RELATIVE Space/Time and Lightspeed question

AI Thread Summary
The discussion revolves around the concepts of light speed, space-time, and relativity, particularly in the context of two spaceships moving in opposite directions at significant fractions of the speed of light. It is clarified that while each ship can reach speeds over half the speed of light, the relative speed between them does not exceed the speed of light due to the relativistic velocity addition formula. Each ship perceives the other as moving at a speed calculated to be 4c/5, which remains below the speed of light. The conversation also touches on the implications of time perception between the ships and the theoretical concept of a wormhole connecting them. Overall, the complexities of relativity and time dilation in high-speed scenarios are highlighted.
Riptide
Messages
2
Reaction score
0
Hey everyone,
First off I am not a physics major or a math guru. Physics has always been some thing that I have been interested in though. Physical science and the way things work has always interested me. I mention this, because I do not want to come off sounding like an idiot. I know most people that probably come to these forums probably have a better education and a far greater understanding of these concepts than I do.
The concept of light speed, space time, and relativity has made sense, but something has always alluded me. From what I understand the speed limit of light can not be changed (in a pure vacuum state that is), and it is space and time that change, not the speed of light itself. That brings me to my question:
Say we have two space ships (that is the easiest way I can describe this so just go with me on this one) and both head in opposite directions from one another slowly accelerating. At some point, Ship A is heading one way and reaches over 1/2 the speed of light from it's starting point. Likewise, Ship B hits over 1/2 the speed of light from it's starting point heading in the complete opposite direction. At that point, the differential between the two would exceed light speed. I'm pretty sure that there are objects in our own universe that currently are doing this. What happens in relation to each other?
To ask more specific questions, would Ship A and Ship B still see each other? What would time be like in relationship to each other, would one ship appear to be going backwards in time in relation to the other? If there were a doorway, let's say a 'wormhole', were connected between the two, what would be the difference from walking from ship A to ship B? Would that constitue time travel (even though I would guess that would be a yes, I am just not sure in what direction)?
In case I am missing some law or theory, would it be any different when the ships reached 99.9% the speed of light in opposite directions, in theory meaning they are nearly doubling the speed of light in velocity from one another?
This has been something that has boggled me since I started becoming interested in physics. If someone could answer it, it would be very much appreciated! If possible, please explain in the most basic of terms (equations and "so-and-so's theory of what-not says," will probably be more than I am aquainted with, but you don't have to describe it like you are talking to a kindergartener either). Thank you so much for your time and input. Any help is greatly appreciated!
 
Science news on Phys.org
Welcome to PF!

Hey Riptide! Welcome to PF! :smile:
Riptide said:
… we have two space ships (that is the easiest way I can describe this so just go with me on this one) and both head in opposite directions from one another slowly accelerating. At some point, Ship A is heading one way and reaches over 1/2 the speed of light from it's starting point. Likewise, Ship B hits over 1/2 the speed of light from it's starting point heading in the complete opposite direction. At that point, the differential between the two would exceed light speed. I'm pretty sure that there are objects in our own universe that currently are doing this. What happens in relation to each other?

Each regards the other as moving at 4c/5, see http://en.wikipedia.org/wiki/Velocity-addition_formula#Special_theory_of_relativity :wink:
 
Thread 'A quartet of epi-illumination methods'
Well, it took almost 20 years (!!!), but I finally obtained a set of epi-phase microscope objectives (Zeiss). The principles of epi-phase contrast is nearly identical to transillumination phase contrast, but the phase ring is a 1/8 wave retarder rather than a 1/4 wave retarder (because with epi-illumination, the light passes through the ring twice). This method was popular only for a very short period of time before epi-DIC (differential interference contrast) became widely available. So...
I am currently undertaking a research internship where I am modelling the heating of silicon wafers with a 515 nm femtosecond laser. In order to increase the absorption of the laser into the oxide layer on top of the wafer it was suggested we use gold nanoparticles. I was tasked with modelling the optical properties of a 5nm gold nanoparticle, in particular the absorption cross section, using COMSOL Multiphysics. My model seems to be getting correct values for the absorption coefficient and...
Back
Top