Given that the actual universe is larger than our observable universe, how do sky-mapping surveys show that the universe is infinite?
I don't think that's what @AJC or @davidm said. I'm going to stick my neck out and suggest spatially infinite differs from the concept you and I would immediately imagine, @thirdwind. Spatial infinity as a boundary of spacetime It's another article I don't claim I can read, I get the gist, that's about it. Layperson translation: the math works but don't expect to see a physical representation anytime soon. From NOVA: Science Blogger, Ethan Siegel writes in Starts with a Bang, "How Big Is the Entire Universe?" (as opposed to the 'visible universe'). I love Science Blogs. I like this comment from an earlier blog entry: Greg Laden (also of SB: "Culture as Science/Science as Culture) asked a question and Ethan answered: I thought the guy who came up with the estimate had a smaller number but I can't find it or other sources so I probably have a false memory about it. But I thought some cosmologist/theoretical physicist had done the calculations and it appears that part of my recollection is correct. At least some people think the Universe is finite and the size beyond what is visible can be calculated. I'm not saying that contradicts the other statements in this thread about "spatially infinite" and the other concepts and terminology that fit the mathematical reality of the Universe. I can accept that much cognitive dissonance without worrying I'm not thinking critically.
Yeah, it seems that way. When I think about an infinite universe, I think about a plane extending out to infinity in both directions. Haha. I didn't understand any of that at all. But I have to wonder how much caution physicists use when interpreting the math. The math may be correct, but it may not correspond to the actual physics.
That doesn't make sense, thirdwind. It's actual physical measurements and observations the math is derived from. They aren't just pulling numbers out of the air. It's just that a lot of the observations and measurements are mind boggling, like the distance to another galaxy or the speed of light from a laser bounced off a reflector on the Moon.
For stuff like string theory, there's no way to check if the math actually corresponds to actual observations because no actual observations have been made. At that point you're just trusting the math.
String theory is different from what we've been talking about but if that's the "may" you were talking about, I get it.
I can't speak for the sky survey because I don't know the details about it, but mathematically speaking, spacetime is different from Euclidean space. Actually, the concept of infiniteness or infinity is different in general. The rules of math that apply in "finite math" may not apply in "infinite math." There's pretty good indication that the math explains how the universe works fairly well. However, I do see your point. Even in real world applications, such as engineering, the person doing the math has to throw away mathematically sound solutions because they don't agree with real world results. For cases where you don't have real world data, you just have to trust the math and hope for the best.
