This is all well and good, but what the article is talking about is the speed of the propagation of gravity waves. I've never heard anyone who wasn't a crank argue that gravity waves travel at anything other than the speed of light. As the article confirms, observation of pulsars has confirmed the speed of gravity waves to very close to the speed of light.
However, I think the larger objection goes something like this:
Gravitational attraction contains information about the location of an object (say, for the purposes of argument, a singularity). Information may not travel faster than the speed of light, by relativity. Information may not escape the event horizon of a black hole, because to do so would require it to travel faster than the speed of light (or to use some funny quantum teleportation that Hawking describes as the mechanism behind Hawking radiation), but which is not described by relativity.
Therefore it follows that the information about the location of a singularity behind the event horizon of a black hole is somehow travelling "faster than light". This is of course impossible if relativity is correct, which leads to a big WTF?
My guess, and I am most emphatically not a physicist, is that you get some funny macroscopic quantum effects near a black hole, which allows Hawking radiation (and therefore also the encoded information about the objects that fell into the black hole) out, and also lets out the information about the location of the singularity itself, so that objects outside the event horizon can be attracted to it.
Perhaps studying black holes in sufficient depth (pardon the pun) will allow us to finally unify QM and relativity.
Yes, in some sense gravitational attraction carries information about the location of the object.
Yes, Information may not escape the event horizon of a black hole, because to do so would require it to travel faster than the speed of light (up to small quantum corrections)
No, it doesn't follow that information about the singularity is getting out of the black hole. The information got out, and stayed out. The horizon prevents updates from getting out, leaving the previous information and attraction "frozen in" to the shape of space-time.
What is the technical definition of "information"? I know what information is in a colloquial sense, and I know something about it's technical definition in the field of computer science, but I don't know what physicists mean when they use the word. Is information the same thing as light? Is it analagous to light? Is it a property of light? Matter?
I guess that information is change of state that is clearly distinguishable from some "random" change of state and caries a "meaning".
Eg. If you had an entangled pair of particles on this side of galaxy and another on other side of galaxy. Now you "wiggle" (change its state) one then the other one "wiggles" too - but you didn't send any information - since the other observer cannot know if the particle changed state because of your message - or it changed state "of its own accord". Thus you would still need to notify him of you wiggling the first particle eg. via photon - thus information only moves at the speed of light :)
Bear with my awful analogy - since I really don't know anything about physics :)
I just define it for myself as "If it can transmit information, it could also be used given enough technology to send any kind of data, such as a Microsoft word document."
That definition would probably work. Have a look at Feynman's lectures on computer science. He also investigates how much energy has to be used for computing. (Or to be more precise, how much entropy has to be created.)
You don't have to go 'faster than the speed of light' to escape a black hole if you're not affected in the usual manner by gravity. And I'm not aware of any suggestion that gravity itself is affected by gravity.
Gravity absolutely is affected by gravity. The Einstein field equations are non-linear, so gravitational energy is itself a source of gravity. All forms of energy, and momentum, and even stress and pressure are combined into the "stress energy tensor" which determines the local curvature of space-time.
> The Einstein field equations are non-linear, so gravitational energy is itself a source of gravity.
Non sequitur? I mean, non-linearity is not the same as feedback. Linear system can exhibit feedback (and still stay linear), and non-linear systems do not have to exhibit feedback.
The equations describing a field theory contain terms which are the product the field, the thing it couples to (could be another field) and the strength of the interaction. When a field couples to itself, there are terms non-linear in the field. So the non-linearity of GR indicates that the gravitational field couples to itself, i.e. that gravity gravitates.
However, I think the larger objection goes something like this:
Gravitational attraction contains information about the location of an object (say, for the purposes of argument, a singularity). Information may not travel faster than the speed of light, by relativity. Information may not escape the event horizon of a black hole, because to do so would require it to travel faster than the speed of light (or to use some funny quantum teleportation that Hawking describes as the mechanism behind Hawking radiation), but which is not described by relativity.
Therefore it follows that the information about the location of a singularity behind the event horizon of a black hole is somehow travelling "faster than light". This is of course impossible if relativity is correct, which leads to a big WTF?
My guess, and I am most emphatically not a physicist, is that you get some funny macroscopic quantum effects near a black hole, which allows Hawking radiation (and therefore also the encoded information about the objects that fell into the black hole) out, and also lets out the information about the location of the singularity itself, so that objects outside the event horizon can be attracted to it.
Perhaps studying black holes in sufficient depth (pardon the pun) will allow us to finally unify QM and relativity.