Lorentz invariance is an essential part of special relativity, which basically specifies that speeds of objects observed by one observer are seen by different observers such that the speed of light always ends up the same. Another way to interpret it is that Lorentz invariance specifies the laws of physics are exactly the same for any non-accelerating observer, no matter what speed they're moving at. Applying this to Maxwell's equations for electromagnetism, this means that the speed of light would have to be the same no matter who the observer is.
Lorentz invariance has become a cornerstone of modern physics, with tons of experiments for special relativity confirming the principle. So it's always interesting to hear about possible new tests that might disprove it. Researchers from Indiana University are proposing experiments to test whether gravity works the same way it does with antimatter as it does with matter. By extending the Standard Model of particle physics, they describe the possible ways in which Lorentz invariance could be violated by the different gravitational influences on matter and antimatter, with possible seasonal changes as the Earth revolves around the Sun.
It is one more way to confirm special relativity that has not been tested before, given that it's likely the proposed experiments will only confirm Lorentz invariance with its track record, even if the headline for the ScienceDaily article makes it sound like there has already been observations of Lorentz violations. Not much is known about the gravitational behavior of antimatter, given how incredibly difficult it is to collect enough of it and keep it from annihilating long enough, and it will be tremendous news if such observations are actually made. However, I do wonder what analyses of previous gravitational free fall experiments that take season into account would suggest, and I also wonder what previous experiments that very indirectly show the gravitational equivalence of matter and antimatter imply for the proposed tests.