86 reputation
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bio website dcgeorge.com
location Eureka, California
age 76
visits member for 1 year, 4 months
seen 7 hours ago

I'm a theoretical physicist (old-amateur/hobbyist division).


Apr
21
revised How does gravity escape a black hole?
Given all the interest in the question and considering there are no comments or votes on my answer, I thought it needed to be expanded and made more clear.
Nov
5
comment Does a black hole have an interior or does the spacetime manifold itself end at the event horizon?
Thanks Ben, I had that totally screwed up (we're dealing with a 75 year-old brain here). I edited it accordingly. This mass scaling issue is also mixed up somehow with entropy and surface area and Bousso's take on the holographic principle. I'm trying to sort it out.
Nov
5
revised Does a black hole have an interior or does the spacetime manifold itself end at the event horizon?
Correction needed as noted by Ben Crowell
Oct
27
revised Does a black hole have an interior or does the spacetime manifold itself end at the event horizon?
I wanted to re-word the title to make it more clear, as suggested.
Oct
24
comment Does a black hole have an interior or does the spacetime manifold itself end at the event horizon?
The equivalence principle doesn't allow anything special to happen at the event horizon. Only if you assume that the spacetime manifold is unbroken, that it continues past the event horizon. Which means you also have to ignore the whole issue of black hole firewalls and Bousso's idea that "space and time actually end there."
Oct
24
comment Does a black hole have an interior or does the spacetime manifold itself end at the event horizon?
The Schwarzschild solution has m∝r. It's proportional to neither its area not its volume. This is wrong, Ben. The Schwarzschild radius is proportional to the mass but the mass of the black hole itself is proportional to either the radius squared or cubed depending on who you ask. Ron Maimon says "... the scaling of the Schwarzschild radius is linear in mass, while the scaling of mass is cubic in the radius, ..." Raphael Bousso (re the holographic principle) says the black hole's mass is proportional to its radius squared, i.e. its surface area. This is the black hole scaling problem.
Oct
23
comment Does a black hole have an interior or does the spacetime manifold itself end at the event horizon?
We discussed this here. It's not wrong, just meaningless. With all due respect, Ben, in that discussion, you tried to disparage the paper by calling the MNRAS a crap journal (guilt by association, I guess). Now you're saying their conclusion isn't wrong, it's just meaningless. Frankly, I don't understand your conclusion that all the mass of a black hole being outside the event horizon is meaningless. The meaning is perfectly clear to me. Not only is it clear, since it is directly counter to the accepted view, if it's correct, it's astoundingly significant.
Oct
23
revised Does a black hole have an interior or does the spacetime manifold itself end at the event horizon?
added 764 characters in body
Oct
22
asked Does a black hole have an interior or does the spacetime manifold itself end at the event horizon?
Oct
7
comment About the Ether Theory acceptance
A great answer, Trevor. I find it fascinating that the Michelson-Morley experiment actually had two conclusions, the second of which is almost universally ignored. The alternate conclusion was that it is simply not possible to detect the ether drift because of Lorentz contraction effects.
Sep
20
comment Does the total mass of an isolated object include the mass stored in its gravitational field?
"... If their measure of energy density implies that all the energy of a black hole is outside the horizon, then that's in fact an argument against taking their result as having any deep significance." It does indeed imply that. But, if it disagrees with the general consensus and is correct, it's likely of great significance. Lynden-Bell and Katz are not exactly lightweights in the field.
Sep
20
comment Does the total mass of an isolated object include the mass stored in its gravitational field?
"... MNRAS is a crap journal that publishes lots of papers that are nonsense ..." That may be true but you might want to take a look at Lynden-Bell's Wikipedia page before you conclude the paper is nonsense. en.wikipedia.org/wiki/Donald_Lynden-Bell
Sep
20
comment Does spacetime in general relativity contain holes?
@Ben Crowell. Sorry Ben, my intention wasn't to reduce your answer to a sound bite. You give very interesting and informative answers. For instance: "The singularity is not considered part of the spacetime manifold, ..." That's fascinating. I assume the same could be said for a hole (a 3D singularity) in the manifold.
Sep
17
comment Does spacetime in general relativity contain holes?
@Ben Crowell. "There is no restriction on the size of the hole or its topological features such as whether it's knotted, etc. The only condition is that what's left over after cutting is still a manifold." So, am I understanding it correctly that, given the above conditions, you think holes or cutouts in the spacetime manifold are possible? Do I have that right?
Sep
17
comment Does the total mass of an isolated object include the mass stored in its gravitational field?
"There is no logical connection to the event horizon." I should have quoted more of the paper's summary. The authors claim: "We show by physical arguments that static spherical systems have a coordinate-independent field energy density. ... the field energy outside a Schwarzschild black hole totals Mc^2. In this sense all the energy remains outside the hole." I was surprised by this conclusion so I was hoping someone would weigh in on their arguments. In any case, I can see more clearly now how confusing the whole issue of field mass is. Thank you for your insights.
Sep
13
asked Does the total mass of an isolated object include the mass stored in its gravitational field?
Sep
5
comment Does spacetime in general relativity contain holes?
@Ben Crowell (There is no such controversy.) Perhaps you could elaborate? I googled the phrase and got over a hundred thousand results. Here's one: "With the general theory of relativity, the traditional debate between absolutism and relationalism has been shifted to whether or not spacetime is a substance, ... " en.wikipedia.org/wiki/Philosophy_of_space_and_time
Sep
5
comment Does spacetime in general relativity contain holes?
@Ben Crowell (the metric is not degenerate at the horizon) That's true from the presently accepted perspective where spacetime is assumed to continue inside the horizon, but viewed in the context of the OP's question about "holes" in the spacetime manifold ... if such cutouts could exist ... would the metric not have to end and become degenerate at the edge of the hole? Black holes might not be such cutouts but the two would have the same vacuum metric and would therefore be indistinguishable.
Sep
5
comment Does spacetime in general relativity contain holes?
@Ben Crowell (The infinity at the horizon) Here's my source: "It's customary to assert that the Schwarzschild solution is unequivocally non-singular at r = 2m, and that the intrinsic curvature and proper time of a free-falling object are finite and well-behaved at that radius. ... However, ... with respect to the proper frame of an infalling test particle, we found that there remains a formal singularity at r = 2m. ... The free-falling coordinate system does not remove the singularity, but it makes the singularity analytically removable." mathpages.com/rr/s8-07/8-07.htm
Sep
1
awarded  Editor