I am just sad for all the victims of rape in the UK that haven't probably seen, even remotely, the same police efforts made for this accusation. It happened in a different country, and parts of the accusation wouldn't even be a crime in the UK, and obviously there are political goals behind, given the strange sequence of police work.
I'm thinking about what would happen if instead of Assange we were dealing with a person from a country where religion and government are intertwined, and that person was asking for asylum to the UK for accusations that are not crimes in the UK.
The issue is not only about mass. Any mass could form a black hole, the main point is about mass density, and that's not trivial to obtain.
That aside, real infinities is a vague concept. What's important is that any theory of gravity has to deal with the fact that the current understanding of classical gravity and quantum field theory make (when you combine them) a theory that has problems at the Planck scale. Those are problems that any theory of quantum gravity or every theory of everything have to deal with.
But it doesn't mean that those potential theories would have any infinities. Such a theory, though, has been very elusive.
With the exception of string theory, which is the leading theory in terms of its success, most theories tend to have fundamental problems. String theory research is certainly not complete, but it's in my opinion currently the best shot we have. Online, and in academia, you can find lots of very opinionated discussions about it, which include aspects of testability, predictivity, etc. which means that some people really dislike string theory and prefer other approaches.
From a physics perspective, the many-world, as ridiculous as it sounds, is a more sound theory (believed to be correct by some top physicists) than negative gravity.
The explanation of why gravity is only positive is a complex one, but physicists believe it's almost axiomatic.
This doesn't mean that you can't have repulsive type of effects, similar to one of the contributions that's believed to make the universe expand more quickly than with the simple 4 fources (often called fifth force, maybe related to dark energy, and to the rate of the universe expansion acceleration).
PS.
There are a number of Sci-Fi stories that use this idea, including a famous one from Asimov, in which if I recall correctly the normal gravitational force was working negatively when traveling in FTL speed. Obviously that seemed fishy but the book was cool (Nemesis).
> The explanation of why gravity is only positive is a complex one, but physicists believe it's almost axiomatic
Isn't that a consequence of relativity, the speed of light being constant by definition? I'm not sure that makes any sense, though, what is the physical unit of gravity N? Jf you mean classical mechanics, than there has to be a negative counterforce by the three axioms of newtonian mechanics and it's just a question of frame of reference.
Today is the first day that H-1B for next October are accepted, and apparently they know for sure that the limit will be reached so soon that "the agency is prepared to use a random selection process to meet the numerical limit" [1], like last year.
Steve Carlip used to be my advisor in grad school and his style of writing shows his beautiful way of explaining (and thinking about) deep questions in physics.
One think that I believe is important to point out is that this short essay is focusing on the experimental aspect of the measurement of the speed of gravity. It gives an explanation on why this is even an intelligent question to answer and why the answer we commonly accept is that gravity moves at the speed of light. I will never have better words than him so I won't add anything to what he said.
What I would like to point out, is that this essay is not talking about whether or not theoretically would be possible to have a speed of gravity faster than the speed of light. General relativity and special relativity have been tested on several aspects, and they pretty much are in agreement with all experimental constraint. There is no other theory that can explain everything we see (some theories tend to explain a few things, but not all of them, or they are too vague).
A theory in which the speed of gravity is faster than the speed of light isn't unconceivable per se, but no one has been able to write a completely consistent one yet, mostly because it would have large consequences on what special and general relativity imply for cosmology and particle physics (and causality). If gravity moved faster than the speed of light then we'd have to 'fix' a lot of problems coming down to paradoxes and stuff like that.
So take this essay as a way to appreciate how elegant and fine some experimental questions on gravity (and physics) are.
