Skip to comments.One universe or many? Panel holds unusual debate
Posted on 04/02/2006 7:46:13 PM PDT by snarks_when_bored
One universe or many? Panel holds unusual debate
March 30, 2006
Special to World Science
Scientific debates are as old as science. But in science, debate usually means a battle of ideas in general, not an actual, politician-style duel in front of an audience.
Occasionally, though, the latter also happens. And when the topic is as esoteric as the existence of multiple universes, sparks can fly.
|According to one proposal, new universes could sprout like bubbles off a spacetime "foam" that's not unlike soap bubbles. (Courtesy Lawrence Berkeley National Laboratory)|
Such was the scene Wednesday evening at the American Museum of Natural History in New York.
Museum staff put together five top physicists and astronomers to debate whether universes beyond our own exist, then watched as the experts clashed over a question thats nearly unanswerable, yet very much alive in modern physics.
New universes may appear constantly in a continual genesis, declared Michio Kaku, a theoretical physicist at City College of New York and key supporter of the idea that there exist multiple universes, or a multiverse.
The multiverse is like a bubble bath, with a bubble representing each universe, he added. There are multiple universes bubbling, colliding and budding off each other all the time.
Another panelist backed the multiverse idea, but three more insisted theres virtually no evidence for the highly speculative concept.
A brief history of other universes
Some versions of the many-universes concept date back to ancient Greece, said panelist and science historian Virginia Trimble of the University of California, Irvine. But scientific justifications for the idea began to appear in the second half of the 20th century, when U.S. physicist Hugh Everett proposed it as a solution to a puzzle of quantum mechanics.
Physicists in this field found that a system of subatomic particles can exist in many possible states at once, until someone measures its state. The system then collapses to one state, the measured one.
This didnt explain very satisfactorily why the measurement forces the system into that particular state. Everett proposed that there are enough universes so that one state can be measured in each one. Each time someone makes a measurement, the act creates a new universe that branches off the pre-existing ones.
The multiverse theory later reappeared as a consequence of another theory of physics, that of inflation, developed by various physicists in the late 1970s and early 1980s.
The theory solved several gnawing problems in the Big Bang theory, the idea that the universe was created from an explosion of a single point of extremely compact matter, by postulating that this expansion was stupendously fast in the first infinitesimal fraction of a second, then slowed down.
As part of this initial superheated expansion, known as the inflationary period, the universe could have sprouted legions of baby universes, said Andrei Linde of Stanford University in Stanford, Calif., a panelist at Wednesdays event and a developer of the inflation theory.
A third argument for the multiverse theory comes from string theory, seen by some physicists as the best hope for a theory of everything because it shows an underlying unity of natures forces and solves conflicts between Einsteins relativity theory and quantum mechanics.
String theory proposes that the many different types of subatomic particles are really just different vibrations of tiny strings that are like minuscule rubber bands. The catch is that it only works if the strings have several extra dimensions in which to vibrate beyond the dimensions we see.
Why dont we see the extra dimensions? A proposal dating to 1998 claims were trapped in a three-dimensional zone within a space of higher dimensions. Other three-dimensional zones, called branes, could also exist, less than an atoms width away yet untouchable. The branes are sometimes called different universes, though some theorists say they should be considered part of our own because they can weakly interact with our brane in some ways.
In part the question rests on definitions, noted Lisa Randall, a Harvard University physicist who was one of the panelists on Wednesday night. Different universes can be defined as zones of spacetime that interact with each other weakly or not at all, she said.
Wheres the evidence?
Marshalling their best evidence for extra universes, Kaku and Lindethe two panelists who back the notionpresented a variety of arguments, which all boiled down to two basic points.
One, explained Linde, is that the multiverse solves the problem of why the laws of physics in our universe seem to be fine-tuned to allow for life. If you change the mass of the proton, the charge on the electron, or any of an array of other constants, wed all be dead, he argued.
Why is this so, Linde askeddid someone create this special universe for us?
Steering clear of the straightforward answer many religious believers would give, yes, Linde argued that the multiverse explains the problem without resorting to the supernatural. If there are infinite universes, each one can have different physical laws, and some of them will have those that are just right for us.
The second key argument they presented is the one based on inflation, a theory considered more solidly grounded than the highly speculative string theory and its offshoots. The equations of inflation, Kaku explained, suggest spacetimethe fabric of reality including space and timewas initially a sort of foam, like the bathtub bubbles.
New bubbles could have sprouted constantly, representing new universes, he added. Linde has argued that this occurs because the same process that spawned one inflation can reoccur in the inflating universe, beginning a new round of inflation somewhere else. This would occur when energy fields become locally concentrated in portions of the expanding universe.
Scientists might one day create a baby universe in a laboratory by recreating such conditions, Kaku said. This would involve resurrecting the unimaginably high temperatures of the early universe. A spacetime foam can be recreated by literally boiling space, he said, adding that a sort of advanced microwave oven could do the trick.
Experiments already planned could test the periphery of these ideas, he added including a super-powerful particle accelerator to switch on next year, the Large Hadron Collider in Switzerland.
Randall countered that the new accelerator wont bring particles anywhere near the level of energy needed to recreate the spacetime foam envisioned by multiverse proponents. The energies attained will be lower by a factor of 10 followed by 16 zeros.
Lawrence Krauss, a physicist and astronomer at Case Western Reserve University in Cleveland, said the whole multiverse idea is so speculative as to border on nonsense. Its an outcome of an old impulse, which also gave rise to the correct notion that other planets exist, he argued: We dont want to be alone.
It also caters to our desire for stability, he added: the universe changes, but the multiverse is always the same. And if there are many universes, you dont have to make any predictions that will subject your pet theory to awkward tests, because theres always one in which the answers work out.
Krauss allowed that he might buy the multiverse idea if its a consequence of some new theory that also successfully accounts for many other unexplained phenomena. But otherwise, multiverse concepts are extending into philosophy rather than science, he added, and may not be testable.
A couple of references:
Oldest light shows universe grew fast, researchers say [inflationary cosmology gets a big boost]
Andrei Linde, "The Self-Reproducing Inflationary Universe" [PDF file]
As for the obligatory Lisa Randall pics, I trust they'll be forthcoming...
Yes, it's a ping...
Or something even worse than that ~ I am reminded of this old SciFi story where the folks discovered they were trapped in one of Philip Farmer's "Pocket Universes", and their space ships just bounced off the boundaries somewhere toward Pluto's orbit.
I like how bigger and bigger terms keep being invented to describe the same thing...
Gotta wonder what the anti-Marty would be like.
Interesting that the latest theories keep tending toward the idea that what we see, isolated galaxies, linked by gravity in long chains, could very well be independent universes, and these could be interspersed with universes we can't see ~ black matter/black energy, and all of that encapsulated in a macro-universe that holds all of 'em.
I have to disagree with you on that. The universes of which Linde and Kaku are speaking are not visible to us, nor are they composed of dark matter contained in the visible portion of our universe. They're speaking of completely separate universes lying outside the inflationary bubble that we inhabit.
BTW, I didn't know about Farmer's 'pocket universes' stories. Alan Guth, one of the co-discoverers of inflationary cosmology, speaks of 'pocket universes' when describing separate cosmic bubbles.
an actual, politician-style duel
Perhaps they can bring in some South Korean legislators to show them how these things should be done.
(chuckle) Democracy as fisticuffs...
"...Okay. That means that...our whole solar system...could be, like...one tiny atom in the fingernail of some other giant being....This is too much! That means...one tiny atom in my fingernail could be..."
"Could be one little..."
"...tiny universe...Could l buy some pot from you?"
BTW, when cosmologists refer to "pocket universes" they are usually familiar with Philip Farmer's use of the term ~ all interesting stories ~ I'm not exactly sure who Farmer got his science from, but he knew how to spin a yarn.
Take another look at Billy Pilgrim, the character in several of Kurt Vonnegut's stories. Recall, quickly, that for a long time Kurt and Phil were big buddies ~ until Phil wrote a story for Billy himself.
There you discover a theory of "time" that suggests multi-dimensionality for time in pretty much the same manner as Farmer's pocket universes are expanded out from the point of origin.
As I was saying, and you might not have picked up on it, the current most speculative theories of the Universe's structure are getting closer to some ideas worked out in literature in the 1960s and 1970s by two Indiana writers.
If you haven't read Farmer's stories, here's your chance for some provocative thought.
Definitely some science fiction going on!
The idea of a multiverse is not new. Hugh Everett did his dissertation on the many worlds interpretation of quantum mechanics in 1957. As I understood it, his idea was that all possible quantum states are expressed.
OK OK OK RichInOC hears a Who.
I guess if I had read a bit further in the article I would have seen in print what I attempted to point out.:-)
Would the bozos of that universe worship us a gods? Would they fight Holy Wars over balrog666 vs snarks_when_bored?
What delicious possibilities!
We know how far we can see, but that's not the same as the boundary of all the inflationary space there could be.
Correct. Check out Linde's article (referenced in post #1). There he mentions that some inflation theories suggest that the radius of our cosmic bubble could be as large as 101,000,000,000,000 centimetersthat's a 1 followed by a trillion zeros. By contrast, the part of our universe that we can currently see has a radius which is only about 1026 centimeters, exceedingly miniscule by comparison.
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