Well, one would have to ask if hydrogen or some things could exist in another state. If they could, then merely seeing them would not mean all is homogenous. Name one star in Andromeda that behaves the same as stars in the Milky Way? (not that I doubt)In the data we get from the light from Andromeda we see all sorts of similarities to physical laws on Earth including the spectral signatures of known elements, stars that seem to behave the same way as ones in our own galaxy,
So far you have talked about material existing (ammonia or etc) in Andromeda, ans some unspecified star behavior being 'the same'. That is not enough to determine what is 'likely'. Not yet.so we determine that it is far more likely that the laws of physics are the same in Andromeda as they are here that they are different.
As for mainstream science evidence I don't think we have had any evidence that they are the same. So no evidence is needed to say they are not.What evidence is there that they would be different?
I think there's a lot of evidence that the laws would be the same. We observer billions of galaxies in the universe and Andromeda and our own would appear to both be typical ones. Things like the spectral signature of Hydrogen come out of the laws of physics, and this is the evidence that hydrogen is the same here as in other galaxies, because if the laws were different hydrogen would give a different signature. That is only one of many examples.
Also, I use the word assumption just to be technical. All scientific laws are assumptions based on observational evidence. In the case of generally accepted laws such as Einstein's Special Relativity, there is a preponderance of evidence to back up the assumption, but it is still technically an assumption. So indeed it is an assumption that the laws of physics remain constant in different galaxies but one that is backed up by a lot of evidence (we have enough data from our telescopes to observe the same laws of physics playing out there).
So there is evidence for that assumption. Is there evidence to assume that the laws are different?
Okay stardad, this has gone on far enough now, if you have a bone to pick with the standard model of the universe (as you have claimed in post #19, then you take it to ATM and you present your case. Coming to Q&A and pursuing a hidden ATM goal is not acceptable.
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New blog 28-07-2013: Summer School Alpbach 2013: "Space Weather: Science, Missions and Systems"