A small question

[swansont]

It is my understanding that inertial space has to be flat.

[losfomot]

It is my understanding that inertial space has to be flat.

 

 

If this is true then is there such a thing as truly inertial space (and hence an inertial frame of reference) in the universe we live in? I thought a body was inertial as long as it felt no forces acting on it.

[Johnny5]

It is my understanding that inertial space has to be flat.

 

Let me see if i understand you right.

 

Are you saying that if there is an inertial frame somewhere, a frame in which Newton's law of inertia is true, then using the formulas from GR, the conclusion is that space is flat?

 

Do I have that right?

 

Regards

[swansont]

If this is true then is there such a thing as truly inertial space (and hence an inertial frame of reference) in the universe we live in? I thought a body was inertial as long as it felt[/b'] no forces acting on it.

 

I don't know if I can cover all the possible scenarios (as I've stated a number of times, my expertise in GR is limited). I was thinking of the "straight-line" (as described in recent posts) motion at constant speed. If the space is curved, there is a force, or what would classically be called a force, acting on the object.

 

As for other cases, straight-line freefall in a gravitational field is an inertial frame - that's the standard example in equivalence principle argument. But I was discussing things in context of the given scenario.

[IsraelUnoone]

It's like being a car driving and watching another car or the side pass by you... it does not seem as fast even when a and b are in relation to speed that defys a parking mode.

Johnny5,

Help me out here.

Assuming time dilation and your statement are true that after each complete the round trip of the universe, moving in straight line, A and B will see the other's watch slower than his own. As the ships pass each other at the point where earth was located when A and B started their voyage, each releases a piece if paper on which is printed the time of the A and B watches (each assumed slower than the other). What are the times printed on each piece of paper?