Backwards

[mulreay]

Hi guy's my first post on this forum but would like to add something. I'm no scientist but my friends and I had an argument about space-time the other day. This may seem trivial to you but I argued that there is no such thing as backwards in space-time and they argue that there is. My argument simply put was that even moving backwards you are still moving forwards. Is there a way I can put it to them that is understandable?

Thanks in advance

[iNow]

Hi mulreay,

 

I'm not sure, but I'll take a whack at it. This is just a guess, and there may be another member here who can offer a better answer than me. With that said...

 

The concepts of "forward" and "backward" are relative, and depend entirely on the frame of reference (basically, depends on who is making the comment). It sounds to me like you and your friends are talking about different reference frames.

 

From the reference frame of an external observer, the motion could very well be described as "backward," and that would be accurate. It's sort of like when you and I are facing one another, my left is your right, yet we're describing the exact same side... that's the idea, anyway.

 

However, when you discuss this in terms of the person moving (from their "reference frame"), then you are correct that the only motion is forward.

 

 

Does that make sense? It depends on who you ask as to whether or not the motion is "forward" or "backward."

 

 

Alternatively, in your argument, you could say that the issue is one of "magnitude" and not "direction." I think that's what you are arguing (again, I'm sort of guessing here, so I apologize for my lack of certainty). Your point seems to be that the individual who is moving starts that movement having traveled zero distance, and when they're done, they will have traveled a non-zero distance ( 0.0 --> +... ). That distance is ALWAYS a positive number, regardless of their direction.

 

Sound about right?

[mulreay]

Thanks for that very helpful. I'm more of a space buff than anything else.