I would like to know what data is used from gravitational wave detections to calculate black hole masses and how.  Also, what else can you deduce from gravitational wave detections? What was the exact difference between the detection of the black hole mergers and the one of neutron star collision?  I am writing an extended essay on this (4000 words), and it would be very helpful. Many thanks.
24059
The  was observed, giving us the frequency and amplitude of the event. Because LIGO has two detectors a  could be derived.  But how do these three factors allow for the mass of the black holes and their distance to be calculcated? If the wave strengths are in a square relationship to distance, then couldn't there be an infinite number of other masses and distances which would give the same signals?
2906
In Interstellar, the team hopes that data collected from the inside of a black hole will solve “the gravity problem” (presumably the question of how to get a massive space station to escape the Earth’s atmosphere, explained in more detail ).  Two related questions on this:   How can “data” alone solve this scientific problem? Is it that they have too many possibilities to manually test, and their question is just “which is the right one?” Are there any real-world historical examples of good data leading to a breakthrough on achieving what was previously thought to be impossible? Why does the data have to come from a black hole? Isn’t this counter-intuitive, because a black hole is the one place where gravity doesn’t behave as it does on Earth, which is where the problem applies?
53075
I have four questions about black holes and universe formations.   Do new universes form on the other side of black holes? Was our own universe formed by this process? Was our big bang a black hole seen from the other side? Are there solid reasons why this might not be the case?
2077
Assume two black holes in the most common size range, spiraling into each other until they merge. The event releases significant amounts of energy via gravitational waves, which warp the space-time.  If the distortion is powerful enough, it would get noticed in daily life, or perhaps even detected by the proprioceptors in the human body.  How close, as an order of magnitude estimate, would you have to be to the merger to perceive it like that, without any instrument?
55245
Pedestrian question from a non-physicist:  I read on Wikipedia that larger black holes emit less net Hawking radiation than smaller black holes.  This seems counterintuitive to me. If black holes are essentially sucking in mass and converting it to Hawking radiation, why wouldn't a more massive black hole emit more Hawking radiation?  Moreover, how is it that Hawking radiation can escape black holes in the first place when visible light (which I know to be another form of radiation) cannot?
108727
I read on wiki that gravitational shielding is considered to be a violation of the equivalence principle. Is that so, How? A conceptual description without lot of mathematics will be helpful.   I am not sure whether the wiki article refers to shielding only by materials, or it also includes mechanisms - e.g a rotating disk. I know rotating disk does not shield gravity, but just to describe what a mechanism could mean.  It goes on to say that any evidence of gravitational shielding would falsify GR, is this true?  It is hard for me to believe because - suppose gravitational shielding is demonstrated somehow, then how GR can be falsified all of a sudden, which has been verified by so many experiments and phenomena. So, that makes me think gravitational shielding would not invalidate GR.
55819
Let's say we have one black hole that formed through the collapse of hydrogen gas and another that formed through the collapse of anti-hydrogen gas. What happens when they collide? Do they (1) coalesce into a single black hole or do they (2) "annihilate" into radiation?  One would expect (1) to be the case if the No Hair Theorem were to hold. So I guess what I'm really asking for is a modern understanding of this theorem and its applicability given what we know today.
59955
BH mass is a conserved quantity and cannot escape the horizon of a BH. Yet in mergers some percent (in GW150914 it was about 5 percent, or 3 solar masses) of the binary's mass escaped either before (one of the two BHs horizons) or after the merger started (one horizon merger, from the merged horizons), and turned into gravitational waves. The argument is that it is potential energy or maybe kinetic energy of the black holes that is radiated. It does not matter. The question is how did the BHs mass get reduced? Did some virtual negative mass particles fall into the BH, and if so it would have been gravitons? If so is it a quantum effects? If so has anyone worked out the linearized quantum gravity of that happening right outside the horizons, like they did for the very small Hawkings radiation, and isn't that a contradiction of the small effects expected for 30times solar mass BHs? So, if not that, how does the negative potential binding mutual gravitational energy of the two BHs steal mass from the binaries?  Please, no hand waving. I've looked everywhere and only see hand waving arguments about potential or other energy outside the BHs, but mass is an internal (inside the horizons) and conserved quantity of BHs.   Charge, another conserved quantity, and angular momentum, can be extracted (i.e., escape the EH). Angular momentum through the Penrose process, maybe charge too. Is it the same for mass? If so, where is it wel explained in some detail, and not simply 'it was calculated numerically'?
66497
According to NASA      a black hole is anything but empty space. Rather, it is a great amount of matter packed into a very small area   According to the documentary  about Black Holes     Gravity here is so strong even light cannot escape   Which leads me to believe that Black Holes basically are masses so compact but great which gives them very strong gravitational influence (Newton's Gravitational Law) that light is not allowed to go out of, hence a "Black" hole.  If my above understanding of Black Holes is correct, then why is those Spiral Galaxies pictured using Hubble Telescope is showing a big shiny ball instead of a "Black" hole ? What is the obvious clue that I am missing here ?  Here is the image of Andromeda Galaxy image taken using Hubble.
637
My friend and I have been wracking our heads with this one for the past 3 hours... We have 2 point masses, $m$ and $M$ in a perfect world separated by radius r.  Starting from rest, they both begin to accelerate towards each other. So we have the gravitational force between them as:  $$F_g ~=~ G\frac{Mm}{r^2}$$  How do we find out at what time they will collide?  What we're having trouble with is this function being a function of $r$, but I have suspected it as actually a function of $t$ due to the units of $G$ being $N(m/kg)^2$.  I've tried taking a number of integrals, which haven't really yielded anything useful.  Any guidance?  No, this is not an actual homework problem, we're just 2 math/physics/computer people who are very bored at work :)
99901
{{Under Construction}}      Short question: What published works and what research groups are investigating the possibility of non-existence of gravity at quantum level?  Long question: I am no physicist, but of what I read and understand of the subject, no-one has been able to fit the graviton into the standard model, it seems that the equations won't re-normalize, thus it would be useless for predictions. Gravity also is undetectable at the quantum level, it seems because the force is too small. Also, about every book about the subject traces a strong distinction between "quantum level" and "classical level", almost if they were different worlds that obey different laws of nature, and how they relate to each other is an open question. Finally, at least two sources I have seen state that Einstein's General Relativity is the most well verified theory of all physics, because of something related to pulsars.  Thus there are two distinct "worlds": in one gravity is pretty much settled, while in the other, it is neither detectable nor mathematically explainable in the most successful model. From that, the most logical and simple explanation I can have is that simply there is no such thing as quantum gravity, and that it is a purely classical phenomenon that arises from whatever may be the relation between both "worlds".  I like to imagine that space coordinates of both worlds are not quite the same, although very similar locally, thus, if classical world emerges from a projection of the quantum world, like a shadow, gravity is bumps in the surface where that shadow is projected (holographic principle comes in my mind now).  It doesn't seems to be the mainstream view of the problem, with millions of dollars spent in trying to find the mythical graviton (that is what a physicist of INPE, Brazilian's spacial research institute, told me yesterday). Thus, I want to know, what are the works, and what people shares with me this view of the problem?
79549
If time stops at the event horizon, can we ever detect two black holes merging? In other words, if you are a short distance away, would you encounter a spherically symmetric gravitational field, or a dipole field?
98752
Orbiting planets and stars can create gravitational waves, . But are they also losing mass-energy. Beside that, the kinetic energy associated with their orbital angular momentum is reduced.  For instance, in September 2015 the LIGO detected the merger of two black holes with masses of $35^{+5}_{-3}$ times and $30^{+3}_{-4}$ times the mass of the Sun (in the source frame), resulting in a post-merger black hole of $62^{+4}_{-3}$ solar masses. The mass–energy of the missing $3.0±0.5$ solar masses was radiated away in the form of gravitational waves.  So it looks like 3 solar masses were lost. But is that mass coming from the stars itself, or from their kinetic energy?
103146
I have been trying to imagine ways to visualise the gravitational field of the earth... It's near zero at the outer edges of the atmosphere, strong at sea level, strongest at the quarter point, then drops off to zero again towards the middle as the masses cancel each other out... Something like a 3D donut?  This got me thinking about black holes. Would they also have an area of zero g right at the centre where all the surrounding mass cancels each other out?
34931
From observer point of view an object, which falls into black hole never crosses its horizon. Then how does black hole appears and grows its mass?  Or does any black hole looks (and feels by all other information sources) for us like a void sphere with all mass around its horizon?
122988
I'm making several assumptions, not sure if any are correct:   there is a black hole at the center of a galaxy the black hole is eating the galaxy   Eventually the galaxy will be gone, right?  Has this been observed? Do we know what happens afterwards?  Posting here since astronomy got merged into physics
321
As the title suggests, Can the effects of a person's mass upon the local gravitational field be detected and measured remotely?  I am aware any mass produces and effects gravity but couldn't find anything in my searching if it is possible or theoretically possible to detect this effect remotely.