Bell's Spaceships Paradox explained.

[Wizardsblade]

something I see 1 light second away happened 1 second ago, it is not happening right now.

Assume that both space and time have the same properties at every event, and that the speed of light is c in every inertial frame. Now pick one of those inertial frames and suppose that there's a mirror at some point along the x axis. Suppose also that you emit light from x=0, in the positive x direction, at t=-T, and that it's reflected by the mirror and returns to x=0 at t=T. Now the reflection event must have been simultaneous with the event t=0,x=0. That implies that we must assign time coordinate 0 to the reflection event, and the fact that the speed of light is c implies that we must assign the x coordinate cT to the reflection event.

What you see is nothing but photons hitting your retina, it is not something away, it is a local event.

How do you measure that distance, without first having a notion of simultaneity?

Do you guys not see that what I said is equivalent to what Fredrik said? Make T=1 second so that -T = -1 second then it is clear that at x = 1 light second t=0 simultaneously with x=0, t=0. Ergo what I am currently seeing with my eyes at a distance x=1 light second is what happened when my T=-1 second. I just do not have the finesse that Fredrik has =).

 

[Fredrik]

OK, I'm glad we agree. I misunderstood you then.

 

[MeJennifer]

Ergo what I am currently seeing with my eyes at a distance x=1 light second is what happened when my T=-1 second. I just do not have the finesse that Fredrik has =).

We cannot see at distances, that is just popular speak.

What you are currently seeing with your eyes are photons hitting your retina with a distance of 0 and it is happening now. Yes these photons have an origin but so does a tennis ball hitting one's head. Would you say that you feel a tennis ball currently hitting your head from a distance that happened in the past?

 

[peter0302]

Ok, now that's nitpicky.

 

[Wizardsblade]

We cannot see at distances, that is just popular speak.

What you are currently seeing with your eyes are photons hitting your retina with a distance of 0 and it is happening now. Yes these photons have an origin but so does a tennis ball hitting one's head. Would you say that you feel a tennis ball currently hitting your head from a distance that happened in the past?

This is off topic, but our eyes (plural) can distinguish distance by triangulation. Of course we only see what is currently hitting our eyes, hence the definition of simultaneity is not what we see but rather what has already been stated above.