Okay Veeky Forums, I have two spaceships that I launch from earth in opposite directions...

The distance between two objects can change at a rate that surpasses the speed of light but that's too abstract to really count.

lengths contract you fucking idiot

Gr8 b8 m8 I r8 8/8

Thank you :)

>Now, relative to one ship, the other one is travelling at 120% the speed of light.
no, relative to one ship the other one is traveling at 99.999% the speed of light, possibly even lower
that's why it's called the Theory of Relativity, because speed and mass and time are relative to the speed of light (which is really the speed of all fundamental forces)

>relative to one ship, the other one is travelling at 120% the speed of light
Uhm, no.

Reference frame we're in is the one you're measuring from, inertial frame is whatever speed a relatively inertial frame measures it as.
Because of the Lorentz transformation these discrepancies are eliminated

"Inertial frame" is any coordinate set not undergoing acceleration other than from gravitational force.
"Your" inertial frame is the one in which you are stationary in that coordinate system.

If you are freely-falling (no rockets burning) a light-year from the Sun, you are in an inertial frame.
Anybody else who is _also_ in an inertial frame will agree that you are in an IF -- though maybe a different one than theirs.

I kek'd

[math]c_{A:0°}[/math] [math]c_{B:180°}[/math]

in this example, you imply that A and B would only travel at c away from each other?
or that because A and B are traveling at c×2 relative to each other, A and B would not be able to see each other?

cause the latter is what attempts to explain the observable universal horizon.

get your shit straight.