Expansion of space and planck length

[JoshWallace]

Firstly excuse my ignorance on this subject I was watching an interview with Neil deGrasse Tyson and he described how POSSIBLY the fabric of space time itself may be unable to endure an infinite amount of expansion, and would simply tear at some point. This concept seems unintuitive to me, as it describes the expansion of space as a kind of "stretching" wich has many implications..

 

Now im having trouble thinking about this as a 4 dimensional problem, but obviously it has implications in the 3rd dimension as we are observing objects in the unvierse growing farther apart. So for now I'm going to stay in 3 dimensions and hopefuly not appear too ignorant, I am thinking about 2 possible scenarios :

 

1. space really is stretching, in wich case the planck length itself would be increasing uniformly across all space and time, and we wouldnt even notice any expansion on the larger scale, just a greater distance between fundamental particles. Now if gravity is able to work against this, and the attraction between objects brings space back together again, that would mean plancks constant only appears constant to us on earth where space is compacted, in the void it would be stretched out between large bodies.. the implication of this means the speed of light would also no longer be constant, as distance itself is no longer constant.

 

2. space is not actually stretching, but "new" 3 dimensional planck "volumes" are literaly unfolding from 1 dimensional points between planck lengths, in wich case atoms would be drawn together again by gravity, pushing this extra space outwards into the void.. in this scenario there is no stretching or possible tearing from expansion.

 

Now thinking in 4 dimensions for a moment. If the effects of gravitation are ascribed to the curvature or "stretching" of spacetime, and spacetime is already stretching as it expands, wouldnt logic dictate gravity should become weaker over time as the 4th dimension becomes less "flexible" ?

[mathematic]

My guess: Stretching of space is hypothetical. All that is known is that at large scales galaxies are becoming further apart, and also this separation is speeding up. Underlying mechanism is guesswork.

[Strange]

Underlying mechanism is guesswork.

 

The underlying mechanism is accurately described (predicted, even) by General Relativity.

[Lightmeow]

Firstly excuse my ignorance on this subject I was watching an interview with Neil deGrasse Tyson and he described how POSSIBLY the fabric of space time itself may be unable to endure an infinite amount of expansion, and would simply tear at some point. This concept seems unintuitive to me, as it describes the expansion of space as a kind of "stretching" wich has many implications..

 

Now im having trouble thinking about this as a 4 dimensional problem, but obviously it has implications in the 3rd dimension as we are observing objects in the unvierse growing farther apart. So for now I'm going to stay in 3 dimensions and hopefuly not appear too ignorant, I am thinking about 2 possible scenarios :

 

1. space really is stretching, in wich case the planck length itself would be increasing uniformly across all space and time, and we wouldnt even notice any expansion on the larger scale, just a greater distance between fundamental particles. Now if gravity is able to work against this, and the attraction between objects brings space back together again, that would mean plancks constant only appears constant to us on earth where space is compacted, in the void it would be stretched out between large bodies.. the implication of this means the speed of light would also no longer be constant, as distance itself is no longer constant.

 

2. space is not actually stretching, but "new" 3 dimensional planck "volumes" are literaly unfolding from 1 dimensional points between planck lengths, in wich case atoms would be drawn together again by gravity, pushing this extra space outwards into the void.. in this scenario there is no stretching or possible tearing from expansion.

 

Now thinking in 4 dimensions for a moment. If the effects of gravitation are ascribed to the curvature or "stretching" of spacetime, and spacetime is already stretching as it expands, wouldnt logic dictate gravity should become weaker over time as the 4th dimension becomes less "flexible" ?

 

Well, if time goes on, then space time should be stretching anyways. I don't get what you mean by the forth dimension getting less flexible though.

[ajb]

I was watching an interview with Neil deGrasse Tyson and he described how POSSIBLY the fabric of space time itself may be unable to endure an infinite amount of expansion, and would simply tear at some point. This concept seems unintuitive to me, as it describes the expansion of space as a kind of "stretching" wich has many implications..

I think the main problem here is talking an analogy too far. The mechanism for the expansion is in general relativity where we see the distance between two point in 3d increase with time.

 

The idea that at some point space-time could tear is interesting, but not part of general relativity. It would have to be something more like a quantum theory and here the notions of space and time become blurry.