Kieran Healy at Crooked Timber notes with approval that more than 83% of Americans now think that interracial dating is acceptable. Now, some of you might be thinking, “Hey, that means that there’s still 17% of Americans that think interracial dating is not okay.” Well, yes. But everything is relative. Apparently the folks at the General Social Survey, just for kicks, decided to ask Americans to come clean about their feelings toward heliocentrism. As it turns out, about 18% of Americans are in the “Sun moves around the Earth” camp. A full 8% prudently declined to have an opinion, leaving only 74% to go along with Copernicus. (Of which, nearly three-quarters understood that it took a year for this process to unfold.) So, you take what you can get.
I hope our blog didn’t confuse them.
All this discussion… It’s like arguing about what point on the surface of the Earth is the central one.
CIP, it was mostly Neil B.’s comment that got at me, so it was probably unfair to address the same reply to both of you. I largely agree with you, but it does seem to me that some people are championing the view that the question is incorrectly formulated just to be contrary.
wow, I’m in the majority on the sun deal and interracial dating—far out!
Joe Fitz, et al:
Please keep in mind the difference between championing an idea from just expressing “That’s what they say, I’m just telling you…”
I presented the official orthodoxy about what is “really moving” during accelerated relative motion, along with my own counterarguments. Sure, the sun presents the closer approximation to an inertial frame, but remember that IFs aren’t defined by their motion per se, but by the physics of motion in them: a free-falling elevator is nearly an inertial frame, but the surface of the earth isn’t, because of gravity. (The surface of the sun isn’t either, but the center is pretty close to being one, except for tidal field.) In any case, the question about “moving” is not by definition about inertial frames, however appealing they are as simpler arenas for doing physics.
As for simplicity: Simplicity may have value in building explanations (overrated IMHO), but it’s not a paste at will answer to every distinction. The problem of defining non-relative “moving” is not simple, as all the mess over gravity, the equivalence principle, Mach’s principle, inertia, etc., will attest.
PS: I will be happy when the webmaster can bring back the WYSIWYG viewer.
“tyrannogenius”
The closest thing we could get to an inertial frame on Earth would be a non-spinning observer in the center of the planet. As Neil said, if that were the case, it would be as inertial as a non spinning observer in the center of the sun, hence, since they both have null intrinsic acceleration, we really cannot say which is revolving around which. If we wanted to put an observer on the face of the Earth/Sun, a gyroscope (Fermi-Walker parallelism) would not accuse any significant difference either. I do not see what the problem is. The fact that we say the Earth revolves around the sun is a consequence of the more appropriate sun-centered coordinates we use to describe the solar system.
Hag, essentially I agree with what you are saying. I may well have confused the issue by considering the spinning of the earth. I was implicitly including it, since it is what determines from our perspective how the sun appears to move. If you do not consider it, then that changes things.
Actually folks, spinning versus revolution of the earth is ultimately beside the point. In Machian GR, even the forces and perspective of the spinning earth are all relative. The earth isn’t “really spinning”, but is subject to the effect of relative angular displacement in a matrix of actual surrounding matter. Pleased re-read over my previous comments.
I didn’t say I agreed with that. Consider the following argument: If you believe that linear motion is relative, but at least the product of that relationship is “real”, then a rotating body has actual relative velocity vectors of parts of itself relative to a given other part! The magnitudes depend on omega, which is then real per that consideration (which does not invoke any mechanical or inertial effects…)
Update: I started an NG discussion in sci.physics etc, titled “Rotation is not relative, since it creates relatively real linear velocities”
Here it is:
Thoroughgoing Machian GR says that *all* motion is relative, even
accelerated motion. Hence, a “spinning” wheel can be thought of at rest,
with the centrifugal forces on it being created by motion of the matter
beyond it. (Actually, not in the same sense as when charges start to
accelerate at a distance, for then there would be a time delay..) But assume that at least linear motion is relative and real to that extent.
Then, since relative linear motions are “real” they can be used to make distinctions between situations. Consider that a rotating body has actual relative velocity vectors of parts of itself relative to any given other part! (For example, each other point (if v
Still, in Machian GR you have the background of “fixed stars” (or all the matter in the universe) that does create an inertial frame. What you cannot have in Machian GR, as opposed to the usual GR is an overall rotation *of the Universe*. This just doesn’t make any sense in Machian GR, but we do have some such models in GR, such as Godel’s Universe.
As enlightening as this commentary thread turned out to be, i doubt those 18% were competent enough to invoke relativistic principles or even “simple” frame selection arguments to justify their stance. They’re are just following the book. And that’s what the survey originally intended to highlight; not the answer, but the method behind arriving at it.