4 ms·
Space expands faster than light. Don't forget that C is the max speed of stuff in space, not of space itself.
by gostsamo 5y ago
Space expands faster than light. Don't forget that C is the max speed of stuff in space, not of space itself.
- wolverine876 5y agoAnd space without stuff creates gravitational waves? How? Thanks for the impromptu physics lesson, BTW.
- TeMPOraL 5y agoSpace expands uniformly across all its volume, so the parts far away from us also have stuff in it. Some stuff already moves away from us faster than light.
- gostsamo 5y agoWhen space expands, it carries matter with itself just like our dog ran away with my sandwich so many years ago.
- wolverine876 5y agoSorry 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 agoIf 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 agoImagine 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 agoThank 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.
- alpaca128 5y agoI'm not an expert, but as far as I understand it the universe expanding means space itself is stretching at every point. Meaning if something was 1ly away in the past, it might be farther away due to that effect. This also applies to gravitational waves and anything else inside the universe.
- contravariant 5y agoYou need something with mass to generate gravitational waves, but those waves themselves can pass through empty space without any medium, or rather the empty space itself is the medium.
- hanoz 5y agoWait, what, so atoms, neutrons, quarks etc. are all growing and moving apart at the same rate as the Universe?
- simonh 5y agoThe expansion at a local level is too slow and is overwhelmed by the local forces holding these structures together. Only at the cosmic scale, where the gravitational forces between galaxies and clusters or super-clusters of galaxies are very tenuous, the expansion takes over.
- herrkanin 5y agoThe forces that keep atoms, neutrons, quarks etc bound to each other is stronger than the force caused by space expanding. Therefore, space expanding is mostly observed when measuring distance between galaxies.