hidden factors

In my last post, I tried to emphasize the difference between the evolution and climate change debates. I made a joke about god being less easily measured than sea ice. I was mostly trying to emphasize that we ought to all be able to come to a basic agreement about the plain facts that are relevant to the climate change debate, so the comparison to a theological debate was a bit of a throwaway comment.

In the climate change debate, the issue is whether anthropogenic factors can explain most or all of the observed climate fluctuations. Are there hidden factors that should be considered? In the evolution debate, the issue is whether Darwinian mechanisms can explain the observed variety of species from a primordial starting point. Or is there a hidden factor such as a biblical-style creator god?

My throwaway comment made the mistake of presuming that the existence of god is a defining issue when debating evolution. This is of course not the case, given that there are loads of Christians and other theists who embrace evolution, several of whom do me the honour of regularly reading this blog. There is of course yet another debate, the most fundamental one of all, in which the question is, whether a scientific view of the world can potentially explain everything, and if not, what kind of hidden factor should one add in to the model?

Both the evolution and climate change debates revolve around a set of observations that have been made in the present and near past and include the interpretation of records that stretch way way back into geologic time. In the case of evolution, these ancient records are fossils and also the genetic record. In the case of climate change, the ancient records are the isotopic concentrations of bubbles of gas trapped at various depths in the cores of ice that are brought to the surface.

All scientists know that extrapolating even a relatively simple graph beyond the range of actual measurements can be extremely dangerous. In the case of evolution, it is not a graph that is being extrapolated but a fundamental principle of how living organisms change over time. So if there is adequate evidence that this principle operates over some observable time-scale, the simplest explanation is that this principle operated all the way back. This does not rule out the possibility that some radically different mechanism may have operated at some earlier, unobserved time. But for someone proposing another scenario, the onus is on them to find supporting evidence.

Climate depends on numerous factors. Unlike evolutionary theory, climate change science is not about a simple principle. It is all in the details: specifically, whether the recently observed changes are attributable in large part to human activity. We all know that there have been some huge climate changes that occurred on this planet way before living organisms started to pump massive amounts of oxygen into the atmosphere, let alone before humans found all that organic matter and gave it the chance to release its rightful contribution of carbon dioxide into the atmosphere. We also know that life itself is capable of having a profound influence on the composition of the atmosphere: the presence of oxygen being the obvious example.

Apart from the apparent seriousness of the climate change debate, it's a fascinating situation in terms of assessing the credibility of scientists' claims. On the one hand, the doubters do have a point: when you look back at past records of scientists' attempts to extrapolate into the future, they have often overlooked other perhaps hidden factors that become the dominant aspects of the issue over time. Some explanations we accept far more readily than others. When we are told that certain species of fish are disappearing from our oceans, nobody denies that it is due to anthropogenic overfishing. But when we see the loss in sea ice over a roughly equivalent period of time, we are understandably not so sure. We know that humans can dramatically impact global aspects of the biosphere, but we expect the earth's climate to be more resilient, especially with respect to something as ubiquitous as carbon dioxide.

Frankly, I know relatively little solid information about climate change science, and I am hoping to thoroughly educate myself in this area over the next year or so. Even when I have a certain gut belief in something, I like to approach it as a skeptic. I believe that is what science is all about. So I hope to bring some critical appraisals of climate change science over the next few months.

politically-influenced shrinkage factors

When scientists with an atheistic bent argue with fundamentalists about whether God did or did not have a hand in the manifestations of life on this planet, the trickiest aspect of the debate is that it concerns an entity that does not reveal himself directly enough to be weighed or photographed.

But the other great science-related debate of our times concerns physical quantities that can be measured, such as whether there has been any change in the extent of sea ice over the last few decades. Given the accuracy with which these quantities can be measured, the facts should be the same, whether they are perceived by left-wing "let's intervene and fix it" types or laissez-faire right-wing types.

Earlier this month, conservative columnist George F. Will let rip with some skeptical opinions concerning global warming. This included a claim that the sea ice extent has rebounded to 1979 levels. But the research group he was supposedly quoting in fact claims that the arctic sea ice is down 8% compared to the same time of the year in 1979, as visualized here.

Now my point is not in fact to criticize anyone who honestly doubts whether humans are dramatically affecting the climate on this planet. My point is that the debate should be focused on the interpretation of the facts, which is quite a tricky business, not the facts themselves, most of which are pretty hard to dispute. Once humanity figured out how to get satellites up, measuring the extent of sea ice is frankly not rocket science. And for a newspaper of the supposed quality of the Washington Post, checking a simple fact like this is a whole lot easier than checking whether Deep Throat was telling the truth during their award-winning reporting of the Watergate scandal back in the 70s!

Of course the proposed solutions to an acknowledged problem will likely be different according to one's political stripe; that's as it should be and is what makes democracy so much fun. Of course this sets up a bias in how believing or skeptical one is concerning a certain interpretation of the facts, which is regrettable but is hard to avoid. But in a "climate" (groan!) of intelligent debate, it should be in neither side's interest to cherry-pick or distort the facts, because by doing so they ought to lose credibility.

I actually only got around to seeing Al Gore's "An Inconvenient Truth" last weekend. I found it quite persuasive and Gore appears to have a lot of facts at his disposal, probably a lot more than someone like George F. Will. Well I would hope he does, since he is devoting so much of his time and energy to the climate change issue. It occurred to me that, impressive as his rhetorical analogies are, and sincere and extremely well educated about the data as I believe him to be, his one-man show ends up further polarizing the debate - at least in the US - precisely because he can be labeled as anti-Republican.

In the 2000 presidential election, Gore won the popular vote (by a 0.27% margin) but Bush won the all-important electoral vote with a confused counting of the Florida vote where he won by a controversial 0.01% margin. Because this margin was so slim, the facts themselves were subject to debate - whether the votes had been accurately counted in Florida. Compared to these numbers, an 8% decrease in sea ice is huge. In the global warming debate, the facts are the easy part.

high-speed orbits

The news a week or so ago about the high speed crash between the Iridium communications satellite and a defunct Russian military satellite got me wondering about why orbiting satellites have to go so damn fast. The artist's impressions of these things always give you the feeling that they are just drifting around up there but clearly that ain't so. So I got out my envelope and started to doodle on the back of it...

First of all let's figure out how fast someone on the equator is moving simply due to the Earth's rotation. The radius of the Earth r₀ = 6,400 km. A person on the equator covers a distance equal to the Earth's circumference = 2 π r₀ = 40,000 km in 24 hours, corresponding to a speed of 1,700 km/hr! Of course we don't notice this because everything around us is moving the same way, but it gives us a reference point to work from.

Next, let's figure out what radius (r) orbit will keep a satellite over the same patch of Earth using only the effect of gravity to keep it at the right speed. Gravity must pull on the satellite just enough to change the direction of its velocity vector v through a certain angle over time, i.e. at a certain angular velocity (ω = v/r = 360^o/day). This change in velocity corresponds to an acceleration = v ω = r ω².

We know that the acceleration due to gravity at a distance r from the center of the Earth g(r) is proportional to 1/r².

So g/g₀ = (r₀/r)², where g₀ = g(r=r₀) = 9.8 m/s² (the acceleration due to gravity that we experience at the Earth's surface).

Now we equate g = (r₀/r)² g₀ = r ω² (*)

which gives a geosynchronous orbit at a radius r = 42,000 km. A satellite in this orbit must travel at v = r ω = 11,000 km/hr.

What about a low orbit such as the unfortunate Iridium satellite was recently in? These satellites apparently orbit about 780 km above the Earth's surface, i.e. r = 6400+780=7180 km. Plugging this into equation (*) gives ω = 360^o every 100 min, i.e. a complete circuit around the Earth every 100 min. This corresponds to a velocity of 27,000 km/hr.

Of course, if you're outside the Earth's atmosphere in nice empty space, any velocity feels like you're just drifting around. Unless it's not quite empty and you hit something.

colliding submarines

So what is the actual probability of any two objects colliding at random in the Atlantic? Well it was high enough for the Titanic to come a cropper on its maiden voyage of 1912, but then again there had been warnings of large numbers of icebergs and the Titanic was steaming right through their path as they drifted down from the coast of Greenland. And, needless to say, the Titanic and the icebergs were constrained to move around on the two dimensional surface of the sea.

Now of course neither of the two crew members posted to look out for icebergs had binoculars. Similarly, nuclear subs nowadays spend a lot of time in stealth mode, which means turning off their sonar in order to be more invisible. Blind but invisible. Now take two equally blind subs and let them prowl around the bottom of the Atlantic and see what happens. By choice, they constrain themselves to the lower depths of the ocean which increases the probability of a collision. Then they have their favourite trenches to hide in and apparently use temperature gradients to help evade detection - assuming another sub has actually turned its sonar on of course!

So earlier this month it really happened. A French and British sub - both nuclear powered and loaded with nuclear weapons - went bump in the night. Imagine how that must have freaked them out! The funniest part is that in a way - assuming the crews weren't all just fast asleep at the tillers - it shows how amazingly successful both subs were being at what they were supposed to be doing.

So this has been quite the month for spectacular collisions, what with the Iridium communications satellite smashing into a defunct Russian satellite at very high speed. These satellites were in low pole-to-pole orbits. Unlike the much higher geostationary orbits above the equator, the pole-to-pole orbits look like lines of longitude and in fact the satellites crossed paths almost at right angles to each other. They were travelling about 10000 times faster than the two subs so I guess it's a good thing that - unlike the subs - they weren't armed to the teeth.

Darwin, Wallace and consciousness

There are several reasons why Charles Darwin got more credit for the theory of natural selection than did his contemporary Alfred Russel Wallace, who entertained some rather similar thoughts on the subject. I think it is well established that Darwin's original thinking did indeed precede Wallace's and I am not about to spoil our commemoration of Darwin's achievements on this bicentennial of his birthday by discussing whether Wallace deserved more of the credit.

While Wallace was certainly quite the free thinker, Darwin was intellectually the bolder of the two. For him, the mechanics of evolution were powerful enough to bring forth adaptations as striking as consciousness itself. Wallace, on the other hand, believed not only in the materialistic workings of evolutionary theory but felt the need for an additional spiritual force in order to create life in the first place and later to create forms of consciousness in animals and humans.

Today, it is probably true enough to say that people who have thought about how consciousness might be explained can be divided into three main groups. There are the die-hard evolutionists, who believe that life and consciousness evolved from the raw materials of a materialistic universe. There are those, like Wallace, who believe that evolution can explain huge physical adaptations such that fish can turn into mammals just as shallow seas can become thrown up into dramatic mountain peaks, but reckon that some extra ingredients are required to explain consciousness. Lastly, there are those who believe above all in a spiritual force and choose sources of evidence supposedly revealed to us by this spiritual force instead of the materialistic implications of evolutionary theory.

Unlike modern-day creationists, Wallace was a very independent thinker and was certainly not hung up on issues of biblical truth. But he epitomizes the many people who are quite prepared to give evolutionary processes enormous powers over the physical adaptation of life-forms but who baulk when it comes to the evolution of consciousness. While it is easy to see the irreconcilable differences between the evolutionists and the creationists, the differences as exemplified between Darwin and Wallace with respect to this problem of consciousness are surely more worthy of sustained intellectual discussion.

Humans have in the past naturally been drawn to assume that an all-intelligent force created the universe, such that thought must precede existence. Everything we know about existence itself is a conscious knowledge, hence Descartes' assertion that "I think therefore I am." But Darwin's (and Wallace's) theories lead inexorably to the notion that our own ability as a species to develop self-conscious thoughts as individuals must have been the product of evolution, although Wallace could not accept it. And this is what we observe every time a couple of bags of DNA come together to form a new human being - a potential for conscious thought develops into another self-aware individual. Here indeed the emergent property of an individual's consciousness in some sense recapitulates its initial evolutionary development as an adaptive feature of an increasingly complicated central nervous system.

We live neither in a world of mechanical determinism nor in a world where strange spiritual forces must be invoked to breathe life and consciousness into dead matter. It takes a while to get used to the reality that the forces of random change and natural selection can create something as adaptively superb and complicated as an eye. There seems to be no scientific reason not to take the leap and include fully the organ of consciousness within evolution's grasp. By all accounts, Darwin himself probably had more difficulty understanding how on earth peacocks came up with those ridiculous tail feathers than the more sensible accomplishment of consciousness.

debating evolution

As you can see, I've stuck up an icon for the Blog for Darwin carnival. Please click on it if you want to help celebrate the 200th anniversary of Darwin's birthday (12th Feb) by writing a post or just reading the resulting "blog swarm." Thanks to eTrilobite.com for making me aware of it.

The phrase "blog swarm" makes me a tiny bit nervous. It seems to imply more than just an educational opportunity. Of course, the carnival rubric makes it clear that the intelligent design proponents are not welcome, which could be criticized as a lack of open debate, but it will at least prevent the otherwise inevitable slugfest. It still amazes me that the battle-lines are drawn so sharply between the Evolutionists and the Creationists. When I first thought about writing a science blog, my initial browsing put me right off because it seemed that all science bloggers ever did was to trade insults with creationists.

Now I do realize that there are real battles to be fought over how children should be educated in public schools. But outside of this quite specific concern, I see no point in either side wasting endless hours attempting to logically argue their case, when each side comes to the debate with completely different axiomatic starting points. If the children whose education both sides claim to care about ever hear the vitriolic abuse that too many on both sides hurl at their opponents, I only hope they can learn to behave in a more civilized manner when they themselves grow up, whether they believe themselves to be made in the likeness of god or of monkeys.

There is something fascinating about how radically different are these two opposing viewpoints concerning where we all come from and where we're all headed. In so many ways, it makes almost no difference to how people objectively appear to go about their actual day-to-day lives. One might think that religious conviction would turn most adherents into monkish types who shun all earthly concerns and focus purely on some spiritual dimension. And the materialist atheists should surely succumb to despair over the meaningless of existence. The fact that most of us strive to make the most of our time on this earth fits in with Darwin's ideas but is also not incompatible with a religious search for something "higher."

I believe creationists to be tremendously misguided. I also find that many scientists exude an arrogance that leads me to have more sympathy with those who search for a greater meaning behind it all. Surely some of the hatred that passes for debate about evolution is a sign of an insecurity that exists on both sides because, let's face it, the existence of this universe, with us sitting around on this earth contemplating it, is in fact a complete and utter mystery to us all.

oncogenes

Counting down to the 200th anniversary of Darwin's birth, I'm going to keep with biology related posts for a while. I think they're more popular than quantum mechanics anyway!

When I was a graduate student in medical biophysics more than twenty years ago, there was a group of physicists like myself interested in medical imaging and then there were the cell biologists. We spoke rather different languages, but every week we would have a double seminar so that we would all be exposed to talks given by members of both groups. Having had no biology education whatsoever, I found the cell biology talks quite exciting, when they were at least slightly comprehensible to me.

One factoid that I grabbed onto was about oncogenes. A normal cell has bits of DNA that code for proteins that help regulate how much the cell manufactures other proteins, which then affects what type of cell it is. Everyone knows that cancer has to do with a breakdown of normal cellular regulation. So, not surprisingly, when these bits of DNA suffer some mutation, they can become cancer-causing oncogenes.

But the really interesting thing is that certain viruses are carrying these very same oncogenes and this explains how some viruses can induce cancer when they enter the body's cells. The origin of viruses is uncertain. Whether they were totally derived from cellular genetic material that escaped from cells or whether they coevolved as separate entities, they are always replicating inside host cells and so have a rather intimate relationship with cellular DNA. And so, at some stage, a virus can pick up an oncogene from a cell where a mutation has occurred, and can then spread it around. We normally think of viral or bacterial infections as a transmission of the viruses or bacteria themselves. But here, the virus basically picked up "cancer" some time in the past, and can do harm not only in the normal way - killing infected cells - but by destabilizing cells that take in the oncogene so that they become cancer-forming.

Now unless such a virus manages to infect a germ cell, this process is not going to directly affect our genetic lines. But for single-celled bacteria etc, it's another story. For these little creatures, the family tree can have strange horizontal paths that connect up totally different species. Bacteria grow by dividing asexually, but the viruses that infect them (called bacteriophages) can transfer DNA in a "sexual" sort of way with a virtuosity that we multi-cellular beings know nothing about. From the point of view of messing up a family tree, it would be like getting a whale to mate with a chaffinch. Then again, bacteria are pretty flexible about their group identity over time.

the first step

Have you ever wondered whether life may have actually started up from scratch more than once on this planet? There are several issues to consider. First, the conditions in primordial times were probably much more favourable to the genesis of life than at any subsequent period. Second, once life got established, with its universal currency of nucleotides encoding amino acids to produce proteins etc., any second shot at reinventing life would presumably not stand a chance unless it could integrate with what was already thriving in abundance. Mind you, some believe life started up around hot deep sea vents. Have they changed much? Maybe they have, I honestly don't know. But one can just about imagine the odd isolated colony of new life - maybe with a different genetic code - lurking in the depths. Then again, maybe the way life turned out on this planet, with the genetic code just so, was the only possible or the only really favourable one? In which case, if life started up from scratch again, we would never notice.

Almost as fascinating is to consider whether life was invented only once in those primordial days. After all, researchers have looked at genetic similarities and differences across the whole spectrum of modern-day life-forms, and have attempted to trace us all back to a last common ancestral cell. Again, since we all share the same genetic code, this is not so crazy. Now in all probability, if you went back further, you would find an increasing number of common ancestors, so this does not in itself resolve the issue.

From a scientific standpoint, it is perhaps almost irrelevant whether critical discoveries in self-replication etc can be credited to more than one molecule, experimenting in the primordial soup. After all, scientific discoveries are often made by more than one scientist at about the same time - namely, when the state of prior knowledge creates a fertile breeding ground for the next creative step. But wouldn't it be amazing if we knew that every living cell on this planet was connected by an unbroken thread of DNA replication all the way back to a single crucial innovation by some molecular configuration several billion years ago?