Steven, the idea is not that GR requires Mach_n (then Mach_n would be generally accepted, of course!) but that GR permits Mach_n for some ns. From Einstein’s perspective, this is an improvement over Newton’s Bucket and it is a major historical motivation of GR.
Steven, the idea is not that GR requires Mach_n (then Mach_n would be generally accepted, of course!) but that GR permits Mach_n for some ns. From Einstein’s perspective, this is an improvement over Newton’s Bucket and it is a major historical motivation of GR.