You are currently browsing the monthly archive for August 2010.
I’ve written before about Cloverfield Pond. On a recent visit there, I had an odd thought. What would happen if I just walked into the pond and sat down?
Well, the water’s probably not more than a foot or two deep, maybe three in the middle, so I’d probably still be able to breathe. But eventually, if I sat there long enough and didn’t defend myself, I’d be eaten. Nature is full of beauty and mystery and wonder, but it’s also hungry. And, not to sound egotistical, but I taste good.
What does that mean? It means that my body is chock full of low entropy stuff that other creatures crave. They can use my low-entropy ingredients to extract energy and/or build their own low-entropy bodies. Wherever there’s a resource, some creature will exploit that resource. And resource means low entropy.
But why should I be build of such tasty stuff? It’s not just me, of course. It’s you, too. It’s all of us. In order to be alive, we have to be made of low-entropy materials. That’s part of what being alive is. How’d we get that way?
Well, we ate other low-entropy individuals. Probably not other people, but certainly plants, and (if you’re like me) other animals, too (vegetarians taste better). We took those low-entropy materials, extracted the usable energy, utilized the most useful structures such as proteins, and, um, got rid of the rest. All living things are engines for extracting what they need from low-entropy materials, then returning high-entropy waste to the environment.
Plants are the crucial link, of course. They grab low-entropy sunlight and transform high-entropy materials (carbon dioxide and water vapor) into low-entropy materials (sugar). Everything else depends on their ability to do this amazing transformation trick. But notice how they do it. They capture very high-entropy sunlight and, overall, return lower-entropy ingredients to the environment.
This isn’t a criticism of plants; rocks would do much worse. A rock just absorbs low-entropy sunlight and then just radiates back much higher entropy radiation, without producing anything useful in the process.
But why, we have to ask, does sunlight have such low entropy? Because it was produced in a low-entropy environment, the Sun. There, low-entropy hydrogen is fused into higher-entropy helium, changing mass into light energy.
Let’s keep following the reductionist chain. Why is hydrogen lower entropy than helium? Because in reacting, hydrogen must fire off positrons and neutrinos, all of which carry away energy. The resulting helium atom has a mass just low enough to match the lost energy.
But where did the hydrogen come from? Hydrogen came originally from the Big Bang itself. Here, finally we reach the crucial mystery. The Big Bang began as an incredibly tiny dot of hugely low entropy (extreme high order). Ever since that event, the overall entropy of the universe has been increasing. Though, fortunately for us, overall entropy is a subtle concept.
Occasionally, gravity may pull a star together, lowering the local entropy. But because huge amounts of heat are released, the overall entropy still goes up. Even more rarely, the low-entropy light of the star may support life on a nearby world. Like stars, living things reduce their own local entropy, always at the cost of increasing the entropy of their surroundings (by, for instance, eating their neighbors, then releasing the waste).
One of those living things, me, has been increasing the entropy of his surroundings for over four decades now. But I know it can’t last forever, because I taste so good.
And so do you. The next time you go to the zoo and notice the tiger or polar bear eying you hungrily, the next time you get bitten by a mosquito or even just catch a cold, remember why these creatures are after you. You taste good because of the amazing order that existed just before the Big Bang. Yum!
Thereafter he walked very carefully, with his eyes on the road, and when he saw a tiny ant toiling by he would step over it, so as not to harm it. The Tin Woodman knew very well he had no heart, and therefore he took great care never to be cruel or unkind to anything.
“You people with hearts,” he said, “have something to guide you, and need never do wrong; but I have no heart, and so I must be very careful.”
– The Wonderful Wizard of Oz, chapter 6
“I don’t have any people of my own, chief. I’m my only hope for a hero.”
– Joe Versus the Volcano
and of course
“All right, then, I’ll go to hell”
– Adventures of Huckleberry Finn
I wish I knew more.
I’m often blown away by statements you sometimes hear that “scientists think they know everything.” A quick google search came up with over 60 pages with that exact quote – admittedly some are put-ons, though not all. It makes for entertaining reading. But I digress.
I’m not a scientist (though I sometimes play one on Youtube, but I digress again). Still, I spend a lot of my time reading and writing about scientists. They know, and are perfectly willing to admit, that they don’t come anywhere near knowing everything. In fact, a good definition of science might be, “we don’t know, but we can use the methods of science to try to find out.”
By the way, this admission doesn’t affect my atheism. I don’t say (and I’m pretty sure no one else says), “we’ve looked in every possible corner and hiding place and there is no God.” Instead I say “let’s see what we can explain without resorting to something that we can’t explain.” That’s what makes me an atheist, nothing else. OK, this digression thing is getting out of hand. My point is . . .
I’m re-reading The Fabric of the Cosmos by Brian Greene. You might have heard of his more famous book, The Elegant Universe. They’re both amazing, but if I had to pick one over the other, I’d pick FoC. I’ve reached the part, early in the book, where he deals with quantum entanglement. It is absolutely jaw-drop-to-the-floor mind-boggling. I find myself wishing I could understand the mathematics behind it all better, because it’s so easy to get tangled in imprecise mental pictures. But since that’s all I’ve got, here goes.
Greene tells the story of Einstein, Podolsky, and Rosen (or EPR), and their attempt to show that quantum mechanics must not be a full description of the world. Even though they weren’t trying to, what these three did, instead, was lead us to something even weirder, much weirder, than ordinary quantum mechanics. To use Einstein’s word, it’s downright spooky.
Here’s the experiment. Suppose you’ve got some process that always produces two particles flying off in opposite directions. Maybe the particles are electrons, maybe they’re photons. Let’s suppose they’re photons. The way they’re created, we can be absolutely certain that one of the photons must have spin in one direction, and the other must have spin in the opposite direction. We don’t know which particle has which spin until we measure it. So great, the photons fly off some distance and we measure the spin of one. Now we know, without even looking, what the spin of the other one must be.
What EPR said was that the photons must have had those spins to start with, but quantum mechanics couldn’t tell us that. Therefore, quantum mechanics is incomplete. Seems reasonable to me.
Quantum mechanics, on the other hand, makes the bizarre claim that photons don’t have properties like spin until we measure them. It seems to work in the mathematics, but is it just a bookkeeping trick? I always kind of felt in my bones that it was. Sure, we say that Schroedinger’s cat is neither alive nor dead until we look in the box, but come on! That can’t really be true, can it?
And this experiment seems to point out the silliness of the whole idea. For according to quantum mechanics, the act of measuring the spin of one of the photons doesn’t just give it a spin. The act of measuring gives its partner a spin, too. But wait a cotton-pickin’ minute! That photon is shooting off in the other direction, at the speed of light (since, after all, it is light!), and by the time we get around to measuring the first photon, the two photons might be very, very far apart. How could the second photon know instantly that the first photon just got measured? EPR’s answer was, well, it couldn’t , so both photons had to have a spin to start with. Quantum mechanics said, well, I don’t know, but that’s the way it has to be.
Things might have remained in the philosophical jumble forever, except for a very smart guy named John Bell. Bell realized that by using statistics you could tease out whether or not a particle has definite properties like spin, or whether those properties are set only at the moment they are measured. Greene tells a great story using TV characters and titanium boxes. The real experiments were less entertaining than that, but amounted to the same thing.
What it comes down to is this. In the experiments to test Bell’s idea, either EPR would have been proven right, and the photons really would have had spin the whole time, or else quantum mechanics would have been proven right, and the spin wouldn’t be there until we measure it.
The outcome of it all is that quantum mechanics is right, and EPR is wrong. The moment you measure the spin of one photon, instantly the other photon’s spin is set. Before that single measurement, neither photon had a definite spin. The cat was neither dead nor alive, in both places.
This is amazing and strange, and shows just how far scientists are from knowing everything. No one knows what this means, except that it means there’s something deep and fundamental that we just don’t get. Yet.
The two photons are entangled. They can be a mile, or a thousand miles, or a thousand light years apart. Yet somehow they are connected. When something happens to one photon, the other “feels” it – not just soon, but instantly. The space between the two is no barrier. The time you’d think it would take to send this information is no barrier. Somehow, despite what we think of as a separation in space, the two photons are still connected.
We still have a lot to learn. And I have more reading to do.
I’m not sure I buy Davies’ argument from the previous post. There’s lots of potential big steps that might have taken less time than anticipated. Why the origin of life? Why not the origin of eukaryotic cells, multicellular animals, life on land, big brains? Why did those things all take a long time? The most straightforward answer is that those things are hard. If life’s origin is hard, too, then why didn’t it take at least a while to start here?
Even so, I agree with Davies (and Ward and Brownlee), about complex life, and intelligent life. I think it is very rare, so rare that we might be the only one.
I’m persuaded by Fermi’s Paradox: “where are they?” We’re talking here about intelligent life that, at least in some cases, must be many millions, even billions, of years old. If they were there, I believe we’d know it. Maybe not every intelligence would make their presence known, but it only takes one. It’s an old, old universe, and we just got here. Where is everybody else?
We can imagine a universe in which extraterrestrial intelligent life is obvious. We’d look up in the sky, and we’d know. Clearly we don’t live in that kind of universe. There are two potential reasons. One, they’re not there. Two, they’re there, but no one’s doing anything we’d recognize across the light years. Not one? In millions, even billions, of years? Really?
You can, of course, think of lots of scenarios explaining why we seem to be alone even if we’re not. But they are all special pleading. The most straightforward explanation for us seeming to be alone is that we are.
Some people might find this depressing, and I admit, I’d love for us to discover other intelligences. Just a single discovery could change everything tomorrow. I hope it happens. Assuming it doesn’t, though, I’m not so sad about the alternative. If we really are alone, then we have a huge universe that is ours and ours alone. We are the eyes and ears of that universe. Let’s see what we can learn.
I just finished “The Eerie Silence” by Paul Davies. Davies is deeply involved with SETI, and so took some time to speculate on the possibility of extraterrestrial intelligence.
It’s a subject I find fascinating, though I recognize that it’s all speculation. Still, it’s fun to think about.
I’ve been influenced by Peter Ward and David Brownlee, who wrote an amazing book called Rare Earth and another called The Life and Death of Planet Earth, and I’ve very much adopted their argument.
The argument goes like this: life itself may be quite common in the universe. After all, life seems to have appeared on our planet as soon as it possibly could have. It would be quite a coincidence if life began here so quickly, but then never appeared anywhere else.
But Davies points out a flaw in this argument. We are not a random sample, but a very special circumstance. We are a place where life has gone from single cells to complexity and intelligence. It took a very, very long time to get there – most of the time that the Earth will be inhabitable. We humans just barely made it, sneaking in under the wire before, in just 1 billion more years, the Sun gets so hot that it sterilizes the planet.
If that is typical, then it is no surprise that we happen to live on a planet where life started quickly. If it hadn’t, if it had taken billions of years instead of millions or less for life to form, there wouldn’t have been time for humans to develop. In the “space” including all those planets that have life, only those on which life started quickly is there any chance of finding intelligence. Naturally, since we’re here to ask the question, we live on one of those lucky early-life worlds.
It’s an interesting argument, and I’m still thinking about it. I think I’ll write about it again.