emc wrote:Sorry but I am still confused... if there is no direction we can look and the origin lies outside the 3 dimensions we reference but at the same time we can look deeply in any direction and be closer to the origin... has thrown me into a tail spin.
I can understand why we can't see the origin if we are looking back into time and can't see that far. And the farther we look the closer we are to it...
I hope you can forgive my ignorance, and I appreciate you patient answers... What is still holding me back is that if the universe has been expanding then how can the origin be away in every direction? Maybe I just can't shake my simple 3D roots?
Our whole existence is based on those 3D roots, so shaking them isn't easy. I'm afraid there's no rule that says everything about the Universe needs to be obvious or intuitive.
First, lets distinguish between the origin in terms of
time and the origin in terms of
space. We can observe the former if we can see something far enough away (although as previously noted, we can't observe with photons quite to the very beginning). But we don't observe the latter in any meaningful way because, at least in 3D space, it doesn't exist as a point.
There is a popular analogy used to describe the Universe, using a balloon. It has been used here and elsewhere, and is very useful if not misused. You are asked to imagine that the balloon represents the Universe, expanding outwards from the center. But unlike the real Universe, this is a 3D universe with a 2D surface. The entire contents of this universe lie on the surface of the balloon. Points on it are getting farther from each other with time. Beings living on the surface could look all around, but not "up" or "down" because those directions don't exist for them. It is obvious to them that their universe is expanding, but there is no center of expansion on the 2D surface they have access to. Some 2D Einstein might work out the math demonstrating that this universe is actually undergoing a 3D expansion, but most of his 2D friends won't really grasp what that means in any intuitive sense.
Now try to extend that analogy to the Universe we live in. All matter and energy lies on the 3D surface of this 4D universe. There is a center of expansion (the origin of the Big Bang) but it doesn't lie on the 3D surface we can study. Theory predicts this center, and the theory is well supported by experimental evidence, but we still can't observe that center directly.
By looking at distant objects we can learn about conditions near the beginning of the Universe, because we see those objects as they were. But we don't see them
where they were with respect to the Big Bang, because every point [we can see] is equidistant from the origin, and always has been.
[quote="emc"]Sorry but I am still confused... if there is no direction we can look and the origin lies outside the 3 dimensions we reference but at the same time we can look deeply in any direction and be closer to the origin... has thrown me into a tail spin.
I can understand why we can't see the origin if we are looking back into time and can't see that far. And the farther we look the closer we are to it...
I hope you can forgive my ignorance, and I appreciate you patient answers... What is still holding me back is that if the universe has been expanding then how can the origin be away in every direction? Maybe I just can't shake my simple 3D roots?[/quote]
Our whole existence is based on those 3D roots, so shaking them isn't easy. I'm afraid there's no rule that says everything about the Universe needs to be obvious or intuitive.
First, lets distinguish between the origin in terms of [i]time[/i] and the origin in terms of [i]space[/i]. We can observe the former if we can see something far enough away (although as previously noted, we can't observe with photons quite to the very beginning). But we don't observe the latter in any meaningful way because, at least in 3D space, it doesn't exist as a point.
There is a popular analogy used to describe the Universe, using a balloon. It has been used here and elsewhere, and is very useful if not misused. You are asked to imagine that the balloon represents the Universe, expanding outwards from the center. But unlike the real Universe, this is a 3D universe with a 2D surface. The entire contents of this universe lie on the surface of the balloon. Points on it are getting farther from each other with time. Beings living on the surface could look all around, but not "up" or "down" because those directions don't exist for them. It is obvious to them that their universe is expanding, but there is no center of expansion on the 2D surface they have access to. Some 2D Einstein might work out the math demonstrating that this universe is actually undergoing a 3D expansion, but most of his 2D friends won't really grasp what that means in any intuitive sense.
Now try to extend that analogy to the Universe we live in. All matter and energy lies on the 3D surface of this 4D universe. There is a center of expansion (the origin of the Big Bang) but it doesn't lie on the 3D surface we can study. Theory predicts this center, and the theory is well supported by experimental evidence, but we still can't observe that center directly.
By looking at distant objects we can learn about conditions near the beginning of the Universe, because we see those objects as they were. But we don't see them [i]where[/i] they were with respect to the Big Bang, because every point [we can see] is equidistant from the origin, and always has been.