Does SR actually forbid FTL travel?

  • Thread starter DrSnarl
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  • #101
DaveC426913
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So if a rocket had side boosters near the front - so that both the front and the back were accelerating independently but at the same rate - then the rocket would break in half as the front portion and back portion were contracted away from each other?
Only inasmuch as any rocket would suffer these kinds of stresses. Remember, in the rocket's reference fame, it is stationary.

If a rocket is sitting in orbit, and it turns on its bow thrusters, well technically, its front end and its rear end are undergoing two stresses:
1] the thrusters are pulling on one end and only moving the other end via normal mechanical forces that are transmitted at the speed of sound (yeah, crafts will creak when their propulsion is turned on.)

2] So, for a brief fraction of a second, the bow of the craft is moving relative to the stern of the craft. Technically, this does mean that there is a theoretical relativistic contraction effect. But it is difficult to express just how small this effect is.
 
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  • #102
PAllen
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So if a rocket had side boosters near the front - so that both the front and the back were accelerating independently but at the same rate - then the rocket would break in half as the front portion and back portion were contracted away from each other?
It depends on how they accelerate. If they accelerate independently so as to maintain constant distance as measured in an inertial frame, the rocket will break. If they accelerate independently so as to maintain absence of stress (or minimal stress) throughout the rocket, there will be no breakage, but the inertial frame will measure the rocket shrinking, and will measure different acceleration profiles for the front and back.
 
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  • #103
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Thank you for the explanations, Dave and PAllen! I think I get it now. I will read through those papers to try to iron out the remaining kinks.

Thanks for being patient!
 

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