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Posted

I think I have figured out a method. Famous last words. But anyway, I cannot find a flaw under certain assumptions on how bubbles work.

So, first we have to understand something about relativistic travel. I am sorry, but I will have to do a bit of Special Relativity simplified to brutal shortness. What happens if you just keep accelerating? That depends on viewpoint - hence relativity. Very well let's say that before you start you determine the distance between the point A and B you are going to travel. From your (moving) point of view the voyage will take less time (given enough acceleration) than light would need to travel from A to B, because from your view point the distance between A and B shrinks. From the view point of an external observer at rest with respect to A and B, your travel will take at least as long as light will need and your (the traveller's) time will slow down.

Now let's suppose there is a bendalloy bubble between A and B. We all probably agree that it will take less time from the viewpoint of an external observer than your time. That is kind of the point of a speed bubble. If we take an interstellar bubble this is a deeply problematic solution to the traveller. So what prevents us from putting the traveller into a smaller cadmium bubble? That should do it and it seems surprisingly simple. But I cannot find a flaw, under one major condition: speed bubbles do not alter the speed of light. You just need a moving cadmium bubble inside a stationary bendalloy bubble.

Posted

I think you are asking the right questions.  Is this conceptually similar to the Alcubierre drive (See Below)?

 

FTL Clues:

 

 

Quote

 

Steeldancer (paraphrased)

Have you ever heard of the Alcubierre Drive

Brandon Sanderson (paraphrased)

Yes, I know about the Alcubierre drive. 

Steeldancer (paraphrased)

So, if we took two speed bubbles--mechanized, because Allomancers aren't powerful enough to pull it off--could we create a functioning Alcubierre drive?

Brandon Sanderson (paraphrased)

You are theorizing in the right direction. 

FanX Spring 2019 (April 19, 2019)

 

 
Posted
1 minute ago, Quantus said:

 

 

I think the two relevant things we've learned since then are:

- Time bubble is anchored to the planet if used in a small vehicle like a carriage, but anchored to the vehicle if used in a large vehicle like a train (from the scene in BoM with Marasi experimenting with the Primer Cube in the carriage) - so anchoring time bubbles to spaceships will work. But that's not really a new 'ability'

- Mechanical use of Allomancy (Primer Cubes). That could be the new ability.

We still don't know enough though, I think. I am not sure how conservation of energy issues apply- even unlimited energy can't give you FTL.

Posted
5 hours ago, cometaryorbit said:

We still don't know enough though, I think. I am not sure how conservation of energy issues apply- even unlimited energy can't give you FTL.

It seems to me that there is a problem with that. Suppose you are on an object lrge enough to anchor a bubble to. You are on a collision course with another object. You use a bendalloy bubble. To an external observer you are now faster. Which momentum do you have on impact? The one you would calculate or the one the people outside would calculate?

Posted

I feel like since the whole bubble is moving, it'd be the outside one - your speed within (relative to) the bubble is basically zero so your motion isn't really accelerated.

And when your bubble hits the other object it distorts and eventually pops so at the actual moment of collision there's no bubble?

Maybe?

Posted
5 hours ago, cometaryorbit said:

I feel like since the whole bubble is moving, it'd be the outside one - your speed within (relative to) the bubble is basically zero so your motion isn't really accelerated.

And when your bubble hits the other object it distorts and eventually pops so at the actual moment of collision there's no bubble?

Maybe?

Fair enough. So we complicate the experiment a little. We have the objects narrowly miss. They, however, obviously do have a gravitational attraction to each other. Which one feels which attraction?

Posted

I think that is beyond what our current knowledge can tell us. If bubbles worked 100% like RL time dilation there would be a clear answer (though one beyond my physics knowledge) but since we don't know if bubble FTL is a relativity compatible trick like an Alcubierre drive or breaks relativity (some things in the cosmere do, Oathgates and I think spanreeds), I don't think we know yet.

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