Re:How far could a spaceship go if we never ran out of thrus...
by stavros on Tuesday August 10, 2021 @10:31AM
(#28129312)
Ah I see, so this all happens at a quantum level that doesn't translate well to our intuition? That makes a certain amount of sense, thank you.
Re:How far could a spaceship go if we never ran out of thrus...
by cygx on Tuesday August 10, 2021 @10:50AM
(#28129558)
This is still relativity, not quantum mechanics.
Point is, illustrative models and analogies are limited. Ideas like 'space itself expanding' or 'space flowing like a river and falling into a black hole like a waterfall' might help visualize some things, but can also lead to wrong ideas if taken too seriously.
Re:How far could a spaceship go if we never ran out of thrus...
by stavros on Tuesday August 10, 2021 @10:53AM
(#28129581)
> This is still relativity, not quantum mechanics.
Oh hmm, I see.
> but can also lead to wrong ideas if taken too seriously.
Yeah, and it's hard to know how far to take the analogy unless you're already familiar with the concept it's trying to describe, unfortunately.
First, like any other gravitational effect, locally, spatial expansion would manifest as pseudo-forces that can be counter-acted by all the other forces that are far more relevant at human scale.
Second, the local effect of spatial expansion should be an indirect one: Friedmann cosmology - which is how we describe an isotropic, expanding universe - is a large-scale approximation. More realistic would be 'swiss-cheese' models, where spacetime in our neighbourhood can look vastly different from the Friedmann one, except that the spacetime patches need to properly fit together to yield the correct large-scale behaviour.