Has anyone found any science to give evidence that space is a thing?
Gravity bends light... how do you think that is possible?
All this talk about expanding space is fantasy unless space is a physical thing. In order to expand a thing has to have physical properties.
Oh, I dunno... You can expand a mathematical matrix. You can expand your mind.
Anyway, spacetime is where physical properties reside. Even your own rule here takes place within spacetime. Its kind of its own thing, and not necessarily subject to the rules that take place within it.
Welcome to EvC, Lurkey! So much for lurking Thanks for joining up and posting.
If we could magically break our bodies down into a cloud of the smallest particles possible, then trace all those bits back through space time – say to when the universe was the size of a tennis ball – and then magically reassemble ourselves there, how big would it all look?
I guess it would look to be the size of a tennis ball, but the pressure from the density would be so great that you be crused to death.
In a sense, all of us were there at the time, right?
Not really. Back then there weren't the same kinds of matter as there is today.
Eg i love the thought that there is a lineage line going from me all the way back to that first single cell organism....i'm asking is there a similar lineage line from my atoms (or whatever) all the way back to the origin of the universe?
Heavier elements are fused inside of stars and then blasted across the universe via supernova. It'd be a very convoluted path back to the origin. I'm picturing it quite a bit differently than a genetic lineage.
But doesn’t all matter ultimately date back to the big bang?
No, there was "some time" after the Big Bang before matter even existed:
click to enlarge
It was "really fucking short" but it was there nonetheless.
Just some ideas are so hard…eg I HATE the universe-wrapping-back-on-itself kind of infinity,
In order to concepualize it, you're gonna have to be able to reduce dimensions in your mind. So, take a cube, it's 3-dimensions, and reduce it to 2 dimensions: It becomes a plane. That is, the plane is the "shadow" of a cube. Think about how your shadow on the sidewalk is a 2-D representation of yourself. Now, reduce that 2-d plane to one dimension: it becomes a line. If you take a sheet of paper (2D) and look at it just from its edge, it makes a line. Again, you can reduce a 1D line into a point in the same way: Take a pencil and look at it down the shaft and it becomes a "point" (0D). That's reducing dimensions in a nutshell.
So, on to the analogy. Imagine the globe, the Earth. But just the surface of the Earth. Nothing on the inside just the surface, like a balloon. Let that 2 dimensional surface represent all three spatial dimensions, they're just reduced as per the above. Now, imagine that the lines of latitude represent the timeline. The closer you get to the North Pole, the farther back you are going in time. As you approach the North Pole, as you go back in time, the size of the Universe, the radius of the Earth, keeps getting smaller and smaller. That's the Universe getting smaller and smaller as we go back in time. So what happens when you get to the North Pole? You can't go farther north than that, i.e. you can't go back further in time than that. The surface "wraps back upon itself". That is, it is an asymptote <--. clicky. Asking what's before the Big Bang is like asking what's north of the North Pole. Your immediate reaction might be "upwards" from the surface, but due to the dimension reduction, there is no such thing as that. For, when you're at the North Pole, all directions are south. If you're confined to the surface, there is no upwards to point towards.
That point, the North Pole, represents the singularity that the Big Band describes. All directions are "forward" in time and there is no such thing as "before". Time, itself, is an integrated part of the dimensions of spacetime, that is there are 3 spatial dimensions and one temporal one. So we're really talking about a 4 dimensions manifold <--. again, clicky. That manifold has a finite "shape" and that shape suggests a finite past, but that past "folds back onto itself" and exists at all points that time exists. Its like the Eath exists at all points of latitude even though there is only so far northwards that you can go.
So that's the best analogy I've come across, let me know if you have any questions.
Edited by Catholic Scientist, : Type. 2D --> 1D for a line. Added (0D) to point
How the distances work on a particular manifold is given by an object called the metric.
So the metric is 'how the distances work'. It can be a mathematical equation where you input some particular of the manifold and determine the distance between them.
So lets look at the metric we're all familiar with:
The old X-Y Plane. To find the distance to the green dot, we use . That's the metric.
You can make the manifold more complicated by adding more dimensions:
And this will change the metric.
Some shapes (or spaces, which is the technical term) are too bizarre to be described using real numbers, although the use of these spaces is limited in physics.
If the manifold has a notion of distance between its points, then it is called a Riemannian manifold or a Pseudo-Riemannian manifold if one of the dimensions is time. The surface of the Earth is a Riemannian manifold, since there is a distance between points on the Earth's surface. The space of states is not, as you can't really say how far states are from each other.
People can use these manifolds to create some pretty cool shapes.
quote:The Riemannian manifold is a very important extension of integral calculus, the idea of being able to take an integral over a complex and possibly curved surface, instead of just taking a measure over a simple flat surface like a line or a plane. The pictures here are a model of the real projective plane, a two dimensional surface that cannot be truly built in three dimensions because it must pass through itself without having a hole in the surface. The idea of the manifold is that this odd looking shape, and many other odd looking shapes, can be defined by covering the surface with a patchwork quilt of flat or nearly flat patches, and if two patches overlap, there is an "easy" method of matching points on one patch to the corresponding points on the other.
quote:Destruction of coral reefs is a serious issue, so surely no hyperbole? Ah, a simple error of diction. Actually hyperbolic space is a recognised mathematical model. As most people know, “hyperbolic n-space, denoted Hn, is the maximally symmetric, simply connected, n-dimensional Riemannian manifold with constant sectional curvature −1.”
You can create manifolds to see if and how they match observations to get a better understanding of the underlying causes of the way things happen. Some of the manifolds more accurately match observations of our Universe, itself, even. Like how Einstein's have.
As you say:
Einstein's Theory of General Relativity basically says that the energy density of matter determines the metric of spacetime.
That is, the energy density of matter at a point affects how the rules of distance work near that point.