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Don't judge a black hole by its area
+Plus ^ | Yen Chin Ong

Posted on 05/07/2016 8:24:24 AM PDT by MtnClimber

The shape of a Schwarzschild black hole is that of a sphere, and so its area is $A=4\pi r_ h^2$. We might be tempted to use our ordinary intuition about geometry, and deduce that the volume of a Schwarzschild black hole must be $V=4/3 \pi r_ h^3$. This is, however, not necessarily the case. It turns out that the volume of a black hole is not a well-defined notion in general relativity. The reason is that general relativity is a geometric theory of a four-dimensional spacetime, that is, three dimensions of space and one dimension of time. In order to specify a spatial volume, one has to specify a specific moment in time......

Even though a Schwarzschild black hole looks the same forever to an outside observer (ignoring something called Hawking radiation that would shrink the black hole), its volume actually gets larger with time.

When the time $\nu $ is sufficiently large, the volume is given by:

\[ V \approx 3\sqrt{3}\pi M^2 \nu . \] From this expression one sees that the volume of a black hole continues to grow larger and larger, although its surface area never changes! To give an idea of how large the interior of a black hole could become, this formula estimates that the volume for Sagittarius A*, the supermassive black hole at the centre of our Milky Way Galaxy, can fit a million solar systems, despite its Schwarzschild radius being only about 10 times the Earth-Moon distance. (Sagittarius A* is actually a rotating black hole, so its geometry is not really well-described by the Schwarzschild solution, but this subtlety does not change the result by much.) Growing with dimensions

(Excerpt) Read more at plus.maths.org ...


TOPICS: Science
KEYWORDS: blackhole; relativity

1 posted on 05/07/2016 8:24:25 AM PDT by MtnClimber
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To: MtnClimber

A very well written article. I had to cut and cut to get the exerpt to fit in 300 words.


2 posted on 05/07/2016 8:25:23 AM PDT by MtnClimber (For photos of Colorado scenery and wildlife, click on my screen name for my FR home page.)
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To: MtnClimber

We can verify all of that next time we actually go see one in person ...


3 posted on 05/07/2016 8:26:19 AM PDT by PIF (They came for me and mine ... now it is your turn ...)
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To: MtnClimber

4 posted on 05/07/2016 8:30:17 AM PDT by DannyTN
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To: MtnClimber
The inside is bigger than the outside?

That sounds vaguely familiar...


5 posted on 05/07/2016 8:41:21 AM PDT by null and void ("when authority began inspiring contempt, it had stopped being authority" ~ H. Beam Piper)
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To: MtnClimber

must not post picture of wookie’s derriere


6 posted on 05/07/2016 9:19:14 AM PDT by BenLurkin (The above is not a statement of fact. It is either satire or opinion. Or both.)
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To: MtnClimber
>>deduce that the volume of a Schwarzschild black hole must be $V=4/3 \pi r_ h^3$.

No, no. The volume is well known to be $V=2/3 \rhu r_ lsmft_egbd%%sf h<> 4c

7 posted on 05/07/2016 9:30:42 AM PDT by pabianice (LINE)
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To: pabianice
In high school we learned it was B4i4qru/18QTπ
8 posted on 05/07/2016 10:01:20 AM PDT by FredZarguna (And what rough beast, its hour come round at last, slouches towards Fifth Avenue to be Born?)
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To: MtnClimber
Sheesh, talk about symbology being trashed, this one takes the cake!

The key equation is the following; When the time $\nu $ is sufficiently large, the volume is given by:
\[ V \approx 3\sqrt{3}\pi M^2 \nu . \]

Untangling this mashup of ill-conversion leaves us with the following;
When the time ν is sufficiently large, the volume is given by;
V≅ 3√3 π M^2 ν

Remember the 'distributive property'

Unicode, love it or ...

9 posted on 05/07/2016 11:01:51 AM PDT by SES1066 (Quality, Speed or Economical - Any 2 of 3 except in government - 1 at best but never #3!)
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To: MtnClimber

Black Hole = racist and sexist.


10 posted on 05/07/2016 11:05:34 AM PDT by TruthWillWin (The problem with socialism is that you eventually run out of other peoples money.)
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To: SES1066
FYI, for this website you can use the entity coding (& α ... ;) rather than the HTML codings. See the UNICODE Table.
11 posted on 05/07/2016 11:11:56 AM PDT by SES1066 (Quality, Speed or Economical - Any 2 of 3 except in government - 1 at best but never #3!)
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