@PdotdQ Let me know if I’ve understood this correctly.
Newton formulated his laws assuming absolute frames.
Though he believed absolute frames existed, he realized that they could not be humanly known so he incorporated Galilean invariance into his mechanics for “real world” calculations.
Einstein assumed relativity and therefore his equations are formulated only for such and therefore cannot be used with absolute frames.
The only way isotropy could be observed is if it were possible to have a “God’s eye view.”
I apologize if you already addressed my earlier example, but I thought I would bring it up again.
If there is an absolute frame of reference, then it seems we should be able to run some sort of non-relativistic experiment to measure our velocity in that frame.
To that end, let’s say you wake up in a spacecraft with no memory of the past. In this universe there is no matter or energy other than the spacecraft you are in. You can not measure any acceleration in any direction for the spacecraft. What experiments would you run in order to determine if you have a velocity within this universe?
The way I understand it, and I believe this is how Newton viewed it, the only way of conducting a non-relativistic experiment would be to come up with a way in which a “God’s eye view” is humanly possible.
However, the fact is, that’s just not humanly possible, at least not presently that I’m aware of, nor does it seem to be something that ever would be possible. So the only recourse for investigating the possible existence of absolute space, it seems, is through metaphysics. It’s just not something that is within the scope of physics as far as I can tell.
If every experiment we do is the same in the spacecraft regardless of its velocity with respect to the absolute frame, then what does it mean to say that an absolute frame exists?
I’m not sure I follow your question. What exactly do you mean when you say “with respect to absolute frames?” Don’t you have to know what the absolute frame is before you can say that?
My understanding is that absolute space is a metaphysical claim. I believe MM was concerning the “aether,” which as I understand it is a physical claim.
If there were an absolute frame, we would expect the speed of light to be relative to that frame. The Michelson - Morley experiment counts as evidence against that (in my opinion).
I think the problem is that it’s not possible to physically “know” the absolute frame. So “relative to that frame” doesn’t seem to make sense if there isn’t something “known” from which a relative association can be established.
But it was not necessary to know the absolute frame. The natural assumption (from heliocentrism), was that the earth itself could not be stationary in the absolute frame. And Michelson - Morley challenged that.
If all of your measurements and observations are the same no matter what velocity you are travelling, then how can there be an absolute frame?
I don’t think it is a metaphysical claim because you can run experiments to determine if there is an absolute frame. Repeating what I said above, if all frames are equal then there isn’t an absolute frame.
Going back to your “God’s eye view”, how does God determine that he isn’t moving within the universe? If there is just your spaceship and God, and they are moving towards each other, who is moving? Are they both moving, or is just one moving? How do you determine that?
Err no, you don’t really understand it correctly. It seems that you heard somewhere that absolute spacetime = “God’s eye view”, which might be an oversimplification some physicists use to try to explain this matter to laypeople, and then you ran away with this oversimplification to some wild conclusions. I suggest learning the mathematics of what absolute spacetime actually means before making any conclusions.
Regardless, I want to first make sure that you agree with the scientific process that we discussed. If you disagree with this, then there is no point in discussing about what absolute spacetimes are.
I don’t see any problem with it. But I would simplify it in order to better illustrate the point I was getting at about what I consider an unrecognized distinction between description and explanation.
Basically in the example there are two ideas or explanations, one equation or description, and one observation or measurement. So my question is, what role does the equation play on it’s own in providing evidence for the explanations? None whatsoever that I can see.
As far as I can tell, it’s the observation that provides the evidence, in this case in support of a round earth. Does the equation determine the observation? No. Equations are causally effete. It only provides a description of the observation.
Now imagine the equation had been conceptualized from the first explanation, similar to how I understand equations in GR or SR were conceptualized from particular ideas. Does the fact that the first explanation was used to conceptualize the equation provide any evidence to support that explanation?
I don’t see how. If it doesn’t, my point is that just because an explanation has been used to conceptualize an empirically verified equation, it provides no evidential support at all in making a determination about that explanation.
So with that in mind, it seems to me that in deciding which are the best explanations, they need to be judged on their own merits using relevant criteria. And in that respect I don’t see how their role in conceptualizing an equation has any relevant part to play in making that determination.
The equations describe a model universe or hypothesis. Observations tell us if our universe is like the model universe.
Using Einstein as an example, he constructed a model universe using equations where gravity bends spacetime and the speed of light is the same in all non-accelerating frames. This would result in starlight bending around galaxies and stars, gravitational waves, time dilation, and so forth. Experiments were conducted to see if we lived in a universe like the model universe Einstein’s equations described, and by all observations we do.
What I meant by what I said was not that I was simplifying the process, but simplifying what was being said about it. I agree that the process for developing an hypothesis involves inferring a description, which I believe is also expressed as a prediction or expectation, from the explanation. I just thought that it would be more clear and straightforward in getting my point across to leave out portions that weren’t relevant for that purpose.
And in case it wasn’t clear, when I say the equation on it’s own provides no evidence, I mean that if it were simply an equation without any observation, there would be no evidence. It’s the actual observation that the equation is providing the description of that provides the evidence, not the other way around.
I generally don’t see anything I would take issue with here, except maybe that I’m not exactly sure how the terms hypothesis and model are being used. But from what I can tell this all seems to be about description of behavior.
But in my opinion, explanation of what the underlying reality behind the behavior is is an altogether difference issue. Unlike described behavior which can be observed, explanation is about what cannot be observed, and therefore cannot be approached in the same manner.
It requires looking at available evidence and comparing differing explanations to evaluate which one best accounts for all available evidence.