1. The speed of light is also 'the speed of causality', and the maximum speed of information as well; Second postulate that govern's GR. The moment we assume that speed of light is any other value, GR no longer works. If we do that for a thought experiment, then we should not continue to use GR for that experiment. Ans. You are refering to the assumption that Raju and babu can see things happening at planet X live. Yes, this violates the cosmic speed limit. But every body misses one point. If you take out that assumption, only difference is Babu cannot ‘see’ the future. But still in andromeda galaxy events happening in Babus “Now” is still Rajus future. That doesn’t change. Only thing is Babu cannot see it. 2. No two observers(reference frames) can agree upon a 'NOW' - that is impossible. Ans. No two observers(reference frames) can agree upon a 'NOW'. Of course that is the point. But that have a very profound consequence. There is a concept called “Now Slice”. That is, at the moment that I call now, several things happen in the universe. All that events constitute My “Now slice” of the universe. Similarly there will be a different now slice for another person if his reference frame is different than mine. Now assume that we both passes a common point at the same time. (Basically we meet). Then Both of our Now slices meet at that point. At that very point in space and instant in time, My “now” and his “now” are the same. But all the other points in my now slice and his now slice are different. But we share a common now at that instant. In such a scenario, things in my now slice elsewhere in the universe can be in his future. If something in my now is in his future that means his future is already past to me. Which means his future is predetermined. It is true that I can never see his future before he reaches there, because cosmic speed limit donot permit that. But still fact remains that , at the very moment we meet, for him, there exists a man in his present for whom, His future has become already past. 3. In the above examples the 'NOW' of the observee(what is being observed) is what decides if the future is decided or not. The NOW of the observer, have no effect on deciding the future of the observee. Also the state of the observee in accordance with the observer's NOW, does not have effect on that observer's NOW vs Future. The 'NOW' of the observee will always be the latest when compared to any observer's version of the state of the observe Ans, in the example mentioned, Babus Now coincides with the the day Aliens starting for the attack. It is immaterial whether he sees it or not. His Now is coinciding with Aliens starting date. While Rajus Now is coinciding with Aliens meeting. That is During the time of the meeting of Aliens There exists a person in the universe for whom Aliens starting is “Now”. As you said The “Now” of Aliens meeting and “now” of Babu are independent and personal. But there exist a third person Raju. And at the point of Raju and Babu meets, these two Now slices meet. So For Aliens meeting Raju is Now, For Raju Babu is Now, and For Babu Aliens starting is now. That forms the triangle.

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