Isotropy of the universe is the idea that the universe is the same in all directions, and is a founding principle of the laws of physics. However, that principle has been called into question by observations of galaxy cluster temperatures and luminosities.
https://scitechdaily.com/fundamental-principle-of-cosmology-cast-in-doubt-by-compelling-new-study/
"No matter where we look, the same rules apply everywhere in space: countless calculations of astrophysics are based on this basic principle. A recent study by the Universities of Bonn and Harvard, however, has thrown this principle into question. Should the measured values be confirmed, this would toss many assumptions about the properties of the universe overboard. The results are published in the journal Astronomy & Astrophysics, but are already available online."
The paper (open access):
https://www.aanda.org/articles/aa/abs/2020/04/aa36602-19/aa36602-19.html
Journal Reference (open access):
K. Migkas, G. Schellenberger, T. H. Reiprich, F. Pacaud, M. E. Ramos-Ceja and L. Lovisari. Probing cosmic isotropy with a new X-ray galaxy cluster sample through the L X – T scaling relation , 8 April 2020, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/201936602
(Score: 3, Insightful) by hendrikboom on Saturday April 11 2020, @04:23PM
The only "practical" FTL drives I've seen require large amounts of matter of negative mass.
Since FTL is equivalent to destroying causality I suspect there can be no negative-mass matter.