What do I mean by multiverse wars? I've posted about the mulitiverse before, here Also a little background material is needed.
I rarely view physics blogs before bed but the other night I did and was pleased to see the headline "Big Bang Blunder Bursts the Multiverse Bubble" on Peter Woit excellent math and physics blog Not Even Wrong.. This is about Princeton physics professor Paul Steinhartd's article in Nature with that same title. Basically Steinhartd is saying that BICEPT2's CMB data is probably all from the foreground and not from gravitational waves formed during the inflation period in the early universe. This claim may or may not be true. But the BICEPT2 team interpreted their data to show that the CMB was indeed showing primordial gravitational waves and this was stated as the smoking gun for the inflation theory in cosmology. Anyways, one of the popular models in inflation theory is eternal inflation. In this theory the medium called the "bulk" is eternally expanding and in this bulk different universes are created in what are called "baby universe" in something analogous to nucleation. These baby universes form from bubbles inside that bulk and each of these expand to form a separate universe with our universe being one of the many baby universes being continually created. Thus our universe is one of the many baby universes formed, therefore you have a collection of universes called the multiverse. So much for the old fashioned definition of the universe. We can never directly observe these other universes due to the finite speed of light. If you can never experimentally test their existence how can you tell they exist?
Basically it comes down to any theory that predicts multiverses must be wrong. Since if you can't experimentally verify or falsify a prediction of a theory then that theory is not a scientific theory. It is metaphysics. It might be scientifically informed metaphysics but it is metaphysics not physics. The idea of the multiverse has been around forever in science fiction.
This is where the Multiverse Wars start. Many physicists and philosophers view multiverse theory as physics. Book have been written about them. See my Amazon review of "The Hidden Reality" Brian Greene's new book on multiverse. Note the plural of multiverse, there are like eight of them according to Greene. Max Tegmark in his book "Our Mathematical Universe" has four levels of multiverse's (I'll have a review of this book posted within the week). It's a cool topic to discuss and write book's about, great for parties. Granted both Greene and Tegmark say that the multiverse is a speculative idea.
So you have a group of physicists and philosophers in favor of the multiverse and a group against the multiverse. Recent blog discussions are posted at Scientia Salon.
From June 9, 2014 another excellent post on Scientia Salon The Evidence Crisis. This is an article by Jim Baggott the author of the book "A Farewell to Reality".