I used data in the plural in that title because the editors in the US Geological Survey point out that "data" by definition is more than a singular thing... unless it is a "data point."
For years I was a volunteer and answered questions sent in to the USGS via their "Ask a Geologist" portal. We received questions from elementary school kids, from teens and adults interested in their world, and from some people who were not really asking questions. Sometimes,
their "questions" were not questions, but
someone spouting their personal theories... One man was certain there were "encased human bodies" on his property caused by the Great Comet of 1811. When asked where he got that information, he referred me to his personal website. Of course. If it can be found on the Internet, it must be true, right? We scientists generally try to respond in a considerate
manner, but at the same time we feel that, as scientists, it is always important
to keep the record straight. To keep everything anchored in reality.
That particular individual went on to spout additional theories about the Earth's magnetic field - and then inadvertently made an important point that I felt I should reinforce. This was his final sentence: "if we can do experiments, we can prove which theories are right and which are wrong."
My reply: Your query to Ask-a-Geologist is clearly not a question, but instead a statement of your personal beliefs.
As far as I know, a majority of physicists teaching in universities still at least pay lip-service to the idea that any theoretical conclusion must be verified by experiment. A theory must lead to a hypothesis that can be tested - i.e., it must be a statement or idea that is falsifiable. Falsifiable is an idea that came from the philosopher Karl Popper (1902-1994), and means that if tested, a theory is either false or it is correct - but it must be false-or-correct-TESTABLE in the first place. For a little more than a century after the great physicists Faraday and Maxwell published their work, this was for all practical purposes a working definition of "physics." By the middle of the 20th century, the rather attention-grabbing success of atomic bomb development by physicists led to a golden age in physics, with branches expanding out into plasma physics, solid-state physics (where I come from), cryophysics, biophysics, geophysics, hydrophysics, optics, and other experimental sub-specialties of physics.
However, for at least 40 years now, a whole generation of theoretical physicists (who now dominate some large university physics departments, and thus control the hiring of younger new faculty) have been attempting to reconcile General Relativity with Quantum Mechanics and the particle physics zoo's Standard Model - by invoking String Theory. This theory comes in as many flavors as there are physicists, but they all postulate as a common denominator the existence of undetectably tiny strings - and totally untestable extra dimensions. In an attempt to explain what is generally referred to as the (observed but poorly named) Anthropic Principle, they appeal to a belief in a totally unverifiable and untestable "multiverse": an infinite number of parallel universes, of which we belong to the one populated universe by a sort of Darwinian natural selection. While mathematically elegant, none of these theories are even remotely grounded in testable reality. Not only is there no experimental proof of any of this, but these theoretical physicists (if pressed) will admit that their theoretical approaches are unfalsiable. In other words, they are no longer "doing physics", but instead are indulging in mathematical philosophy.
This is one reason why I left physics as a profession after a Masters Degree and continued my education in geophysics instead. If you are interested in pursuing this theory-vs-experiment issue, I would encourage you to read Peter Woit's book "Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law", and/or Lee Smolin's book "The Trouble With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next", and/or Avi Loeb's book "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth."
Together these books give me peace of mind. There ARE scientists out there based in reality...