Register | Sign In


Understanding through Discussion


EvC Forum active members: 63 (9161 total)
4 online now:
Newest Member: popoi
Post Volume: Total: 915,583 Year: 2,840/9,624 Month: 685/1,588 Week: 91/229 Day: 2/61 Hour: 2/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Is Faster Than Light travel the wrong question?
Son Goku
Inactive Member


Message 56 of 81 (533933)
11-03-2009 4:08 PM
Reply to: Message 49 by onifre
11-02-2009 6:28 PM


Spacetime
Hey guys, if it helps I just thought I'd chime in.
The basic idea is that relativity replaces absolute space and time with relative spacetime. The replacement of absolute with relative is something fairly straight forward. The replacement of space and time with spacetime is not.
Let's take the example of not being able to move backwards in time. If I could move backwards in time I'd be able to stay where I am now, but go from 4pm to 3pm.
However it's the same with space, if I freeze time I can't go left or right or up or down, because to change your locaction in space requires motion and motion takes time.
So I can't stay in the same place and move backwards in time and I can't stay in the same time and move backwards in space.
Of course there is the difference that I can take some time and eventually move backwards in space, where as I can't take some space and move backwards in time.
This is where spacetime becomes important. Basically we live in one giant structure (or more accurately shape) called spacetime. Points in spacetime are called events, with their locations labelled by space and time, basically when and where they are. The relativity basically comes from the fact that different observers can put different space and time labels on events.
However what all observers agree on is the geometry of spacetime. Spacetime has its own geometric rules which mean that certain events can never be connected, that is you can't pass from one event to another.
One such example is travelling into your own past.
Let's say you want stay in the same place but travel to ten seconds ago, you obviously can't. For you the reason is because it's in the past.
For somebody moving past you at high speeds because they'll label events differently they'll see your "now" and your "ten seconds ago" as occuring at the same time, but at different points in space. For them the reason you can't move between these two events is because they occur at the same time and you don't have time to move between them.
These are subjective reasons, the objective reason is that the events are not connected in spacetime. Not being able to move back in time is just one subjective way of viewing the disconnectedness of two events.

This message is a reply to:
 Message 49 by onifre, posted 11-02-2009 6:28 PM onifre has replied

Replies to this message:
 Message 57 by onifre, posted 11-03-2009 4:52 PM Son Goku has not replied
 Message 61 by cavediver, posted 11-03-2009 6:23 PM Son Goku has replied

  
Son Goku
Inactive Member


Message 64 of 81 (533973)
11-04-2009 5:24 AM
Reply to: Message 61 by cavediver
11-03-2009 6:23 PM


Re: Spacetime
Aaarrggghhh!!
What makes it even worse is that I checked the post with another physicist before I posted it. Which means we both didn't spot it!
Thanks, I just got carried away with the analogy without thinking.
Sorry for the mistake everyone, ignore the last paragraph of message #56. I'll try to reword things so that they are still understandable, but actually correct.

This message is a reply to:
 Message 61 by cavediver, posted 11-03-2009 6:23 PM cavediver has replied

Replies to this message:
 Message 65 by cavediver, posted 11-04-2009 6:20 AM Son Goku has not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024