Did the Earth move for you, too? Grav waves sensed from black holes' bang 1.8bn LYs away Scientists have recorded the most accurate reading of gravitational waves yet by using the upgraded LIGO and Virgo observatories together for the first time. The ripples were detected on August 14 at the Laser Interferometer Gravitational-wave Observatories (LIGO) in Louisiana and Washington state in the US, and the Virgo …
... US National Science Foundation, which funds both detectors ...
To be clear, the US NSF funds both LIGO detectors (there are two). The VIRGO detector is funded primarily by CNRS and INFN - the French and Italian national organisations, with important contributions made by many laboratories across Europe.
That's a lot of gravity!
I wonder how near you'd have to be to personally experience the tug.
But gravitational energy is negative and exactly balances the positive mass which creates it. How can positive mass be converted into negative energy as the article suggests?
It makes more sense if three suns' worth of mass were lost as radiation, as that would cause a three-sun ripple or wave in its gravitational field. A black hole itself cannot release mass that fast, so it would have been outlying stuff that hadn't quite fallen in yet.
Or, is my physics farcically bad?
You need gravitational energy defining?
It is minus the work that is done in moving an object in a gravitational field from one place to another. The absolute gravitational potential energy of an object is minus the work needed to move it to a point indefinitely far away from the centre of the field.
I learned that at school, I suppose you need a degree in astrophysics to be taught that these days.
And no, I am not going to post Einstein's equations for the associated curvature of spacetime, which the philosophically-minded may take as a more ontological definition.
Sigh.
Um. I'll share the little secret Ms McEvoylet us into in fourth year GCE physics.
Everything you are taught at O level is a lie. When you do A level, the first thing yhou need to do is forget everything you've been taught.
The the same thing happens at degree level.
Or so she said. She's not around to check with, alas.
The tidal forces (difference between your head and feet) will always swamp the wave effect so you will be spaghettified well before you could feel the waves.
There's a more mathematical answer elsewhere on this site in the comment related to a previous detection by Ken Strain who actually works in this area.
I wonder how near you'd have to be to personally experience the tug.
When the detection as announced last year I worked out what the displacement would be from a light year away. I forget the exact result now, but I think it was on the order of a metre. The problem is, how would you experience that? It's a contraction and expansion of space and time, propagating at the speed of light. Would you even be able to detect that with your human senses? Would the tidal force instantaneously tear apart all matter larger than an atom? I'm having trouble thinking that one through.
Human senses tend to rely on rate of change: a small but sharp change in spacetime would feel much the same scale as a large but leisurely one. Gravitational mass is assumed to be identical to inertial mass, so a change in gravity would be indistinguishable from an acceleration due to change in velocity. But if the wave took say half an hour to peak, then it would have to be stonkingly huge, three suns' worth maybe, before one would feel it.
Interestingly, large black holes have gentler tidal forces than small ones, while the effects of a merger are more dramatic. So one stands a better chance of feeling the wave from a couple of supermassives merging than one does from a couple of babies like the two observed this time round. Yes, the tides would dominate with these two.
If you like such racist comments, aren't you sure those in the US was not due to people firing at each other there? After all, lead has a bigger mass than pizza. Or maybe two obese Americans nearby the detector?
BTW: while pizza today is made everywhere, it came from Naples, not Pisa. Typical food in Tuscany is different.
When I'm asked to visualize Italy, I would probably imagine a series of images gleaned from experience, among them a pizza. Many people like to engage in word play involving such shared images, to the delight of all.
Well, not all. There's you. You don't appear to be having any fun. It's too bad too, because a good chuckle now and then can really brighten up this dreary old world. :)
It wasn't funny. Again, you just show your little knowledge of the world. As if visualizing America I would see hamburgers or cowboys hats only, or visualizing England fish and chips. You also decided to mock only the Italian detector, as if, of course, Italians can't do nothing more than pizza. Just, Pisa is one of the cradles of modern physics. A couple of names like Galileo and Fermi should tell you something....
No, a 53 solar mass BH is fairly massive for a BH which originated from a collapsed star rather than by some long accretion process. In fact I am fairly sure that it's above what the upper limit was expected to be until recently: I think all of the things LIGO has observed so far (certainly the first observation) were rather unexpectedly heavy objects.
(Obviously the 53 solar mass object *didn't* originate from a collapsed star directly but from a merger, but even the two ancestors are rather heavy for stellar BHs I think).
(as to size: they're pretty small: I think the Schwarzschild radius of the resulting object is 156km -- or 7097 brontosaurus (linguine is kind of an impractically small unit here)).
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