Recent content by adrian_m

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    How did black holes merge in finite time?

    LIGO has template for NS-BH mergers also in place for detecting such events, so I am assuming such events are expected to be detectable as well. Large mass NS would also have considerable spactime curvature near them.
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    How did black holes merge in finite time?

    OK, sounds like the event will be completed in finite time even for a distant observer, though the distant observer may not be able to see it happen fully. If it was a smaller neutron star and a much larger black hole scenario (though between them enough to have detectable GWs), would the...
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    How did black holes merge in finite time?

    This question is in context of the recent gravitational wave detection by aLigo. Apparently aLigo has detected the entire process, including the before merger, during merger, and aftermath of the completed merger. My understanding is that two black holes should not be seen to be merging in...
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    Gravitational deviation of matter travelling near c by a massive body

    Thanks for all the answers. Checked out all the references also and they are good. The confirmation I got is that the deviation would be nearly twice the Newtonian value. This is what I suspected would be the case though some other notions were bothering me by throwing up (mistakenly) other...
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    Why Do Physicists Care About Causality?

    You would probably know the often used example: If you went back in time and killed your grandmother before your father was born, then you couldn't have been born. But you are there just the same! So causality is violated. Since causality is assumed to hold under all circumstances, the...
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    Why Do Physicists Care About Causality?

    Currently accepted understanding in science is probably the best way to look at it. If time travel were proven possible tomorrow, causality would be violated (and vice versa). What is interesting is that current understanding of science (with experimental verification!) would allow your son to...
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    Gravitational deviation of matter travelling near c by a massive body

    Agreed. This is the part that was bothering me. The relativistic mass of the particle traveling near c should be very large. Does that not increase its gravitational mass exponentially? If it does, then why does it not increase GMm/R^2 proportionately? I am extrapolating from the...
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    Gravitational deviation of matter travelling near c by a massive body

    Light traveling transverse to a massive body (e.g. Sun) is deviated by an angle twice the amount predicted by Newtonian gravitational theory. This is predicted by GR and proven experimentally. What would be the deviation of a matter particle traveling near c transverse to a massive body...
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    Can an Object Falling in Infinite Gravity Break the Speed of Light?

    I have a question about neutrinos in this respect. Understanding from relativity is that if something has mass, not only can it not travel faster than c, but it must travel at less than c (i.e. cannot even travel at c). Neutrinos qualify as having mass. However, all recent experiments...
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    General relativity and accelerated frames

    Thanks PD, WBN. I think you have clarified the situation. Now let me ask you a more "thorny" question. I am not sure the question is appropriate, and if it is whether you have the answer... Replace the second scenario of 'pebble on string' to a scenario where there is a central negative charge...
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    General relativity and accelerated frames

    That helps. I think I mostly understand. Will have to think further about it...
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    General relativity and accelerated frames

    I think what you are saying is right, and I am getting a sense of it, but there's something I am still not quite able to understand... First, how are the two scenarios different from Einstein's elevator example... and maybe I am missing the understanding of the word 'tidal' ... will help if...
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    General relativity and accelerated frames

    Then let us consider the 'pebbles' to be 'satellites' with human beings inside. Would they be able to tell the difference in the two scenarios (without any reference to the outside)? I feel in the second case also the centrifugal force will match the pull on the string, so inside observers would...
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    General relativity and accelerated frames

    OK, I am trying to get a simple answer, and an example may help. Situation (a): A pebble is moving in a circular orbit around Earth at a distance R from center of Earth, under Earth's gravitational influence. Situation (b): An alien sitting in a rocket in deep space is whirling about a...
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    General relativity and accelerated frames

    A bit confused. How does this fit in with the Equivalence Principle? Does it mean that a non-gravitational accelerated frame (even if tidal/central) is not equivalent to a true gravitational field? (If not, in what way?)
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