I'm trying to figure out or find how fast Earth is moving due to the Hubble constant. I'm runnng into two answers and have difficulty understanding either one. --- One answer is a number of kilometers per second per megaparsec. But that's a distance per time unit per distance unit. I don't understand why the number is not reduced to one distance unit per time unit, much as we say for aircraft (a number of miles per hour or a number of kilometers per hour). My problem seems to center on the "per megaparsec" part. When I look it up, I see that a megaparsec is a number of light-years, which is the distance traveled by electromagnetism (e.g., light) in a year, and it relies on electromagnetism because, as far as we know, it's the fastest thing traveling. So I don't understand why the distance units are not being combined. --- The other answer is that the constant measures the expansion of the universe, which I'm fine with, but then it's assumed that we decree an arbitrary center and then find that everything else moves away from that center, so that the center is arbitrarily assumed to not be moving. That's fine when we want to be arbitrary, but Earth is not at the center of the Milky Way and the Milky Way is not at the center of either the universe of known and observable matter and energy or, as far as we know, at the center of the infinite universe (the universe as understood by children). So, even just from the Hubble constant, there should be a speed number for Earth's travel from the center of a universe. I understand that, without counting the Hubble constant's effect but counting Earth's travel toward the Great Attractor (I just learned about that and don't know if that's still in a scientific consensus), Earth is traveling at about two and a half million miles an hour. I expect to get an upper speed by adding the Hubble constant's speed at Earth's location to the non-Hubble combined speed, much as we'd add the speed at which someone climbs a rope located in an elevator to the upward speed of the elevator itself, even though sometimes one speed would be subtracted from the other, such as when Earth is moving around the sun in a direction of travel opposite of that of the universe's expansion.