It’s fairly well-known that general relativity and quantum mechanics don’t get along, so the mock surprise that this happens is a little tedious, but that’s the state of (science) journalism. Once you get beyond that, it’s pretty neat.
Numerous experiments, measuring all types of phenomena, have proven that the equivalence principle holds. However, a new thought experiment published in a recent version of Physical Review Letters demonstrates that, depending on how you measure temperature, a scientist in the sealed laboratory could tell where she is. On the surface, this result would seem to suggest that the equivalence principle it not valid under all conditions, but there is a wrinkle—the researchers here suggest making a local quantum mechanical measurement. The fact that quantum mechanics is an inherently non-local phenomenon may provide a way of cheating the prerequisites that Einstein put on his equivalence principle.
One caveat here is that this is still a thought experiment, and it’s still possible that someone else will come along and show that it’s not a problem. One needs to recognize that papers are a way that scientists “think out loud” and get feedback. No doubt that this idea went through discussions and then peer-review, which are steps that should weed out obvious loopholes and problems, but when you’re at the edge of GR and QM there might be more subtle concepts lurking.
One thing to note in the article is the ambiguity/error they have presented in explaining GR
Einstein proposed the equivalence principle in 1907, a full nine years before his publication of general relativity. The idea, however, guided the development of general relativity. When combined with Einstein’s theory of special relativity, it gave rise to the prediction that clocks will run at different speeds in gravitational fields with differing strengths, and that light would be bent by gravitational fields.
If strength means the acceleration (or force), and that’s usually what is meant, then this is wrong. Time dilation depends on the gravitational potential, which is the depth of the potential well. The acceleration is the slope of the side of the well. It’s possible to be very deep in a well and have a large amount of time dilation while having a local value for g that is small.