Space-Like Intervals: Can Events Effect Each Other?

[Ed Quanta]

So if the interval between two events is spacelike, does that mean that the two events cannot effect each other? Does that also mean that no observer can observe both events?

 

[MeJennifer]

So if the interval between two events is spacelike, does that mean that the two events cannot effect each other?

Yes.

Does that also mean that no observer can observe both events?

If you mean by observe the reception of light signals originating from such an event then some observers will be able to observe both events. Just be aware that the reception of light signals originated from an event, which is by itself an event, is not the same as the observed event.

 

[matheinste]

Hello MeJennifer.

Quote:-

---If you mean by observe the reception of light signals originating from such an event then some observers will be able to observe both events.-----

If only some observers can see both events doesn't this imply that there can be an event that some observers never see ? I note your caveat about the difference between the reception of light from an event and the event itself and assume it is relevant but the relevance is not understood by me.

Matheinste.

 

[MeJennifer]

Hello MeJennifer.

Quote:-

---If you mean by observe the reception of light signals originating from such an event then some observers will be able to observe both events.-----

If only some observers can see both events doesn't this imply that there can be an event that some observers never see ? I note your caveat about the difference between the reception of light from an event and the event itself and assume it is relevant but the relevance is not understood by me.

Matheinste.

Consider for instance FRW spacetimes where some observers will forever be outside the future light cone of the event in question.

 

[matheinste]

Hello MeJennifer.

Thanks for your reply. I have not yet learned about FRW spacetimes so this is unfortunately lost on me as yet. Is the OP at such a level of understanding.

Matheinste.