"Where am I going wrong?"

Surely a metaphysical dilemma rather than an astrophysical one, csteele?

As for the accretion of mass to a black hole I simplistically imagine it as a subtraction of that mass from the spacetime field on this side as it passes through the event horizon... or else I think of it as a phase transitional thing. The black hole has a mass 'x' now and it will have a mass of 'x+' as matter transits the event horizon. So not a gravitational field 'escaping' the black hole so much as the current gravitational effect being increased through drainage.

Alternatively, the entire concept is wrong and the grafitti is right, "There is no such thing as gravity, the earth sucks."

csteele,

I've been reading some stuff on black holes, so my mind is basically comprehensively boggled at present : )...however, I'm still grappling with your question.

Are you saying "How come gravity escapes from the event horizon but not light?"

My answer would be that the "gravity" of the black hole is merely the warp the black hole's mass makes, or the ripples that are emitted from its presence in spacetime - and, therefore, it doesn't "escape" from the black hole, it is the "effect" on spacetime of the black hole's existence.

Stephen Hawking wrote:

"Th event horizon, the boundary of the region of spacetime from which it is not possible to escape, acts rather like a one-way membrane around the black hole: objects....can fall through the event horizon into the black hole, but nothing can ever get out of the black hole through the event horizon. (Remember that the event horizon is the path in spacetime of light that is trying to escape from the black hole, and nothing can travel faster than light)..."

But, as I say, I'm slightly boggled at present : )

Poirot,
Einstein riding on a sunbeam (or the sudden removal of a bowling ball from a trampoline) are attempts at EXPLAINING to NON-SPECIALISTS the Minkowskian geometry of special relativity, (and the curvature of space-time caused by the presence of matter, respectively). I doubt it that this is how Einstein’s intuition worked when he arrived at his theories, although, of course, I cannot know.

These are popularizing explanations, very different from the situation where one uses a thought experiment to make predictions based on a theory (in this case Einstein’s gravitation) that one understands only in its popularized form.

As to my skepticism expressed above, I might understand a thought experiment looking for answers available from Einstein’s gravitation theory relating to the Sun being ACCELERATED OUT OF its present position (though still, one would wonder by what agent), better than speculations about a “supernatural” (i.e. not accountable for from the physical theory) agent removing the Sun SUDDENLY from the field it creates.

(By the way, the answer is trivial within Newton’s theory, which assumes gravity is an external - to space and time - FORCE acting instantaneously.)

Please note that these are all personal opinions, based on how I understand the “workings” of physical theories, while being neither a physicist nor a philosopher of science. So my skepticism might be overruled by a professional physicist who might or might not be able to explain his reasons to me, a non-physicist.

csteele,
Sorry, I cannot express myself better than in that quote from Wikipedia. You probably confuse speed (a scalar) with velocity (a vector). If you circle around a fixed point at a constant (angular) speed your velocity vector will keep on turning around, hence not constant. Only the speed, i.e. its length, will remain constant. “With respect to the Sun” means assuming Sun is that fixed point.

George,

I realise that complicated theories are simplified to popular jargon for non-specialists.

Nevertheless, Einstein's genius was to build upon his knowledge and curiosity by employing his imagination. His imagination furnished him with the necessaries to go forward.

From "Einstein. A life in Science"

[on the nature of light, which Einstein had been studying earlier in that year]

"The question Einstein puzzled over was this. If you could travel alongside a beam of light, at the same speed as the light, what would you see?....."

On general relativity:

"Einstein began worrying about how to extend the special theory to include a description of gravity almost as soon as the special theory had been published, and even before Hermann Minkowski came up with his geometrical description of the special theory in terms of four dimensional spacetime. Like most of Einstein's great ideas, the theory of general relativity began with a piece of physical intuition..."

(Einstein)

"[In 1907] There occurred to me the...happiest thought of my life....'for an observer falling freely from the roof of a house there exists' - at least in his immediate surroundings - 'no gravitational field'. Indeed, if the observer drops some bodies then these remain relative to him in a state of rest or uniform motion, independent of their particular chemical or physical nature (in this consideration the air resistance is, of course, ignored) the observer therefore has the right to interpret his state as 'at rest'"

and

"I was sitting in a chair in the patent office at Bern when all of a sudden a thought occurred to me: 'If a person falls freely he will not feel his own weight.' I was startled. This simple thought made a deep impression on me. It impelled me toward the theory of gravitation."

It seems that imagination and intuition had a lot to do with Einstein's breakthroughs. It's probably the reason why he leaped such bounds.

"This simple thought...."

Poirot,
Well, I concede, Einstein riding on the sunbeam was probably also part of the intuition that lead him to special theory of relativity, although it is a good exmple to explain the property thereof concerned with time dilatation.

However, I still maintain the that there is a difference between

(a) various thought experiments meant to explain to laymen how the given theory works

(b) the using of thought experiments by specialist physicists who want to understand the ramifications of given theory that they properly understand (including the mathematics involved) or - as in the case of Einstein - who want to extend it to a theory applicable to a wider family of physical phenomena,

(c) the using of thought experiments by non-specialist only to try to predict the outcome of a thought experiment as an outcome of a theory that he/she can understand only on the popular (including non-mathematical) level.

But could Einstein, or any extant person contributing to this thread, tell me what the TRUE time is here, right now!

Officially the time is 12.20pm here at Aldinga Beach, south of Adelaide. But that’s daylight saving time. So perhaps the true time is 11.20am.

Or perhaps the true time should be determined whereby midday is the midpoint between sunrise and sunset, in which case the time would be different as you move east/west, but not if you move absolutely north/south.

Or perhaps there are other ways of determining it.

I think that there are multiple truths here, depending on how you define the parameters, as I have explained earlier in this thread.

Any comments?