03 November 2009


Scary stuff, kiddies

Gravitational lensingFor a long time (maybe a couple of years now), I've been having an on-and-off discussion with a friend via Facebook about God and atheism, evolution and intelligent design, and similar topics. He's a committed Christian, just as I'm a convinced atheist. While neither of us has changed the other's mind, the exchange has certainly got each of us thinking.

Something that came up for me yesterday when I was writing to him was a question I sort of asked myself: what elements of current scientific knowledge make me uncomfortable? I try not to be someone who rejects ideas solely because they contradict my philosophy. I don't, for instance, think that there are Things We Are Not Meant to Know. However, like anyone, I'm more likely to enjoy a teardown of things I disagree with. Similarly, there are things that seem to be true that part of me hopes are not.

Don't be afraid of the dark

Recent discoveries in astrophysics and cosmology are a good example. Over the past couple of decades, improved observations of the distant universe have turned up a lot of evidence for dark matter and (more recently) dark energy. Those are so-far hypothetical constructs physicists have developed to explain why, for instance, galaxies rotate the way they do and the universe looks to be expanding faster than it should be. No one knows what dark matter and dark energy might actually be—they're not like any matter or energy we understand today.

But we can measure them, and they make up the vast majority of the gravitational influence visible in the universe—96% of it. So the kinds of matter and energy we're familiar with seem to compose only 4% of what exists. The rest is so bizarre that Nova host and physicist Neil deGrasse Tyson has said:

We call it dark energy but we could just as easily have called it Fred. The same is true of dark matter; 85 percent of all the gravity we measure in the universe is traceable to a substance about which we know nothing. We can call that Wilma, right? So one day we'll know what Fred and Wilma are but right now we measure the distance and those are the placeholder terms we give them.

We've been here before. Observations about the speed of light in the late 1800s contradicted some of the fundamental ideas about absolute space and time in Newtonian physics. Analysis yielded a set of new and different theories about space, time, and gravity in the early years of the 20th century. The guy who figured most of it out was Albert Einstein with his theories of relativity. It took a few more years for experiment and observation to confirm his ideas. Other theorists extended the implications into relativity's sister field of quantum mechanics—although there are still ways that general relativity and quantum mechanics don't quite square up with each other.

And if that seems obscure, keep in mind how much of the technology of our modern world—from lasers, transistors, and digital computers to GPS satellite systems and the Web you're reading this on—wouldn't work if relativity and quantum mechanics weren't true. Indeed, the very chemistry of our bodies depends on the quantum behaviour of electrons in the molecules that make us up. Modern physics has strange implications for causality and the nature of time, which make many people uncomfortable. But there's no rule that reality has to be comfortable.

Bummer, man

To the extent that I understand them, I've come to accept the fuzzy, probabilistic nature of reality at quantum scales, and the bent nature of spacetime at relativistic ones. Dark matter and energy are even pretty cool as concepts: most of the composition of the universe is still something we have only learned the very first things about.

But dark energy in particular still gives me the heebie-jeebies. That's because the reason physicists think it exists is that the universe is not only expanding, but expanding faster all the time. Dark energy, whatever it is, is pushing the universe apart.

Which means that, billions of years from now, that expansion won't slow down or reverse, as I learned it might when I was a kid watching Carl Sagan on Cosmos. Rather, it seems inevitable that, trillions of years from now, galaxies will spread so far apart that they are no longer detectable to each other, and then the stars will die, and then the black holes will evaporate, and the universe will enter a permanent state of heat death. (For a detailed description, the later chapters of Phil Plait's Death From the Skies! do a great job.)

To understate it rather profoundly, that seems like a bummer. I wish it weren't so. Sure, it's irrelevant to any of us, or to any life that has ever existed or will ever exist on any time scale we can understand. But to know that the universe is finite, with a definite end where entropy wins, bothers me. But as I said, reality has no reason to be comforting.

Either dark energy and dark matter are real, or current theories of cosmology and physics more generally are deeply, deeply wrong. Most likely the theories are largely right, if incomplete; dark matter and energy are real; and we will eventually determine what they are. There's a bit of comfort in that.

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07 March 2009


Links of interest (2009-03-07):

  • The first animals that people domesticated were wolves—we call them dogs now. Coincidentally, within an hour last night I read a Slate article and saw an episode of "Martin Clunes: A Man and His Dogs" on that very topic.
  • From Salon: "To this day when I walk into a grocery store and see a mom with her teenage daughters, I have to leave. Every time I just get tearful, I just can't be in the same room, even after all these years. It just kills me that I don't get that time back."
  • The Economist makes a compelling argument that all recreational drugs—yes, even hard drugs like heroin and cocaine—should be legalized (via Dan Savage). That's a pretty radical position, but the magazine posits it as the "least bad" option, after "the war on drugs has been a disaster, creating failed states in the developing world even as addiction has flourished in the rich world. By any sensible measure, this 100-year struggle has been illiberal, murderous and pointless."
  • Don't forget to put your clocks forward by an hour tonight for Daylight Saving Time, if you're in a part of the world that invokes it early Sunday morning.
  • Scanwiches are sandwiches, cut in half and imaged on a flatbed scanner—which I presume needs very frequent and thorough cleaning (via J-Walk).
  • New Homestar Runner meta-cartoon: 4 Gregs.

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20 March 2008


A billion years, or 600 million, give or take

Woven DNA (#1) at Flickr.comA friend of asked me today:

How does evolution explain something like DNA and how it's decoded? Natural selection/chance-change over billions of years doesnt seem adequate to explain it. Are there other evolutionary mechanisms that might explain it?

Also, DNA seems very clearly to be instructions/information. From an evolutionary standpoint, would that be an illusion because [we humans interpret] what turns out to be chance results as something more meaningful and organized because the result kind of works?

Now, beware, since IANAEBOP (I Am Not An Evolutionary Biologist Or Philosopher). I do have pretty decent background in biology generally, it being my degree and all, and that means I need to understand natural selection well. So here goes my take.

What's chance, what isn't?

One of the issues here is that too often people talk about natural selection, including the initial appearance of DNA, as a random process. It's actually much the opposite: yes, mutations (i.e. the source material or "seeds" for evolutionary change) occur randomly, but the ones that persist because they lead to greater reproductive success are completely non-random. Non-random rules arising from natural processes filter out almost all the random stuff, leading to evolutionary processes that build upon themselves to generate new things.

But non-randomness doesn't have to imply conscious agency (at least I don't think so). Nor does it imply inevitability, or even directionality, really. If you rolled back the clock and started things over again with the first simple microorganisms, or at any later stage, even with essentially the same conditions, the result might very well have turned out very differently.

Evolution is a historical process, and like human history, there are so many inter-related, contingent influences going on that if we, say, started over again 75 million years ago with dinosaurs, even if an asteroid still wiped them out, there's no guarantee a human-like intelligence would arise later. Or if it did, that primates would necessarily be what did it.

Similarly, roll back farther, and would insects end up as the dominant multicellular animals again? Might woody flowering plants once more come to dominate over ferns and other now less common forms? Maybe not.

You can think of an analogy in something like the pattern of a streambed. Yes, the movement of individual water molecules or sand grains may be essentially random, but gravity and friction and a variety of other simple laws of nature, interacting in a very complex way, make it so that the result—the tree-like form of a drainage basin—has a very non-random structure. (If you drop something on earth, it falls down. If things were random, you'd have no way to predict which direction it would go.)

But, yet again, if you rolled back the clock and started the erosion process all over again, the stream's course might run in a very different direction. There would still be a tree-like structure constrained by natural laws, but the details of it would be totally different, so you couldn't plan to build a house or waterwheel or hydro dam in a particular location in advance.

The vastness of time

Another issue is time. Our brains really aren't well equipped to handle the kinds of time scales this stuff happens on. Something like DNA seems irredeemably complicated to have arisen by the hit-and-miss processes we're talking about. It's too well built. (Of course, the process also has its flaws, which is why people like me get cancer.) But we're used to watching stuff happen over the course of minutes or hours or days or weeks or months or years or maybe decades. The rise and fall of civilizations may take centuries. To us that seems like a long time.

Evidence seems to indicate that DNA first appeared pretty early on in earth's history. But it still took something like 600 million years, or maybe closer to a billion. Even if it were completely random (rather than a rule-driven process with random "seeds"), a lot of amazing things could happen totally by chance in 600 million years. And a lot of amazing things have happened in the 4 billion years since, some random, some not.

Humans have never witnessed a large asteroid impact on earth. As far as our actual experience (even on an evolutionary time scale) is concerned, it has never happened. But given enough time, tens or hundreds of millions of years, it pretty much must happen again, and it has happened several times before. So we can consider things impossible when, in the long run, they are inevitable, or at least probable.

Would DNA, or something like it, inevitably have arisen on earth, given enough time? We don't know, and can't know yet. That's why looking for unrelated life elsewhere is important: even if it's non-intelligent life, finding something that arose separately from life on earth would tell us that life-driving processes are at least reasonably likely in this universe.

Or maybe it really is nearly (but not quite) impossible, and it only happened here, once in all these billions of years there have been stars and planets. I hope not, but it could be.

Saving a step

Now, if you step back and ask why natural laws are structured in such a way that contingent, historical evolution can happen even once (or even why atoms and molecules can form at all in the first place, rather than just creating a universe that's nothing but a soup of plasma), that enters into realms of philosophy that I don't think we may ever be able to answer.

Many will answer that God must have made those rules. But if I think like that, I always have to ask: then what made the God (or gods) that could make those rules, and by what meta-rules? In my mind, it's the same problem, just one step further, so it isn't really an answer at all.

I'm comfortable enough thinking that life and the DNA that lets it propagate "just happened" (perhaps the greatest oversimplification it would ever be possible to make in any circumstance). And with observation and intelligence, we're able to understand very much about how things have happened since, without having to resort to supernatural explanations that, by definition, we cannot analyze because their rules must be inscrutable to us.

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