You are currently browsing the monthly archive for September 2010.
On September 28, 1980, PBS aired the first episode of Carl Sagan’s Cosmos: a Personal Voyage. For me, it was like someone finally showing me the back room of the museum, you know, where all the good stuff is. I was 12.
I’d been learning about science in school, of course, but I was always disappointed by it. Where was all the good stuff? Where were the connections, the links to my life experience, the relationship between science and religion, art, culture, music, and so on? Cosmos brought it all together for me, showed me that science was not just a subject in school. It was a way of seeing the world. A way of seeing with new eyes.
Since I’ve already reviewed all 13 episodes of Cosmos on this blog, for this 30th birthday I’ll just list some of my favorite Sagan quotes from the series. There are so many more, and of course the context is greater still – an emergence that changed me (and others, too) forever.
“The Cosmos is all that is or ever was or ever will be. Our feeblest contemplations of the Cosmos stir us — there is a tingling in the spine, a catch in the voice, a faint sensation of a distant memory, as if we were falling from a great height. We know we are approaching the greatest of mysteries.”
“We on Earth have just awakened to the great oceans of space and time from which we have emerged. We are the legacy of 15 billion years of cosmic evolution. We have a choice: We can enhance life and come to know the universe that made us, or we can squander our 15 billion-year heritage in meaningless self-destruction. What happens in the first second of the next cosmic year depends on what we do, here and now, with our intelligence and our knowledge of the cosmos.”
“What an astonishing thing a book is. It’s a flat object made from a tree with flexible parts on which are imprinted lots of funny dark squiggles. But one glance at it and you’re inside the mind of another person, maybe somebody dead for thousands of years. Across the millennia, an author is speaking clearly and silently inside your head, directly to you. Writing is perhaps the greatest of human inventions, binding together people who never knew each other, citizens of distant epochs. Books break the shackles of time. A book is proof that humans are capable of working magic.”
“National boundaries are not evident when we view the Earth from space. Fanatical ethnic or religious or national identifications are a little difficult to support when we see our Earth as a fragile blue crescent fading to become an inconspicuous point of light against the bastion and the citadel of the stars.”
“If you wish to make an apple pie from scratch, you must first create the universe.”
“A googolplex is precisely as far from infinity as is the number 1.”
“We speak for Earth.”
“We make our world significant by the courage of our questions and by the depth of our answers.”
“Every one of us is precious in the cosmic perspective. If a human disagrees with you, let him live. In a hundred billion galaxies, you will not find another.”
“The Cosmos if full beyond measure of elegant truths, of exquisite interrelationships, of the awesome machinery of nature.”
“We embarked on our cosmic voyage with a question first framed in the childhood of our species and in each generation asked anew with undiminished wonder: What are the stars? Exploration is in our nature. We began as wanderers, and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars.”
” . . . the Cosmos is also within us; we are made of ‘star stuff’ – we are a way for the Cosmos to know itself.”
Happy birthday Cosmos!
I’ve read and reread the passages on quantum erasers and delayed choice in Brian Greene’s wonderful book The Fabric of the Cosmos. I think I’m finally getting a feel for what it means. And I also think the existence of quantum erasers says something amazing about, believe it or not, free will.
Stay with me here, because the going will be a bit treacherous. I’ve written before about the double slit experiment. I’ve also written a little bit about entanglement. When you combine those two crazy ideas together, you get, well, craziness. But a very particular kind of craziness, the kind that makes the whole mind-blowing subject, I think, a little more human.
OK start with the basic idea. You can’t know both the particle-nature of a photon (which slit it went through) and the wave-nature of that same photon (interference pattern). Anything you do that reveals “which path” information automatically makes the interference pattern disappear.
What’s interesting about the quantum eraser is that you can set up things so that which path information exists, but is still hidden. One way Greene describes this is by polarizing the photon either clockwise or counter-clockwise. If you do this, even if you don’t collect the information, the interference pattern is destroyed. This is key: the mere potential of collecting which path information destroys the interference pattern. This is important for later.
The quantum eraser takes that information back out. The polarization is erased by removing the tag. Now the photons can interfere once more. Remember, as long as the potential for which path information exists, the interference pattern disappears. But (and again, this is key) once that potential is erased, the interference pattern comes back. This is important, too.
OK, now let’s think about another way to make which path information potentially available. This is a method that is even less invasive than the polarized tag. This time, we use something called a down-converter. Where at first one photon existed, we now create two, each with half the frequency of the original photon, and each entangled with the other. Call one photon the signal photon, the other the idler photon.
Suppose we send the signal photons toward a double slit. Will they form an interference pattern? The answer is, it depends on the idler photons. As long as these idler photons exist and give us the potential to discover which path information, the answer is no, no interference pattern will form. If, on the other hand, these idler photons are recombined in such a way that which path information becomes impossible to retrieve, then the interference pattern, in a certain specific sense, reappears.
Here’s the incredible part, though. The choice about what to do with the idler photons, whether to measure them directly or to recombine them to erase which path information, can happen after (even well after) the signal photons have formed their pattern. Note that, due to some clever bookkeeping by nature, you can never actually “see” the interference pattern until you obtain some extra information about the recombined idler photons. It’s all part of that amazing way that nature has of covering her tracks. It’s pretty clever, and if you want to know more about it I urge you to read Greene’s book, this Wikipedia article, or even the original paper (look at how graphs 3 and 4 each show an interference pattern, but when you combine them into graph 5, as always happens in the real experiment, the pattern disappears. Nature is shrewd!)
But astounding as all that is, it’s still not the most amazing piece of this. Here’s the most amazing piece. We already saw that we can reveal honest-to-goodness, no-mistaking-them interference patterns if we erase the which path information before the photons hit the screen. Remember the important points bolded above. What we can’t do is reveal an honest-to-goodness, no-mistaking-it interference pattern if the which path information is erased after the signal photons hit the screen. There’s a before-after dichotomy. The universe behaves differently regarding a choice that’s been made and a choice that might be made. And while it would be mind-blowing either way, I find this result (the future can’t affect events that have already happened) just as mind-blowing, maybe even more mind-blowing, than the alternative. Why? Because as long as the idler photons exist, as long as the potential for which-path information is there, the signal photons will not form an interference pattern. It’s as if they’re saying, “You might find out, you might not, so we’re not taking any chances.” But if we might find out and we might not, then we have the choice. We aren’t constrained by the past, and all future paths are open to us.
The refusal of those stubborn signal photons to form an interference pattern, no matter how we promise that no, really, we’d never go and detect your idler friends, demonstrates to me an amazing fact. We have free will. The future is open. We can make our own choices.
This is a big deal, because there are philosophies that say the future is just as determined as the past, that time is an illusion, that all future events are controlled by conditions right now. But the delayed choice quantum eraser denies that idea. It says that I control my own destiny, and the universe, recognizing my autonomy, must behave accordingly. And that’s pretty cool. Damned be determinacy! Long live the idler photons, for they have set us free!
I’ve been researching brain imaging technologies for a project I’m working on. It is incredible stuff. SQUIDs, superconductive quantum interference devices, can detect the tiniest of electrical currents in the brain. MEG (magnetoencephalography) uses an array of SQUIDs to observe how these electric currents change over time. PET scans and MRI scans reveal thoughts as they happen. We can actually see into a person’s brain and watch her think. It’s amazing, and it drove home an idea that of course had to be true all along.
Everything is real.
What I mean is this: if a person says she’s heard the voice of God, or thinks an angel has visited him, or just has a “feeling” about one or another fact about the nature of the world, then that voice, that vision, that feeling are all real things. We can map them in the brain. We can see what started the thought, where it came from, even. If you hear a voice, maybe there was no sound to vibrate your eardrum, but that doesn’t make the voice any less real in your brain. A real event happened in there. Thoughts are real things.
That doesn’t mean the origin of the thought is supernatural. Just the opposite, in fact. Everything is real. Did that thought come from some outside signal? If so, we have a chance of detecting it. Did it come from another part of the brain? We have a chance of detecting that, too. Suppose these voices are beamed to us from the second planet circling Epsilon Erandi (I’m not saying they are, but just suppose). Now that we can see the brain in action, we have a chance of figuring that out. If supernatural claims have any basis in reality, at some point the stimulus stops being supernatural and becomes a real thing happening inside someone’s brain. If every effect has a cause, even inside a brain, then the whole notion of supernatural starts to lose its mystery. Maybe, like the brain was for so long, it’s just something we don’t (yet) understand.
Terry Jones wants to burn something.
I suggest The Turtle and the Universe (I hear it’s on sale at Amazon).
If you do so, Pastor Jones, I promise I won’t blow anything up. I won’t riot in the streets. I won’t even write a strongly-worded letter. Of course if I did, you’d probably burn that, too.
But why burn a children’s science book?
Well, take a look inside and the reasons become quite obvious. I claim that the Earth is 4.6 billion years old. I claim that dinosaurs and people never walked together. I lead children (innocent children!) down a path of moral decay, into a world where they believe in, no I can’t type it, you know, the e-word.
So here’s what I suggest you do, Pastor Jones. Purchase 1000 copies of my book. Toss them in a heap and light them on fire. Dance around the bonfire and celebrate the souls you’ve just rescued. It’ll make you feel better. Do it for the children!
And, on the odd chance that Pastor Jones isn’t a regular reader of Turtle Universe (unlikely as that may be), any of you loyal readers out there (both of you) are encouraged to get the ball rolling by purchasing your own copy of The Turtle and the Universe and having it shipped directly to:
Dove World Outreach Center
5805 NW 37th St
Gainesville, FL 32653
If it works out, just turn the other cheek. It’ll all be ok, really it will.