3 ms·

When space expands, it carries matter with itself just like our dog ran away with my sandwich so many years ago.

wolverine876 5y ago
Sorry to be pedantic or if I'm missing the obvious: The article says: Using gravitational waves we can sense what is 45 billion light years (bly, for purposes of this post) away. That implies that something(s) at 45 bly once did generate gravity waves. If matter can't move faster than C, and if it has only been on the move for 13.x billion years, it must be less than 28 bly distant. I am given to understand that the universe can expand faster than C; I presume that the universe must lack matter beyond 28 bly. I confess that I'm not sure what exactly is expanding. Therefore, what could be located between 28 and 45 bly distant that is generating gravity waves? One possibility: the matter moves no faster than C relative to points in the universe as it stretches, but is carried faster than that relative to other parts of the universe, like a sandwich.
- Hikikomori 5y ago
  If we receive light that is 13b years old the light has travelled that distance, but the source of that light is now 45bly away from us because the universe expands.
- gostsamo 5y ago
  Imagine it like that: you are in a train and per the rules of the railway company, nobody can run in the corridors aboard the trains. Your train passes by another train where the same no-run rule applies. If you can't run and a person in the other train cannot run, how the two of you can see each other for only a brief moment before you are carried kilometers from each other? Well, the rules do not apply to the trains both of you are occupying. So, though the two of you are relatively static, the underlying infrastructure is moving in different directions with speeds which are unfeasible for the passengers. In my previous comment, me and the sandwich were sharing the brief moment of unity that was broken apart by the runaway trajectory of the dog which made reunification impossible.
  - wolverine876 5y ago
    Thank you. I recognize the trains analogy, BTW, and perhaps frames of reference, but my knowledge of the topic is very spotty. And I've also had a sandwich snatched from my fingertips, seemingly faster than light.

Sorry to be pedantic or if I'm missing the obvious: The article says: Using gravitational waves we can sense what is 45 billion light years (bly, for purposes of this post) away. That implies that something(s) at 45 bly once did generate gravity waves. If matter can't move faster than C, and if it has only been on the move for 13.x billion years, it must be less than 28 bly distant. I am given to understand that the universe can expand faster than C; I presume that the universe must lack matter beyond 28 bly. I confess that I'm not sure what exactly is expanding. Therefore, what could be located between 28 and 45 bly distant that is generating gravity waves? One possibility: the matter moves no faster than C relative to points in the universe as it stretches, but is carried faster than that relative to other parts of the universe, like a sandwich.

Hikikomori 5y ago
If we receive light that is 13b years old the light has travelled that distance, but the source of that light is now 45bly away from us because the universe expands.
gostsamo 5y ago
Imagine it like that: you are in a train and per the rules of the railway company, nobody can run in the corridors aboard the trains. Your train passes by another train where the same no-run rule applies. If you can't run and a person in the other train cannot run, how the two of you can see each other for only a brief moment before you are carried kilometers from each other? Well, the rules do not apply to the trains both of you are occupying. So, though the two of you are relatively static, the underlying infrastructure is moving in different directions with speeds which are unfeasible for the passengers. In my previous comment, me and the sandwich were sharing the brief moment of unity that was broken apart by the runaway trajectory of the dog which made reunification impossible.
- wolverine876 5y ago
  Thank you. I recognize the trains analogy, BTW, and perhaps frames of reference, but my knowledge of the topic is very spotty. And I've also had a sandwich snatched from my fingertips, seemingly faster than light.