|Nov29-12, 08:09 AM||#137|
Oppenheimer-Snyder model of star collapse
I don't see how that is "additional", it is exactly what O and S used. Even if OS "did not get that far" in their analysis of their solution there is nothing "additional" added to the model for the modern analysis.
|Nov29-12, 08:24 AM||#138|
Secondly , there's opportunity to apply the exact same arguments to other situations involving event horizons that don't involve black holes. Specifically, the Rindler horizon. These would be difficult to test with our current technology, though. The experiment is interesting, so I'll spell it out in more detail, since I've been alluding it to some time in the belief it was obvious (but perhaps it isn't to you? )
The experiment involves launching a spaceship that accelerates at 1g for a year shiptime - or .1g for 10 years shiptime - or .001 g for 1000 years shiptime.
The spaceship observes the Earth through a telescope. The prediction of SR in this case (you don't even need GR) that the Earth appears to fall behind an event horizon There will be some last event that the spaceship sees - say year 2100 exactly on the new years day celebration in Grenwich.
The metric from the accelerating spaceship looks like this, assuming the spaceship accelerates in the z direction. (There are some variant forms of the metric, this version is normalized so that g_uv = diag(-1,1,1,1) at the origin.
ds^2 = -(1+ gz)^2 dt^2 + dx^2 + dy^2 + dz^2
http://en.wikipedia.org/w/index.php?...ldid=522511984 has the details if you're interested (but you may see minor details differ, these could be confusing).
As the observer on the spaceship watches the Earth approach New Years 2100,, the spaceship sees the image grow dimmer and dimmer, and the Earth's clocks appear to slow down. Just as it would if the Earth were falling through the event horizon of a very large black hole, as g_00 falls towards zero at the critical value z = -1/g. (In non-geometric units, that's z = c^2/g). This is the critical value because g_00 goes to zero. I believe you call it something like "time stopping?" I forget how you referred to this condition.
Now, if we apply your argument, the Earth ceases to exist in the year 2100 at new Years in some philosophically meaningful sense. At the very least, something dramatic happens on that date, as "time stops".
My position is that it's pretty obvious the Earth won't cease to exist at New Years day on the year 2100 in any sort of meaningful sense. And that the people on Earth won't even notice this, or notice anything about "time stopping" or anythign like that. In fact, they'll find New Years day 2100 quite unremarkable.
As far as modern goes, the reason I say that is the following quote that I gave earlier.
|Nov29-12, 08:52 AM||#139|
A quick comment, though: you seem very quick to jump to conclusions about what people would "surely" agree to. I don't think particle physicists would say that quarks are "theoretical"; particle physicists appear to me to believe overwhelmingly that quarks are as physically real as tables and chairs. (Some, the extreme reductionists, may even believe that quarks are *more* physically real than tables and chairs, since quarks are fundamental particles and tables and chairs are not. I don't agree with that view, but it's hard not to believe that at least some physicists hold it when you see what they say and read what they write. Eddington himself delivered a famous lecture, which I think got put into his book "The Nature of the Physical World", in which he argued that the table in front of him was not real, only the atoms making it up were. I can only guess what he would have said if he'd known about quarks.) The term "actual theory of physics" doesn't seem to me to match that very well.
|Nov29-12, 01:44 PM||#140|
Regretfully more than ever the discussion is hindered by incompatible definitions based on different schools of teaching. I intend to do a "retake" of that illustration in the new thread, with a brief summary of comments by different people, including yours.
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