jacksonb62 said:
Astronomers say that there is neither an edge or center to the universe, yet we live in a finite universe. I understand how our universe can be finite yet have no edges due to the curvature of the universe, but I can't understand how it doesn't have a center. Space must be being curved around something right? is it possible that a supermassive (and I mean SUPERmassive) black hole could lie at the center of the universe curving the entire visible universe around it? just a thought
Jackson, be careful to distinguish between "entire visible universe" and the universe.
Astronomers don't say the universe is finite. They don't know whether finite or infinite.
They say the visible universe, or socalled observable universe HAS center (our solar system) and they say it IS FINITE. The radius as of today is estimated approximately 46 billion lightyears, with us at the center naturally.
That's the OBSERVABLE universe. But when they talk about the UNIVERSE that is a completely different thing. Not to be confused with the observable portion. Like what Dave just said: what you can see of the Earth's surface, out to your horizon, is different from the entire surface of the earth.
=====================
About cosmology. It is a mathematical science which means finding the simplest math model which best fits the data. Adjusting the model to match the past observations and seeing if it then predicts future observations. The present model has been amazingly successful. That doesn't mean it's RIGHT. As soon as anyone can offer a simpler model with a better fit, people will go for it. The current model is just the best the best we can do for the present with the math tools and the data which we've got. But it does not mean that the current model is RIGHT.
And it is true that the current model has no center and no edge or boundary. And the matter is approximately evenly distributed (largescale average) throughout the space.
And the largescale average curvature is either zero or very close to zero.
This geometry is described by the 1915 law of evolving geometry called Gen. Rel. (GR).
It is both a law of gravity and a law of how geometry interacts with matter and changes over time. (The expansion you hear about is according to this law and has been checked.)
This takes a while to understand.
Astronomers say that there is neither an edge or center to the universe, yet we live in a finite universe
Lets be a little more careful. Astronomers do NOT say the U is finite. They say the observable portion is finite. Which it obviously is.
About the whole U, we don't KNOW, and astronomers do not claim to know. They can tell you about the math models they use, which fit the data remarkably well and have a remarkable track record for predicting accurately.
The good cosmic models we have are a great human achievement and it's right to be proud of them and want to describe their features (like no center, no boundary or edge, approx even distribution of matter, expansion, a calculable history of structure formation, the microwave background...) But ultimately we don't know some basic things.
We don't know whether the finite version of the model is best or whether the infinite version is best. They give almost the same numbers so the fit about equally well. So we can't distinguish! More observation is needed, in order to tell. And so on. Things like that.
They really shouldn't say they KNOW and I don't think they do say that typically. There is usually some modest reservation stuck in, if you read carefully. Like "according to our theory" or "according to our model" blah blah X Y and Z. And of course the theory or model can be eventually proven wrong and improved 5 or 10 years down the road.
Anyway that's my take on it, as an interested bystander. Keep asking questions. It's fun.
