Yeah they are, they just cannot be verified - or cannot be verified yet.
The higgs boson theory was theorised in 1964 and it was untestable at the time, but that theory got the funding together to create one of the largest and most expensive scientific instruments built to prove the theory.
Nuclear fusion was theorised in 1915, again untestable at the time, and look how far we've come.
The above comment is an anti-science comment if I've ever seen one.
Usually when people say something is untestable they don't mean like the Higgs Boson. It was testable, they just needed the proper tools. This was always known and was being actively worked towards. An untestable theory is one that cannot be tested regardless of the tools due to the nature of the theory. Multiverse is an example of an untestable theory. There is no way we know of to actually prove or disprove it. And its fair to question their legitimacy as theories. As testing a hypothesis is the core action of the scientific method, it logically follows that anything untestable is fundamentally not science and therefore not a theory.
In this case I think multiverse is both. Testability and falsifiability are closely related. But its possible to make a testable statement that can't be falsified in most examples I can think of the test can't be exhaustive.
A theory can be untestable but also falsifiable. For example, while the multiverse theory/interpretation may be untestable, it could be immediately falsified if QM were falsified.
Popper's falsifiability criterion was more aimed at theories like Marxism, where it seemed that within the theory there was always something available to account for an exception or challenge.
The other big theories aren't completely untestable, the issue is basically that the models have a lot of parameters which can often be tuned in a way that leaves a possibility for the general theory to still work, and testing them to the point that any corrections seem too unreasonable is even more difficult and expensive.
Not reflecting to this particular theory, but in general history is full of theories which were not testable at their birth, but both engineering and the evolution of the theory eventually found a way to do so, even if it took a century.
Black holes, Higgs bozon and neutrinos are a few popular examples.
Some theories are only untestable for practical reasons, like needing a particle accelerator the size of the solar system. That doesn't make them unscientific or "not theories". That is not the kind of falsifiability that Karl Popper had in mind.
Yes, it does. The word "theory" has a specific meaning. What this article is about is really a hypothesis, not a theory. I saw no evidence or data to back up what they think might be happening, thus not a theory.
"In scientific reasoning, a hypothesis is constructed before any applicable research has been done. A theory, on the other hand, is supported by evidence: it's a principle formed as an attempt to explain things that have already been substantiated by data."
Most people in this thread, as well as the writers of the article seem to be confused about the meaning of the word theory.
Maybe that should give you a hint that professional working scientists don't care much for definitions from wordbooks.
Besides, I was commenting on the topic of falsifiability. To be a scientific hypothesis or theory it must be falsifiable - in principle, not practically. At least that's my claim in the context of Popper. Evidence didn't even enter the discussion.
> The CCM will be an important stepping stone toward an ultimate Planck-
scale collider, with a centre-of-mass energy of ∼10^16 TeV, that would require a minimum size equal
to a tenth of the distance from Earth to Sun.
