3 ms·

> faster than light How? From what frame?

twawaaay 4y ago
It is just a mental shortcut. Of course, things cannot be moving faster than light because speed addition cannot lead to relative speeds faster than light. What you will see is a slowing, red-shifting, darkening image of everything else as it speeds away from you asymptotically reaching speed of light until space between any two particles starts expanding so fast that no radiation can reach anything anymore and each particle forever lives in its own universe. Of course we don't know that because we really don't understand how the universe is built and this is just our faulty formulas extrapolated way more than we can reasonably support with our experimental data.
wahern 4y ago
> While objects within space cannot travel faster than light, this limitation does not apply to the effects of changes in the metric itself. Objects that recede beyond the cosmic event horizon will eventually become unobservable, as no new light from them will be capable of overcoming the universe's expansion, limiting the size of our observable universe. https://en.wikipedia.org/wiki/Expansion_of_the_universe https://en.wikipedia.org/wiki/Expansion_of_the_universe We can already observe this phenomenon happening at large scale. Our observable universe shrinks as galaxies effectively accelerate away from us faster than the speed of light (i.e. the space between us and them expands faster than the speed of light). Whether this phenomenon is inevitable at a local scale, especially an atomic scale, is unclear, AFAIU. See https://en.wikipedia.org/wiki/Big_Rip https://en.wikipedia.org/wiki/Big_Rip But in principle, IIUC, our own bodies are experiencing this effect right now. For now it's beyond miniscule, but slowly accelerating. This tiny local expansion and acceleration, summed over cosmic scales, is ostensibly how galaxies far enough apart can move away from each other faster than the speed of light. Fundamentally it's the continuation of the Big Bang.

It is just a mental shortcut. Of course, things cannot be moving faster than light because speed addition cannot lead to relative speeds faster than light. What you will see is a slowing, red-shifting, darkening image of everything else as it speeds away from you asymptotically reaching speed of light until space between any two particles starts expanding so fast that no radiation can reach anything anymore and each particle forever lives in its own universe. Of course we don't know that because we really don't understand how the universe is built and this is just our faulty formulas extrapolated way more than we can reasonably support with our experimental data.

wahern 4y ago

> While objects within space cannot travel faster than light, this limitation does not apply to the effects of changes in the metric itself. Objects that recede beyond the cosmic event horizon will eventually become unobservable, as no new light from them will be capable of overcoming the universe's expansion, limiting the size of our observable universe. https://en.wikipedia.org/wiki/Expansion_of_the_universe https://en.wikipedia.org/wiki/Expansion_of_the_universe We can already observe this phenomenon happening at large scale. Our observable universe shrinks as galaxies effectively accelerate away from us faster than the speed of light (i.e. the space between us and them expands faster than the speed of light). Whether this phenomenon is inevitable at a local scale, especially an atomic scale, is unclear, AFAIU. See https://en.wikipedia.org/wiki/Big_Rip https://en.wikipedia.org/wiki/Big_Rip But in principle, IIUC, our own bodies are experiencing this effect right now. For now it's beyond miniscule, but slowly accelerating. This tiny local expansion and acceleration, summed over cosmic scales, is ostensibly how galaxies far enough apart can move away from each other faster than the speed of light. Fundamentally it's the continuation of the Big Bang.