Not a troll, I'll delete the thread when I'm answered

[OP !OudrPWaUDQ No.1205232]

Picture sort of related, but not really.

I know that there is something wrong with this, and there is most likely a very good answer to my question. I'm not trolling here, I'm simply not skilled in the subject. To avoid any accusations of being a troll, when I get a good explanation I will delete this thread. I'm not here for a discussion as much as I am here for an answer.

This is probably one that you guys have heard of before.

Take four objects: A, B, C, and D. A, B, and C are all attached, and D is far off in the distance, relatively stationary to the starting point of A.

Say the three objects were propelled by A to 0.5c. The two other objects then detach from A and propel themselves to 0.5c relative to A. C, the remaining object, then detaches itself from B and propels itself to 0.5c relative to B. The relative speeds are laid out like the following:

A,D: 0.5c
B,D: c
C,D: 1.5c

Where is the problem with this? I know there probably is one, and as soon as I know I'll delete this thread. I don't want any trouble, I just want to educate myself

[Anonymous No.1205242]

You are adding the velocities incorrectly.

In special relativity, the velocity addition law is modified.

http://en.wikipedia.org/wiki/Velocity-addition_formula

[Anonymous No.1205254]

>>1205232
You should not be ashamed for asking a serious science question. There ought to be more of them on the board.

[Anonymous No.1205274]

>>1205254
>>1205242
these. when space is curved, relative velocities don't just 'add' up like we're used to.

bump
don't delete the thread.

[OP !OudrPWaUDQ No.1205293]

>>1205242
Brilliant. I never knew about that before, and this is a question that stumped me for years. Thanks

>>1205274
Per your request, I won't delete the thread. I'm not sure what left there is to discuss, though

[Anonymous No.1205303]

>>1205274
I appreciate your kindred spirit, but just to clarify, this has nothing to do with curved space. Special relativity in fact is only correct in flat space.

[Anonymous No.1205350]

I thought the OP was a diagram of an SLBM and got all excited only to find it was some silly space sail thing
FUCK YOU

[Anonymous No.1205360]

Someone answer this

[Anonymous No.1205369]

>>1205360
it was answered in the first reply

[Boomer !!MBwbEofHcyx No.1205372]

>>1205303
Yep, curved space only further details the entire mechanics of it, the way gravity and friction explained why despite the laws of motion stuff still fell down and slowed down.

Yep, good old relativity, nothing moves faster than light relative to anything else.

[OP !OudrPWaUDQ No.1205377]

Using a special relativity calculator I found, I found that the factor of change is 1.1547005383792517. Using this, I think I can calculate that object A would appear to be moving 0.433012702c to D, as would B to A, C to B, etc.

I find, though, that object B to D would be moving at almost the same speed as A to D. The factor of change would be 2.0000000014934534, which gives just about the same result as A to D. This is a bit weird, but can anyone correct me if I'm wrong, or tell me if I'm right?

[Anonymous No.1205406]

>>1205377
In the earth frame, i.e. standing on earth looking at all of these rockets, the speeds you'd observe are
A: 0.5c / B: 0.8c / C: 0.9286c / D: 0.9756c

if you were sitting on A, you would say
A: 0 / B: 0.5c / C: 0.8c / D: 0.9286c

if you were on B
A: -0.5c / B: 0c / C: 0.5c / D: 0.8c

[OP !OudrPWaUDQ No.1205423]

>>1205406
Ah. This is what I get for trying to use a relativity calculator instead of doing the math myself :\

I get it now, and /sci/'s solved a problem that's been in my head for years; I've just never really bothered to ask someone.

[Anonymous No.1205425]

Speed is measured in unit of distance per unit of time. As you're probably aware time appears to take longer to pass when you're near the speed of light (to a stationary observer), so if you're in a ship travelling at 0.5c and you throw a ball at 100km/hour it will look like you've thrown the ball much slower to anyone outside the ship.

[Anonymous No.1205439]

>>1205230

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