- #1
Galactic explosion
- 35
- 9
I understand that there are many forums and topics written on the fact that space is expanding. But I've looked and looked, and couldn't find an answer to my specific question.
How do we know space is expanding, rather than galaxies just regularly moving apart?
How do we know galaxies are actually "riding" space like a surfer on a wave in the ocean (or that typical answer you get with a balloon blowing up with dots on it)? Is there even an actual difference? Can't they just be striding along in all directions without including such a weird phenomenon where the geometry of space is increasing in magnitude, and dragging everything with it like some kind of warp drive?
With the balloon analogy, it's quite obvious the balloon is inflating because we can actually differentiate the balloon as a separate object from the dots. But when it comes to actual space, isn't space an emergent consequence of there being many objects relative to each other? In order for space to even exist, you naturally need to have a measurable distance between two objects. No objects? No space. And vise versa.
For example, all that exists are 3 things; two objects, and a hand to push the objects. If the hand pushed one object in the opposite direction of the other, it would at least from some point of view, appear that both objects are moving away from each other equally, depending on the frame of reference. Let's say the hand forgot that it pushed that one object, and wanted to measure both their motions. Would it come to the conclusion that the space between the objects is expanding, or the objects are simply moving away from each other because there was an initial force at some point?
I hope that example made sense and I didn't butcher my question.
How do we know space is expanding, rather than galaxies just regularly moving apart?
How do we know galaxies are actually "riding" space like a surfer on a wave in the ocean (or that typical answer you get with a balloon blowing up with dots on it)? Is there even an actual difference? Can't they just be striding along in all directions without including such a weird phenomenon where the geometry of space is increasing in magnitude, and dragging everything with it like some kind of warp drive?
With the balloon analogy, it's quite obvious the balloon is inflating because we can actually differentiate the balloon as a separate object from the dots. But when it comes to actual space, isn't space an emergent consequence of there being many objects relative to each other? In order for space to even exist, you naturally need to have a measurable distance between two objects. No objects? No space. And vise versa.
For example, all that exists are 3 things; two objects, and a hand to push the objects. If the hand pushed one object in the opposite direction of the other, it would at least from some point of view, appear that both objects are moving away from each other equally, depending on the frame of reference. Let's say the hand forgot that it pushed that one object, and wanted to measure both their motions. Would it come to the conclusion that the space between the objects is expanding, or the objects are simply moving away from each other because there was an initial force at some point?
I hope that example made sense and I didn't butcher my question.