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Kimberly Roots, "Physicist plucks away at our tightly strung universe. Stanford university physicist Leonard Susskind on a “theory of everything”" (2005)
"Science & Theology News" January 1, 2005; http://www.stnews.org/package-5-147.htm
Physicist plucks away at our tightly strung universe
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<!-- Blurb --><span class="smallHeader">Stanford university physicist Leonard Susskind on a “theory of everything”<span> >
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<span class="dateText">(January 1, 2005)<span>
Theories of everything: Leonard Susskind is on the hunt.
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(Courtesy photo: Leonard Susskind)<span>
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| Commentary
Science & Religion Guide
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If the way we think about the universe can be considered a landscape, few people wield bigger brushes than Leonard Susskind. The Felix Bloch Professor in Physics at Stanford University, Susskind has had a hand in some of theoretical physics’ biggest advances. The innovative string theory he and Yoichira Nambu proposed in 1969 is the most popular candidate for a potential “theory of everything”: one that would serve to decode the order of the universe.
Turns out, Susskind has a way with words, too. He penned a popular article on the multiverse in an issue of New Scientist last year, and will follow that with two books due this year: The Landscape and An Introduction to Black Holes, Information, and the String Theory Revolution: The Holographic Universe. He recently spoke with Science & Theology News’ Kimberly Roots about framing quantum physics and the multiverse for the masses.
There’s so much terminology wrapped up in the concept of multiple universes. You prefer the term “environments” instead of “universes.”
Yes. I like to think of it as just different environmental conditions that are allowed by the equations of the theory.
Do you think that might help people wrap their minds around the idea of multiple universes a little bit better?
I think so. We can call it “different solutions of the theory.” We can call it “different vacuums.” The word that physicists like is “vacuum.” But all that a vacuum means is an environment in which different kinds of things can happen. The physicists would say some vacuums permit electrons, some vacuums permit this, some vacuums permit that. I think, in lay-person terms, perhaps the world “environment” might be better.
Your New Scientist piece, in particular, does a very good job of getting at the big ideas, but still puts them into terms that a general reader can understand.
Well, I sort of enjoyed it. People liked it. Hey, why don’t I spend a little more time and make a little money out of it?
In that piece, you wrote that cosmologists see big messy worlds that seem to be, for whatever reason, finely tuned.
Full of accidental coincidences and so forth.
Right, and that idea frustrates strict physicists.
However, I must say that the attitude about it has changed enormously in the last couple months.
Really?
Yes, there are very, very few people who are willing to dismiss this idea out of hand now. There has been a real sea change in that very, very few — particularly string theorists — will automatically react and say that’s something, which will be the case.
Do you think the recent NASA deep space probe results [which which validated the field of cosmology by confirming the inflationary theory of the universe] had something to do with it?
No, I don’t think it had anything to do with that. It should have had to do with that. I think there were four things that happened which drove me to this conclusion and I think the logic of it which is driving other people to the same conclusion, although they’re getting a little bit of help from being pushed around by me, I suppose. But the logic had to do with four things. Two of them had to do with measurements of the kind you’re talking about and two of them had to do with theoretical solutions.
The first was the evidence for the inflationary theory of the universe. And the inflationary theory of the universe, the evidence for it has become good, strong experimental evidence. What it tells us is that the universe is very much bigger than we thought it was. We don’t know how big, but probably many, many orders of magnitude bigger than we ever thought of originally. So that’s one fact. The second fact, also coming from the microwave background in part and another thing also, is that the world seems to have a cosmological constant: dark energy.
Why the cosmological constant is so small was always a mystery. It’s a very small number on the scale of numbers it could actually be. It’s 120 orders of magnitude smaller than a physicist would have estimated not knowing any better. That’s incredibly small. Why is it so small? Well, a physicist like myself always took that to mean that, for unknown reasons, it was exactly zero. And the logic or the psychology that went with it tended to be something like this: String theory is the right theory of nature; we know that because it’s the only mathematically consistent theory, it’s a wonderful theory, we made it up, it’s got to be right. The cosmological constant in nature seemed to be so small that it must be zero and therefore there must be some mathematical miracle in the string theory that makes it zero. This was the logic before now.
When it turned out to be not exactly zero, then people began to wonder: Wait a minute now, why is it so small if it isn’t zero? And the only explanation was Stephen Weinberg’s explanation in 1987 that the only known reason — not that this is a reason, it’s really not a reason — but the only known thing that we can connect it to is that if the cosmological constant was very much bigger, galaxies could not have formed. His demonstration would, just maybe, have something to do with this anthropic idea.
The fact that a cosmological constant was discovered and that it’s not very likely to be zero because of some wonderful mathematical miracle certainly pushed me in the direction of thinking, “Well, could this anthropic idea make any sense at all?”
Then there were two fundamental theoreticals — facts that were uncovered. The first historically was the fact that this inflationary idea tends to populate the universe with all of the possible solutions of the equation — so that these kind of pocket universes that Alan Guth talked about or that Andrei Linde talked about, and all of the different possibilities, appear somewhere. These little pockets of bubble space which expand and grow, become the universes with every possible property that’s possible.
On the other hand, most theories, most of the oldest theories just had a handful of possibilities. With three or four possibilities, the chances that any one of them were just right to describe our world and to have a cosmological constant and to have all the other properties that are needed for galaxies, for everything else, were minute.
What happened, which drove me past the point of no return on this, was the realization, the string theory, the favorite theory, the most advanced theory, the most sophisticated theory — and this happened a long time ago, but physicists were in a state of denial about it — it started to produce more and more possibilities. First five, and then a million, then a billion. From all that we’ve learned over the last couple of years, the number of possible environments may be as large as 10 to the five hundred or even bigger, so it’s an enormous number, so large that the chances are very much higher that you’ll find in there something with a small cosmological constant and so forth.
That’s my favorite explanation, and I think to some extent it’s becoming more or less the default theory now. There is no other explanation.
In the same way, you’re saying now that physics and cosmology didn’t really go together until very recently. Do you think there’s ever going to be a place for faith or philosophy in this discussion?
Individual scientists believe in individual things. I have a friend, a good friend, who’s an extremely good scientist who’s an evangelical Christian. So we all understand one thing: that the whole point of science, the whole game that we’re playing, is to try to explain nature without introducing what I call the “supernatural.” It is what science is.
It’s not what every scientist believes, but it’s what the whole enterprise is about. How much of nature can we explain without having to resort to these kind of things, to faith, to God, whatever it is you like?
We don’t know how much we can explain that way, and thus far we have not come to a point where we have not been able to explain the properties of nature by what I call “science.” We don’t have the option to revoke these other things because that’s not what science is. On the other hand, individual scientists believe an entire spectrum of things, and they’re entitled to believe what they want. They tend not to bring it into their science.
What do you believe?
What I believe? I am, with respect to any existing idea about religion, meaning existing religions and so forth, I completely disbelieve them. What I believe is that religion originated in human psyche for evolution reasons and Darwinian reasons, and some of those reasons are rather dark. I think some of them had to do with advantage that a small society had in believing that God was with them, that they had a higher purpose. That made them bold. That made them brave and that made them killers. That’s what I’m inclined to believe was part of the origin of religion, a very, very dark view of it.
If you ask me, is there anything in modern science that tells us that there was not an intelligent agent that was involved in the very earliest creation of the universe, I think nothing in science told us that’s impossible. But everything we know about science says that whatever created the universe doesn’t go on intervening in it. I see no evidence whatsoever scientifically that there is any need to believe in a deity that intervenes with the universe as it now exists.
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Kimberly Roots, "Physicist plucks away at our tightly strung universe. Stanford university physicist Leonard Susskind on a “theory of everything”" (2005)
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