What Is (And Isn’t) Scientific About The Multiverse
“In this physical Universe, it’s important to observe all that we can, and to measure every bit of knowledge we can glean. Only from the full suite of data available can we hope to ever draw valid, scientific conclusions about the nature of our Universe. Some of those conclusions will have implications that we may not be able to measure: the existence of the multiverse arises from that. But when people then contend that they can draw conclusions about fundamental constants, the laws of physics, or the values of string vacua, they’re no longer doing science; they’re speculating. Wishful thinking is no substitute for data, experiments, or observables. Until we have those, be aware that the multiverse is a consequence of the best science we have available today, but it doesn’t make any scientific predictions we can put to the test.”
The multiverse is one of the most controversial topics in science today. On the one hand, it’s a remarkable story: perhaps our Universe, even beyond what we can observe, isn’t the only one out there. Perhaps there are many others, all generated in some early, pre-Big-Bang state, all disconnected from one another. This isn’t speculation; this part of it arises by combining the two well-established theories of cosmic inflation and quantum physics. Yet if we start trying to go further, such as making statements about the laws of physics, the values of fundamental constants, or the suitability of our Universe for life, we’ve lept out of the realm of science and into wild speculation or, worse, wishful thinking.