Last time, we talked about how many observers notice that the universe seems fine-tuned to accommodate life, “almost as if a Grand Designer had it all figured out” (1). This has led some people to attempt to develop theories to explain the fine-tuning of the Universe which do not require a designer. The most prominent theories call for the existence of a vast number of universes, which could have different physical laws from ours. If they are accurate, they would help to skew the odds in favor of a gradual evolutionary development of life on our planet. In that case, evolution could have taken place in many of these universes, and we would randomly happen to be in the universe that “made it”.
Before accepting that we have a universe that is finely tuned to support life, just because there are very many randomly formed universes, and we just happened to be in the one that was capable of supporting life, we need to ask about the scientific basis of this claim. Is there reason to believe that many other universes exist? Is there experimental evidence for them?
Proponents of these theories point to evidence from other parts of physics. Here is one example. Let’s say that we shine a light on a wall, with two plates in between: one with one slit, and another with with two parallel slits between the light and the wall. Now in this case, light acts as a wave; the light spreads out as it passes through the slits and interferes with the other “wave” of light. Look at the two pictures:
Photo courtesy of EPZCAW, en.wikipedia.org
The most common interpretation of how this happens is that the light is acting like a wave, until it “crashes” when it hits the wall, where it “collapses” into a single spot, which means it is not a wave anymore. (For the physicists reading this, I am attempting to describe the Copenhagen interpretation of quantum mechanics in very simple terms).
However, another interpretation, provided without supporting evidence, is that when the light hits the wall, some of the properties of its wave (of its wavefunction) stay in this universe, and some automatically go to another universe, which (depending on who you ask) may newly have been created on the spot. Since there is a lot of light hitting objects around us, this explanation predicts a lot of new universes.
The question I would invite you to ask is this: where is the experimental evidence for the existence of any other universe besides ours? We can see in the lab that the light beams interfere with each other, but what reliable evidence do we have that part of that light beam, once it hits the wall, is now in another universe? What evidence is there for any other universes at all?
I have not been able to find any evidence at all. There are quite a few smart people trying to support this experimentally, but if you read carefully, you will see that they are drawing vast conclusions from limited and unclear evidence, or even trying to support this unproven theory with other unproven theories. Here are five examples:
#1: The “first evidence” many people see for the existence of multiple universes was found by a satellite called the Wilkinson Microwave Ansiotropy Probe (WMAP), which basically took pictures of invisible microwave “light” coming to us from outer space. Some people say that there are patterns in the microwaves that show that other universes are like “bubbles” “colliding” into ours, but if you read the actual papers carefully, they actually show that there is NO EVIDENCE FOR OTHER UNIVERSES from WMAP:
“We therefore conclude that this data set does not favor the bubble collision hypothesis for any value of Ns.” (2)
“The WMAP 7-year data-set does not favor the bubble collision hypothesis for any value of Ns”. (3) (see also )
#2: Cosmologist Laura Mersini-Houghton has claimed to have unmistakable evidence for the existence of another universe by predicting the discovery of the CMB cold spot. Her rationale for her equations for a “wave-like equation” (a waveform) of the universe (on which her predictions are based) are sensible, but those equations do not appear to assume the existence of other universes. So even if her equations are correct, I see no reason to conclude that her theory explains other universes, although it might explain some things about this one! Besides, her prediction of a northern cold spot and of “dark flow” have not panned out (though several other predictions of hers have) (5) (6) (7).
#3: Scientists in the last few years have realized that the existing data does not support the existence of multiple universes very well. As of 2013, everyone was looking forward to the high-definition pictures of the microwave radiation coming from outer space, that we were supposed to get from the new, higher-resolution Planck satellite (5):
Future data from the Planck experiment will allow us to greatly improve on these results. If confirmed, the presence of bubble collisions in the CMB would be an extraordinary insight into the origins of our universe.
(Note that the researchers recognize the “great” need to improve their results, and that those results have not yet been confirmed.)
The pictures from Planck were supposed to be much higher resolution than the WMAP pictures. But now that the Planck pictures have come out (they were released on March 21, 2013 ), there have been no new discoveries based on it supporting a multiverse. Search for scientific papers on it (not newspaper articles!). As of this writing, on June 24, 2013, I found none. In spite of the absence of new experimental findings, British newspapers still claim that the previously known patterns in the microwave, which were seen by Planck, constitute new evidence for multiple universes (8), (9). This is poor science, since all we are seeing higher resolution pictures of things we already knew about, without anything to cause new conclusions.
#4: Scientific American recently ran an article by Vilenkin and Tegmark promoting the existence of multiple universes, but the arguments both used were not sound, and they did not present experimental evidence in support of their position. Vilenkin uses an example of using a broader model of a single universe to predict constants of nature for our local region of the cosmos (this is fair in principle); but then applies this without justification to suggest the existence of universes OUTSIDE of the single universe he just talked about.
Tegmark enthusiastically defends the multiverse position without providing reasonable, clear evidence of how current theories, robustly supported by experimental evidence, predict the existence of multiple universes (10).
He cites predictions of the density of dark energy, made on the basis of string theory, as evidence of the validity of a nearly infinite number of multiple universes. But string theory has just as little experimental evidence to support it:
“Until some way is found to observe the yet hypothetical higher dimensions, which are needed for consistency reasons, M-theory [a unified form of string theory] has a very difficult time making predictions that can be tested in a laboratory. Technologically, it may never be possible for it to be experimentally confirmed” (11).
“As of 2010, there are no feasible experiments to test the differences between MWI [the many-worlds interpretation of multiple universes] and other theories” (12).
#5: Paul Davies, professor of natural philosophy at the Australian Center for Astrobiology, argures in the NY Times that although multiple universes are not impossible, they are difficult to prove, and should not be taken seriously. Although opposed to the concept of God as creator, he states the following (13):
How seriously can we take this explanation for the friendliness of nature? Not very, I think. For a start, how is the existence of the other universes to be tested? To be sure, all cosmologists accept that there are some regions of the universe that lie beyond the reach of our telescopes, but somewhere on the slippery slope between that and the idea that there are an infinite number of universes, credibility reaches a limit. As one slips down that slope, more and more must be accepted on faith, and less and less is open to scientific verification.
Extreme multiverse explanations are therefore reminiscent of theological discussions. Indeed, invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen Creator.