3 ms·
Two events with « time-like separation » like those have a definite order. If one is in your past light cone and the second is in your future light cone, it do
by kgwgk 5y ago
Two events with « time-like separation » like those have a definite order.
If one is in your past light cone and the second is in your future light cone, it does indeed mean that they can't be the reverse for any observer.
- tsimionescu 5y agoOops, you're right, I thought about that wrong. Still, the example I gave is correct - an alien that visited the earth 2022 years ago could also arrive again today, and from their point of view, the journey could have taken 20 years let's say. And during this journey, they may have seen a star explode whose light will only reach Earth 2000 years from now, right? Edit: the answer to my second question is also no - that would require them obviously moving faster than the light of the star... But, what is possible is that from their point of view the star exploded before my birth, while from my point of view it exploded after my birth. Still, by the time they arrive, we will both agree that the explosion of the star is in the past.