Warp wrote:
> Orchid XP v8 <voi### [at] devnull> wrote:
>> On 25/01/2011 08:11 PM, Warp wrote:
> 
>>>    My take: If there is life in the Universe (which happens to be the case),
>>> some of that life must have been the first one to form. Well, we might just
>>> be that first, don't you think?
> 
>> My understanding of general relativity is limited, but I was under the 
>> impression that "first" is not a meaningful concept at relativistic 
>> velocities.
> 
>   That would be paradoxical.
> 
>   Assume that intelligent life evolves in planet A, and it starts sending
> radio signals to outer space. These radio signals eventually reach planet B.
> 
>   Some time later life evolves in planet B to a point where they can receive
> these signals from A. Clearly, intelligent life evolved in A first, and in
> B after that.

If A and B are separated by space-like distances, neither is first. Here 
you're postulating that A and B (where A and B are the evolution of initial 
radio-emitting life) are separatd by time-like distance.

As you say, if one is in the past light-cone of the other, there's a first 
and a second. It only gets ambiguous where neither of the two 4D events are 
in the direct past light-cone of the other.

-- 
Darren New, San Diego CA, USA (PST)
  "How did he die?"   "He got shot in the hand."
     "That was fatal?"
          "He was holding a live grenade at the time."

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