<div dir="ltr">Interesting ... Still, what's bothering me is also the super-massive black hole in our Galaxy, five orders of magnitude closer and about five orders of magnitude as massive, orbiting by many massive stars ... but no gravity waves from there.<div><br></div><div>That was my line of reasoning all along. If we can't gravitationally see this, how we could see something much smaller, so far away?</div><div><br></div><div>I am not saying that it is entirely impossible, I am just hard to be convinced in such circumstances.<br><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Feb 12, 2016 at 10:38 PM, John Clark <span dir="ltr"><<a href="mailto:johnkclark@gmail.com" target="_blank">johnkclark@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_extra"><span><div class="gmail_quote">On Fri, Feb 12, 2016 at 10:28 AM, Tomaz Kristan <span dir="ltr"><<a href="mailto:protokol2020@gmail.com" target="_blank">protokol2020@gmail.com</a>></span> wrote:</div><div class="gmail_quote"><br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">> <div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">></div> The strain produced by the waves decays with 1/r. Tidal forces are proportional to 1/r^3 so they decay very fast as you move away from the source.</blockquote> <br><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">></div>It's then either G-wave originated 10^9 ly away, or some tidal effect 10^3 ly away. Like a neutron star inner collapse to a black hole, for example.<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>Those two are indistinguishable for LIGO, I presume<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">.</div><br></blockquote><div><br></div></div></span><font size="4">One way LIGO can distinguish a gravitational wave from other sources of distortion of the mirrors is that if it's a<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>gravitational<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>wave then as one leg of the L shaped LIGO<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>detector<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>shrinks the other must expand<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>by the same amount; and if it were caused by tidal forces something would have to be circling the Earth 250 times a second. And <div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">nothing can be in orbit around the </div>Earth like that.</font></div><div class="gmail_extra"><font size="4"><br></font></div><div class="gmail_extra"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font size="4"> John K Clark</font></div><br></div></div>
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