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For someone who knows more than me: what is space? If it's able to "move" in the sense of expanding into existence faster than light can travel, what is the com

For someone who knows more than me: what is space? If it's able to "move" in the sense of expanding into existence faster than light can travel, what is the composition of it? Is this what dark matter is meant to explain? For something to expand faster than C means it has to be pushed at least that quicky by some other thing or some other force, right? I have no science background at all, just a few decades of sysadmin work. Is there a book I should start with?

Sharlin 5y ago
No need to push anything. Distances between objects (that are sufficiently far away from each other) just increase as if there’s "more space" inserted between them in some sense. There’s the concept of spacetime metric, a function that’s sort of a universal measuring stick for distances in the universe, and it is "shrinking" (as in there’s a parameter that varies as a function of time) so that a distance that used to be three measuring sticks long is now three point one.
erikpukinskis 5y ago
“A Brief History of Time” by Stephen Hawking is written for the average reader and wonderful.
simonh 5y ago
The acceleration of the expansion of the universe is sometimes attributed to “dark energy”, but that’s a placeholder term. We don’t actually know what is doing it exactly. We can just see that it seems to be happening. The ‘faster than the speed of light’ thing is only if you measure the rate of divergence of objects at very great distances from each other, tens of billions of light years. At more local scales, such as between our neighbouring galaxies and clusters, the effect is relatively small and negligible compared to gravity.
TheOtherHobbes 5y ago
No one knows what space is. We know there's a thing we call "spacetime", because space and time are closely related. And we know some things about its properties. But we know nothing at all about what it's made of, or why it has the properties it does.
317070 5y ago
You can think of this space as something that tells for every point a path passes through, how long the distance of the path in that point is. So when I connect A and B with a path, and I take the integral of space on that path, I get the length of the path I would travel if I go from A to B along this path. One step further, the distance from A to B is the shortest length of all paths from A to B. Now if for every point in the universe, we have those numbers for each path through that point, we call that a "metric". Einsteins laws tell us how those numbers all relate to each other and how changing the numbers at one point affects the numbers at other points over time. And from those laws, you can see that you can have waves within those numbers. So it is not "something" that is waving, it is space itself, the thing that defines distances, the metric, that is waving. Now the annoying thing is that that means that two points at rest with each other, can be at a changing distances from each other. What happened is that the space between them was waving, changing which path between the points was the shortest path, and how long that path was.

Sharlin 5y ago

No need to push anything. Distances between objects (that are sufficiently far away from each other) just increase as if there’s "more space" inserted between them in some sense. There’s the concept of spacetime metric, a function that’s sort of a universal measuring stick for distances in the universe, and it is "shrinking" (as in there’s a parameter that varies as a function of time) so that a distance that used to be three measuring sticks long is now three point one.

erikpukinskis 5y ago

“A Brief History of Time” by Stephen Hawking is written for the average reader and wonderful.

simonh 5y ago

The acceleration of the expansion of the universe is sometimes attributed to “dark energy”, but that’s a placeholder term. We don’t actually know what is doing it exactly. We can just see that it seems to be happening. The ‘faster than the speed of light’ thing is only if you measure the rate of divergence of objects at very great distances from each other, tens of billions of light years. At more local scales, such as between our neighbouring galaxies and clusters, the effect is relatively small and negligible compared to gravity.

TheOtherHobbes 5y ago

No one knows what space is. We know there's a thing we call "spacetime", because space and time are closely related. And we know some things about its properties. But we know nothing at all about what it's made of, or why it has the properties it does.

317070 5y ago

You can think of this space as something that tells for every point a path passes through, how long the distance of the path in that point is. So when I connect A and B with a path, and I take the integral of space on that path, I get the length of the path I would travel if I go from A to B along this path. One step further, the distance from A to B is the shortest length of all paths from A to B. Now if for every point in the universe, we have those numbers for each path through that point, we call that a "metric". Einsteins laws tell us how those numbers all relate to each other and how changing the numbers at one point affects the numbers at other points over time. And from those laws, you can see that you can have waves within those numbers. So it is not "something" that is waving, it is space itself, the thing that defines distances, the metric, that is waving. Now the annoying thing is that that means that two points at rest with each other, can be at a changing distances from each other. What happened is that the space between them was waving, changing which path between the points was the shortest path, and how long that path was.