparison the average person gets just under 4 millisieverts per annum, although a CT scan can give you 8. Space agencies limit astronauts to 1000 millisieverts during their entire career. There appear to be two views to this. The first is radiation is probably still the least of an astronaut’s worries. The second it, radiation could get worse than this.

There are two sorts of radiation that are relevant: protons expelled from the sun, which may be in great blobs of plasma, and cosmic rays, from the rest of the universe (and probably originating in supernovae). On earth, we are protected from the sun’s emissions by the earth’s magnetic field, which diverts charged particles, but on an average space ship, there will be no such protection, nor will there be such protection on the surface of Mars. There is less you can do about cosmic rays because they have so much energy. So what can be done to protect the intrepid space traveller?

The first step is obvious: get there faster. Think of crossing the Atlantic. Curiosity was about the slowest you could travel and still get there, and could be compared with crossing the Atlantic in a Viking longboat. Jet planes make what was then a highly risky and very prolonged trip rather ordinary now. Curiosity took so long because chemical propulsion does not provide enough power, so the first step is to devise better propulsion systems. The second step is to provide the astronauts with protection against such radiation, which should include shielding at a minimum. Once at Mars, the atmosphere will provide some shielding, because while the pressure is low, there is still a fairly thick layer, and of course, while inside a building, or even in a suit, there is protection. A massive solar flare would go through a simple wall or a suit, but such flares are detectable and the astronaut should get a couple of days warning. On Mars, getting underground provides any amount of shielding.

Several science fiction books have a lead-shielded zone in their space ship to protect themselves. Actually, plenty of water would do a fairly good job, and of course you have to take plenty of water anyway. Design features help, and do we want to take a huge mass of lead for no other purpose? In my novel, Red Gold, the setting of which involved the colonization of Mars, I proposed two fusion-powered ships, the fusion units to provide electricity and energy for materials production once there. The ships were each about twenty million tonne mass fully laden so they were not small, but they had to be about that big to carry enough stuff required to make a settlement work and give two hundred settlers a reasonable lifestyle. The mass provided some shielding, but the large disks also had large magnetic fields. How much good that would do is debatable. However, I also proposed a massive space station at the Mars sun L1 position, which is the nul gravitational point between Mars and the sun, and that was intended to generate a massive magnetic field powered by solar energy and superconductors. The concept was if charged particles were even given a small nudge, from that distance they would miss Mars. Finally, I had my key settlement underground. I suppose one can debate the effectiveness of these schemes, but I think that if we are going to colonize Mars we have to consider radiation, and I think part of the point of fiction is to alert readers to some of the relevant issues. Meanwhile, I gather there is a Dutch reality TV program intending to send a very limited number of people on a one-way trip to Mars. Read what I think is a dead minimum that should be taken, and see if you would want to be part of that TV show.