Spaceships 5 question

[malloyd]

Originally Posted by Ulzgoroth

The relative velocity looks the same from both positions, yes.

Only in the special case of one of the gas velocity being either zero or c in one of the frames, which admittedly is likely to be close to the case for interstellar gas in a frame moving with one or the other of the endpoint stars, but it doesn't have to be for both if the end points have high relative proper motions. If it's not, then you get to do a relativistic velocity addition problem.

I can't really imagine why anybody would write a rule where you measured anything at all about an interstellar voyage between points with low relative proper motions in anything but the "rest" frame they aren't moving much in.

[Flyndaran]

So everyone agrees the rule is for the long time not the shorter ship time?

[vierasmarius]

Originally Posted by Flyndaran

So everyone agrees the rule is for the long time not the shorter ship time?

Yup. Consider this - what happens as you exceed 0.9c and approach, say, 0.99c? The trip time from an outside observer doesn't change significantly, but the time aboard the ship shortens dramatically. If the damage interval is based on the ship time, this means it takes significantly less damage as it approaches lightspeed. Tracking damage based on the observer's reference frame means the ship takes a relatively consistent amount of damage based on the distance traveled.

[scc]

Originally Posted by vierasmarius

Yup. Consider this - what happens as you exceed 0.9c and approach, say, 0.99c? The trip time from an outside observer doesn't change significantly, but the time aboard the ship shortens dramatically. If the damage interval is based on the ship time, this means it takes significantly less damage as it approaches lightspeed. Tracking damage based on the observer's reference frame means the ship takes a relatively consistent amount of damage based on the distance traveled.

That's the way it works in practice, but No Initial Frames Of Reference (I think that's the physics term for it) says that you can say that your at rest and that the observer is the one that's moving and thus experiencing temporal dilation, don't let the party munchkin use this against you

[Fred Brackin]

Originally Posted by scc

That's the way it works in practice, but No Initial Frames Of Reference (I think that's the physics term for it) says that you can say that your at rest and that the observer is the one that's moving and thus experiencing temporal dilation,

It'll say that you could be standing still and the entire Universe is moving instead. It will also say that it is the moving mass of the Universe that's creating the acceleration forces you feel, but the apparent force level will not change.

The lesson there is that end results stay the same. If one Observer's results could be shown to be correct and the other's false then one of the Observers would have a "privileged" frame. It's the end equivalence of the results that keeps you from picking one frame to be "right".

The guy in the spaceship thinks the incoming number and energy of particles is going up rather than his time frame is slowing down. The total number of particle impacts and their relative energy will stay the same in both frames.