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<blockquote data-quote="freyar" data-source="post: 6737835" data-attributes="member: 40227">Two quick points: (1) it's not at all clear that our universe has areas forever out of causal contact with earth.&nbsp; For example, in a universe with a cosmological constant, people on earth will eventually be able to see the entire universe, even though it will take infinite time to see an infinite distance away.&nbsp; That's just saying that we need to wait 8 minutes to see the sun, but we need to wait umpteen-gazillion years to see something umpteen-gazillion lightyears away, and we need to wait longer to see farther.&nbsp; Off the top of my head, I am not thinking of an easy way to change that, either, but I admit I'd have to look at a few papers to say more than that.&nbsp; (Unless you are maybe talking about disconnected components of the universe, where there is literally no space between them.)(2) In a relativistic theory, if you can travel FTL to anywhere, no matter how far away (whether forever out of causal contact with your initial point or not), you can build a time machine by using FTL travel, a rocket, and more FTL travel.</blockquote>

[QUOTE="freyar, post: 6737835, member: 40227"] Two quick points: (1) it's not at all clear that our universe has areas forever out of causal contact with earth. For example, in a universe with a cosmological constant, people on earth will eventually be able to see the entire universe, even though it will take infinite time to see an infinite distance away. That's just saying that we need to wait 8 minutes to see the sun, but we need to wait umpteen-gazillion years to see something umpteen-gazillion lightyears away, and we need to wait longer to see farther. Off the top of my head, I am not thinking of an easy way to change that, either, but I admit I'd have to look at a few papers to say more than that. (Unless you are maybe talking about disconnected components of the universe, where there is literally no space between them.) (2) In a relativistic theory, if you can travel FTL to [B]anywhere[/B], no matter how far away (whether forever out of causal contact with your initial point or not), you can build a time machine by using FTL travel, a rocket, and more FTL travel. [/QUOTE]

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