Starship Asterisk*

http://en.wikipedia.org/wiki/NGC_1128 wrote:

http://chandra.harvard.edu/photo/2006/a400/more.html wrote:

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This image from the Digitized Sky Survey (DSS)/Palomar 48-inch Schmidt telescope shows NGC 1128 in visible light. The peculiar dumbbell structure of this galaxy is thought to be due to two large galaxies that are in the process of merging. Such mergers are common in the relatively congested environment of galaxy clusters. An alternative hypothesis is that the apparent structure is the result of a coincidence in time when the two galaxies are passing one another, like ships in the cosmic sea. (Credit: Pal.Obs. DSS)

madtom1999 wrote:So we have two black holes whose event horizons are, according to relativity, not moving as far as we can see, circling each other.

Chris Peterson wrote:

madtom1999 wrote:So we have two black holes whose event horizons are, according to relativity, not moving as far as we can see, circling each other.

What exactly do you mean by this? The event horizons move with the black holes.

• _____ King Lear Act IV, scene I
  
  Old Man: 'Tis poor mad Tom.
  
  EDGAR: [Aside] And worse I may be yet: the worst is not
  _____ So long as we can say 'This is the worst.'

biddie67 wrote:The sense of what could be the possible ripple effect on our little world if those two black holes collide and explode, black hole style, is fearsome to speculate.

Chris Peterson wrote:

biddie67 wrote:The sense of what could be the possible ripple effect on our little world if those two black holes collide and explode, black hole style, is fearsome to speculate.

I wouldn't worry. Gravity waves are not destructive. Black holes like these have collided many times in the history of the Universe, without effect outside their immediate environs. It is only now that we have the technology to possibly detect the waves created by such collisions- nothing but the most exquisitely sensitive instruments can do so.

http://en.wikipedia.org/wiki/Ligo wrote:
<<Based on current models of astronomical events, and the predictions of the general theory of relativity, gravitational waves that originate tens of millions of light years from Earth are expected to distort the Laser Interferometer Gravitational-Wave Observatory (LIGO) 4 kilometer mirror spacing by about 10⁻¹⁸ m, less than one-thousandth the "diameter" of a proton. Equivalently, this is a relative change in distance of approximately one part in 10²¹. A typical event which might cause a detection event would be the late stage inspiral and merger of two 10 solar mass black holes, not necessarily located in the Milky Way galaxy, which is expected to result in a very specific sequence of signals often summarized by the slogan chirp, burst, quasi-normal mode ringing, exponential decay.

As of November 2005, sensitivity had reached the primary design specification of a detectable strain of one part in 10²¹ over a 100 Hz bandwidth. The baseline inspiral of two roughly solar-mass neutron stars is typically expected to be observable if it occurs within about 8,000,000 parsecs (26,000,000 ly), or the vicinity of our Local Group of galaxies, averaged over all directions and polarizations. In 2004, it was reported that theorists were estimating the chances of unambiguous direct detection by 2010 at one in six.

In February 2007, GRB 070201, a short gamma-ray burst, arrived at Earth from the direction of the Andromeda Galaxy, a nearby galaxy. The prevailing explanation of most short gamma-ray bursts is the merger of a neutron star with either a neutron star or black hole. LIGO reported a non-detection for GRB 070201, ruling out a merger at the distance of Andromeda with high confidence. Such a constraint is predicated on LIGO eventually demonstrating a direct detection of gravitational waves.>>

madtom1999 wrote:Chris P - perhaps but the black holes must, by their own definition appear stationary to us. The event horizon is, to all intents and purposes, an immutable, immoveable thing.

Chris Peterson wrote:

madtom1999 wrote:Chris P - perhaps but the black holes must, by their own definition appear stationary to us. The event horizon is, to all intents and purposes, an immutable, immoveable thing.

I'm afraid I still don't understand your point. Black holes are simple objects. We can see them move like any other object. If one were in orbit around the Sun, we'd observe it moving just like the planets. We do see actual motion in the case of binary black holes. Black holes do not appear stationary with respect to other objects. The event horizon itself is just a surface. It has no features that would allow us to see it move with respect to the center of the black hole. But that doesn't necessarily mean it isn't moving. Black holes have spin, and that may mean that the "surface" defined by the event horizon is spinning as well.

neufer wrote:Hmmmmmm.....this is a conundrum.

We have always been taught that from our frame of reference the event horizon is a "frozen" surface above which falling objects hang in suspended animation while barely radiating at all. And yet we know that both gravitational & electromagnetic fields are spinning rapidly outside the black hole ejecting "johnny come late-lies" out from the poles.

So can one really say that <<the "surface" defined by the event horizon is spinning as well?>>

Chris Peterson wrote:I agree with your description of the behavior of an event horizon as seen from a distant frame of reference- except for your use of the term "frozen". Where does that come from?

neufer wrote:Time comes to a stop; ergo: frozen as in no internal (as well as external) motion.

neufer wrote:It is a black hole because all thermal radiation has effectively stopped.