“It wasn’t that long ago that the “sound barrier” was just that: a barrier.”
The sound barrier had nothing to do with physics, it was just a barrier some people thought, without any evidence, was unbreakable.
Physics is what governs our universe. Clearly, there are things about physics we don’t yet understand, but the fact is that mass increases as we approach the speed of light. This law was discovered by Einstein and has already been proven to be correct. No one yet has defied the laws of physics in any form.
Ahem. The sound barrier was very real given the aerodynamics of aircraft at that time. A high pressure standing wave positions itself on the control surfaces of any aircraft not designed to fly above the speed of sound. This is physics as related to fluid mechanics. The engineers had to expand their knowledge before craft could be constructed to fly past that barrier.
Just because Einstien's theories have yet to be broken doesn't mean they eventually won't be broken. One really does have to factor in the observations of thousands of credible witnesses, and assume those craft came from somewhere. If they came from "way out there", then it is a certainty that there is physics we do not know.
When something is observed that transends conventional wisdom, it is best to assume that there are holes in that wisdom. If that were never done, there would never be any new theories. Theories are made to match observations. It is silly and unscientific to discount observations just because they don't fit the theory.
Let me give you a real example. When I was in college many years ago, I wrote software for a digitally-controlled ultraviolet spectrometer that was capable of counting individual photons. Spectra were made of the ultraviolet emissions from a carbon film struck by sulfer-hexafloride molecules accelerated by a 2 MEV linear accelerator. The resultant spectrums contained many small peaks that did not have origin in the current theories at that time. The research team, consisting of several PHDs, abandon the project. Three years later another team built the same instrument, and then managed to explain the peculiar peaks with a modified theory. They won the Nobel Prize. They guys that invented the apparatus wept and knashed their teeth for many years.
It is better to suspect the theory when the observations from reliable sources don't fit the mould.