In a recent blog, Columbia University mathematical physicist Peter Woit discusses this topic by starting with reference to Bob Berman’s article in Astronomy magazine. In his article Berman present the case for the multiverse and the counter one of why scientists such as Woit are so very skeptical. Overall, there is great enthusiasm among many of the physicists, but because there is no nearterm approach by anybody that could prove the existence of the multiverse, Berman leaves the last word to a Woit quote of this subject:
“Physicists had huge success in coming up with powerful compelling fundamental theories during the 20th century,” he explains, “but the last 40 years or so have been difficult, with little progress. Unfortunately, some prominent theorists have now basically given up and decided to take an easy way out. The multiverse is invoked as an all-purpose, untestable excuse. They allow theoretical ideas like string theory that have turned out to be empty and consistent with anything to be kept alive instead of abandoned. It’s a depressing possibility that this is where physics ends up. But I still hope this is a fad that will soon die out. Finding a better, deeper understanding of the laws of physics is incredibly challenging, but it’s within our capability as humans, as long as the effort is not overwhelmed by those selling a non-answer to the problem.”
I personally think the concept of parallel universes is real, but currently unprovable by early 21st-century. But this is not the multiverse concept that physicists are proposing. Their concept of the multiverse is one of multiple physical dimensions that is a natural “fallout” of supersting theory with its 10 or 11 dimensions and physical dimensions where only a few of the dimensions can be expressed together (such as our 3-dimensional physical universe).