> This is a foundational philosophy-of-science kind of thing that is often not taught much Why is that? > The lenses in the optics change shape, not the gridl

> This is a foundational philosophy-of-science kind of thing that is often not taught much Why is that? > The lenses in the optics change shape, not the gridlines of the rest of the universe. And so the observer can correct for distorted measurements, if they can measure the distortion factor. But a distortion factor in measurement has no bearing on what is actually being observed. > There's no difference between "spacetime expanding" and "matter shrinking". At first glance, but can you satisfactory explain redshift/Hubble's law and the fact that objects at sufficient distance from the observer have an apparent size which is larger than expected? As well as a host of consistency issues in other known physical constants that would arise, such as a corresponding increase in the strength of the electromagnetic force? In general, we would have to throw away special relativity, as the only realistic explanation would be that the speed of light is slowing down. Until we can experimentally verify this, the idea that matter could be shrinking is purely theoretical, other problems aside. I'm happy to check out any credible literature on the subject, if you can provide it.